Immune Response Ebook

The Immunity Crisis in America

Have you ever wondered WHY you get sick from different things, sometimes seemingly for no reason? Haven't you ever wished that you could find some way to stop yourself from getting sick and stay healthy all the time? Well, that might be more possible than you thought at first! Your immune system is an odd system, that many scientists are still struggling to understand. However, there have been some amazing breakthroughs! Once you get access to this detailed and helpful book, you will be able to find REAL and Applicable ways to improve your immune system and keep yourself from getting sick all of the time. This book teaches you everything that you never learned about your immune system Start learning what you can Really do to improve your immune system's health and keep your body healthier for longer! It's not hard at all Get started today! Read more here...

Immunity Crisis Summary


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Innate And Adaptive Immunity

The fundamental purpose of the immune system is to distinguish between self and non-self. Foreign antigens are eliminated in a variety of ways by both the so-called innate and adaptive components of the immune system. The innate immune system deals with foreign invaders through rapid, albeit fairly nonspecific, responses. Moreover, there is no recall or memory within the innate immune system. By contrast, the adaptive immune system takes a bit longer to respond, but retains memory for the specific antigen, and is able to respond in an accelerated fashion in the event of re-encounter with the same antigen. Indeed, it is this ability to ''learn'' and remember specific antigens that is the basis for vaccination. The two major types of lymphocytes that comprise the adaptive immune system are B cells and T cells. Both are derived from hematopoetic stem cells in the bone marrow, but they function in entirely different ways. B cells produce soluble proteins known as antibodies, which can...

Innate Immune Response To Systemically Applied Ad

Even though natural infections with Ads are largely harmless in humans, intravenous Ad administration for gene delivery purposes, especially at high doses, stimulates strong innate and adaptive immune responses and can be fatal for the host (91a,92,94). It is currently recognized that the initiation of this acute systemic inflammation depends on interactions of the Ad capsid with host cells. Upon systemic application of Ads in rodents, rhesus monkeys, and humans, a rapid liver-mediated vector removal from the circulation was observed (5a,88a,89a,93). Despite significant knowledge regarding Ad interactions with cells in vitro, the molecular mechanisms governing Ad biodistribution, hepatic tropism and toxicity in vivo remain poorly understood. Systemically applied Ads induce two phases of inflammatory gene expression in the liver. The first phase of acute inflammation depends entirely on virus capsid interactions with host cells and occurs within 24 h after virus administration (2,60a)....

The HLA system and the immune response to HIV

CD8 T-cells recognize their antigen (peptide) in context with HLA class I molecules on antigen-presenting cells, whereas CD4+ T-cells require the presentation of antigenic peptides in context with HLA class II molecules. The generation of an HIV-specific immune response is therefore dependent on the individual HLA pattern. Antigen-presenting cells may bind HIV peptides in different ways within grooves on the HLA class I molecules. Therefore, CD8 T-cells can be activated in an optimal or suboptimal way or may not be activated at all. Using large cohorts of HIV-1 infected patients, in whom the natural course of disease (fast versus slow progression) is known, HLA patterns were identified that were associated with a slow versus fast disease progression. These studies suggest that the HLA type could be responsible for the benign course of disease in about 40 of patients with a long-term non-progressive course of disease. Homozygosity for HLA Bw4 is regarded as being protective. Patients...

The HIVspecific cellular immune response

In comparison to HIV-1-infected patients with a rapid decline in CD4+ T-cell numbers, patients with a long-term non-progressive course of disease ( LTNP long-term non-progressors) have high quantities of HIV-1-specific CTL precursors with a broad specificity towards various HIV-1 proteins. The different capacities of certain HLA alleles to present viral particles more or less efficiently and to induce a generally potent immune response may explain why certain HLA alleles are associated with a more rapid or a slowly progressive course of disease (see above). Individuals have been described, who developed CTL escape mutants after years of stable disease and the presence of a strong CTL response. The evolution of CTL escape mutants was associated with a rapid decline in CD4+ T-cells in these patients, indicating the protective role of CTL (Goulder 1997). Various therapeutic vaccine strategies have been developed during the last few years and mostly tested in SIV-infected rhesus macaques...

The Th1Th2 immune response

Depending on the secretion pattern of cytokines, CD4+ T-cells may be differentiated into TH1 and TH2 cells. TH1 CD4+ T-cells primarily produce interleukin-2 (IL-2) and IFNy, which represent the cytokines that support the effector functions of the immune system (CTL, NK-cells, macrophages). TH2 cells predominantly produce IL-4, IL-10, IL-5 and IL-6, which represent the cytokines that favor the development of a humoral immune response. Since TH1 cytokines are critical for the generation of CTLs, an HIV-1-specific TH1 response is regarded as being a protective immune response. Studies on HIV-exposed but non-infected individuals have shown, that following in vitro stimulation with HIV-1 env antigens (gp120 gp160) and peptides, T-cells from these individuals secrete IL-2 in contrast to non-exposed control persons (Clerici 1991). Similar studies were undertaken in healthcare workers after needle-stick injuries and in newborns from HIV-infected mothers. Although these observations may...

HIV1 specific humoral immune responses

The association between an HIV-1-specific humoral immune response and the course of disease is less well characterized. In a SIV model, injection of an antibody cocktail consisting of various neutralizing antibodies is able to prevent SIV infection after a mucosal virus challenge (Ferran-telli 2004), indicating that primary protection is mainly dependent on a broad humoral immune response. This data suggests that HIV-specific antibodies are necessary for a preventive vaccine strategy. In contrast, B-cell depletion by a monoclonal antibody directed against B-cells in monkeys with already established SIV infection, does not affect the course of plasma viremia (Schmitz 2003). A slow progression of immunodeficiency was observed in patients with high titers of anti-p24 antibodies (Hogervorst 1995), persistence of neutralizing antibodies against primary and autologous viruses (Montefiori 1996), and lack of antibodies against certain gp120 epitopes (Wong 1993). Long-term non-progressors with...

Development of the Mucosal Immune System

Given their known role in the immune system, it would seem likely that TLR signals induced by the commensal microflora may be important in the development of the mucosa-associated lymphoid tissue of the intestine. However, in initial analyses of adult animals, mice deficient in MyD88, TLR2, or TLR4 do not show gross abnormalities in the development of Peyer's patches,

Mucosal Immune Responses

There is some evidence that the s-IgA antibody induced by immunization with antigens in experimental animals can neutralize HIV-1.75 While IgA responses to HIV- and SIV-derived antigens were shown in early studies, attempts to vaccinate against infections of mucosal tissues have generally been less successful than vaccination against systemic infections, to a large extent reflecting incomplete knowledge about the most efficient means for inducing protective local immune responses at these sites. The large and repeated antigen doses often required to achieve a protective immune response make this vaccination approach impractical for many purified antigens. There is, therefore, a great need to develop strategies for enhancing delivery of antigen to the mucosal immune system as well as to identify mucosa-active immunostimulating agents (adjuvants).76-79 The function of IgA at mucosal surfaces appears to be one of cross-linking pathogens in the lumen and facilitating their clearance by...

Influence of Age Related Decline in Immune Function and Influence on Intestinal Bifidobacteria Microbiota

Immunosenescence is defined as the state of deregulated immune function that contributes to the increased susceptibility of the elderly to infection and, possibly, to autoimmune diseases and cancer (49,50). When immunosenescence appears, the functional capacity of the immune system of the host gradually declines with age. The most dramatic changes in immune function with age occur within the T cells compartment, the arm of the immune system that protects against pathogens and tumors (51-54). The fact that T lymphocytes are more severely affected than B cells or antigen-presenting cells is mainly due to the involution of the thymus, which is almost complete at the age of 60. The host is then dependent on the T cells of various specificities, which eventually leads to changes in the T cell repertoire. CD45RA + native cells are replaced by CD45RA memory cells, and a T cell receptor oligoclonality develops. At the same time, T cells with signal transduction defects accumulate. Age-related...

Within Hostimmune System Models

The compartmental differential equation models described earlier are also adaptable to the study of the dynamics of the immune system in response to infection. Such models can provide novel and useful insights into the observed time course of quantitative clinical measures of infection within the human host and how these might relate to the probable course which may be taken by the infection by providing explanations for observed dynamical changes in such measures they also offer the prospect of illuminating some of the reasons why response to infection appears to differ between hosts. Useful examples of such work may be found in work on HIV by Nowak and Bangham (1996) and Nowak et al. (1997), and on viral hepatitis by Bocharov et al. (2004).

Innate Immune Responses Friend or

Most studies consider the induction of innate immune responses such as cytokines, chemokines, oxidative stress, and proteases to be detrimental to the neuron. This concept has been applied to most neurodegenerative diseases, including HIV-associated cognitive impairment (Fig. 1). However there are reasons to believe that in the setting of viral infections, such responses may not always be hostile to the host. Organisms that lack a cellular immune response often use such innate immune responses to protect themselves from invading pathogens. For example, plants, without a specific adaptive immune system, may use metalloproteinases, along with other innate defense mechanisms, to combat infection. For example, the metallo-proteinases-2 gene of the soybean, Glycine max, is upregulated in response to a variety of infections (1). Thus in circumstances where the cellular immune responses fail to control the pathogen such as persistent HIV infection of the CNS, the innate immune responses get...

