T cell activation

Manufacturing of cellular products for therapeutic purposes like stem cell or cancer therapy requires equipment with specific characteristics not always addressed by conventional technologies. A new integrated cell processing device is presented that can handle all current technical requirements for manufacturing cellular products by automation of the complete process in a GMP-compliant single-use tubing set. Its capabilities are exemplified in the presented study by successful processing of adult stem cells, natural killer cells, and several cell lines. Multiple cell processing workflows can be automated in a functionally closed environment: from cell separation through cell culture to formulation of the final product.

The accessory Nef protein is expressed by all primate lentiviruses--HIV-1,HIV-2 and simian immune deficiency virus (SIV). Its expression in the early stages of the viral life cycle ensures two basic attributes of HIV infection. These are T-cell activation and the establishment of a persistent state of infection. Nef has a positive effect on viral infection and replication by promoting the survival of infected cells. Its role in HIV persistence is based largely on the ability of Nef to downmodulate the surface levels of important molecules at the immune synapse. These include major histocompatibility complex-I (MHC I) and (MHC II) present on antigen-presenting cells (APCs) and target cells, and CD4 and CD28 present on helper T cells. In this review we present these biological properties of Nef from a mechanistic point of view, and relate them to the structural attributes and interactions of the Nef protein. A brief outline of the limited studies on Nef from Indian subtype C HIV-1 iso...

Dengue virus presents a growing threat to public health in the developing world. Four major serotypes of dengue virus have been characterized, and epidemiological evidence shows that dengue hemorrhagic fever (DHF), the more serious manifestation of the disease, occurs more frequently upon reinfection with a second serotype. We have studied dengue virus-specific T-cell responses in Thai children. During acute infection, few dengue-responsive CD8 + T cells were recovered; most of those present showed an activated phenotype and were undergoing programmed cell death. Many dengue-specific T cells were of low affinity for the infecting virus and showed higher affinity for other, probably previously encountered strains. Profound T-cell activation and death may contribute to the systemic disturbances leading to DHF, and original antigenic sin in the T-cell responses may suppress or delay viral elimination, leading to higher viral loads and increased immunopathology.

Dengue virus presents a growing threat to public health in the developing world. Four major serotypes of dengue virus have been characterized, and epidemiological evidence shows that dengue hemorrhagic fever (DHF), the more serious manifestation of the disease, occurs more frequently upon reinfection with a second serotype. We have studied dengue virus-specific T-cell responses in Thai children. During acute infection, few dengue-responsive CD8 + T cells were recovered; most of those present showed an activated phenotype and were undergoing programmed cell death. Many dengue-specific T cells were of low affinity for the infecting virus and showed higher affinity for other, probably previously encountered strains. Profound T-cell activation and death may contribute to the systemic disturbances leading to DHF, and original antigenic sin in the T-cell responses may suppress or delay viral elimination, leading to higher viral loads and increased immunopathology.

Vitamin D has received increased attention recently for its pleiotropic actions on many chronic diseases. The importance of vitamin D on the regulation of cells of the immune system has gained increased appreciation over the past decade with the discovery of the vitamin D receptor (VDR) and key vitamin D metabolizing enzymes expressed by cells of the immune system. Animal studies, early epidemiologic and clinical studies have supported a potential role for vitamin D in maintaining immune system balance. The hormonal form of vitamin D up-regulates anti-microbial peptides, namely cathelicidin, to enhance clearance of bacteria at various barrier sites and in immune cells. Vitamin D modulates the adaptive immune system by direct effects on T cell activation and on the phenotype and function of antigen-presenting cells (APCs), particularly of DCs. The purpose of this manuscript is to review the molecular and clinical evidence for vitamin D as a modulator of the innate and adaptive immune system.

