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Mucosal-associated invariant T (MAIT) cells are characterized by a semi-invariant TCR that recognizes vitamin B metabolite Ags presented by the MHC-related molecule MR1. Their Ag restriction determines a unique developmental lineage, imbuing a tissue-homing, preprimed phenotype with antimicrobial function. A growing body of literature indicates that MR1-restricted T cells are more diverse than the MAIT term implies. Namely, it is increasingly clear that TCR a- and TCR b-chain diversity within the MR1-restricted repertoire provides a potential mechanism of Ag discrimination, and context-dependent functional variation suggests a role for MR1-restricted T cells in diverse physiological settings. In this paper, we summarize MR1-restricted T cell biology, with an emphasis on TCR diversity, Ag discrimination, and functional heterogeneity. [ABSTRACT FROM AUTHOR]

T cell factor, the effector transcription factor of the WNT signaling pathway, was so named because of the primary observation that it is indispensable for T cell development in the thymus. Since this discovery, the role of this signaling pathway has been extensively studied in T cell development, hematopoiesis, and stem cells; however, its functional role in mature T cells has remained relatively underinvestigated. Over the last few years, various studies have demonstrated that T cell factor can directly influence T cell function and the differentiation of Th1, Th2, Th17, regulatory T cell, follicular helper CD4+ T cell subsets, and CD8+ memory T cells. In this paper, we discuss the molecular mechanisms underlying these observations and place them in the general context of immune responses. Furthermore, we explore the implications and limitations of these findings for WNT manipulation as a therapeutic approach for treating immune-related diseases. [ABSTRACT FROM AUTHOR]

IL-17 is a potent proinflammatory cytokine that drives pathogenesis of multiple autoimmune diseases, including psoriasis. A major source of pathogenic IL-17 is a subset of γδ T cells (Tγδ17) that acquires the ability to produce IL-17 while developing in the thymus. The mechanisms that regulate homeostasis of Tγδ17 cells and their roles in psoriasis, however, are not fully understood. In this paper, we show that the heparan sulfate proteoglycan syndecan-1 (sdc1) plays a critical role in regulating homeostasis of Tγδ17 cells and modulating psoriasis-like skin inflammation in mice. sdc1 was predominantly expressed by Tγδ17 cells (but not IL-172 Tγδ cells) in the thymus, lymph nodes, and dermis. sdc1 deficiency significantly and selectively increased the frequency and absolute numbers of Tγδ17 cells by mechanisms that included increased proliferation and decreased apoptosis. Adoptive transfer experiments ruled out a significant role of sdc1 expressed on nonhematopoietic cells in halting expansion and proliferation of sdc1-deficient Tγδ17 cells. When subjected to imiquimod-induced psoriasiform dermatitis, Tγδ17 cells in sdc1KO mice displayed heightened responses accompanied by significantly increased skin inflammation than their wild-type counterparts. Furthermore, transferred sdc1-deficient γδ T cells caused more severe psoriasiform dermatitis than their sdc1-sufficient counterparts in TCR-β δ KO hosts. The results uncover a novel role for sdc1 in controlling homeostasis of Tγδ17 cells and moderating host responses to psoriasis-like inflammation. [ABSTRACT FROM AUTHOR]

Acute respiratory virus infection (ARI) induces CD8+ T cells with diminished cytokine production and functional impairment. The role of cellular mediators of immune impairment, specifically CD4+ regulatory T cells (Tregs), is incompletely understood in ARI. Tregs are known suppressors of effector T cell function, but whether they are detrimental or beneficial in ARI remains controversial. We show in this paper that Treg depletion leads to increased CD8+ T cell function and lower virus titer in mice infected with human metapneumovirus. We further demonstrate that Tregs play a temporal role in the immune response to human metapneumovirus and influenza: Treg depletion before infection pathologically reduces virus-specific CD8+ T cell numbers and delays virus clearance, whereas depletion 2 d postinoculation enhances CD8+ T cell functionality without reducing virus-specific CD8+ T cell numbers. Mechanistically, Treg depletion during immune priming led to impaired dendritic cell and CD8+ T cell migration. Further, early Treg depletion was associated with immune skewing toward a type 2 phenotype characterized by increased type 2 innate lymphoid cells and TH2 CD4+ T cells, which was not observed when Treg depletion was delayed until after inoculation. These results indicate that the presence of Tregs at inoculation is critical for efficient priming of the CD8+ T cell response to ARI, whereas later in infection, Tregs are dispensable for virus clearance. [ABSTRACT FROM AUTHOR]