Alternative Sites for Immune Responses

Consistent with an essential role of secondary lymphoid organs in adaptive immune responses, splenectomized mice lacking LNs and PPs because of a mutation in the aly aly allele have a severe defect in primary immune responses to a variety of microorganisms (Karrer et al. 1997 Miyawaki et al. 1994), Ags (Rennert et al. 2001), and allografts (Lakkis et al. 2000). When mucosal LNs are removed in normal mice, the spleen can partially replace the function of the LNs, indicating that compartments of primary immune responses are highly dynamic. Similarly, the BM can compensate for the lack of LNs and generate primary immune responses to blood-borne Ags (Feuerer et al. 2003 Tripp et al. 1997). In PP-deficient animals, mucosal immune responses and oral tolerance are still observed, leading to the concept that mesenteric LNs may serve as an alternative site for the induction of immune responses (Spahn et al. 2001 Yamamoto et al. 2000). In addition, inducible lymphoid tissues exist that can...

Brief Review Of Immune Responses Innate Immunity

Cells responsible for the innate immunity provide the first line of host defense monocytes macrophages, dendritic cells (DC), natural killer cells (NK), and neutrophils. These are the body's sentinels, able to detect danger and signal it to other cells, by the synthesis of molecules, such as NO (nitric oxide) which displays antibacterial activity, cytokines, and chemokines, which are small peptides acting by means of specific receptors expressed at the surface of targeted cells. Some of them have pro-inflammatory properties, and increase expression of surface markers on some cells allowing migration into neighboring lymphoid organs. DCs and macrophages are able to display a phagocytic activity, and by production of inflammatory chemokines and cytokines, to modulate other cells such as neutrophils, polymorphonuclear cells and eosinophils in the case of hypersensitivity, which increase the inflammatory action, and ultimately B and T cells, which will set up an acquired immune response...

The Intestinal Immune System

The IIS is a particular immune system anatomically and functionally distinct from that present at the peripheral level (30-32). It is in contact with an enormous quantity of Ags, food proteins and intestinal bacteria, and does not mount an inflammatory response against them. At the same time, it has to protect against enteric pathogens and toxins. Three lines of defense are present (i) natural defenses stomach acidity, bile salts, mucus, motility, permeability, (ii) innate immune responses Ag capture, cytokine secretion, TLRs, and (iii) acquired immune responses namely oral tolerance (OT) and secretory IgA (sIgA) response. All of them interact together.

Activation of the Intestinal Immune System

As described above, the intestine is populated by some characteristic subsets of DCs, which are believed to play a pivotal role in the orientation of the acquired immune responses towards tolerance. Is the intestinal microbiota the main factor that determines such characteristics Currently, only few studies exist in this field. Another question concerns the specific functions of intestinal DCs. Are there specific distinct lineages of DCs attracted into the intestinal mucosa under the control of specific chemokines or adhesion molecules, or are precursor DCs modified after their arrival in the tissue In his interesting review (31), Mowat explains that, given the plasticity of DCs in other tissues, it is reasonable to believe the latter hypothesis, and mucosal DCs are the cells that integrate the genetic and environmental factors to shape T-cell responses to local Ags in ways such that homeostasis is maintained. Intestinal epithelial cells, by the ability to constitutively produce TGF-b...

The Immune Response To Heparin

The finding that anti-PF4-heparin antibodies can be of the IgM, IgG, or IgA isotype (Visentin et al., 1994 Greinacher et al., 1994 Kelton et al., 1994 Amiral et al., 1995, 1996b Arepally et al., 1997 Suh et al., 1997) indicates that class switching, likely requiring helper T cells, may occur in patients mounting a humoral immune response to PF4-heparin. Although HIT is a drug-induced disorder, parallels for the role of T cells in HIT may be drawn from studies of autoimmune

Modulation of Specific Immune Responses The IgA Anti Rotavirus Response

Little information is available regarding the role of intestinal microbiota composition on the modulation of the specific sIgA Ab response against enteropathogens. Indeed, it can be assumed that, according to the composition of the digestive microbiota and the presence, or not, of some bacteria in the dominant microbiota, the specific immune responses might be different. This fact is of particular importance in babies where the poorly diversified intestinal microbiota is strongly influenced by the type of milk. Indeed, it is well known that breastfed babies are more resistant to enteric infections than formula-fed babies (69,70). Human breast milk contains abundant bioactive components that may provide direct protective effects to infants against enteric pathogens (71), but breast-feeding also influences the intestinal microbiota composition enhancing Bifidobacterium development. To test the influence of the intestinal microbiota on the modulation of a specific intestinal sIgA-Ab...

Regulation of the Immune Responses

The role of the intestinal microbiota on the OT process has been demonstrated by various experimental studies using GF mice. Results depend on the immune response considered, oral Ag, and experimental schedule used. In these experiments, immune responses to a specific Ag are compared in two groups of mice the tolerant group where mice are fed with an Ag prior to the peripheral immunization with the same Ag, and the control group fed with only the buffer before the same peripheral immunization. Specific immune responses to the Ag used are then evaluated (Ab responses in serum or cellular response by delayed-type hypersensitivity) in both groups. The tolerant state is present when peripheral immune responses to the Ag are abolished or significantly decreased in the group Ag-fed as compared with the control group. In an initial study, Wannemuehler and coworkers (81) showed that, in contrast to what is observed with the CV mice, gavage of GF mice with a particular antigen, sheep red blood...

Activation of the Immune System

Innate immunity plays a very important role in the activation of the immune system and the ability to develop specific acquired immune responses. Through their Ag-presenting activity and the synthesis of numerous pro-inflammatory chemokines and cytokines (IL-8, IL-1, IL-6, TNF-a, and IL-12), macrophages, and DCs play a key role in the regulation of immune responses. They are the gatekeepers of the host, generating innate resistance to pathogens, and specific immune responses by the stimulation of T-cell-acquired immunity and regulation of the TH1 Th2 balance.

Adenoassociated Virus For Immunotherapy

The potential of AAV vectors for cancer immunotherapy is evident from recent studies using cytokine gene transfer and in vivo immunization approaches (108-110). Active immunization with tumor cells transduced with rAAV encoding cytokines either by a plasmid based-delivery system or by a recombinant virus-mediated infection has resulted in regression of tumor growth upon further challenge. In a separate study, high-level IFN-y and elevated major histocompatibility complex (MHC) class I expression was observed following transfer of D122 gene-modified murine lung cancer cells that significantly delayed tumor development (111). Similar findings of antitumor immunity following transfer of cytokine-encoding AAV DNA in a rat prostatic tumor model (112) were reported. Enhancements in antitumor T-cell response was observed in vitro by AAV-mediated transduction of B7.1 and B7.2 genes in a human multiple myeloma cell line (113). In a vaccination scheme, Liu et al. have recently shown that...

Trial design for testing immunotherapy in tuberculosis

In view of the increasingly widely accepted need for immunotherapy as the only real hope for the improvement of treatment under realistic field conditions, the failure of the Durban trial to yield interpretable data raises important questions about future exploitation of immunotherapy, whether immunological or endocrinological. Is it possible to devise a trial in patients with drug-resistant disease that would conform to regulatory requirements The sporadic distribution of these patients and their lack of uniformity has frustrated attempts to devise such trials in the past. Secondly, and more importantly, would it be possible to design a study that could be performed under realistic field conditions that would satisfy regulatory bodies Until these dilemmas are resolved, it may not be possible to test immunotherapy for tuberculosis in a meaningful way.

Immune Responses Against Hiv2

Many viral infections are controlled by the host immune system and can thereby also be eliminated. Both cellular and humoral arms of the immune For HIV there are several problems for the immune system to overcome. HIV in its latent proviral form can infect a small number of host cells while remaining invisible for both arms of the immune system until the infected cells are activated. In those cells in which the virus replicates with a high rate there are many mutations. Thus, there are many opportunities for the virus to escape the immune system. Furthermore, HIV infects the CD4+ T cells of the immune system such as T helper cells, dendritic cells, and macrophages. Since the majority of the functional immune response is directed against the envelope glycoproteins and gag proteins, a more detailed description of the different epitopes, B cell (Table I), antibody-dependent cellular cytotoxicity (Table II), and cytotoxic T be mostly focused on the structural proteins. Both linear sites...

Propionibacteria and the immune system

The impact of propionibacteria on the immune system was mainly studied regarding the cutaneous species, which display marked immunomodulatory properties (Roszkowski et al., 1990). Indeed, P. avidum KP-40, administered parenterally to mice, increase significantly mice thymocyte proliferation and peripheral blood lymphocytes and monocytes counts (Isenberg et al., 1995). Oral supplementation by the same strain furthermore counteracts the drop in lymphocytes counts triggered by anaerobic exercise in young male healthy sportives (Pottkamper et al., 1996). Such properties were thus sought in the dairy group of propionibacteria. A pioneer study in this field was undertaken with the species P. acidipropionici, orally administered to mice. The treatment resulted in an enhanced phagocytic activity of peritoneal macrophages activity, assessed using killed salmonella in a phagocytosis assay (Perez Chaia et al.,

Immunotherapy for HCC

To improve the prognosis of progressive HCC and the recurrence-free survival rate after topical treatment, we need to develop whole-liver treatment based on a new point of view. It is in this context that there are high expectations for immunotherapy to treat HCC (Butterfield, 2004 Palmer et al., 2005 Avila et al., 2006). Immunotherapy for cancer has been developing from nonspecific to specific, from those using unknown mechanisms to those where the mechanism has been clarified. To holistically activate immune responses in vivo, immunomodulating therapy using bacterial compounds has been replaced by cytokine therapy. Adoptive immunotherapy using lymphokine-activated killer cells (LAK) has been replaced by therapy using tumor-infiltrating lymphocytes (TIL) that are tumor-specific, and nonspecific immunostimulation has been replaced by specific treatment using DC or tumor-specific antigens. In addition, conventional approaches have been reevaluated from an up-to-date point of view...