Renal transplantation is the standard of care for patients with end-stage renal disease. Although maintenance immunosuppression with calcineurin inhibitors yields excellent one-year survival, it is associated over the long term with high rates of death and graft loss, owing in part to the adverse renal, cardiovascular, and metabolic effects of these agents. The use of potentially less toxic agents, such as belatacept, a selective blocker of T-cell activation, may improve outcomes.

gating DC maturation, cytokine profiling, and CD8-specific T-cell stimulation function followed by a second signal. Vpr impaired the expression of CD80, CD83, and CD86 at the transcriptional level without altering normal cellular transcription. Cytokine profiling indicated that the presence of Vpr inhibited production of interleukin 12 (IL-12) and upregulated IL-10, whereas IL-6 and IL-1␤ were unaltered. Furthermore, DC infected with HIV-1 vpr ؉ significantly reduced the activation of antigen-specific memory and recall cytotoxic-T-lymphocyte responses. Taken together, these results indicate that HIV-1 Vpr may in part be responsible for HIV-1 immune evasion by inhibiting the maturation of costimulatory molecules and cytokines essential for immune activation.

The first findings that depression is characterized by cell-mediated immune activation and inflammation were published between 1990. Recently, it was reported thatbased on meta-analysis resultsdepression is an inflammatory disorder because the plasma levels of two cytokines are increased, i.e. interleukin-(IL)-6 and tumor necrosis factor-α (TNFα). The same meta-analysis found that plasma IL-2 and interferon-(IFN)γ levels are not altered in depression, suggesting that there is no T cell activation in that illness. The present paper reviews the body of evidence that depression is accompanied by cell-mediated immune activation. The findings include: increased serum levels of the soluble IL-2 receptor (sIL-2R) and the sCD8 molecule; increased numbers and percentages of T cells bearing T cell activation markers, such as CD2+CD25+, CD3+CD25+, and HLA-DR+; increased stimulated production of IFNγ; higher neopterin and sTNFR-1 or sTNFR-2 levels; induction of indoleamine 2,3-dioxygenase (IDO) with lowered levels of plasma tryptophan and increased levels of tryptophan catabolites along the IDO pathway (TRYCATs); and glucocorticoid resistance in immune cells. Interferon-α (IFNα)-based immunotherapy shows that baseline and IFNα-induced activation of T cells, IDO activity and TRYCAT formation are related to the development of IFNα-induced depressive symptoms. Animal models of depression show that a cell-mediated immune response is related to the development of depression-like behavior. Antidepressants and mood stabilizers suppress different aspects of cell-mediated immunity and rather specifically target IFNγ production. This review shows that inflammation and cell-mediated immune activation are key factors in depression.

Phosphodiesterases hydrolyse intracellular cyclic nucleotides, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) into inactive 5′ monophosphates, and exist as 11 families. They are found in a variety of inflammatory and structural cells. Inhibitors of PDEs allow the elevation of cAMP and cGMP which lead to a variety of cellular effects including airway smooth muscle relaxation and inhibition of cellular inflammation or of immune responses. PDE4 inhibitors specifically prevent the hydrolysis of cAMP, and PDE4 isozymes are present in inflammatory cells. Selective PDE4 inhibitors have broad spectrum anti-inflammatory effects such as inhibition of cell trafficking, cytokine and chemokine release from inflammatory cells, such as neutrophils, eosinophils, macrophages and T cells. The second generation PDE4 inhibitors, cilomilast and roflumilast, have reached clinical trial stage and have some demonstrable beneficial effects in asthma and chronic obstructive pulmonary disease (COPD). The effectiveness of these PDE4 inhibitors may be limited by their clinical potency using doses that have minimal effects on nausea and vomiting. Topical administration of PDE4 inhibitors may provide a wider effective to side-effect profile. Development of inhibitors of other PDE classes, combined with PDE4 inhibition, may be another way forward. PDE5 is an inactivator of cGMP and may have beneficial effects on hypoxic pulmonary hypertension and vascular remodelling. PDE3 and PDE7 are other cAMP specific inactivators of cAMP. PDE7 is involved in T cell activation and a dual PDE4-PDE7 inhibitor may be more effective in asthma and COPD. A dual PDE3-PDE4 compound may provide more bronchodilator and bronchoprotective effect in addition to the beneficial PDE4 effects.

