Protein translocation and retro-translocation across the endoplasmic reticulum are crucial to inflammatory effector CD4(+) T cell function

Effector CD4(+) T cells can be classified by the cytokines they secrete, with T helper 1 (Th1) cells generating interferon (IFN)gamma and Th17 cells secreting interleukin (IL)-17. Both Th1 and Th17 cells are strongly implicated in the initiation and chronicity of autoimmune diseases such as multiple sclerosis. The endoplasmic reticulum (ER) has been implicated as a potentially crucial site in regulating CD4(+) T cell function. Secretory and transmembrane proteins are shuttled into the ER via the Sec61 translocon, where they undergo appropriate folding; misfolded proteins are retro-translocated from the ER in a p97-dependent manner. Here, we provide evidence that both processes are crucial to the secretion of inflammatory cytokines from effector CD4(+) T cells. The pan-ER inhibitor eeeyarestatin-1 (ESI), which interferes with both Sec61 translocation and p97 retro-translocation, inhibited secretion of interferon (IFN)gamma, interleukin (IL)-2 and tumor necrosis factor (TNF)alpha from Th1 cells in a dose-dependent manner. Selective inhibition of Sec61 by Apratoxin A (ApraA) revealed that ER translocation is crucial for Th1 cytokine secretion, while inhibition of p97 by NMS-873 also inhibited Th1 function, albeit to a lesser degree. By contrast, none of ESI, ApraA or NMS-873 could significantly reduce IL-17 secretion from Th17 cells. ApraA, but not NMS-873, reduced phosphorylation ApraA had modest effects on activation of the Th17 transcription factor Stat3, while NMS-873 had no effect. Interestingly, NMS-873 was able to reduce disease severity in CD4(+) T cell-driven experimental autoimmune encephalomyelitis (EAE). Together, our data indicate that CD4(+) T cell function, and Th1 cell function in particular, is dependent on protein translocation and dislocation across the ER.Peer reviewe

T-bet negatively regulates autoimmune myocarditis by suppressing local production of interleukin 17

Experimental autoimmune myocarditis (EAM) appears after infectious heart disease, the most common cause of dilated cardiomyopathy in humans. Here we report that mice lacking T-bet, a T-box transcription factor required for T helper (Th)1 cell differentiation and interferon (IFN)-γ production, develop severe autoimmune heart disease compared to T-bet−/− control mice. Experiments in T-bet−/− IL-4−/− and T-bet−/− IL-4Rα−/− mice, as well as transfer of heart-specific Th1 and Th2 cell lines, showed that autoimmune heart disease develops independently of Th1 or Th2 polarization. Analysis of T-bet−/− IL-12Rβ1−/− and T-bet−/− IL-12p35−/− mice then identified interleukin (IL)-23 as critical for EAM pathogenesis. In addition, T-bet−/− mice showed a marked increase in production of the IL-23–dependent cytokine IL-17 by heart-infiltrating lymphocytes, and in vivo IL-17 depletion markedly reduced EAM severity in T-bet−/− mice. Heart-infiltrating T-bet−/− CD8+ but not CD8− T cells secrete IFN-γ, which inhibits IL-17 production and protects against severe EAM. In contrast, T-bet−/− CD8+ lymphocytes completely lost their capacity to release IFN-γ within the heart. Collectively, these data show that severe IL-17–mediated EAM can develop in the absence of T-bet, and that T-bet can regulate autoimmunity via the control of nonspecific CD8+ T cell bystander functions in the inflamed target organ

Spontaneous tumor rejection by cbl-b–deficient CD8+ T cells

The concept of tumor surveillance implies that specific and nonspecific components of the immune system eliminate tumors in the early phase of malignancy. Understanding the biochemical mechanisms of tumor immunosurveillance is of paramount significance because it might allow one to specifically modulate spontaneous antitumor activity. We report that inactivation of the E3 ligase Casitas B cell lymphoma-b (Cbl-b) confers spontaneous in vivo rejection of tumor cells that express human papilloma virus antigens. Moreover, cbl-b−/− mice develop significantly fewer ultraviolet B (UVB)–induced skin malignancies and reject UVB-induced skin tumors. CD8+ T cells were identified as key players in the spontaneous tumor rejection response. Loss of Cbl-b not only enhances antitumor reactivity of CD8+ T cells but also occurs in the absence of CD4+ T cells. Mechanistically, cbl-b−/− CD8+ T cells are resistant to T regulatory cell–mediated suppression and exhibit enhanced activation and rapid tumor infiltration. Importantly, therapeutic transfer of naive cbl-b−/− CD8+ T cells is sufficient to mediate rejection of established tumors. Even up to 1 yr after the first encounter with the tumor cells, cbl-b−/− mice carry an “anticancer memory.” These data identify Cbl-b as a key signaling molecule that controls spontaneous antitumor activity of cytotoxic T cells in different cancer models. Inhibition of Cbl-b is a novel approach to stimulate long-lasting immunity against cancer