Acquired immune deficiency syndrome

Infection with HIV, a retrovirus of the lentivirus subgroup is these days one of the most frequent causes of immune deficiency. This syndrome give rise to a diverse range of symptoms and the development of opportunistic infections and malignancies. Most infections in the West result from the B clade of HIV-1, but different clades (HIV families, that can be distinguished on the basis of viral sequence) predominate in other parts of the world. In South Asia the E clade predominate and in sub-Saharan Africa the A and C clades are the most common. Infection with the related retrovirus, HIV-2, which is found predominantly in West Africa. This infection gives rise to a more protracted disease course. Patients infected with this virus have fewer signs of immune deficiency.

Immune response to a cancer

There is some evidence that cancer cells have surface membrane antigens called tumour-specific antigens (TSA) or tumour-associated antigens (TAA) that are recognized by the immune system as non-self, and can elicit an immune response. Antibodies secreted by B-lymphocytes will coat tumour cells and with the help of complement and phagocytic cells can cause tumour cell destruction. CD8+ T-lymphocytes and NK cells can cause direct tumour cell killing, whereas CD4+ T-cells release cytokines to augment tumour cell killing by macrophages. The concept of immune surveillance as protection against cancer, whereby lymphocytes continuously check dividing cells for mutations and destroy unacceptable cells, has not been proved (Fig. 11.15).

Immunotherapy of cancer

Numerous attempts have been made to employ immuno-logical methods to treat cancer, but none have been very successful. The different techniques can be grouped together as active, passive and adoptive immunotherapy. Active immunotherapy refers to those techniques designed to enhance components of the immune system most likely responsible for antitumour activity. Bacillus Calmette-Guerin (BCG) has been used to enhance cellular immunity, particularly macrophage function, and various cytokines such as IFN, IL-1, IL-2, IL-4, IL-12 and TNF are being tested to enhance immune function. Passive immunotherapy usually refers to the use of monoclonal antibodies directed against TSA in an attempt to destroy the tumour cell. Adoptive immunotherapy refers to the transfer of immune components such as macrophages and NK cells from one individual to another. The most extensively studied in this group are known as lymphokine-activated killer (LAK) cells.

Organization of the Mucosal Immune System

The mucosal immune system may be divided into two functional components, inductive and effector tissues.424546 Inductive sites include tissues where antigen-specific B and T cells are first sensitized to specific antigen, while effector sites are those sites where antigen-specific immune responses are detected. Inductive tissues are identified as organized lymphoid tissues adjacent to mucosal surfaces and include (in the mouse) the Peyer's patch for the gastrointestinal tract and the nasal-associated lymphoreticular tissue (NALT) for the upper respiratory tract. In humans, the tonsils appear to serve as the inductive sites for mucosal immune responses active in the upper respiratory tract and oral cavity. Inductive tissues contain all the cellular components required for the induction of antigen-specific B and T (CD4+ and CD8+) cells.47-51 At the inductive site, antigen is sampled from the environment via specialized antigen-sampling cells known as M cells, processed by...

Hspapc Interactions Initiation Of Immune Responses

Center for Immunotherapy of Cancer and Infectious Diseases, University of Connecticut School of Medicine, Farmington, CT 06030-1601 Abstract The immunogenicity of HSPs is exquisitely dependent on its interaction with professional antigen presenting cells. The interaction is specific and occurs through surface receptors on the APC such as CD91. Other molecules such as CD40, LOX-1, CD36, Toll-like receptor-2 & 4, SR-A and SREC-I have also been proposed to be HSP receptors and are discussed. The physiological situations where the HSP-APC interaction is necessary such as cross-priming of antigens and maturation of the APCs and the implication of these events for the priming of immune responses against infectious agents and tumors and for maintenance of tolerance against self antigens are deliberated

Hspinduced Stimulation Of Immune Responses

Abstract Heat shock proteins have a profound effect on the immune response. Extracellular uptake of antigen-bound HSP can be presented by both MHC class II and class I. Maturation of DC is stimulated by HSP, upregulating the costimulatory molecules CD40, CD80 and CD86, as well as MHC class II, all of which enhance immune responses. The state of maturity of DC may be significant in the balance between immunity and tolerance. Innate immunity is elicited by the production of CCL3, CCL4 and CCL5, IL-1 , IL-6, IL-12 and TNF-a. These extracellular chemokines attract the entire repertoire of immune cells, and the interleukins modulate the cellular responses resulting in effective immunity. Human lymphoid cell activation by microbial Hsp70 appears to be mediated by CD40, expressed mostly by DC and macrophages, and CCR5 in T cells and immature DC. The CD40 molecule is part of the CD40-CD40L costimulatory pathway and the emerging alternative CD40-Hsp70 pathway might prove to be useful in...

Immune Responses to HIV1 and Potential Correlates of Protection 221 Humoral Responses

Antibodies are important in preventing susceptible cells from becoming infected by blocking pathogen binding and or entry into target cells. The humoral arm of the immune system has provided protective responses in several successful viral vaccines. For example, the quantitation of serum-neutralizing activity in recipients of polio or influenza vaccines has been shown to correlate with the efficacy of the vaccine in preventing disease following later exposure to the pathogen. In addition, vaccines against viral diseases such as rabies and hepatitis B have produced high-titer neutralizing antibodies, which have been correlated with vaccine efficacy. Several prospective vaccines using this immunological measure are being tested in animal models using HIV, simian immunodeficiency virus (SIV), and S HIV immunogens. In spite of evidence supporting the role of CTLs and neutralizing antibodies in conferring immunity, it is also important to note that there is evidence to the contrary. Some...

The Role Of Heat Shock Proteins In The Elicitation Of Immune Responses

Abstract Heat Shock Proteins (HSP), well known for their protein polpypetide chaperone activities, display a remarkable ability to elicit peptide-based immune responses. The exact manner in which they do so, their physiological role in this process, and their distinct ability to promote adaptive immune response is the subject of this chapter. The first part of the chapter will deal with the general known antigenic stimulation properties of heat shock proteins, the second will deal with the separation of innate and adaptive immune responses as learned from studies with GP96, Hsp70, and Mycobacterium Hsp70 and finally the third will deal with the subject of chaperone rich cell lysates and means of isolating these HSP immunogenic complexes

Between Commensal Intestinal Bacteria and the Host Immune System

Three main different experimental setups have been used in our lab and others to study the bacterial-host interactions described in this article. First, we can take germ-free animals with no intestinal bacteria whatsoever and study the changes in the host mucosal and systemic immune systems as bacteria colonise the intestine to recolonise germ-free animals it is only necessary to put a normal animal containing an intestinal flora in the same cage. Alternatively, animals may be selectively colonised by deliberate inoculation with one or more bacterial species. Second, we can deliberately challenge specific pathogen-free (SPF) animals with doses of live bacteria given into the stomach, or directly into the intestine. SPF animals have a simple flora of intestinal bacteria (Macpherson and Harris 2004), so challenging them with test doses of organisms increases the bacterial load (Macpherson and Uhr 2004). The test organism can, of course, be engineered to express a chimeric protein in...

Humoral Immune Responses Against Hiv1

Shortly after the primary infection in humans, HIV-1 stimulates a humoral immune response which results in the production of antibodies directed against most of the viral structural components. A particular subset of antibodies is directed against HIV-envelope gp120 and gp41, which are the surface (SU) and transmembrane (TM) glycoproteins, respectively. These important proteins may be involved in the induction of active immunity, as revealed by the production of neutralizing, cell-fusion-inhibiting and antibody-dependent cellular-cytotoxicity (ADCC)-mediating antibodies.

The Immune Response Under Stress Class I Hla Presentation Of Hostderived Peptides

Abstract Major histocompatibility complex (MHC) class I molecules are found at the surface of all nucleated cells. Class I molecules function as immune sentries by scanning the intracellular proteome and then reflecting the proteome at the cell surface. Through class I presented peptides, T lymphocytes and other immune effector cells can continuously survey the intracellular proteome. Viral infection and cancerous transformation results in the presentation of peptides not found on healthy cells. Class I presented peptides therefore act to distinguish infected and cancerous cells in the eyes of the immune response. Here, we review how class I molecules reflect host cell stress resulting from infection and cancerous transformation. Class I molecules display peptides derived from heat shock proteins on both cancerous and virus-infected cells, and these peptides are clearly recognized by the immune response. The class I of diseased cells also reveal less obvious stress-related signals...

Passive Immunotherapy Trials Of Clinical Relevance Utilizing Hiv Immune Serum Globulin

In a lengthy study by Vittecoq et al. in which infusions of HIVIG were provided twice a month for 1 year, no clinical benefit was demonstrated in the recipients.53 Of promise, however, was the passive immunotherapy study involving newborn rhesus macaques by Van Rompay et al.54 SIV hyperimmune serum given subcutaneously prior to oral SIV inoculation protected six newborns against infection.54 This beneficial prophylactic result is

Subversion of the immune system

However, it is clear that once infection has occurred, HHV-6 is able to establish latency and remain quiescent for prolonged periods of time unless the immune system is otherwise immunocompromised. One of the mechanisms by which viruses establish long-lived infections and subvert the immune system is by directly infecting immune cells thereby impairing surveillance. The original report of the isolation of HHV-6 by Salahuddin et al. (1986) described an isolate from patients with a B-cell lymphoproliferative disorder, although these lymphomas frequently contain T lymphocytes that were the likely source of the virus (G. Krueger, personal communication). Horvat et al. (1993) reported that HHV-6 inhibited the lymphoproliferative responses of human peripheral blood monocytes in vitro. Kondo et al. (2002) identified monocytes ma-crophages as target cells during acute infection. According to Lusso et al. (1991, 1993, 1995), HHV-6 is able to productively infect...