The primary role of the immune system is to protect the organism against pathogens, but age-associated alterations to immunity increase the susceptibility of the elderly to infectious disease. The exact nature of these changes is still controversial, but the use of screening procedures, such as the SENIEUR protocol to exclude underlying illness, helped to better characterize the changes actually related to physiological aging rather than pathology. It is generally agreed that the most marked changes occur in the cellular immune response refl ecting profound alterations in T cells. Much of this is due to thymic involution as well as changes in the proportions of T cell subpopulations resulting from antigen exposure, and altered T cell activation pathways. However, a body of data indicates that innate immune responses, including the critical bridge between innate and adaptive immunity, and antigen presenting capacity are not completely resistant to senescence processes. The consequences of all these alterations are an increased incidence of infections, as well as possibly cancers, autoimmune disorders, and chronic infl ammatory diseases. The leading question is what, if anything, can we do to prevent these deleterious changes without dangerously dysregulating the precarious balance of productive immunity versus immunopathology? There are many potential new therapeutic means now available to modulate immunosenescence and many others are expected to be available shortly. One main problem in applying these experimental therapies is ethical: there is a common feeling that as ageing is not a disease; the elderly are not sick and therefore do not require adventurous therapies with unpredictable side-effects in mostly frail individuals. Animal models are not helpful in this context. In this chapter we will fi rst briefl y review what we think we know about human immunosenescence and its consequences for the health status of elderly individuals. We will then discuss possible interventions that might one day become applicable in an appropriate ethical environment.

T cell activation is a critical process in initiating adaptive immune response since only through this process the naïve antigen specific T cells differentiate into armed effector T cells that mediate the actual immune response. During T cell activation, naïve T cells undergo clonal expansion and acquire the capability to kill target cells infected with pathogens or produce cytokines essential for regulating immune response. Inappropriate activation or inactivation of T cells leads to autoimmunity or severe immunodeficiencies. PKC-θ is selectively expressed in T cells and required for mediating T cell activation process. Mice deficient in PKC-θ exhibit defects in T cell activation, survival and activation-induced cell death. PKC-θ selectively translocates to immunological synapse and mediates the signals required for activation of NF-κB, AP1 and NFAT that are essential for T cell activation.

Dendritic cells (DCs) can induce tumor-or pathogen-specific T cell responses in humans. We comprehensively compared the clinically available DC maturation stimuli for their ability to promote uniformly mature DCs that elicit higher levels of T cell responses. We compared the standard maturation stimulus, autologous monocyte-conditioned medium (MCM), with a synthetic double stranded RNA (poly I:C), soluble CD40 ligand trimer, and a defined cocktail of cytokines (TNF-␣, IL-1␤, IL-6) and PGE 2 to promote mature phenotype and function in human monocyte-derived DCs. The cocktail was the most efficient despite the lack of induction of IL-12p70. While these results support the use of the MCM-mimic cocktail in clinical DC immunotherapy trials, the roles of it's individual constituents remain to be completely defined.