Having a large number of sufficiently abundant T cell clones is important for adequate protection against diseases. However, as shown in this paper and elsewhere, between young adulthood and >70 y of age the effective clonal diversity of naive CD4/CD8 T cells found in human blood declines by a factor of >10. (Effective clonal diversity accounts for both the number and the abundance of T cell clones.) The causes of this observation are incompletely understood. A previous study proposed that it might result from the emergence of certain rare, replication-enhancing mutations in T cells. In this paper, we propose an even simpler explanation: that it results from the loss of T cells that have attained replicative senescence (i.e., the Hayflick limit). Stochastic numerical simulations of naive T cell population dynamics, based on experimental parameters, show that the rate of homeostatic T cell proliferation increases after the age of ~60 y because naive T cells collectively approach replicative senescence. This leads to a sharp decline of effective clonal diversity after ~70 y, in agreement with empirical data. A mathematical analysis predicts that, without an increase in the naive T cell proliferation rate, this decline will occur >50 yr later than empirically observed. These results are consistent with a model in which exhaustion of the proliferative capacity of naive T cells causes a sharp decline of their effective clonal diversity and imply that therapeutic potentiation of thymopoiesis might either prevent or reverse this outcome. [ABSTRACT FROM AUTHOR]

The killer-cell Ig-like receptors (KIRs) play a central role in the immune recognition in infection, pregnancy and transplantation through their interactions with MHC class I molecules. KIR genes display abundant copy number variation as well as high levels of polymorphism. As a result, it is challenging to characterize this structurally dynamic region. KIR haplotypes have been analyzed in different species using conventional characterization methods, such as Sanger sequencing and Roche/454 pyrosequencing. However, these methods are time-consuming and often failed to define complete haplotypes, or do not reach allele-level resolution. In addition, most analyses were performed on genomic DNA and thus were lacking substantial information about transcription and its corresponding modifications. In this paper, we present a single-molecule real-time sequencing approach, using Pacific Biosciences Sequel platform to characterize the KIR transcriptomes in human and rhesus macaque (Macaca mulatta) families. This high-resolution approach allowed the identification of novel Mamu-KIR alleles, the extension of reported allele sequences and the determination of human and macaque KIR haplotypes. In addition, multiple recombinant KIR genes were discovered, all located on contracted haplotypes, which were likely the result of chromosomal rearrangements. The relatively high number of contracted haplotypes discovered might be indicative of selection on small KIR repertoires and/or novel fusion gene products. This next-generation method provides an improved high-resolution characterization of the KIR cluster in humans and macaques, which eventually may aid in a better understanding and interpretation of KIR allele-associated diseases, as well as the immune response in transplantation and reproduction. [ABSTRACT FROM AUTHOR]

MicroRNAs govern immune responses to infectious agents, allergens, and autoantigens and function by posttranscriptional repression of their target genes. In this paper, we have addressed the role of microRNA-155 (miR-155) in the control of Helicobacter pylori infection of the gastrointestinal tract and the development of H. pylori-induced chronic gastritis and associated gastric preneoplastic pathology. We show that miR-155 is upregulated in the gastric mucosa of experimentally infected mice and that miR-155-/- mice fail to control H. pylori infection as a result of impaired pathogen-specific Th1 and Th17 responses. miR-155-/- mice are also less well protected against challenge infection after H. pylori-specific vaccination than their wild-type (wt) counterparts. As a consequence of their impaired T cell responses to H. pylori, miR-155-/- mice develop less severe infection-induced immunopathology manifesting as chronic atrophic gastritis, epithelial hyperplasia, and intestinal metaplasia. T cells from miR-155-/- mice that are activated by CD3/CD28 cross-linking expand less and produce less IFN-γ and IL-17 than wt T cells. Finally, we show in this paper using adoptive transfers that the phenotypes of miR-155-/- mice are likely due to T cell-intrinsic defects. In contrast to wt T cells, miR-155-/- T cells from infected donors do not control H. pylori infections in T cell-deficient recipients, do not differentiate into Th1 or Th17 cells, and do not cause immunopathology. In addition, naive miR-155-/- T cells fail to induce chronic Th17-driven colitis in an adoptive transfer model. In conclusion, miR-155 expression is required for the Th17/Th1 differentiation that underlies immunity to H. pylori infection on the one hand and infection-associated immunopathology on the other. [ABSTRACT FROM AUTHOR]