Effect of Glycosylation Changes on the Interaction of Viral Envelope Glycoproteins With the Immune System

Carbohydrates are generally regarded as poorly immunogenic because (1) identical glycan epitopes are also found on host cell glycoproteins, thus are recognized as self by the immune system, (2) glycoproteins display considerable microheterogeneity, and (3) carbohydrates are extensive structures that may mask potential protein-based epitopes (22). Indeed the glycosylation of HIV gp120 is thought to act as an evolving glycan shield, whereby changes in N-glycosylation acceptor sites due to escape mutations in gp120 enable HIV to evade the host immune response by shielding underlying epitopes with variable glycosylation (23,24). Similarly, the acquisition of N-glycosylation sequons in the influenza H3 HA1 glycoprotein is also thought to protect from the binding of neutralizing antibodies (25). Recent studies of antibodies, produced in monkeys inoculated with SIV gp120 glycosylation mutants, indicate that N-linked glycosylation influences immunogenicity in addition to antigenicity (15).

Induction by Dendritic Cells Loaded with Commensal Bacteria Focuses the Process Within the Mucosal Immune System

As described in Sect. 2.1, the systemic immune system of SPF mice remains ignorant of their commensal intestinal flora, but specific serum IgG responses can easily be induced by administration of 104-106 live organisms into the tail vein. On one hand, it makes good sense that the systemic immune system is not repeatedly primed to commensal organisms, because the diverse responses (which would be largely superfluous since innate mechanisms are very effective at killing these bacteria) could potentially trigger allergy or autoimmunity. On the other, it is important not to be generally tolerant of commensal bacteria, as this may lead to an inability to mount neutralising responses against pathogenic bacterial epitopes. The question is, how can a powerful mucosal immune response be achieved while maintaining systemic ignorance of commensals

Diseases Caused by the Immune System

Immune mechanisms that normally protect the body are very complex and subject to errors that can result in diseases. Autoimmune diseases and allergies are two categories of disease that are not caused by an invading pathogen, but rather by a derangement in the normal functions of the immune system. The ability of the normal immune system to tolerate self-antigens while it identifies and attacks foreign antigens provides a specific defense against invading pathogens. In every individual, however, this system of defense against invaders at times commits domestic offenses. This can result in diseases that range in severity from the sniffles to sudden death. Diseases caused by the immune system can be grouped into three interrelated categories (1) autoimmune diseases, (2) immune complex diseases, and (3) allergy, or hypersensitivity. It is important to remember that these diseases are not caused by foreign pathogens but by abnormal responses of the immune system. Autoimmune diseases are...

Adaptive Vs Innate Immune Systems

The immune system is an organization of cells and molecules with specialized roles in defending against infection. There are two fundamentally different types of responses to invading microbes. Innate (natural) responses occur to the same extent however many times the infectious agent is encountered, whereas acquired (adaptive) responses improve on repeated exposure to a given infection. The innate responses use phagocytic cells (neutrophils, monocytes, and macrophages), cells that release inflammatory mediators (basophils, mast cells, and eosinophils), and natural killer cells. The molecular components of innate responses include complement, acute-phase proteins, and cytokines. Acquired responses involve the proliferation of antigen-specific B and T cells, which occurs when the antigen receptors of these cells bind to antigen (Delves and Roitt 2000).

The Essential Role of the Adaptive Immune Response in HCV Clearance

In the absence of high levels of immunosuppression, HCV is a non-cytopathic virus. In the absence of an ongoing immune response, it infects and persists in target cells, predominantly hepatocytes, without inducing inflammation and damage. This has been demonstrated in both experimental chimpanzee models (Thimme et al., 2002) and in drug users or humans who were accidentally infected with contaminated needles during health care practice (Thimme et al., 2001 Timm et al., 2004). In these studies, increases in viremia were not associated with parallel increases in serum transaminase levels, thus reflecting an absence of hepatocyte damage. Furthermore, following liver transplantation, infection does not lead to liver damage for a 3-week period despite high levels of virus. The only cytopathic lesion that has been directly ascribed to HCV is the association of Genotype 3 infection with steatosis, the accumulation of lipids in hepatocytes (Pawlotsky, 2004). Although non-cytopathic, gene...

Hsp60 And The Innate Immune System

Many of the reported pro-inflammatory effects that result from exposure of cells to HSP60 are actually mediated through LPS or other microbial compounds contaminating the HSP60 (Gao and Tsan 2003 Tsan and Gao 2004). In spite of the controversy surrounding the involvement of TLRs in the effects of HSP60 on the immune system, it became clear that HSP60 could play an important role in controlling adaptive immune responses through its effects on APCs and function as a powerful accessory signal in the induction of Th1-like responses (Flohe et al. 2003).

Immune Response to the Transgene Product

The most encouraging results demonstrating prolonged transgene expression from HDAd were all obtained in cases where an immune response was not mounted against the transgene product (62,66). However, in cases where an antibody response was mounted against the transgene product, expression was shortened, although to a lesser extent than when FGAds were used (62). Clearly immune response to the therapeutic proteins is an important issue because they may be antigenic in individuals suffering from some genetic deficiencies. This situation is, of course, not unique to HDAds but universal to gene therapy, regardless of vector type employed. Clearly, strategies such as immunosuppression or induction of tolerance to circumvent this obstacle may be essential for successful gene therapy of many genetic diseases.

Role of the Innate Immune System During HCV Infection

The innate immune response represents the first line of defense against pathogens and is maintained by complement, natural killer (NK), natural killer T cells (NKT) cells, and macrophages. It is widely accepted that this arm of the immune system is effective in removing most pathogens that infect the body. The innate immune response also plays an important role in activating and amplifying the adaptive immune system (Trobonjaca et al., 2001 Chan et al., 2006). Viruses produce viral pathogen-associated molecular patterns (PAMPs) that are able to initiate a cascade Several reports in both chimpanzee and humans indicate that the virus activates the innate immune response before and during acute infection by inducing secretion of endogenous type I interferon (IFN-a and - ) and by activating NK cells. Analysis of gene microarray experiments from experimentally infected chimpanzee liver biopsies has revealed the induction of a broad range of IFN-a inducible genes (ISGs) (Bigger et al.,...

Immune Surveillance And Susceptibility To Infection

Respiratory infections are recognized as the fifth leading cause of death for individuals over age 65 (National Vital Statistics, 2001). There are many factors that make the elderly more susceptible to lung infections. These include declining immune function, impaired oral and mucociliary clearance, neurologic disorders, malnutrition, chronic organ dysfunction syndromes, and the presence of parenchymal lung disease (Meyer, 2004). Although various aspects of systemic immunity decline with advancing age, there is considerable variation among individuals. Fairly robust immune responses can be identified in centenarians (Franceschi et al., 1995), and many other factors such as the presence of a swallowing disorder and aspiration can cause pneumonia in the elderly despite intact immune responses. Both T and B lymphocyte responses tend to gradually wane with advancing age, and antibody responses to vaccines are less robust in the elderly than in younger individuals (Meyer, 2001). Although...

The Role of the Adaptive Immune Response During HCV Infection

The adaptive immune response is mediated by lymphocytes expressing antigen-specific receptors, T and B lymphocytes. B lymphocytes secrete immunoglobulins that play a major role in the capture of pathogens by macrophages (opsoni-sation) and in blocking antigenic sites critical for the life cycle of the pathogen. Adaptive immune responses mediated by T cells are essential in the control of HCV and viral clearance. In both chimpanzees and humans, viral clearance is associated with sustained CD4+ and CD8+ T cells responses and an increase of IFN-y expression in the liver (Thimme et al., 2002). Recent studies in which memory CD4+ and CD8+ T cells were depleted have confirmed the critical role of these cells in controlling HCV infection (Grakoui et al., 2003 Shoukry et al., 2003). The chronological evolution of T cell immune responses in HCV infection can be classically divided into three phases (Bowen & Walker, 2005a) (Figure 1) the first phase corresponds to the first weeks following...

Interfering With the Immune Response Against the Virus

For the viral antitumor effect to succeed, viral replication must out-compete tumor proliferation. However, the fact that oncolytic viruses are attenuated in their replication and that they also provoke an intense immunogenic response may hinder efficient tumor spread and lysis. Therefore, one strategy to improve biologic efficacy may involve interfering with the immune response. The immune response of the body to adenoviruses and HSVs follows a similar pattern consisting of an immediate innate response and a slower adaptive response. The nonspecific early occurring immune response contributes the largest effect to elimination of the viruses (44). This innate response includes the activation of the complement cascade (45) and the recruitment and activation of macrophages, neutrophils, and natural killer cells which kill the infected cells either directly, or indirectly by secreting antiviral cytokines and chemokines (46,47). In addition, the recruitment and activation of...

Immune Response Considerations

The administration of medicinal recombinant proteins raises the potential that the human immune system will recognize these proteins as foreign (1). A number of factors have been shown to either encourage or discourage immune assault. Oral or intravenous administration illicits weak immune responses, whereas subcutaneous or repeated administration strengthens the response (2,3). The immune response is sometimes exaggerated in patients with autoimmune disease and in patients with cancer or those treated with immunosuppressive therapies (4). The presence of extraneous proteins acquired during the industrial manufacturing may act as immune adjuvants, resulting in a heightened immune reaction (5). Simple proteins, proteins with tertiary and quarternary structures similar to other self proteins, and proteins that are soluble tend to be either nonimmunogenic or less immunogenic than those that are complex, degraded, aggregated, or denatured (3,6). Glycosylation prevents exposure of the...

