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Summary: Interleukin‐22 (IL‐22) is a potential therapeutic agent for diseases driven by epithelial injury. To characterize the IL‐22 expressed by rhesus macaques, animals that are irreplaceable for human disease research, rhesus macaque IL‐22 (rhIL‐22) was cloned and expressed, and its biological activity and in vivo distribution were examined. It was found that the rhIL‐22 gene consists of five introns and six exons, including a short non‐coding exon starting 22 bp downstream of a putative TATA box. The amino acid sequence of rhIL‐22 showed 95·5% identity to that of humans, and it shared two conserved disulphide bonds, three N‐glycosylation sites and all the critical residues for binding to IL‐22R1. High levels of IL‐22 mRNA were observed in the liver, pancreas, lymphoid tissues and especially in the outer‐body barriers such as the intestinal tract of rhesus macaques. Functionally, purified rhIL‐22 has a similar but a little earlier effect on signal transducer and activator of transcription 3 phosphorylation at Tyr705 compared with that of commercial human IL‐22. The expression of the antibacterial proteins β‐defensin‐2, S100A8, S100A9, RegIIIα and Muc1 by HT‐29 cells was largely upregulated after stimulation with rhIL‐22. Recombinant rhIL‐22 could also significantly promote the proliferation of human intestinal epithelial cells without affecting cell apoptosis. These data indicate that rhesus macaque IL‐22 is highly similar to that of humans in both structure and function, and tests of therapeutic effects of human IL‐22 on human diseases in rhesus macaques are warranted. [ABSTRACT FROM AUTHOR]

Thalidomide (TM) has been reported to have anti-cancer and antiinflammatory properties, and dexamethasone (DX) is known to reduce inflammation and inhibit production of inflammatory cytokines. Many studies have reported that combinatorial therapy with TM and DX is clinically used to treat multiple myeloma and lupus nephritis, but the mechanism responsible for its effects has not been elucidated. In this study, we determined that TM and DX co-treatment had an enhanced immunemodulatory effect on T cells through regulating the expression of co-stimulatory molecules. Splenic naive T cells from C57BL/6 mice were sort-purified and cultured for CD4+ T cell proliferation and regulatory T (Treg) cell conversion in the presence of TM and/or DX. Following incubation with the drugs, cells were collected and OX40, 4-1BB, and glucocorticoid- induced tumour necrosis factor receptor-related protein (GITR) expression was quantified by flow cytometry. TM (1 or 10 µM) decreased CD4+ T cell proliferation in a dose-dependent manner, whereas TM/DX (0.1 or 1 nM) co-treatment further decreased proliferation. Treg cell populations were preserved following drug treatment. Furthermore, expression of co-stimulatory molecules decreased upon TM/DX co-treatment in effector T (Teff) cells and was preserved in Treg cells. Splenic CD4+ T cells isolated from TM- and DX-treated mice exhibited the same patterns of Teff and Treg cell populations as observed in vitro. Considering the selective effect of TM on different T cell subsets, we suggest that TM may play an immunomodulatory role and that TM/DX combinatorial treatment could further enhance these immunomodulatory effects by regulating GITR, OX40, and 4-1BB expression in CD4+ T cells. [ABSTRACT FROM AUTHOR]

CD4 T cells help immune responses, but knowledge of how memory CD4 T cells are regulated and how they regulate adaptive immune responses and induce immunopathology is limited. Using adoptive transfer of virus-specific CD4 T cells, we show that naive CD4 T cells undergo substantial expansion following infection, but can induce lethal T helper type 1-driven inflammation. In contrast, memory CD4 T cells exhibit a biased proliferation of T follicular helper cell subsets and were able to improve adaptive immune responses in the context of minimal tissue damage. Our analyses revealed that type I interferon regulates the expansion of primary CD4 T cells, but does not seem to play a critical role in regulating the expansion of secondary CD4 T cells. Strikingly, blockade of type I interferon abrogated lethal inflammation by primary CD4 T cells following viral infection, despite that this treatment increased the numbers of primary CD4 T-cell responses. Altogether, these data demonstrate important aspects of how primary and secondary CD4 T cells are regulated in vivo, and how they contribute to immune protection and immunopathology. These findings are important for rational vaccine design and for improving adoptive T-cell therapies against persistent antigens. [ABSTRACT FROM AUTHOR]