A Crucial Role for Kupffer Cell-Derived Galectin-9 in Regulation of T Cell Immunity in Hepatitis C Infection

Approximately 200 million people throughout the world are infected with hepatitis C virus (HCV). One of the most striking features of HCV infection is its high propensity to establish persistence (∼70–80%) and progressive liver injury. Galectins are evolutionarily conserved glycan-binding proteins with diverse roles in innate and adaptive immune responses. Here, we demonstrate that galectin-9, the natural ligand for the T cell immunoglobulin domain and mucin domain protein 3 (Tim-3), circulates at very high levels in the serum and its hepatic expression (particularly on Kupffer cells) is significantly increased in patients with chronic HCV as compared to normal controls. Galectin-9 production from monocytes and macrophages is induced by IFN-γ, which has been shown to be elevated in chronic HCV infection. In turn, galectin-9 induces pro-inflammatory cytokines in liver-derived and peripheral mononuclear cells; galectin-9 also induces anti-inflammatory cytokines from peripheral but not hepatic mononuclear cells. Galectin-9 results in expansion of CD4+CD25+FoxP3+CD127low regulatory T cells, contraction of CD4+ effector T cells, and apoptosis of HCV-specific CTLs. In conclusion, galectin-9 production by Kupffer cells links the innate and adaptive immune response, providing a potential novel immunotherapeutic target in this common viral infection

Lymphocytes in MS and EAE: More than just a CD4+ World

Multiple sclerosis is degenerative disease of the central nervous system (CNS) in which myelin destruction and axon loss leads to the accumulation of physical, cognitive, and mental deficits. MS affects more than a million people worldwide and managing this chronic disease presents a significant health challenge. Multiple lines of evidence indicate that MS is an autoimmune disorder in which immune cells launch an inflammatory attack targeting myelin antigens. Indeed, myelin-reactive T cells and antibodies have been identified in MS patients and in animal models (namely experimental autoimmune encephalomyelitis, or EAE) that recapitulate many features of human disease. Animal model studies have demonstrated that T cells are both necessary and sufficient to initiate and sustain CNS autoimmunity. However, most MS animal models rely on the role played by CD4+ T cells and partially replicate the multiple aspects of MS pathogenesis. Thus, research in the past has focused heavily on the contribution of CD4+ T cells to the disease process; searching PubMed for “MS AND CD4” yields twice the results as corresponding searches for “CD8” or “B cell” and four times that for “NK cells”. While CD4+ T cells may represent the minimum requirement to mediate CNS autoimmunity, it is clear that the immune response underlying human MS is far more complex and involves numerous other immune cells and subsets. This is well illustrated by the observation that MS patients treated with an anti-CD4 depleting antibody did not gain any clinical benefits whereas removal of several lymphocyte subsets using an anti-CD52 depleting antibody has been shown to impede disease progression. In particular, the pathogenic role(s) of non-CD4+ T cell lymphocytes is relatively poorly understood and under-researched, despite evidence that these subsets contribute to disease pathology or regulation. For example, the observed oligoclonal expansion of CD8+ T cells within the CNS compartment supports a local activation. CD8+ T cells with polarized cytolytic granules are seen in close proximity to oligodendrocytes and demyelinated axons in MS tissues. The presence of B cells in inflammatory lesions and antibodies in the CSF have long been recognized as features of MS and Rituximab, a B cell depleting therapy, has been shown to be highly effective to treat MS. Intriguingly, the putative MS therapeutic reagent Daclizumab may function in part through the expansion of a subset of immunoregulatory NK cells. NKT and ?d T cells may also play a role in CNS autoimmunity, given that they respond to lipid antigens and that myelin is lipid-rich. While different animal models recapitulate some of these aspects of human disease, identifying appropriate models and measures to investigate the role of these less well-understood lymphocytes in MS remains a challenge for the field. This Frontiers research topic aims to create a platform for both animal- and human-focused researchers to share their original data, hypotheses, future perspectives and commentaries regarding the role of these less-well understood lymphocyte subsets (CD8+ T cells, B cells, NK cells, NK T cells, ?d T cells) in the pathogenesis of CNS autoimmunity

The X-linked histone demethylases KDM5C and KDM6A as regulators of T cell-driven autoimmunity in the central nervous system