Th cell subsets develop in response to multiple activating signals, including the cytokine environment. IL-9-secreting T cells develop in response to the combination of IL-4 and TGF-β, although they clearly require other cytokine signals, leading to the activation of transcription factors including STAT5. In Th17 cells, there is a molecular antagonism of STAT5 with STAT3 signaling, although whether this paradigm exists in other Th subsets is not clear. In this paper, we demonstrate that STAT3 attenuates the ability of STAT5 to promote the development of IL-9-secreting T cells. We demonstrate that production of IL-9 is increased in the absence of STAT3 and cytokines that result in a sustained activation of STAT3, including IL-6, have the greatest potency in repressing IL-9 production in a STAT3-dependent manner. Increased IL-9 production in the absence of STAT3 correlates with increased endogenous IL-2 production and STAT5 activation, and blocking IL-2 responses eliminates the difference in IL-9 production between wild-type and STAT3-deficient T cells. Moreover, transduction of developing Th9 cells with a constitutively active STAT5 eliminates the ability of IL-6 to reduce IL-9 production. Thus, STAT3 functions as a negative regulator of IL-9 production through attenuation of STAT5 activation and function. [ABSTRACT FROM AUTHOR]

CD4+CD25+Foxp3+ regulatory T (Treg) cell therapy is a promising approach for the treatment of autoimmune diseases. To be effective, Treg cells should be in an activated state in the target tissue. This can be achieved by systemic administration of Ag-specific Treg cells, which are difficult to produce in conditions that can be translated to the clinic. In this paper, we propose an alternative approach consisting of in situ injection of preactivated polyclonal Treg cells that would exert bystander suppression in the target tissue. We show that polyclonal Treg cells suppressed uveitis in mice as efficiently as Ag-specific Treg cells but only when preactivated and administered in the vitreous. Uveitis control was correlated with an increase of IL-10 and a decrease of reactive oxygen species produced by immune cell infiltrates in the eye. Thus, our results reveal a new mechanism of Treg cell-mediated suppression and a new Treg cell therapy approach. [ABSTRACT FROM AUTHOR]

CD28 costimulation is essential for the development of thymic-derived CD4+CD25+Foxp3+ regulatory T cells ("tTregs"). E3 ubiquitin ligase Cbl-b has been shown to regulate CD28 dependence of T cell activation. In this paper, we report that the loss of Cbl-b partially but significantly rescues the defective development of tTregs in Cd28-/- mice. This partial rescue is independent of IL-2. Mechanistically, Cbl-b binds to Foxp3 upon TCR stimulation and, together with Stubl, targets Foxp3 for ubiquitination and subsequently degradation in the proteasome. As Cbl-b self-ubiquitination and proteasomal degradation is impaired in Cd28-/- T cells, the defective development of tTregs in Cd28-/- mice may in part be due to increased Foxp3 ubiquitination and degradation targeted by Stubl and Cbl-b. Treating Cd28-/- mice with a proteasome inhibitor completely rescues defective tTreg development in these mice. Therefore, Cbl-b, together with Stubl, ubiquitinate Foxp3, and regulate tTreg development. [ABSTRACT FROM AUTHOR]

IL-2 has a pervasive influence on the immune system and dictates the survival and differentiation of multiple T cell subsets, including CD4 regulatory T cells, CD4 Th cells, and CD8 memory cells. IL-2 is synthesized by T cells during the early stages of the immune response and promotes T cell expansion and effector cell generation after initial activation via TCR signaling. Based on studies with activated T cell lines maintained in vitro, IL-2 is known to activate multiple signaling pathways that show considerable overlap with the pathways elicited via the TCR. In this paper, we have examined IL-2 signaling under TCR-independent conditions, namely by culturing purified resting naive CD8 T cells with IL-2 in the absence of Ag or APC. Under these conditions, we show in this study that IL-2 elicits a unique pattern of signaling associated with strong lymphocyte-specific protein tyrosine kinase/JAK3-dependent activation of the PI3K/AKT pathway with little or no involvement of STAT5, NF-κB, or the calcineurin/NFAT pathways. Such signaling induces marked proliferation associated with rapid and selective expression of eomesodermin but not T-bet and differentiation into long-lived central memory cells after adoptive transfer. [ABSTRACT FROM AUTHOR]

γδ T cells represent a subset of unconventional T lymphocytes that are known for their reactivity against different pathogens and considered as intermediate mediators between adaptive and innate immunity. We provide in this paper further insights underlying the changes that affect the γδ T cell compartment with advanced age in humans. We show that both aging and CMV infection impact independently on the γδ T cell compartment. Most γδ T cells are significantly affected by age and present a decreased frequency in the elderly. The decline of the γδ T cell pool appears to be independent from the activity of the thymus, arguing in favor of an extrathymic site of γδ T cell production in humans. Of note, CMV infection, which is directly associated with the activation of the pool of Vδ2− γδ T cells, promotes nonetheless the inflation of this compartment throughout life. CMV seropositivity accentuates further the accumulation of highly differentiated lymphocytes in Vδ2− γδ T cell subsets with time, in contrast to Vδ2+ γδ T cells, which maintain a less differentiated phenotype. This is similar to the effect of CMV on αβ T cells and suggests that γδ T cells may vary in differentiation phenotype according to distinct stimuli or pathogens. [ABSTRACT FROM AUTHOR]