Over the past decade, key protein interactions contributing to T cell antigen recognition have been characterized in molecular detail. These have included interactions involving the T cell antigen receptor (TCR) itself, its coreceptors CD4 and CD8, the accessory molecule CD2, and the costimulatory receptors CD28 and CTLA-4. A clear view is emerging of how these molecules interact with their ligands at the cellcell interface. Structural and binding studies have confirmed that the proteins span small but comparable distances and that, overall, they interact very weakly. However, there have been important surprises as well: that TCR interactions with peptide-MHC are topologically constrained and characterized by considerable conformational flexibility at the binding interface; that coreceptors engage peptide-MHC with extraordinarily fast kinetics and at angles apparently precluding direct interactions with the TCR bound to the same peptide-MHC; that the structural mechanisms allowing recognition by costimulatory and accessory molecules to be weak and yet specific are very heterogeneous; and that because of differences in both binding affinity and stoichiometry, there is enormous variation in the stability of the various costimulatory receptor/ligand complexes. These studies provide the necessary framework for exploring how these molecular interactions initiate T cell activation. 0732-0582/03/0407-0659$14.00 659 Annu. Rev. Immunol. 2003.21:659-684. Downloaded from arjournals.annualreviews.org by University of Oxford -Nuffield College on 07/02/09. For personal use only.

Silymarin, a mixture of bioactive flavonolignans isolated from Silybum marianum, exhibits anticarcinogenic, anti-inflammatory and cytoprotective effects. In this study, the in vitro immunomodulatory activity of silymarin was investigated using CD4+ splenocytes from C57/Bl6 mice. Proliferation assay revealed that silymarin, at 50 M concentration, significantly inhibited CD4+ cells proliferation. ELISA analyses indicated that silymarin significantly inhibited IL-2 and IFN-␥ production. Immunofluorescence staining performed on the mouse hybridoma T cell line (3DO) revealed a block of nuclear translocation of transcription factor B (NF-B), which is known to be responsible for IL-2 transcriptional activation. Moreover, silymarin inhibited p65/NF-B phosphorylation in CD4+ T cell. These results suggest that silymarin is able to inhibit T cell activation and proliferation, notably acting on pathways of NF-B activation/translocation.

The success of some chemo-and radiotherapeutic regimens relies on the induction of immunogenic tumor cell death and on the induction of an anticancer immune response. Cells succumbing to immunogenic cell death undergo specific changes in their surface characteristics and release proimmunogenic factors according to a defined spatiotemporal pattern. This stimulates antigen presenting cells such as dendritic cells to efficiently take up tumor antigens, process them, and cross-prime cytotoxic T lymphocytes, thus eliciting a tumor-specific cognate immune response. Such a response can also target therapy-resistant tumor (stem) cells, thereby leading, at least in some instances, to tumor eradication. In this review, we shed some light on the molecular identity of the factors that are required for cell death to be perceived as immunogenic. We discuss the intriguing observations that the most abundant endoplasmic reticulum protein, calreticulin, the most abundant intracellular metabolite, ATP, and the most abundant nonhistone chromatin-binding protein, HMGB1, can determine whether cell death is immunogenic as they appear on the surface or in the microenvironment of dying cells.

Human ageing has been associated with immunological changes including blunted T-cell responses and increased production of pro-inflammatory cytokines. Here, we investigated the role of psychological and endocrine factors in the production of proinflammatory cytokines (tumor necrosis factor-a and interleukin (IL)-6) as well as soluble IL-2Ra, associated with T-cell activation. Forty-six elderly subjects (60 Á/91 yrs) and 33 young adults (20 Á/40 yrs) were recruited accordingly the SENIEUR protocol. The emotional status was measured by structured clinical interviews. Salivary cortisol levels (9, 12 and 22 h) and serum dehydroepiandrosterone (DHEA) were assessed by radioimmunoassays. The elderly were more stressed, depressed and anxious than the young subjects. Cortisol levels were increased whereas DHEA levels were significantly reduced in the elderly. Both groups showed equivalent production of pro-inflammatory cytokines as well as soluble IL-2Ra. Psychological scores were positively correlated to evening cortisol levels and negatively correlated to morning DHEA levels. No relationships were noted between psychological factors and cytokines studied. However, evening cortisol levels were found positively correlated to TNF-a and sIL-2Ra levels. These data indicate that healthy ageing is associated with significant distress and activation of the hypothalamic Á/ pituitary Á/adrenal axis. Our data also suggest that there are complex psychoneuroendocrine relationships involved with cytokine production during ageing. #