T cell-driven autoimmune responses are subject to striking sex-dependent effects. While the contributions of sex hormones are well-understood, those of sex chromosomes are meeting with increased appreciation. Here, we outline what is known about the contribution of sex chromosome-linked factors to experimental autoimmune encephalomyelitis (EAE), a mouse model that recapitulates many of the T cell-driven mechanisms of multiple sclerosis (MS) pathology. Particular attention is paid to the KDM family of histone demethylases, several of which – KDM5C, KDM5D and KDM6A – are sex chromosome encoded. Finally, we provide evidence that functional inhibition of KDM5 molecules can suppress interferon (IFN)γ production from murine male effector T cells, and that an increased ratio of inflammatory Kdm6a to immunomodulatory Kdm5c transcript is observed in T helper 17 (Th17) cells from women with the autoimmune disorder ankylosing spondylitis (AS). Histone lysine demethlyases thus represent intriguing targets for the treatment of T cell-driven autoimmune disorders

Cholesterol and markers of cholesterol turnover in multiple sclerosis: Relationship with disease outcomes

Multiple sclerosis (MS) is a chronic central nervous system disease that is associated with progressive loss of myelin and subsequent axonal degeneration. Cholesterol is an essential component of mammalian cellular and myelin membranes. In this systematic review, we examined the relationship between levels of cholesterol and markers of cholesterol turnover in circulation and/or cerebrospinal fluid (CSF) and disease outcomes in adults with clinically isolated syndrome (CIS) or confirmed MS. Studies suggest that elevated levels of circulating low density lipoprotein cholesterol (LDL), total cholesterol, and particularly, apolipoprotein B and oxidized LDL are associated with adverse clinical and MRI outcomes in MS. These relationships were observed as early as CIS. The studies also suggest that oxysterols, cholesterol precursors, and apolipoprotein E may be markers of specific disease processes in MS, but more research is required to elucidate these processes and relationships. Taken together, the data indicate that cholesterol and markers of cholesterol turnover have potential to be used clinically as biomarkers of disease activity and may even be implicated in the pathogenesis of MS

Interferon-β suppresses murine Th1 cell function in the absence of antigen-presenting cells.

Interferon (IFN)-β is a front-line therapy for the treatment of the relapsing-remitting form of multiple sclerosis. However, its immunosuppressive mechanism of function remains incompletely understood. While it has been proposed that IFN-β suppresses the function of inflammatory myelin antigen-reactive T cells by promoting the release of immunomodulatory cytokines such as IL-27 from antigen-presenting cells (APCs), its direct effects on inflammatory CD4+ Th1 cells are less clear. Here, we establish that IFN-β inhibits mouse IFN-γ+ Th1 cell function in the absence of APCs. CD4+ T cells express the type I interferon receptor, and IFN-β can suppress Th1 cell proliferation under APC-free stimulation conditions. IFN-β-treated myelin antigen-specific Th1 cells are impaired in their ability to induce severe experimental autoimmune encephalomyelitis (EAE) upon transfer to lymphocyte-deficient Rag1-/- mice. Polarized Th1 cells downregulate IFN-γ and IL-2, and upregulate the negative regulatory receptor Tim-3, when treated with IFN-β in the absence of APCs. Further, IFN-β treatment of Th1 cells upregulates phosphorylation of Stat1, and downregulates phosphorylation of Stat4. Our data indicate that IFN-γ-producing Th1 cells are directly responsive to IFN-β and point to a novel mechanism of IFN-β-mediated T cell suppression that is independent of APC-derived signals

IFN-β suppresses Th1 cell proliferation.

<p>A. WT CD4⁺CD62L^hi T cells were labeled with CFSE and stimulated for 5 days with either soluble anti-CD3 plus irradiated splenocytes (APCs), or with plate-bound anti-CD3+anti-CD28, under Th1 or Th17 conditions, with the indicated concentrations of IFN-β. CFSE dilution was assessed by flow cytometry. Data representative of three experiments. B. WT or <i>IFNAR1-/-</i> CD4⁺CD62L^hi T cells were labeled with CFSE and stimulated with plate-bound anti-CD3+anti-CD28 under Th1 conditions with the indicated concentrations of IFN-β for 5 days. CFSE dilution was assessed by flow cytometry. Data representative of two experiments. Gates represent the percentage of cells that underwent at least one division.</p

IFN-β regulates Stat1 and Stat4 expression on Th cells in the absence of APCs.

<p>CD4⁺CD62L^hiCD25^- T cells were sorted from the spleens and lymph nodes of C57BL6/J mice. They were stimulated with plate-bound anti-CD3+anti-CD28 under Th1 or Th17 conditions, with the indicated concentrations of IFN-β, for 48 hours, and cell lysates were generated. A. Expression of Stat1 and pStat1(Y701) were assessed by Western blot. Representative of two experiments. B. Expression of Stat4 and pStat4(Y693) were assessed by Western blot. Representative of three experiments. GAPDH, loading control.</p