GATA-3, a C2C2-type zinc finger transcription factor, regulates many steps of T cell development and differentiation. It is also required for optimal production of type 2 cytokines by CD8+ T cells. However, its role in the development and function of this subset of T cells is still poorly characterized. In this paper, we report that GATA-3 is required for MHC-mediated positive selection and final maturation of CD8 single-positive thymocytes. Deficiency of GATA-3 mediated by a CD4cre transgene led to age-dependent lymphadenopathy partly because of abnormal expansion of CD8+ T cells driven by a cell-extrinsic mechanism. Paradoxically, GATA-3-deficient CD8+ T cells were hyporesponsive to Ag stimulation due to a defect in the maintenance/ progression, but not initiation, of activation signals. More importantly, GATA-3-deficient CD8+ T cells were less efficient in killing Ag-bearing tumor cells in vivo. Taken together, our data further expand the role of GATA-3 in T cells. [ABSTRACT FROM AUTHOR]

Minor histocompatibility (H) Ags are classically described as self-peptides derived from intracellular proteins that are expressed at the cell surface by MHC class I and class II molecules and that induce T ceil alloresponses. We have isolated three different T cell populations from a skin biopsy of a patient suffering from acute graft-versus-host disease following sex-mismatched HLA-identical bone marrow transplantation. The first population was: 1) CD4+/CD8+ double-positive; 2) specific for an HLA class I-restricted autosomal Ag; 3) expressed a Trl profile with high levels of IL-10, but low IL-2 and IFN-γ; and 4) exerted regulatory function in the presence of recipient APCs. The second was CD8 positive, specific for an HLA class I-restricted autosomally encoded minor H Ag, but was only weakly cytotoxic. The third was CD4 single positive, specific for an HLA-DR7-restricted HY epitope and exerted both proliferative and cytotoxic functions. Identification of the peptide recognized by these latter cells revealed a new human HY epitope, TGKIINFIKFDTGNL, encoded by RPS4Y and restricted by HLA-DR7. In this paper, we show human CD4/CD8 double-positive, acute graft-versus-host disease-protective, minor H Ag-specific regulatory T cells and identify a novel HLA-DR7/ HY T cell epitope, encoded by RPS4Y, a potential new therapeutic target. [ABSTRACT FROM AUTHOR]

Induction of Ag-speciflc regulatory T cells (iTregs) by vaccination is a promising strategy for treating autoimmune diseases. We previously demonstrated that DNA and protein covaccination converted naive T cells to Ag-speciflc iTregs by inducing CD11c+ CD40lowIL-10+ regulatory dendritic cells (DCregs). However, it is unclear how coimmunization induces the DCregs. In this paper, we report that the event is initiated by coentry of sequence-matched DNA and protein immunogens into the same DC via caveolae-mediated endocytosis, which leads to inhibition of phosphorylation of caveolin-1 (Cav-1), the main component of caveolae, and upregulation of Tollip. This triggers downstream signaling that upregulates suppressor of cytokine signaling 1 and downregulates NF-kB and STAT-l&agr;. Silencing either Cav-1 or Tollip blocks the negative signaling, leading to upregulated expression of CD40, downregulated production of IL-10, and loss of iTreg-inducing function. We further show that DCregs can be induced in culture from primary DCs and JAWS II DC lines by feeding them sequence-matched DNA and protein immunogens. The in vitro-generated DCregs are effective in ameliorating autoimmune and inflammatory diseases in several mouse models. Our study thus suggests that DNA and protein coimmunization induces DCregs through Cav-1- and Tollip-mediated negative signaling. It also describes a novel method for generating therapeutic DCregs in vitro. [ABSTRACT FROM AUTHOR]