Mycobacterium tuberculosis inhibits optimal T helper type 1 (Th1) responses during infection. However, the precise mechanisms by which virulent M. tuberculosis limits Th1 responses remain unclear. Here, we infected dendritic cells ( DCs) with the virulent M. tuberculosis strain H37Rv or the attenuated strain H37Ra to investigate the phenotypic and functional alterations in DCs and resultant T-cell responses. H37Rv-infected DCs suppressed Th1 responses more strongly than H37Ra-infected DCs. Interestingly, H37Rv, but not H37Ra, impaired DC surface molecule expression ( CD80, CD86 and MHC class II) due to prominent interleukin-10 ( IL-10) production while augmenting the expression of tolerogenic molecules including PD-L1, CD103, Tim-3 and indoleamine 2,3-dioxygenase on DCs in a multiplicity-of-infection (MOI) -dependent manner. These results indicate that virulent M. tuberculosis drives immature DCs toward a tolerogenic phenotype. Notably, the tolerogenic phenotype of H37Rv-infected DCs was blocked in DCs generated from IL-10−/− mice or DCs treated with an IL-10-neutralizing monoclonal antibody, leading to restoration of Th1 polarization. These findings suggest that IL-10 induces a tolerogenic DC phenotype. Interestingly, p38 mitogen-activated protein kinase ( MAPK) activation predominantly mediates IL-10 production; hence, H37Rv tends to induce a tolerogenic DC phenotype through expression of tolerogenic molecules in the p38 MAPK- IL-10 axis. Therefore, suppressing the tolerogenic cascade in DCs is a novel strategy for stimulating optimal protective T-cell responses against M. tuberculosis infection. [ABSTRACT FROM AUTHOR]

Co-receptors, being either co-stimulatory or co-inhibitory, play a pivotal role in T-cell immunity. Several studies have indicated that CD43, one of the abundant T-cell surface glycoproteins, acts not only as a potent co-receptor but also as a negative regulator for T-cell activation. Here we demonstrate that co-stimulation of human peripheral blood (PB) T cells through two distinct CD43 epitopes recognized by monoclonal antibodies (mAb) CD43-6E5 (T6E5-act) and CD43-10G7 (T10G7-act) potently induced T-cell proliferation. However, T-cell co-stimulation through two CD43 epitopes differentially regulated activation of nuclear factor of activated T cells (NFAT) and nuclear factor- κB (NF- κB) transcription factors, T-cell cytokine production and effector function. T6E5-act produced high levels of interleukin-22 (IL-22) and interferon- γ (IFN- γ) similar to T cells activated via CD28 ( TCD28-act), whereas T10G7-act produced low levels of inflammatory cytokines but higher levels of regulatory cytokines transforming growth factor- β (TGF- β) and interleukin-35 (IL-35). Compared with T6E5-act or to TCD28-act, T10G7-act performed poorly in response to re-stimulation and further acquired a T-cell suppressive function. T10G7-act did not directly inhibit proliferation of responder T cells, but formed stable heterotypic clusters with dendritic cells (DC) via CD2 to constrain activation of responder T cells. Together, our data demonstrate that CD43 is a unique and polarizing regulator of T-cell function. [ABSTRACT FROM AUTHOR]

Proliferation of rapidly dividing bone marrow-derived cells is strongly dependent on the availability of free glutamine, whose uptake is mediated through different amino acid transporters. The sodium-coupled neutral amino acid transporter (SNAT) family was previously reported to be associated with the development of collagen-induced arthritis in mice. Here, we tested the hypothesis whether impairment of SNAT proteins influences immune cell function and in turn alters arthritis development. The 2-(methylamino)isobutyric acid (MeAIB), a SNAT-specific substrate, was used to modulate the function of SNAT proteins. We demonstrate that glutamine uptake by murine naive lymphocytes, and consequent cell proliferation, is strongly associated with system A transporters. Physiological impairment of SNAT proteins reduced the antibody-initiated effector phase of arthritis, mainly by affecting the levels of circulating monocytes and neutrophils. MeAIB was also shown to affect the proliferation of immortalized cells, through trans-inhibition of SNAT proteins. Based on our observations, we conclude that SNAT proteins regulate the initial stages of lymphocyte activation by regulating glutamine uptake, and that the effector phase of arthritis can be affected by non-metabolized SNAT substrates. Most probably, metabolically active cells within both the adaptive and the innate immune systems are regulated by SNAT proteins and play a role in modifying arthritis development. [ABSTRACT FROM AUTHOR]