Lymphatic filariasis (LF) is a parasitic disease caused by threadlike worms of the Brugia and Wuchereria species that live in the human lymphatic system. Regulatory T cells (Tregs) may play a key role in the pathogenesis of LF, and cytotoxic T-lymphocyte antigen-4 (CTLA4) expressed by Tregs is a potential candidate gene because it modulates T-cell activation. A case-control study was performed to establish a potential association of 5 CTLA4 gene promoter single nucleotide polymorphisms (SNPs; rs733618, rs11571316, rs5742909, rs231775, and rs16840252) with the occurrence of LF in an East Malaysian population (320 LF-infected individuals and 150 healthy controls). Polymorphisms were evaluated using TaqMan real-time polymerase chain reaction followed by direct sequencing. LF carriers of the rs733618 AG genotypes (p ϭ 0.02) and those with combined minor allele G carriers (AG ϩ GG; p ϭ 0.01) exhibited a significantly decreased risk for LF. Among the asymptomatic amicrofilaremic cases, positive associations were reported for all genotypes and variants of rs733618 with odds ratios (ORs) ranging from 0.27 to 0.45. In the asymptomatic microfilaremic cases, marker rs231775 exhibited a significant decreased risk, with ORs ranging from 0.50 to 0.57. The study has identified SNPs in the CTLA4 promoter gene that may be functionally linked with susceptibility to LF. ᭧

Signal exchange between cells is a key feature of life from humble monads to human beings. Appropriate communication is of particular importance between cells of multi-cellular organisms. Various basic mechanisms of cellcell communication have evolved during phylogenesis, which were subject to organ, tissue and cell type-specific adaptation. These mechanisms range from long-distance communication via hormones to more and more local processes, e.g. via cytokines, chemokines or neuromodulators/neurotransmitters, and eventually direct physical interactions of molecules anchored at cell surfaces. Accordingly, highly specialized transient or stable cell-cell contact sites have evolved that mediate signaling between cells. With few exceptions (e.g. lipophilic hormones, gases) intercellular communication depends on specific signal detection devices at the cell surface coupled to a signal transduction apparatus that mediates the signal transfer across the cell membrane and activates intracellular effector systems, which generate intracellularly decipherable signals.

Over the past few years a great deal of research has examined how T cell-dependent immune responses are initiated and subsequently regulated. Ligation of the TCR with an antigenic peptide bound to an MHC protein on a professional APC provides the crucial antigen-specific stimulus required for T cell activation. Interaction of CD28 with CD80 or CD86 molecules on APC initiates a costimulatory or second signal within the T cell which augments and sustains T cell activation initiated through the TCR. However, recently it has become clear that T cell immune responses are a result of a balance between stimulatory and inhibitory signals. Cytotoxic T lymphocyteassociated molecule-4 (CTLA-4) is a cell surface molecule that is expressed nearly exclusively on CD4 + and CD8 + T cells. Investigation into the role of CTLA-4 in the regulation of T cell immune responses has revealed that CTLA-4 is a very important molecule involved in the maintenance of T cell homeostasis. In the present review, evidence for the proposed inhibitory role of CTLA-4 is examined and a model suggesting a role for CTLA-4 in both early and late stages of T cell activation is presented.