The regulators of Gprotein signaling (RGS) protein superfamily negatively controls Gprotein-coupled receptor signal transduction pathways. RGS16 is enriched in activated/effector T lymphocytes. In this paper, we show that RGS16 constrains pulmonary inflammation by regulating chemokine-induced T cell trafficking in response to challenge with Schistosoma mansoni. Naive Rgsl6-/- mice were "primed" for inflammation by accumulation of CCR10+ T cells in the lung. Upon pathogen exposure, these mice developed more robust granulomatous lung fibrosis than wild-type counterparts. Distinct Th2 or putative Thl7 subsets expressing CCR4 or CCR10 accumulated more rapidly in Rgsl6-/- lungs following challenge and produced proinflammatory cytokines IL-13 and IL-17B. CCRA+Rgsl6-/- Th2 cells migrated excessively to CCL17 and localized aberrantly in challenged lungs. T lymphocytes were partially excluded from lung granulomas in Rgsl6-/- mice, instead forming peribronchial/perivascular aggregates. Thus, RGS16-mediated confinement of T cells to Schistosome granulomas mitigates widespread cytokine-mediated pulmonary inflammation. [ABSTRACT FROM AUTHOR]

Immunopathology is a major cause of influenza-associated morbidity and mortality worldwide. However, the role and regulatory mechanisms of CD4 T cells in severe lung immunopathology following acute influenza infection are poorly understood. In this paper, we report that the emergence of immunopathogenic CD4 T cells is under the control of a transmembrane immunoadaptor DAP12 pathway during influenza infection. We find that the mice lacking DAP12 have unaltered viral clearance but easily succumb to influenza infection as a result of uncontrolled immunopathology. Such immunopathology is associated with markedly increased CD4 T cells displaying markedly increased cytotoxicity and Fas ligand expression. Furthermore, the immunopathogenic property of these CD4 T cells is transferrable. Thus, depletion of CD4 T cells or abrogation of Fas/Fas ligand signaling pathway improves survival and immunopathology. We further find that DAP12 expressed by dendritic cells plays an important role in controlling the immunopathogenic CD4 T cells during influenza infection. Our findings identify a novel pathway that controls the level of immune-pathogenic CD4 T cells during acute influenza infection. [ABSTRACT FROM AUTHOR]

Dendritic cells (DCs) competent to express the regulatory enzyme IDO in mice are a small but distinctive subset of DCs. Previously, we reported that a high-dose systemic CpG treatment to ligate TLR9 in vivo induced functional IDO exclusively in splenic CD19+ DCs, which stimulated resting Foxp3-lineage regulatory T cells (Tregs) to rapidly acquire potent suppressor activity. In this paper, we show that IDO was induced in spleen and peripheral lymph nodes after CpG treatment in a dose-dependent manner. Induced IDO suppressed local T cell responses to exogenous Ags and inhibited proinflammatory cytokine expression in response to TLR9 ligation. IDO induction did not occur in T cell-deficient mice or in mice with defective B7 or programmed death (PD)-1 costimulatory pathways. Consistent with these findings, CTLA4 or PD-1/PD-ligand costimulatory blockade abrogated IDO induction and prevented Treg activation via IDO following high-dose CpG treatment. Consequently, CD4+CD25+ T cells uniformly expressed IL-17 shortly after TLR9 ligation. These data support the hypothesis that constitutive interactions from activated T cells or Tregs and IDO-competent DCs via concomitant CTLA4→B7 and PD-1→PD-ligand signals maintain the default potential to regulate T cell responsiveness via IDO. Acute disruption of these nonredundant interactions abrogated regulation via IDO, providing novel perspectives on the proinflammatory effects of costimulatory blockade therapies. Moreover, interactions between IDO-competent DCs and activated T cells in lymphoid tissues may attenuate proinflammatory responses to adjuvants such as TLR ligands. [ABSTRACT FROM AUTHOR]

In TNF-treated cells, TNFR1, TNFR-associated death domain protein (TRADD), Fas-associated death domain protein, and receptor-interacting protein kinase proteins form the signaling complex via modular interaction within their C-terminal death domains. In this paper, we report that the death domain SXXE/D motifs (i.e., S381DHE motif of TNFR1-death domain as well as S215LKD and S296LAE motifs of TRADD-death domain) are phosphorylated, and this is required for stable TNFR1-TRADD complex formation and subsequent activation of NF-κB. Phospho-S215LKD and phospho-S296LAE motifs are also critical to TRADD for recruiting Fas-associated death domain protein and receptor-interacting protein kinase. I?B kinase β plays a critical role in TNFR1 phosphorylation of S381, which leads to subsequent T cell migration and accumulation. Consistently, we observed in inflammatory bowel disease specimens that TNFR1 was constitutively phosphorylated on S381 in those inflammatory T cells, which had accumulated in high numbers in the inflamed mucosa. Therefore, SXXE/D motifs found in the cytoplasmic domains of many TNFR family members and their adaptor proteins may serve to function as a specific interaction module for the α-helical death domain signal transduction. [ABSTRACT FROM AUTHOR]