CD8 T cells used in adoptive immunotherapy may be manipulated to optimize their effector functions, tissue-migratory properties and long-term replicative potential. We reported that antigen-stimulated CD8 T cells transduced to express an active form of the transcription factor signal transducer and activator of transcription 5 ( STAT5 CA) maintained these properties upon adoptive transfer. We now report on the requirements of STAT5 CA-expressing CD8 T cells for cell survival and proliferation in vivo. We show that STAT5 CA expression allows for greater expansion of T cells in vivo, while preserving dependency on T-cell-receptor-mediated tonic stimulation for their in vivo maintenance and return to a quiescent stage. STAT5 CA expression promotes the formation of a large pool of effector memory T cells that respond upon re-exposure to antigen and present an increased sensitivity to γc receptor cytokine engagement for STAT5 phosphorylation. In addition, STAT5 CA expression prolongs the survival of what would otherwise be short-lived terminally differentiated KLRG1-positive effector cells with up-regulated expression of the senescence-associated p16 INK4A transcripts. However, development of a KLRG1-positive CD8 T cell population was independent of either p16 INK4A or p19 ARF expression (as shown using T cells from CDKN2A−/− mice) but was associated with expression of transcripts encoding p15 INK4B, another protein involved in senescence induction. We conclude that T-cell-receptor- and cytokine-dependent regulation of effector T cell homeostasis, as well as mechanisms leading to senescent features of a population of CD8 T cells are maintained in STAT5 CA-expressing CD8 T cells, even for cells that are genetically deficient in expression of the tumour suppressors p16 INK4A and p19 ARF. [ABSTRACT FROM AUTHOR]

Basophils are known to modulate the phenotype of CD4+ T cells and to enhance T helper type 2 responses in vitro and in vivo. In this study, we demonstrate that murine basophils inhibit proliferation of CD4+ T cells in autologous and allogeneic mixed lymphocyte reactions. The inhibition is independent of Fas and MHC class II, but dependent on activation of basophils with subsequent release of interleukin-4 ( IL-4) and IL-6. The inhibitory effect of basophils on T-cell proliferation can be blocked with antibodies against IL-4 and IL-6 and is absent in IL-4/ IL-6 double-deficient mice. In addition, we show that basophils and IL-4 have beneficial effects on disease activity in a murine model of acute graft-versus-host disease (Gv HD). When basophils were depleted with the antibody MAR-1 before induction of Gv HD, weight loss, Gv HD score, mortality and plasma tumour necrosis factor levels were increased while injection of IL-4 improved Gv HD. Basophil-depleted mice with Gv HD also have increased numbers of CD4+ T cells in the mesenteric lymph nodes. Our data show for the first time that basophils suppress autologous and allogeneic CD4+ T-cell proliferation in an IL-4-dependent manner. [ABSTRACT FROM AUTHOR]

Myeloid dendritic cells ( mDC) are key mediators of innate and adaptive immunity to virus infection, but the impact of HIV infection on the m DC response, particularly early in acute infection, is ill-defined. We studied acute pathogenic simian immunodeficiency virus ( SIV) infection of rhesus macaques to address this question. The m DC in blood and bone marrow were depleted within 12 days of intravenous infection with SIVmac251, associated with a marked proliferative response. In lymph nodes, m DC were apoptotic, activated and proliferating, despite normal m DC numbers, reflecting a regenerative response that compensated for m DC loss. Blood m DC had increased expression of MHC class II, CCR7 and CD40, whereas in lymph nodes these markers were significantly decreased, indicating that acute infection induced maturation of m DC in blood but resulted in accumulation of immature m DC in lymph nodes. Following SIV infection, lymph node m DC had an increased capacity to secrete tumour necrosis factor- α upon engagement with a Toll-like receptor 7/8 ligand that mimics exposure to viral RNA, and this was inversely correlated with MHC class II and CCR7 expression. Lymph node m DC had an increased ability to capture and cleave soluble antigen, confirming their functionally immature state. These data indicate that acute SIV infection results in increased m DC turnover, leading to accumulation in lymph nodes of immature m DC with an increased responsiveness to virus stimulation. [ABSTRACT FROM AUTHOR]