MuS110 is a BiTE antibody bispeciWc for murine EpCAM (CD326) and murine CD3. A recent study has shown that muS110 has signiWcant anti tumor activity at well-tolerated doses as low as 5 g/kg in orthotopic breast and lung cancer models (Amann et al. in Cancer Res 68:143-151, 2008). Here, we have explored the safety pro-Wle of muS110 at higher doses. Escalation to 50 g/kg muS110 caused in mice transient loss of body weight, and transient piloerection, hypomotility, hypothermia and diarrhoea. These clinical signs coincided with serum peaks of TNF-, IL-6, IL-2, IFN-and IL-4, and an increase of surface markers for T cell activation. Because activation of T cells in response to BiTE antibodies is typically dependent on target cells, we analyzed mouse blood for the presence of EpCAM + cells. Various mouse strains presented with a subpopulation of 2-3% EpCAM + blood cells, mostly B and T lymphocytes, which was not detected in human blood samples. In vitro experiments in which the number of EpCAM + cells in blood samples was either reduced or increased suggested that both T cell activation and cytokine release in response to muS110 was dependent on the number of target-expressing cells. In support for a role of EpCAM + lymphocytes in the observed side eVects, reduction of EpCAM + blood cells in mice via a low-dose pre treatment with muS110 dramatically increased the tolerability of animals up to at least 500 g/kg of the BiTE antibody. This high tolerability to muS110 occurred in the presence of non-compromised T cells. No damage to EpCAM + epithelial tissues was evident from histopathological examination of animals daily injected with 100 g/kg muS110 for 28 days. In summary, these observations suggest that side eVects of muS110 in mice were largely caused by an acute T cell activation that was triggered by a subpopulation of EpCAM + lymphocytes. Because humans have extremely low numbers of EpCAM + cells in blood, this toxicity of an EpCAM-speciWc BiTE may be speciWc for mice.

We investigated inflammatory markers in psychotic disorders and their association with metabolic comorbidity, antipsychotic medication, smoking, alcohol use, physical condition, and mood. From the population-based Finnish Health 2000 study, we identified all persons with schizophrenia (n = 45), other nonaffective psychosis (ONAP) (n = 57), affective psychosis (n = 37) and chose controls matched by age, sex, and region of residence. We found that persons with schizophrenia had significantly higher sIL-2Rα, IL-1RA and C-reactive protein (CRP), persons with ONAP significantly higher IL-1RA and CRP and persons with affective psychosis almost significantly higher TNF-α compared to their matched controls. Current antipsychotic use was associated with elevated IL-1RA and CRP. After taking metabolic and lifestyle-related variables that associated with inflammatory markers into account, only antipsychotic medication remained associated with elevated IL-1RA and TNF-α which are markers related to the activation of innate immune system. CRP was influenced by both antipsychotic medication and nonaffective psychosis. sIL-2Rα, a marker of T-cell activation, was associated with depressive symptoms, schizophrenia, and affective psychosis. We conclude that in persons with psychotic disorders, activation of mononuclear phagocyte system was mostly related to metabolic comorbidity and antipsychotic medication use, whereas T-cell activation had a more direct relationship with both psychotic disorders and depressive symptoms.

Signals mediated by chemokine receptors may compete with T cell receptor stop signals and determine the duration of T cellantigen-presenting cell interactions. Here we show that during T cell stimulation by antigen-presenting cells, T cell chemokine receptors coupled to G q and/or G 11 protein were recruited to the immunological synapse by a G i -independent mechanism. When chemokine receptors were sequestered at the immunological synapse, T cells became insensitive to chemotactic gradients, formed more stable conjugates and finally responded with enhanced proliferation and cytokine production. We suggest that chemokine receptor trapping at the immunological synapse enhances T cell activation by improving T cell-antigen-presenting cell attraction and impeding the 'distraction' of successfully engaged T cells by other chemokine sources.

Current methods for the detection and isolation of antigen-specific CD4 + and CD8 + T cells require the availability of peptide/MHC multimers or are restricted to cells that produce cytokines after antigen contact. Here we show that de novo cell surface expression of the TNFreceptor family member CD137 (4-1BB) identifies recently activated, but not resting, human CD4 + and CD8 + memory T cells. Maximum CD137 expression level is uniformly observed in both T-cell subsets at 24h after stimulation with antigen. In experiments with CMV and EBV-reactive T cells, we confirmed the specificity of CD137 expression by co-staining with peptide/HLA tetramers. Substantial proportions of CD137 + T cells did not produce IFN-γ, suggesting that CD137 detects a broader repertoire of antigen-specific T cells. Activated CD137 + T cells could be easily purified by MACS and expanded in vitro thereafter. This CD137-based enrichment method was capable of isolating 2-fold higher numbers of anti-viral CD4 + and CD8 + T cells compared to the IFN-γ secretion assay. In conclusion, antigen-triggered CD137 expression allows the rapid detection and sorting of virus-reactive CD4 + and CD8 + T cells. The CD137 assay is most attractive for the simultaneous targeting of anti-viral T helper and effector cells in monitoring studies and adoptive immunotherapy trials.