TGF-β is required for both Foxp3+ regulatory T cell (Treg) and Th17 commitment. Plasmacytoid DCs (pDC) have been shown to participate to both Treg and Th17 commitment as well. However, few studies have evaluated the direct effect of TGF-β on pDC, and to our knowledge, no study has assessed the capacity of TGF-β-exposed pDC to polarize naive CD4+ T cells. In this paper, we show that TGF-β-treated pDC favor Th17 but not Treg commitment. This process involves a TGF-β/Smad signal, because TGF-β treatment induced Smad2 phosphorylation in pDC and blockade of TGF-β signaling with the SD208 TGF-βRI kinase inhibitor abrogated Th17 commitment induced by TGF-β-treated pDC. Moreover, TGF-β mRNA synthesis and active TGF-β release were induced in TGF-β-treated pDC and anti-TGF-β Ab blocked Th17 commitment. Unexpectedly, TGF-β treatment also induced increased IL-6 production by pDC, which serves as the other arm for Th17 commitment driven by TGF-β-exposed pDC, because elimination of IL-6-mediated signal with either IL-6- or IL-6Rα-specific Abs prevented Th17 commitment. The in vivo pathogenic role of TGF-β-treated pDC was further confirmed in the Th17-dependent collagen-induced arthritis model in which TGF-β-treated pDC injection significantly increased arthritis severity and pathogenic Th17 cell accumulation in the draining lymph nodes. Thus, our data reveal a previously unrecognized effect of TGF-β-rich environment on pDC ability to trigger Th17 commitment. Such findings have implications in the pathogenesis of autoimmune diseases or immune responses against mucosal extracellular pathogens. [ABSTRACT FROM AUTHOR]

Autoreactive CD8+ T lymphocytes play a key role in the pathogenesis of several autoimmune diseases. It is not yet well understood how autoreactive CD8+ T cells, which express TCRs with low reactivity toward self-Ags, gain the ability to respond to autoantigens to cause disease. Previously, we have shown that prior stimulation of CD8+ T cells with synergistic combinations of cytokines produced by the innate immune response, such as IL-21 and IL-15, induces Ag-independent proliferation. Such "cytokine-primed" CD8 T cells displayed increased responsiveness to limiting quantities of the cognate Ag. In this paper, we report that prior stimulation with IL-15 and IL-21 also enables CD8+ T cells to respond to weakly agonistic TCR ligands, resulting in proliferation, cytokine secretion, and cytolytic activity. Using a transgenic mouse model of autoimmune diabetes, we show that cytokine-primed autoreactive CD8+ T cells induce disease following stimulation by weak TCR ligands, but their diabetogenic potential is dependent on continuous availability of IL-15 in vivo. These findings suggest that inflammatory cytokines could facilitate the triggering of autoreactive CD8+ T cells by weak autoantigens, and this mechanism may have important implications for autoimmune diseases associated with microbial infections and chronic inflammation. [ABSTRACT FROM AUTHOR]

CD4 T cells are crucial effectors in the pathology of type 1 diabetes (T1D). Successful therapeutic interventions for prevention and cure of T1D in humans are still elusive. Recent research efforts have focused on the manipulation of T cells by treatment with DNA. In this paper, we studied the effects of a DNA treatment strategy designed to target antigenic peptides to the lysosomal compartment on a monospecific T cell population termed 2.5mi+ T cells that shares reactivity with the diabetogenic T cell clone BDC-2.5 in the NOD mouse. MHC class II tetramer analysis showed that repeated administrations were necessary to expand 2.5mi+ T cells in vivo. This expansion was independent of Ag presentation by B cells. A single peptide epitope was sufficient to induce protection against T1D, which was not due to Ag-specific T cell anergy. Typical Th2 cytokines such as IL-10 or IL-4 were undetectable in 2.5mi+ T cells, arguing against a mechanism of immune deviation. Instead, the expanded 2.5mi+ T cell population produced IFN-γ similar to 2.5mi+ T cells from naive mice. Protection against T1D by DNA treatment was completely lost in NOD.CD28-/- mice which are largely deficient of natural regulatory T cells (Treg). Although Ag-specific Foxp3+ Treg did not expand in response to DNA treatment, diabetes onset was delayed in Treg-reconstituted and DNA-treated NOD.SCID mice. These observations provide evidence for a Treg-mediated protective mechanism that is independent of the expansion or de novo generation of Ag-specific Treg. [ABSTRACT FROM AUTHOR]