Host Immune Responses to Saps

Very few studies have investigated the interaction between Saps and the host immune response. While high titres of anti-Sap IgG antibodies have been demonstrated in sera of candidiasis patients (Macdonald and Odds, 1980 Ruchel and Boning, 1983 Ruchel et al., 1988), few detailed studies on mucosal antibody responses, using saliva or vaginal secretions, against the Saps have been performed. Although Sap2 is known to be immuno-genic and can induce antibody responses, the protective potential of Sap antibodies in vivo remains unclear. De Bernardis et al. (1997) showed a protective effect of anti-Sap2 IgA antibodies in experimental vaginitis in rats. This not only demonstrated that Sap2 contributed to vaginal infections and was a target of the host immune response, but also suggested that anti-Sap IgA antibodies could afford protection against C. albicans infections at mucosal sites in vivo.

TCell Immune Responses

Little data exist about the HDV-specific cellular immune response. Two studies in humans identified CD4+ and CD8+ T cells that, interestingly, were only identified in patients with inactive HDV disease (HDV RNA negative). The number of investigated patients, however, was very low and no study has explored the kinetics of the HDV-specific immune response up to now.

TCell Immune Responses After Immunization of Mice or Woodchucks

In woodchucks a proliferative Th-cell immune response was detected after immunization and after challenge, and was further characterized using a panel of overlapping synthetic peptides spanning the whole HDAg (D'Ugo et al. 2004 Fiedler et al. 2001). In both studies the small HDAg expressed in yeast was used. In our study HDAg CpG immunization induced a Th-cell response in WHV carrier woodchucks equivalent to that induced in WHV negative ones by immunization with protein and complete Freund's adjuvant (CFA). Both protocols are known to induce a strong Th1 cell immune response (Chu et al. 1997 Forsthuber et al. 1996 Schirmbeck et al. 1999). A polyspecific, but weak lymphoproliferative response was seen. Overall, 10 peptides were able to induce a Th-cell immune response (Fig. 2). The recognized epitopes grouped into two clusters, one near the N terminus and one closer to the C terminus of HDAg. We did not investigate the proliferative response after challenge. D'Ugo et al. detected a...

Exosomes As Immune System Regulators

The role of DC derivate exosomes in the induction of antitumoral immune response have been establish (Zitvogel et al., 1998) and presence of molecules associated with antigen presentation (MHC Class I and II) and with cell adherence (some integrins ICAM-1) (Review in Thery et al., 2002), facilitates the induction of this immune response. The role of tumor or infected cells derived exosomes in vivo have not been completely assess. In fact, exosome secretion is normally made by somatic cells as normal cell waste discarding mechanism (Johnstone et al., 1987) and is possible that secretion and capture of exosomes by DC will maintain suppressor immune response homeostasis against self antigens. Is also feasible that in inflammatory and infectious processes, exosomes will be carriers of target antigens that are to be transported into the extracellular milieu and presented by APCs. Effective activation of DC, and the type of peptide contained in exosomes, could depend upon the cytokine...

Stimulating the Immune System

Different gene therapy approaches have been put forward to stimulate the immune system. The basic principle underlying immunotherapy in cancer is that tumors have Stimulating the immune system. Transfer of suicide genes. Replacement of tumor suppressor genes. Inhibition of oncogenes. Inhibition of angiogenesis. Induction of apoptosis. antigens that are capable of provoking weak humoral or cellular reactions. By activating this immune response against tumor cells through gene transfer it is hoped that tumors can be eradicated either by the transferred gene product or activation of the patient's own immune system. In animal models, the administration of cytokines such as inter-leukin (IL)-2, IL-4, IL-6, IL-7, IL-12, tumor necrosis factor (TNF)-a, interferons and granulocyte macrophage colony-stimulating factor (GM-CSF) have resulted in tumor regression (8). The systemic administration of cytokines in human trials though has been limited by the severe toxicity of these cytokines. Gene...

Recognition in the Context of a Humoral Immune Response

An understanding of the parameters governing the HIV-1 receptor interactions would be incomplete without an understanding of the context in which this recognition occurs. While all recognitions pit specific versus non-specific interactions, HIV-1 receptor recognition occurs in the context of a persistent infection. In order to bind to receptor while simultaneously eluding neutralization by the humoral immune system, gp120 has evolved sophisticated strategies of evasion (Fig. 3) 17,22,27 . Carbohydrate masking involves covering exposed protein surfaces with a dense array of N-linked glycans. Because these glycans are derived from host biochemical pathways, they are interpreted as self by the immune system and do not elicit antibodies. In addition, the carbohydrate sterically inhibits access to the underlying protein surfaces. Epitopes protected by carbohydrate masking are thus immunologically silent. In terms of the potentially vulnerable receptor binding surfaces, the virus must...

Immunotherapy for Cancer

Besides interleukin-2 and gamma interferon, other cy-tokines may be useful in the treatment of cancer and are currently undergoing experimental investigations. Interleukin-12, for example, seems promising because it is needed for the changing of uncommitted helper T lymphocytes into the TH1 subtype that bolsters cell-mediated immunity. Scientists are also attempting to identify specific antigens that may be uniquely expressed in cancer cells in an effort to help the immune system target cancer cells for destruction.

IgA Immune Responses

These findings suggest polyclonal activation of the natural B cell pool. TLR ligands, including LPS, are well known to be polyclonal activators of B cells (Andersson et al. 1972 Armerding and Katz 1974). It is thus very likely that ligation of TLRs either directly on B cells or on accessory cells (such as DC) in the intestine, may be responsible for the polyclonal expansion of B cells and production of intestinal IgA on conventionalization of germ-free animals (Fagarasan and Honjo 2003 Jiang et al. 2004). Although the functions of the natural IgA induced nonspecifically by commensals remain unknown and controversial, it is possible that these antibodies function similarly to natural serum IgM although these are not commensal dependent (Haury et al. 1997), acting as an early defense system, before the induction of an antigen-specific immune response (Baumgarth et al. 1999 Ochsenbein et al. 1999) . Thus this may be another example in which a commensal dependent benefit to host biology...

Immune System

The immune system, which has the job of making the body immune to infection and disease, consists of the bone marrow, thymus gland, spleen, lymph nodes, and tonsils. Lymphocytes, or white blood cells, are produced in the bone marrow. Some of these cells travel to the thymus, mature into T cells, and are then sent into the bloodstream to become killer or helper T cells. Killer T cells reject foreign tissue and destroy viruses, fungi, and parasites, whereas helper T cells assist another group of white cells known as B cells. B cells are lymphocytes that have traveled from the bone marrow to mature in the spleen or lymph nodes. At maturity, B cells enter the bloodstream, where they produce antibodies to resist bacteria. In addition to the two types of lymphocytes, two other types of cells that contribute to immunity are monocytes and leukocytes. The effectiveness of white blood cells, and hence the efficiency with which the body is able to eliminate foreign substances, decreases with...


Immunotherapy with crude extracts of M. tuberculosis is not possible, and it causes necrosis and disease exacerbation (Anderson 1891, Koch 1891). In contrast to the necrotic skin test responses to the antigens of tuberculosis itself, tuberculosis patients have defective skin-test responses to the common antigens (Kardjito et al 1986), so injection of these antigens, or of environmental saprophytes that contain them, causes trivial local reactions. These antigens can be protective when they evoke an exclusively Th1 response (Fig. 2), and they are safe to administer. These points, together with the Th2-to-Th1 switching properties of the M. vaccae-derived preparation SRL172, justify its investigation as a potential immunotherapeutic in tuberculosis. It has been shown to be effective in mice (without any chemotherapy Rook & Hernandez-Pando 1996) and in pilot studies in humans (Corlan et al 1997). bacterial clearance, weight gain or ESR at eight weeks. These results may indicate that in...

From Primary Cultures to the Aging Organism Lessons from Human T Lymphocytes

One of the prominent clinical features of human aging is the dramatic increase in morbidity and mortality due to infections. Aging is also the most significant risk factor for developing cancer. Both phenomena are related to the age-associated decline in immune function, particularly within the T cell compartment, the part of the immune system that patrols the body for cells that appear foreign, which would indicate they are infected or cancerous. Development of long-term cell culture protocols for analyzing the effect of chronic antigenic stimulation on primary T cells from young adult donors has led to the identification of multiple characteristics of the terminal stage of replicative senescence in this cell type. These include inability to divide, altered cytokine patterns, resistance to apoptosis, shortened telomeres, reduced antiviral cytolytic function, and loss of expression of a major signaling molecule, CD28. Many elderly persons have high proportions of T cells with similar...

Overview of the Glycal Assembly Approach

Carbohydate blood group determinants in the form of glycoproteins or glycolipids were found to play key roles in cell adhesion and other binding phenomena 25,26 . Furthermore, glycoconjugates related to these blood group substances have been recognized as markers for the onset of various tumors. These tumor-associated antigens are currently being studied in vaccines for cancer immunotherapy 27,28 . The

Characteristics Of Senescent T Cell Cultures

As CD8+ T cells undergo increasing numbers of cell divisions in long-term culture, they show a variety of alterations that would be predicted to dramatically affect in vivo immune function. For example, alloantigen-specific cultures from healthy donors produce increasing amounts of two pro-inflammatory cytokines, IL-6 and TNFa, as they approach replicative senescence (Effros et al., 2005), and virus-specific CD8+ T cells show decreased antigen-specific production of IFNg (Dagarag et al., 2004). HIV-specific CD8+ T cell cultures initiated from T cells of HIV-infected persons show a progressive decline in the ability to perform antigen-specific lysis of target cells pulsed with HIV peptides, a change that is accompanied by reduced expression of perforin (Dagarag et al., 2004 Yang et al., 2005). Moreover, one of the key antiviral activities believed to function protectively in vivo inhibition of HIV replication is markedly reduced in senescent HIV-specific CD8+ T cells (Dagarag et al.,...