The generalized anxiety disorder (GAD) is often a debilitating chronic condition, characterized by longlasting anxiety that is not focused on any object or situation. Besides being clearly linked to increased susceptibility to infectious diseases, anxiety is also known to contribute to the pathogenesis of many inflammatory/autoimmune disorders. The present work aimed to explore the T cell profile following in vitro activation in cultures obtained from a group of individuals with GAD, comparing them with healthy control individuals. Our results demonstrated that cell cultures from GAD group proliferated less following T cell activation as compared with the control group. The analysis of the cytokine profile revealed Th1 and Th2 cytokine deficiencies in the anxious group, as compared with the control subjects. On the other hand, this cellular and humoral immune damage was followed by enhanced production of Th17-derived cytokines. In particular, the levels of TNF-α and IL-17 were significantly higher in cell cultures containing activated T cells from GAD individuals. Therefore, besides a deficiency on Th1 phenotype, an elevated proinflammatory status of these individuals might be related to both glucocorticoid immune resistance and lower IL-10 levels produced by activated T cells. In conclusion, our results demonstrated a T cell functional dysregulation in individuals with GAD, and can help to explain the mechanisms of immune impairment in these subjects and their relationship with increased susceptibility to infections and autoimmune diseases.

Recent studies in genetically deficient mice indicate that numerous components of both the innate and adaptive immune systems can act as extrinsic tumor suppressors 1,2 . However, the immune system is generally tolerant of established cancers 3,4 . It has been proposed that dendritic cells play a central role in immunologic decisions 5,6 . In the absence of inflammation, dendritic cells do not become fully activated and induce tolerance rather than immunity 5,6 . Evidence has also been emerging that tumor cells can secrete factors that inhibit dendritic cell maturation 7,8 . Here we evaluate the role of Stat-3 activity in blocking the initiation of antitumor immunity. Stat-3 is a potential negative regulator of inflammatory responses, as mice devoid of the Stat-3 gene in macrophages and neutrophils have enhanced inflammatory activity, leading to the development of chronic enterocolitis 9 . Recently, Stat3 -/macrophages have been shown to produce increased amounts of interleukin-12 (IL-12) and RANTES, which are involved in restoring the responsiveness of tolerant CD4 + T cells as well as in reversal of systemic tolerance 10 . Stat-3 is commonly constitutively activated in diverse cancers of both hematopoietic and epithelial origin. Constitutively activated Stat-3 enhances tumor cell proliferation and prevents apoptosis 11-13 . We show here that constitutive Stat-3 activity in tumors inhibits the production of multiple proinflammatory cytokines and chemokines while inducing the release of factors that inhibit dendritic cell maturation through activation of Stat-3 in dendritic cells. These results indicate that Stat-3 activation in tumors negatively regulates induction of adaptive immunity.