We previously described the NOD.c3c4 mouse, which is protected from type 1 diabetes (T1D) because of protective alleles at multiple insulin-dependent diabetes (Idd) genes, but develops autoimmune biliary disease (ABD) resembling primary biliary cirrhosis (PBC). In this paper, we characterize the NOD.ABD strain, which is genetically related to the NOD.c3c4 strain but develops both ABD and T1D. Histologically, NOD.ABD biliary disease is indistinguishable from that in NOD.c3c4 mice. The frequency of effector memory (CD44+CD62L-) and central memory (CD44+CD62L+) CD8 T cells is significantly increased in the intrahepatic lymphocyte fraction of NOD.ABD mice, and NOD.ABD CD8 T cells produce more IFN-γ and TNF-α, compared with controls. NOD.ABD splenocytes can transfer ABD and T1D to NOD.c3c4 scid mice, but only T1D to NOD scid mice, suggesting that the genetic origin of the target organ and/or its innate immune cells is critical to disease pathogenesis. The disease transfer model, importantly, shows that biliary duct damage (characteristic of PBC) and inflammation precede biliary epithelial cell proliferation. Unlike T1D where both CD4 and CD8 T cells are required for disease transfer, purified NOD.ABD CD8 T cells can transfer liver inflammation into NOD.c3c4 scid recipients, and disease transfer is ameliorated by cotransferring T regulatory cells. Unlike NOD.c3c4 mice, NOD.ABD mice do not develop anti-nuclear or anti-Smith autoantibodies; however, NOD.ABD mice do develop the antipyruvate dehydrogenase Abs typical of human PBC. The NOD.ABD strain is a model of immune dysregulation affecting two organ systems, most likely by mechanisms that do not completely coincide. [ABSTRACT FROM AUTHOR]

Overexpression of the T cell cytokine IL-22 is linked to the development of some chronic diseases, but little is known about IL-22 deficiency in humans. As demonstrated in this study, acne inversa (AI; also designated as Hidradenitis suppurativa) lesions show a relative deficiency of IL-22 and IL-20, but not of IL-17A, IL-26, IFN-γ, IL-24, or IL-1β. Moreover, AI lesions had reduced expression of membranous IL-22 and IL-20 receptors and increased expression of the natural IL-22 inhibitor, IL-22 binding protein. AI is a chronic inflammatory skin disease with prevalence up to 4% of the population and in which cutaneous bacterial persistence represents an important pathogenetic factor. Accordingly, we also found a relative deficiency of antimicrobial proteins (AMPs) in AI lesions and a positive correlation between lesional IL-22 and IL-20 versus AMP levels. IL-22, like its tissue cell downstream mediator IL-20, upregulated AMPs in reconstituted human epidermis and was critical for increased AMP levels under inflammatory conditions. The relative IL-22 deficiency in AI was not linked to lesional T cell numbers or Th22/Th1/Th17 subset markers and -inducing cytokines. However, IL-10 was highly expressed in AI lesions and correlated negatively with IL-22 expression. Moreover, IL-10 inhibited IL-22 but not IL-17 production in vitro. The IL-10 overexpression, in turn, was not associated with an elevated presence of regulatory T cells but with the enhanced presence of an IL-10-inducing cytokine. We conclude that IL-22 deficiency may contribute to the pathogenesis of certain chronic disorders as postulated in this paper for AI. [ABSTRACT FROM AUTHOR]

Certain virus infections depend on the presence of T cell help for the generation of primary CD8+ T cell responses. However, the mechanisms that render these particular viral infections T cell help dependent is largely unknown. In this study, we compared CD8+ T cell responses elicited by lymphocytic choriomeningitis virus infection, as prototype of a T cell help independent infection, with T cell help dependent CD8+ T cell responses induced by vaccinia virus infection. In this paper, we show that a key parameter decisive for T cell help independence is the ability of an infectious agent to stimulate early and robust production of type I IFN. Experimental provision of type I IFN during VV infection rendered the ensuing CD8+ T cell response completely T cell help independent. Our results support a model in which type I IFN has to be present during the first 3 d of Ag encounter and has to act directly on the responding CD8+ T cells to promote their survival and effector differentiation. We show that type I IFN signaling on responding CD8+ T cells induces profound upregulation of CD25 and increased IL-2 expression; however, neither this nor IL- 15 accounts for the type I IFN effects on responding CD8+ T cells. Thus, type I IFN can effectively replace the requirement of T cell help by directly promoting CD8+ T cell survival and differentiation independent of the type I IFN-induced cytokines IL-2 and IL-15. [ABSTRACT FROM AUTHOR]