Telomerase And T Cells

A major difference between mice and humans with respect to this important facet of cell biology. In terms of the aging immune system as well, the life-long exposure to pathogens also differentiates elderly humans from aged mice housed in barrier facilities, further underscoring the value of using a human cell culture model for analysis of the role of T cell replicative senescence in human aging. Results of these experiments showed significant effects of hTERT on proliferative and functional aspects of the T cells. Briefly, we observed that hTERT trans-duction led to telomere length stabilization and reduced expression of the p16INK4A and p21WAF1 cyclin-dependent kinase inhibitors, implicating both of these proteins in the senescence program (Dagarag et al., 2004). Indeed, the transduced cultures showed indefinite proliferation, with no signs of change in growth characteristics or of karyotypic abnormalities. In terms of protective immune function, the ''telomerized'' HIV-specific CD8+...

Replicationdefective Adenovectors

Various in vivo studies have demonstrated that an E1-deleted adenovector can efficiently deliver transgenes to a variety of tissues in various animal models, including mouse, rat, rabbit, swine, dog, and monkey. However, these studies have also revealed that the transgene expression and therapeutic effects that occur in adenovirus-mediated gene transfer in immunocompetent animals are transient, primarily because of the host immune response to the E1-deleted recombinant adenoviral vectors and to the transgene product expressed in transduced cells (46-48). This transient expression suggests that repeated administration would be required for treating most genetic disorders and cancers. Unfortunately, in these studies host humoral immune responses to the vectors abrogated any therapeutic effects of the adenovirus-mediated gene transfer after repeated systemic administration (47,49).

Alzheimers Disease And Atherosclerosis

There is some evidence that chronic activation of T cells, leading to increased proliferation and telomere shortening, may be involved in other age-related diseases as well. The etiology of Alzheimer's disease (AD) is not known, but our recent studies suggest a possible involvement of T cells. We observed that the telomere length of T cells, but not of B cells or monocytes, correlates with mental function tests in AD patients (Panossian et al., 2002). Those patients with lower Mini Mental Status Examination (MMSE) scores, which is a marker of disease status, had T cells with shorter telomeres than those persons with higher MMSE scores. These findings suggest that the immune system of AD patients is perturbed in some way and may not necessarily respond normally to therapeutic vaccines aimed at retarding AD disease progression. Interestingly, one such therapeutic vaccine trial was recently interrupted due to unanticipated brain inflammation in some participants (Nicoll et al., 2003).

Senescent T Cells And Mortality

The ultimate effect of T cells on aging is with respect to mortality itself. Early work suggested a connection, based on correlative data, between T cell proliferative responses in cell culture and mortality over the subsequent few years (Wikby et al., 1998). More recently, telomere analysis of total lymphocytes in a group of 60 year olds was shown to be predictive of mortality many years later (Cawthon et al., 2003). In these studies, it was shown that the individuals who had telomeres in the lowest quartile were 7-8 times more likely to die from infections compared with those with the longest telomeres. Longitudinal studies of elderly Swedes over several decades confirm the link between immune parameters and lifespan. These data show that early mortality is associated with a so-called immune risk phenotype, which includes a cluster of T cell parameters, including high proportions of senescent CD8+ T cells (Nilsson et al., 2003). Interestingly, the presence of these risk factors is...

Dermatomyositis Polymyositis

A variety of specific autoantibodies may be present in some patients with DM or PM, implicating the immune system in their pathogenesis. In DM, humoral immune mechanisms may be particularly important, given the predilection for inflammatory cellular infiltration in nonnecrotic muscle fibers and around blood vessels. Vasculopathy can be a particularly prominent feature of childhood disease, with deposition of immunoglobulins and complement components in blood vessels sometimes making skin biopsy specimens indistinguishable from those found in SLE patients. In PM, cell-mediated antigen-specific cytotoxicity appears to be more in pathogenesis, since increased expression of major histocompatibility class I molecules and increased numbers of T cells are found in the muscle in this disorder.

Immunological and virological events during acute HIV1 infection

During acute HIV-1 infection, the virus replicates extensively in the absence of any detectable adaptive immune response, reaching levels of over 100 million copies HIV-1 RNA ml. It is during this initial cycle of viral replication that important pathogenic processes are thought to occur. These include the seeding of virus to a range of tissue reservoirs and the destruction of CD4+ T-lymphocytes, in particular within the lymphoid tissues of the gut. The very high levels of HIV-1 viremia are normally short-lived, indicating that the host is able to generate an immune response that controls viral replication. Over the following weeks, viremia declines by several orders of magnitude before reaching a viral setpoint. This setpoint, following resolution of the acute infection, is a strong predictor of long-term disease progression rates (Mellors 1995). Several factors can influence viral replication during acute infection and the establishment of a viral setpoint. These include the fitness...

Oncolytic Adenoviruses

P53-negative or-mutant cells would thus be regarded as a powerful anticancer agent. However, subsequent studies indicated that a lytic infection of cells with an E1B-mutated adenovirus did not depend on the cellular p53 status and that p53 might play a necessary part in mediating cellular destruction via a productive adenovirus infection (75,76). Nevertheless, the notion that in situ amplification of CRADs and the resulting burst of viral progeny from the lysed cancer cells could enhance the local spread and penetration of these vectors, thereby greatly increasing therapeutic efficacy, spurred the creation and testing of various other CRADs for cancer therapy. This is because pre-clinical and clinical studies have shown that one of the major limitations of a replication-defective adenovector was the incomplete transduction of target cells because of poor vector penetration in tumor tissue. Indeed, the intratumoral injection of E1-deleted vectors often resulted in the transduction of...

Release Of Heat Shock Proteins Passive Versus Active Release Mechanisms

Abstract There is now no doubt that heat shock proteins have a profound immunoregulatory effect on the host's immune system. This knowledge has successfully been harnessed to generate a number of important clinical trails. However, one intriguing question that remains to be answered is how heat shock proteins (HSP) which do not have peptide leader sequence targeting secretion can gain access to the extracellular milieu. This chapter will discuss the most recent findings in the area of HSP release and attempts to broadly categorize these findings into two basic mechanisms the passive and active mechanisms

Copper In Diseases And Genetic Diseases Of Copper Metabolism

Copper metabolism is altered in inflammation, infection, and cancer. As already mentioned, plasma ceruloplasmin is an acute-phase reactant, and synthesis and secretion of the protein by hepatocytes is stimulated by inflammatory cytokines (particularly interleukin-1 IL-1 and IL-6) (1,5). The increase in ceruloplasmin may protect cells from radicals released to combat the influx of foreign organisms or antigens, because it is a general radical scavenger, and most cells (including erythrocytes) have specific receptors on their surface that are likely to be saturated with ceruloplasmin at normal plasma concentrations. (These receptors may have dual roles, depending on cell type, providing a means for delivering copper to some and protecting the vulnerable cell membrane fatty acids in others.) Copper itself is important for many aspects of the immune response, including production of IL-2 by activated lymphocytic cells (160), and supports the activity and effectiveness of cellular and...

Efficacy Toxicity and Immunogenicity of Adenoviral Vectors

Factors Affecting Efficacy of Ad as an Anticancer Agent Pathways of Ad Infection In Vitro and In Vivo Understanding the Host Responses to Natural Ad Infection Innate Immune Response to Systemically Applied Ad Animal Models for the Analysis of Innate Immune and Inflammatory Responses to Systemically Applied Ad Summary

Kinetics of the Host Defense

The reduction in bacterial numbers during the first two hours probably depends largely on mechanic factors, like the urine flow. Even phase II is too short to allow for a specific immune response. There is little or no preexisting mucosal immunity against a specific pathogen in the uninfected urinary tract, and the induction of a primary specific immune response in the urinary tract takes at least 7 days. Infection is cleared before the specific immune response needs to be activated. We have therefore sought to explain host resistance as a function of innate immunity.

The Role Of Leukemia Inhibitory Factor In Cancer And Cancer Metastasis

Abstract Leukemia inhibitory factor (LIF) is a cytokine that exerts pleiotropic activities. LIF is a member of the interleukin-6 family of cytokines which share a similar receptor complex and signal through the gp 130 receptor subunit. Several neoplastic cells originating from various tissues express either LIF, its receptor, or both and respond to this cytokine. Data accumulated thus far provide a complex picture of LIF activities with LIF being stimulatory, inhibitory or having no effect, depending on the system in which it is studied. LIF appears to play an important role in stimulating the growth of certain tumours, and in affecting the surrounding tissue and the target organ of tumour metastases, particularly bone and skeletal tissue. Overproduction of LIF is likely to have significant constitutional effects. Studies using animal models have shown that LIF induces cachexia, metastatic-type bone calcifications, thrombocytosis, and an abnormal immune response. It is therefore...

The structure of HIV1

Using electron microscopy, HIV-1 and HIV-2 resemble each other strikingly. However, they differ with regard to the molecular weight of their proteins, as well as having differences in their accessory genes. HIV-2 is genetically more closely related to the SIV found in sootey mangabeys (SIVsm) rather than HIV-1 and it is likely that it was introduced into the human population by monkeys. Both HIV-1 and HIV-2 replicate in CD4+ T-cells and are regarded as pathogenic in infected persons, although the actual immune deficiency may be less severe in HIV-2-infected individuals.