Interleukin 10 (IL-10) is a key cytokine produced by a multitude of immune effector cells and possesses distinct regulatory effects on immune functioning in the skin. In this article we report the current understanding of the immunobiology of IL-10 and identify the role of IL-10 in cutaneous infection as well as in autoimmune and neoplastic processes. We reviewed the literature to examine the function of IL-10 in different cutaneous disorders. IL-10 can influence and potentially treat T1/T2 differentiation, antigenpresenting cell functioning, antigen-presenting cell-mediated T-cell activation, and T-cell, B-cell, and mast cell growth and differentiation that is aberrant in various disease processes. The literature consensus is that the multitude of effects of IL-10 contribute to the pathogenesis of different skin disorders. In certain circumstances IL-10 could represent novel therapeutic approaches to treating cutaneous diseases. (J Am Acad Dermatol 2004;50:657-75.) Learning objective: At the conclusion of this learning activity, participants should be acquainted with the role of IL-10 in many infectious diseases, autoimmune skin disease, inflammatory processes, and malignancy. Its possible role in the resolution of various skin diseases should be better understood.

Inappropriate T cell responses cause the four classical types of hypersensitivity immune reactions. All of these can target the kidney and cause distinct forms of glomerulonephritis. CD4 + T cells can mediate glomerular immunopathology by cytokine secretion, by activating effector cells such as macrophages or by inducing autoantibodies or immune-complexes. Cytotoxic CD8 + T cell responses and failure of regulatory T cells may represent two additional types of anti-renal hypersensitivity. T cell activation is critically dependent on dendritic cells (DC), whose role in renal disease appears to be protective, but underlying mechanisms are largely unknown. In this paper, we summarized mechanistic information from rodent models on the roles of DC and T cells in glomerular immunopathology.

TNF-␣ mediates both protective and detrimental manifestations of the host immune response. Our previous work has shown thalidomide to be a relatively selective inhibitor of TNF-␣ production in vivo and in vitro. Additionally, we have recently reported that thalidomide exerts a costimulatory effect on T cell responses. To develop thalidomide analogues with increased anti-TNF-␣ activity and reduced or absent toxicities, novel TNF-␣ inhibitors were designed and synthesized. When a selected group of these compounds was examined for their immunomodulatory activities, different patterns of cytokine modulation were revealed. The tested compounds segregated into two distinct classes: one class of compounds, shown to be potent phosphodiesterase 4 inhibitors, inhibited TNF-␣ production, increased IL-10 production by LPS-induced PBMC, and had little effect on T cell activation; the other class of compounds, similar to thalidomide, were not phosphodiesterase 4 inhibitors and markedly stimulated T cell proliferation and IL-2 and IFN-␥ production. These compounds inhibited TNF-␣, IL-1␤, and IL-6 and greatly increased IL-10 production by LPS-induced PBMC. Similar to thalidomide, the effect of these agents on IL-12 production was dichotomous; IL-12 was inhibited when PBMC were stimulated with LPS but increased when cells were stimulated by cross-linking the TCR. The latter effect was associated with increased T cell CD40 ligand expression. The distinct immunomodulatory activities of these classes of thalidomide analogues may potentially allow them to be used in the clinic for the treatment of different immunopathological disorders. The Journal of Immunology, 1999, 163: 380 -386.

Tribodies are multifunctional recombinant antibody derivatives, which utilize the natural in vivo heterodimerization of the heavy chain (Fd fragment) and light chain (L) of a Fab fragment, to form a scaffold, upon which additional functions can be incorporated, such as additional binders -e.g. scFv binding domains.

The pivotal role that glutamate plays in the functioning of the central nervous system is well established. Several glutamate receptors and glutamate transporters have been extensively described in the central nervous system where they, respectively mediate glutamate effects and regulates extracellular glutamate levels. Recent studies have shown that glutamate not only has a role as neurotransmitter, but also as an important immunomodulator. In this regard, several glutamate receptors have recently been described on the T-cell surface, whereas glutamate transporters have reportedly been expressed in antigen presenting cells such as dendritic cells and macrophages. On the other hand, an increasing number of reports have described a protective autoimmune mechanism in which autoantigen specific T cells in the central nervous system protect neurons against glutamate neurotoxicity. This review integrates and summarises different findings in this emerging area. A role of glutamate as a key immunomodulator in the initiation and development of T-cell-mediated immunity in peripheral tissues as well as in the central nervous system is suggested.