Abstract SJL mice immunized with proteolipid protein (PLP) 139-151 show a gender disparity in the development of autoimmune encephalomyelitis in that only females show a chronic relapsing-remitting type of paralysis, but their underlying mechanisms are unknown. We tested the hypothesis that sex steroids differentially regulate the expansion of autoreactive T cells. To this end, we have established an in vitro system to determine the effects of sex steroids on the expansion and functions of antigen-specific T cells based on proliferation assay, major histocompatibility complex class II dextramer staining, cytokine analysis and cell viability assays. Regardless of gender, we noted that the T cell responses to PLP 139-151 were significantly lower in cells exposed to either testosterone or estradiol as compared to vehicle-treated cultures, but the threshold for hormone-sensitivity is two-fold higher in males than females. Importantly, the reduced proliferative responses were found not to be due to hormonal inhibition, rather, the hormones promoted cell death. Conversely, while, the hormones reduced the number of interferon-gamma-producing cells in both the genders, interleukin (IL)-17-producing cells were reduced only in females; whereas other cytokines, such as IL-2, IL-4, IL-10, and IL-22 remained unaltered. Taken together, the data suggest that the immunomodulatory effects of sex steroids involve multiple pathways, and cell death may be the primary underlying mechanism.
Myelin proteolipid protein (PLP) 139–151 is an immunodominant peptide that induces experimental autoimmune encephalomyelitis (EAE) in H-2s SJL/J mice. While PLP 139–151-specific TCR transgenic (tg) 4E3 mice develop fulminant spontaneous disease on the susceptible SJL/J background, spontaneous EAE is dramatically reduced on the H-2s congenic B10.S background. On this resistant background, we observed a high frequency of positively selected tg CD4−CD8− (DN) thymocytes and peripheral DN tg T cells. Splenic DN tg T cells responded to anti-CD3 stimulation similarly to CD4+ cells, but proliferative and cytokine responses to PLP 139–151 were blunted, implying that CD4 co-receptor down-regulation modulated T cell responses to the self-antigen in vitro. Adoptive transfer of tg DN CD3hi cells into RAG-deficient wild-type (WT) recipients induced EAE less efficiently than transfer of CD4+ T tg cells indicating the blunted responses of DN tg T cells to self-antigen in vivo. The frequency of tg DN T cells was irrespective of thymic expression of the autoantigen. These data implicate that down-regulation of CD4 co-receptor in the thymus, which is independent from the expression of thymic autoantigen, results in a blunted response to the autoantigen in the periphery and limits the incidence of spontaneous autoimmunity in genetically resistant mice bearing a large autoreactive tg T cell repertoire.
Myocarditis/dilated cardiomyopathy (DCM) patients can develop autoantibodies to various cardiac antigens and one major antigen is β1-adrenergic receptor (β1AR). Previous reports indicate that animals immunized with a β1AR fragment encompassing, 197-222 amino acids for a prolonged period can develop DCM by producing autoantibodies, but existence of T cell epitopes, if any, were unknown. Using A/J mice that are highly susceptible to lymphocytic myocarditis, we have identified β1AR 171-190, β1AR 181-200, and β1AR 211-230 as the major T cell epitopes that bind major histocompatibility complex class II/IAk or IEk alleles, and by creating IAk and IEk dextramers, we demonstrate that the CD4 T cell responses to be antigen-specific. Of note, all the three epitopes were found also to stimulate CD8 T cells suggesting that they can act as common epitopes for both CD4 and CD8 T cells. While, all epitopes induced only mild myocarditis, the disease-incidence was enhanced in animals immunized with all the three peptides together as a cocktail. Although, antigen-sensitized T cells produced mainly interleukin-17A, their transfer into naive animals yielded no disease. But, steering for T helper 1 response led the T cells reacting to one epitope, β1AR 181-200 to induce severe myocarditis in naive mice. Finally, we demonstrate that all three β1AR epitopes to be unique for T cells as none of them induced antibody responses. Conversely, animals immunized with a non-T cell activator, β1AR 201-220, an equivalent of β1AR 197-222, had antibodies comprising of all IgG isotypes and IgM except, IgA and IgE. Thus, identification of T cell and B cell epitopes of β1AR may be helpful to determine β1AR-reactive autoimmune responses in various experimental settings in A/J mice.
Abstract Female B10.S mice are highly resistant to proteolipid protein (PLP) 139–151-induced experimental autoimmune encephalomyelitis (EAE) and depletion of PLP 139–151-reactive CD4+CD25+ regulatory T (Treg) cells can slightly increase their EAE susceptibility. Although male B10.S mice are moderately susceptible to EAE, we report that depletion of Treg cells in male B10.S mice before immunization with PLP 139–151 renders them highly susceptible to severe EAE with more CNS neutrophil infiltrates than nondepleted controls. Increased susceptibility is associated with an enhanced PLP 139–151-specific T cell response and greater production of IFN-γ, IL-6, and IL-17. Male CD4+CD25− effector cells depleted of Treg cells proliferate to a greater degree than those from females in response to either anti-CD3 or PLP 139–151. These data suggest that because of their capacity to regulate potent autoaggressive effector cells, Treg cells partly contribute to the resistance to autoimmunity in the male mice.
Selenium and selenoproteins are known to have immunomodulatory properties. 15 kDa selenoprotein (Sep15) was previously shown to interact with UDP‐glucose:glycoprotein glucosyltransferase, a protein involved in the calnexin quality control cycle for many secreted glycoproteins, including proteins with the immune protection function (e.g., MHC class I receptor). In this study, we examined the resistance of Sep15 knockout mice (Sep15 KO) to viral infection and autoimmune disease. In both cases the development of the disease in the Sep15 KO group was different from that in wild type mice, and resulted in higher severity of symptoms and higher percentage of death cases. Examination of immunological parameters in mouse spleenocytes, including MHC class I and II, and CD4/CD8 population of T cells, did not show significant differences between WT and Sep15 KO groups. However, cell culture experiments with Sep15 KO MEFs demonstrated a decrease in â2‐microglobulin subunit when Sep15 KO was combined with deficiency in a distant Sep15 homolog, Selenoprotein M. Altogether, these data show the role of Sep15 family members in the immune function.