CD4 as a primary receptor for HIV

CD4 attaches to the T cell receptor complex (TCR) on CD4+ T-cells and binds to HLA class II molecules on antigen-presenting cells. The binding of gp120 to CD4 is not only a crucial step for viral entry, but also interferes with intracellular signal transduction pathways and promotes apoptosis in CD4+ T-cells (Banda 1992). Interestingly, monoclonal antibodies against CD4 induced conformational (CD4i) epitopes to bind to the gp120 of CD4-independent viruses. This observation suggests that the gp120 of CD4-independent viruses already exposes the regions that are necessary for coreceptor recognition and binding and therefore binding to CD4 is not a prerequisite of entry for these viruses. CD4-independent viruses are easy to neutralize using the serum of HIV-infected patients, suggesting that the immune response selects against CD4-independent viruses (Edwards 2001).

Viral Related Proteins in Immune Dysfunction Associated with AIDS

The mechanisms of pathogenesis associated with infection with human immunodeficiency virus (HIV), initially discovered in 1983,1,2 and the development of acquired immune deficiency syndrome (AIDS) are complex and are undiscovered or poorly understood. Perhaps for no disease in history has there been such a focused research effort to understand exactly how a known etiological agent effects its pathogenesis. As summarized in Table I, soluble HIV Tat protein has been reported to have a wide range of potentially deleterious effects on human immune cells which could play a role in the immune dysfunction associated with AIDS. One of the first studies reporting the ability of Tat to inhibit in vitro immune functions of human cells was that of Viscidi et al. in 1989.7 They demonstrated that recombinant HIV-1 Tat (amino acids 1-72), expressed in Esche-richia coli, inhibited the proliferation of human peripheral blood mono-nuclear cells (PBMCs) in response to stimulation by tetanus toxoid (66-...

Chemokine receptors as coreceptors for HIV entry

The expression of coreceptors on CD4+ T-lymphocytes depends on their activation level. CXCR4 is mainly expressed on naive T-cells, whereas CCR5 is present on activated and effector memory T-cells. During the early course of HIV-1 infection, predominantly M-tropic HIV-1 isolates are detected. Interestingly, M-tropic HIV-1 isolates are preferentially transmitted regardless of whether or not the donor predominantly harbors T-tropic isolates. At present, it remains unclear whether this in vivo preference of M-tropic HIV-1 isolates is determined by selected transportation of M-tropic isolates by sub-mucosally located dendritic cells or whether the local cytokine chemokine milieu favors the replication of M-tropic viruses. Recent intriguing studies by Cheng Meyer et al. suggest that M-tropic HIV-1 viruses are able to 'hide' more easily from the immune system by replicating in macrophages, in comparison to T-tropic viruses, thus giving them a survival advantage in the infected individual.

Dendritic cells as prototypes of antigenpresenting cells

Dendritic cells, macrophages and B cells represent the main antigen-presenting cells of the immune system. Dendritic cells (DC) are the most potent inducers of specific immune responses and are considered essential for the initiation of primary antigen-specific immune reactions. DC precursors migrate from the bone marrow towards the primary lymphatic organs and into the submucosal tissue of the gut, the genitourinary system and the respiratory tracts. They are able to pick up and process soluble antigens and migrate to the secondary lymphatic organs, where they activate antigen-specific T cells. Because DC have a crucial role in adaptive immunity, there is an increasing interest in using dendritic cell to induce or expand HIV-specific T-cells. DC from HIV-infected patients have been purified, incubated with inactivated, non-infectious HIV particles and subsequently used for vaccination (Lu 2005) therefore linking the innate to the adaptive immune system.

Prospects for prevention and control

For the epidemic diseases, other challenges remain. The caliciviruses pose the greatest epidemic threats, and investigation often identifies a breach of sanitation with faecal contamination of water or food (either at its source or by a food-handler) that can be corrected. At the same time, the virus can be transmitted by person-to-person contact or perhaps by aerosols, and therefore much disease is not easily prevented (Becker et al 2000). Control of calicivirus disease outbreaks is currently directed at halting those outbreaks where problems of contamination of food or water can be easily corrected. This approach leaves many outbreaks to run their course despite the best public health interventions and intent. Efforts to develop vaccines against the caliciviruses are being pursued with the hope that even mimicking the short-term natural immunity of infection would be a useful preventive measure for travellers and soldiers, provided that the vaccine contained the proper broad mix of...

Lymphatic tissue as the site of viral replication

After entry of HIV-1 into a quiescent CD4+ T-cell and after completion of reverse transcription, the viral genome is represented by proviral unintegrated HIV DNA. In vitro experiments have shown that HIV-1 preferentially integrates into active genes ( hot spots ) (Schroder 2002). The activation of CD4+ T-cells is necessary for the integration of the HIV DNA into the host cell genome and is therefore a prerequisite for the synthesis of new virions. In this regard, the micromilieu of the lymphoid tissue represents the optimal environment for viral replication. The close cell-cell contact between CD4+ T-cells and antigen-presenting cells, the presence of infectious virions on the surface of the FDC, and an abundant production of pro-inflammatory cytokines such as IL-1, IL-6 or TNFa promotes the induction of viral replication in infected cells and augments viral replication in cells already producing the virus. It should be noted that both IL-1 and TNFa induce NFkB, which binds to the...

Target Cells of HCMV In Vivo

Et al. 1989 Schwartz et al. 1990 Grefte et al. 1993). Likewise, detection of late structural viral proteins in infected cells argues in the same direction, and the combination of the latter approach with the additional detection of cell marker proteins allowed for a reliable identification of the respective cell types (Sinzger et al. 1993, 1996, 1999a Digel and Sinzger 2006). Together with the often focal distribution of clusters of infected cells this provided strong evidence that mucosal epithelial cells, connective tissue cells, smooth muscle cells and endothelial cells can produce and transmit viral progeny to their environment (Fig. 1a). HCMV replication can be detected in almost every organ during acute infection under certain conditions, e.g., severe cases of intrauterine infection (Bissinger et al. 2002). Liver, gastrointestinal tract, lung, retina and brain are predominant sites of clinical manifestations of HCMV infections in immunocompromised hosts (Plachter et al. 1996)....

Nk Cells And Tumor Cell Killing

Apart from their intracellular chaperoning functions, HSP have been found to play key roles in tumor immunity. Most immunotherapeutic approaches exploit the carrier function of HSP for tumor-derived peptides. Following cross-presentation of HSP-chaperoned peptides on MHC class I molecules (Arnold-Schild et al., 1999 Basu et al., 2001 Binder et al., 2000 Binder et al., 2004 Sondermann et al., 2000) an antigen-specific CD8+ T cell response is thus initiated (Binder et al., 2001 Doody et al., 2004 Schild et al., 1999 Srivastava et al., 1998). However, even in the absence of immunogenic peptides, HSP serve as danger signals for the host's immune system (Asea et al., 2000). Exosomes have recently been described as export vehicles for Hsp70 from the endosomal compartment into the extracellular milieu (Bausero et al., 2005 Gastpar et al., 2005 Lancaster and Febbraio, 2005). NK cells comprising 5-20 of peripheral blood lymphocytes (PBL) are important players of the innate immune system that...

Reported Effects Of Hiv1 Nef On Immune Cell Function

Early interest in an extracellular role for Nef was most likely restrained because of the known physical characteristics of the molecule and its common detection in infected cells in the cytoplasm or associated with cell membranes. However, antibodies to Nef have been routinely detected in HIV-infected patients beginning at the earliest stages of infection. Thus it is reasonable to conclude that the immune systems of patients are exposed to Nef proteins or peptide fragments early in infection these might be shed either from virions or infected cells, expressed on the surface of infected cells, or released from dying cells.

A vaccine against HIV

The documentation of exposed but uninfected individuals and findings in LTNP suggests that, besides a genetic predisposition, HIV-specific protective immune mechanisms could potentially confer protective and possibly even preventive immunity. Results from animal studies suggest that immune protection might be generated when the immune system is stimulated in the appropriate way. The induction of an HIV-specific CD8 response in non-human primates is able to ameliorate the course of disease. On the other hand, in vivo depletion of CD8+ T-cells in nonhuman primates by monoclonal antibodies will lead to an increase in viral load. Immunogens that induce neutralizing antibodies in non-human primates will prevent infection with the homologous viral strain. Transfer of neutralizing antibodies to uninfected primates or human SCID mice is able to prevent infection with the homologous HIV strain. The spectrum of vaccine strategies against HIV includes HIV-derived peptides or proteins, the use of...

General Health Benefits

2004) (3) Increases immunity Increased levels of immunoglobulin A, an essential antibody used by the immune system to protect against viral infections, were found in college students reporting having sex at least three times per week (Charnetski and Brennan, 2004) (4) Associated with reduced stress Participants who had vaginal sex in the last 2 weeks had lower blood pressure and stress response to stress-inducing tasks (Brody, 2006). Among medical residents, stress negatively affected desire, sexual arousal , and sexual satisfaction (Sangi-Haghpeykar et al, 2009) and (5) Increases physical fitness Sexual intimacy was associated with physical fitness level among Fifty Plus Fitness Association members (Bortz and Wallace, 1999) frequency of sexual activity was higher among men enrolled in an intensive physical fitness program (White etal, 1990).

Evolutionary Dynamics of HCV Envelope Genes

HCV can be classified into six genetically distinct genotypes and further subdivided into a large number of subtypes, of which the six major genotypes differ by approximately 30 and the subtypes differ by 20 -25 at the nucleotide level (Simmonds et al. 2005). A significant challenge for vaccine and immunotherapeu-tic development is the identification of protective epitopes conserved in the majority of viral genotypes and subtypes. This problem is compounded by the fact that the envelope E1E2 proteins, the natural targets for the Vn response, are two of the most variable proteins (Bukh et al. 1995). The error-prone nature of the RNA-dependent RNA polymerase together with the high HCV replicative rate in vivo (Neumann et al. 1998) results in the production of viral quasispecies (Martell et al. 1994 Bukh et al. 1995). Quasispecies can respond to and overcome a variety of selective pressures including host immunity (Cooreman and Schoondermark-Van de Ven 1996 Cooreman and Schoondermark-Van...