A major obstacle to transplantation tolerance is humoral immunity. In this paper, we demonstrate that the intrinsic developmental propensity of the B lymphocyte compartment for acquisition of self-tolerance can be harnessed to induce humoral unresponsiveness to transplanted alloantigens. In the current study, when transitional B cells developed in the presence of donor lymphoid cells, the mature B lymphocyte compartment failed to mount a donor-specific alloantibody response to an organ transplant-despite unrestrained acute T cell-mediated allograft rejection. Specifically, we generated an experimental system wherein a B6 strain B cell compartment developed de novo in the presence of F1 (B6xBALB/c) lymphoid cells and in a T cell-deficient setting. Following establishment of a steady-state B cell compartment, these B6 mice were transplanted with heterotopic cardiac allografts from allogeneic BALB/c donors. The mice were then inoculated with purified syngeneic B6 T cells. As expected, all cardiac allografts were acutely rejected. However, the B lymphocyte compartment of these mice was completely inert in its capacity to form a BALB/c-specific alloantibody response. Using an alloantigen-specific Ig transgenic system, we demonstrated that this profound degree of humoral tolerance was caused by clonal deletion of alloreactive specificities from the primary B cell repertoire. Thus, de novo B cell compartment development at the time of transplantation is of critical importance in recipient repertoire "remodeling" to a humoral tolerant state. [ABSTRACT FROM AUTHOR]

The cytokines generated locally in response to infection play an important role in CD8 T cell trafficking, survival, and effector function, rendering these signals prime candidates for immune intervention. In this paper, we show that localized increases in the homeostatic cytokine IL-15 induced by influenza infection is responsible for the migration of CD8 effector T cells to the site of infection. Moreover, intranasal delivery of IL-15-IL-15Rα soluble complexes (IL-15c) specifically restores the frequency of effector T cells lost in the lung airways of IL-15-deficient animals after influenza infection. Exogenous IL-15c quantitatively augments the respiratory CD8 T cell response, and continued administration of IL-15c throughout the contraction phase of the anti-influenza CD8 T cell response magnifies the resultant CD8 T cell memory generated in situ. This treatment extends the ability of these cells to protect against heterologous infection, immunity that typically depreciates over time. Overall, our studies describe what to our knowledge is a new function for IL-15 in attracting effector CD8 T cells to the lung airways and suggest that adjuvanting IL-15 could be used to prolong anti-influenza CD8 T cell responses at mucosal surfaces to facilitate pathogen elimination. [ABSTRACT FROM AUTHOR]

We identified CD8+CD122+ regulatory T cells (Tregs) and demonstrated their importance in the maintenance of immune homeostasis and in the recovery from experimental autoimmune encephalomyelitis. In this paper, we show that CD8+CD122+ Tregs effectively prevent and cure colitis in a mouse model. In our experiments, colitis was induced in lymphocyte-deficient RAG-2-/- mice by transferring CD4+CD45RBhigh cells that were excluded with CD4+ Tregs. Cotransfer of CD8+CD122+ cells clearly suppressed the development of colitis, and this suppressive effect was similar to that of CD4+CD45RBlow cells that were mostly CD4+ Tregs. CD8+CD122+ cells obtained from IL-10-/- mice were unable to suppress colitis, indicating that IL-10 is an important effect-transmitting factor in the suppression of colitis. CD8+CD122+ cells showed a suppressive effect when they were transferred 4 wk after CD4+CD45RBhigh cells, indicating the therapeutic potential of CD8+CD122+ cells. A mixture of CD8+CD122+ cells and CD4+CD45RBlow cells was far more effective than single Tregs, indicating the synergistic effect of these Tregs. These overall findings demonstrate the potential role of CD8+ Tregs, and possibly together with CD4+ Tregs, in the medical care of inflammatory bowel disease patients. [ABSTRACT FROM AUTHOR]

The article offers information on several papers on immunology that was published in the year 1980 and 1989. Topics discussed include the generation of muromonab CD-3 (OKT3) monoclonal antibodies (mAb) to the human T cells and CD3, the characterization of monoclonal antibodies to the murine T-cell receptorβ-chain (TCR β-chain), and the immunoglobulin (Ig)-binding properties of streptavidin and protein A.

An introduction to the journal is presented which discusses various papers published within the issue, including one on the efficacy of prestimulated polyclonal regulatory T cells (Treg) using a mouse model of uveitis, one on the herpes simplex virus/varicella zoster virus (HSV/VSV) cross-reactive T cell population, and another on effect of vitamin C on the epigenetic regulation of Treg subsets.

The article reports on findings of two research papers including one on T lymphocyte with restricted antigen receptor diversity by Masaru Taniguchi & others, and another on human cells by Steven Balk & colleagues. Topics include the effects of invariant natural killer T cells on immune system, use of denaturing gel electrophoresis, polymerase chain reaction, and cloning for sequencing two invariant T-cell receptor (TCR) rearrangements & discovery of lymphocytes with restricted TCR diversity.