The Consensus Binding Site on Fc

An alternative hypothesis is that the innate physiochemi-cal composition of this site is inherently sticky and promotes binding as well as antigenicity. If the biological role for protein A and G is primarly to localize IgGs to the bacterial surface, perhaps to evade immune system surveillance, then it might simply be the case that the CH2 CH3 hinge region was the most evolutionarily efficient IgG surface to target for binding. Likewise, if this region is an innately attractive part of the protein surface, then that would explain the frequent emergence of autoimmune rheumatoid factors targeting Fc. We chose to evaluate this hypothesis by evolving novel IgG-Fc binding domains in the laboratory to discover if molecules selected purely for binding would indeed target the CH2 CH3 hinge region.

Advantages Of Retroviral Vectors A Fully Defective Vectors

Cell for efficient gene transfer to occur and can simply be provided in trans in the producer cell. In addition, no de novo viral protein synthesis is needed to maintain or repair the integrated provirus. This has implications for long-term gene expression in the transduced cells as even a low-level production of viral proteins will increase the likelihood of an unwanted immune response being triggered against the transduced cells (in addition to any immune response that may be mounted against the transgene itself). Such vector antigenicity is largely responsible for the transient nature of the gene expression seen with current adenoviral vectors, although the problem is being aggressively pursued through the development of helper-dependent or ''gutless'' adenoviral vectors.

From Bench To Bedside

As mentioned earlier, screening of primary human tumors and metastases derived there of revealed that Hsp70 is frequently expressed on the cell surface of malignant cell types. In contrast, the corresponding normal tissues were always found to be Hsp70 membrane-negative. Therefore, we hypothesized that membrane-bound Hsp70 might act as a tumor-specific recognition structure for the immune system. Since we observed that the cytolytic activity of NK cells in vitro could be further enhanced by incubation with IL-2 plus Hsp70 peptide TKD, we asked the question as to whether these NK cells might be superior in the eradication of tumors compared to NK cells that had been stimulated with IL-2 alone. In two independent xenograft tumor mouse models we studied the immunological effects of ex vivo IL-2 TKDactivated NK cells (Moser et al., 2002). A single intravenous (i.v.) injection of IL-2 TKD-activated NK cells resulted in a significant regression of colon tumors in SCID beige mice. In the...

Modes of IgSuperfold Interaction

Several IgSF molecules that act as cell-surface receptors or coreceptors in the immune system employ interaction modes similar to those used by immunoglobulins for antigen recognition. one obvious example is the T-cell receptor, an IgSF molecule that is discussed in detail elsewhere in this handbook (see Chapter 11). A second, closely related example is provided by the cytotoxic T-cell coreceptor CD8. Like the T-cell receptor, CD8 interacts with major histocompatibility complex (MHC) class I molecules. Both TCR and CD8 have an MHC class I binding surface composed of the two sets of CDR-like loops (BC, C'C , and FG) from a dimer of variable domains. The structure of the CD8aa-MHC class I complex (Fig. 2) for both human and murine molecules reveals CD8 binds one MHC class I molecule, interfacing with the MHC a2 and a3 domains as well as contacting P2-microglobulin 13,14 . The focal point of the interaction is the DE loop of the MHC class I a3 Ig-like domain, which is clamped between the...

Host Response To Vaccinia

Vaccinia virus has mechanisms to avoid detection and clearance by the immune system. The vaccinia has evolved expression of immunosuppressive proteins (38). Viral surface proteins act as complement inhibitors and the extracellular envelope is known to be almost completely resistant to antibody neutralization (39). Understanding vaccinia's immune evasion strategies may help optimize the virus as a vector for clinical use. The virus is effective in suppressing both innate immunity and the development of T-helper cells. Vaccinia virus has adopted genes whose product can block the function of the interferon family members interferon- (IFN) a p,y or that can inhibit chemokines, which are some of the earliest substances produced during the initiation of a viral host immune response (42-47) (Table 1). Gene Products which Inhibit the Immune Response Gene Products which Inhibit the Immune Response

Peptide Binding to MHC Class I and II

In the cellular immune response, peptides are displayed to T cells in complex with class I or class II MHC molecules. Both classes of MHC are heterodimers of similar structures they are composed of three domains, two Ig-like and one a p domain (MHC fold) that forms the peptide binding site.

Discrepancy Between Magnitude of Structural Changes and Biological Outcomes

Alloreactivity is the phenomenon in which a strong immune response can be generated against foreign pMHC molecules to which one's T cells have not been previously exposed 35,36 . Thus, an important practical corollary in defining the structural rules of T cell recognition is to explain alloreactivity 37 . So far, three complexes have addressed this issue 30,38,39 . The complex of the BM3.3 TCR with the allogeneic MHC H-2Kb is perhaps the most structurally distinct so far, but the corresponding syngeneic complex is currently not known. The BM3.3 TCR tilts substantially towards the P-chain side (Fig. 3), with the a-chain making few direct contacts with the MHC. In fact, the long central CDR3a is flared back such that it makes no contacts with the peptide and only two with the MHC. The majority of the interactions are with the P-chain, consistent with that proposed for the interaction of H-2Ld with TCR 2C, where an extreme bulge in the C-terminal half of the peptide is

Strategies In Vaccinia Gene Therapy To Evade Immune Clearance

The clearance of the virus in vivo needs to be overcome in order to deliver an adequate amount of virus to the tumor and allow time for viral replication. Several strategies have been tested to overcome this barrier. The first strategy is to create a virus that is less recognizable by the immune system. The problem with this method is that the vaccinia virus presents a broad spectrum of antigens to the host. Hence, one or two mutations in the viral envelope would probably not be sufficient to avoid detection by the immune system. The other issue with altering the viral envelope is that the alteration may result in decrease infectivity of the virus. The third strategy involves using immunosuppressive agents to increase the viral load and the time of expression in tumor cells. Unpublished studies from our group have found that immunosuppressive therapy increased viral recovery and tumor response in animal models without increasing the pathogenicity. Because of the knowledge gained from...

Animal Models for AIED

Animal models have definitively demonstrated that the immune response of the inner ear can lead to reversible or permanent damage to the delicate inner ear structures. One of the first animal models for AIED was developed by Beickert who immunized guinea pigs with homologous inner ear tissue. Although the guinea pigs developed cochlear lesions, hearing loss was not demonstrated and antibodies to inner ear antigens were not identified (24).

Role Of Carbohydrate In Vaccine Strategies To

Cells with pseudotypes could be blocked with anti-HTLV-I serum, but failed to be significantly inhibited with anti-HIV serum or a V3-neutralizing anti-gp120 monoclonal antibody. This may represent a possibility for pseudotypes to escape neutralization by the immune system in vivo. Importantly, the neutralizing capacity of lectins and anticarbohydrate monoclonal antibodies was found to block infection by cell-free pseudotypes in CD4 negative cells. These data suggest that although viral cofactors might expand the tropism of HIV in vivo, HIV and HTLV-I seem to induce common carbohydrate neutralization epitopes which might be conserved targets in a vaccine design strategy. affect both titer and avidity of a humoral response.40 Immunodominant epitopes are known to suppress a primary immune response to other anti-genic determinants by a number of mechanisms. This concept was originally discussed as a means to induce a biological smoke screen thwarting the immune response.50 Many pathogens...

The Tau Hypothesis And Tau Pathology

Promoter (Oddo et al., 2003a Oddo et al., 2003b). The APP and tau genes both incorporate at the same locus, greatly simplifying the breeding by ensuring that they are co-inherited. These animals develop synaptic dysfunction before plaques or tangles appear, and the deficits in LTP correlate with the accumulation of intraneuronal A . The patterns and relative timing of A and tau deposition, which are distinct, closely resemble those in AD brain. While closer to AD-like tangle morphology, the tau deposits have not been definitively characterized as NFTs. Interestingly, A immunotherapy in these animals results in the clearance of amyloid plaques and of early, but not established, tau pathology (Oddo et al., 2004).

Coreceptor antagonists

HIV-variants use either the CCR5- or the CXCR4-receptors for entry into the target cell. According to their receptor tropism, HIV variants are termed R5 if they use CCR5 as a co-receptor, whereas viruses with a preference for CXCR4 are termed X4-viruses. R5 viruses are viruses that predominantly infect macrophages (previously M-trope viruses) X4 viruses mainly infect T cells (previously T-trope viruses). Dual-trope viruses can use both receptors, and in addition, there are still mixed populations of R5- and X4 viruses. In most patients, R5 viruses are found in the early stages of infection the more virulent X4 viruses, which are probably able to infect a wider spectrum of cell types, first occur in the later stages. The change in the tropism is frequently a consequence of illness progression (Connor 1997, Scar-katti 1997). It is still not clear why this happens after several years of infection, although the tropism shift only needs a few small mutations. It is possible that R5 viruses...

Robert E Antosia md mph

The medical consequences of drought include an increased incidence of malnutrition and infectious diseases. The resultant lack of nutrition can ultimately lead to the classic conditions of marasmus (the lack of caloric intake) and kwashiorkor (lack of protein intake). Collectively, the states of inanition are referred to as protein-energy malnutrition (PEM). PEM results in impaired immune system function and increased mortality.

How To Bolster Your Immune System

How To Bolster Your Immune System

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