Transcription factors of the interferon regulatory factor (IRF) family contribute to the regulation of cell proliferation and apoptosis. Here, we show that CD4+ T helper (Th) cells lacking IRF4 (IRF4−/−) are highly sensitive to apoptosis. After infection of IRF4−/− mice with the protozoan parasite Leishmania major, the lesion-draining lymph nodes developed the prototypic lymphadenopathy of wild-type mice after 4 wk, but demonstrated almost total loss of cellularity and enhanced apoptosis after 7 wk. In vitro, activation of IRF4−/− CD4+ Th cells led to greatly increased apoptosis compared with wild-type cells. Coculture of IRF4−/− and IRF4+/+ CD4+ cells did not increase survival of IRF4−/− CD4+ cells, indicating that the enhanced rate of IRF4−/− Th cell apoptosis was neither transferable nor due to lack of a cytokine. Enhanced CD4+ cell apoptosis was also observed after anti-CD95 mAb treatment, despite normal CD95 expression. Removal of endogenous cytokines, notably interleukin (IL)-4, led to increased and equally high levels of IRF4−/− and IRF4+/+ cell apoptosis, whereas the protective activity of exogenous IL-4 was reduced in IRF4−/− CD4+ cells despite normal expression of the IL-4 receptor. Therefore, IRF4 is central in protecting CD4+ cells against proapoptotic stimuli.
TNF receptor-associated factor 2 (TRAF2) is a key intracellular signaling mediator that acts downstream of not only TNFα but also various members of the TNFα superfamily. Here, we report that, despite their lack of TNFα signaling, TRAF2(-/-)TNFα(-/-) mice develop an inflammatory disorder characterized by autoantibody accumulation and organ infiltration by T cells with the phenotypes of activated, effector, and memory cells. RAG1(-/-) mice reconstituted with TRAF2(-/-)TNFα(-/-) bone marrow cells showed increased numbers of hyperactive T cells and rapidly developed progressive and eventually lethal inflammation. No inflammation was observed in RAG1(-/-) mice reconstituted with TRAF2(-/-)TNFα(-/-)T-cell receptor β(-/-) or TRAF2(-/-)TNFα(-/-)NFκB-induced kinase(+/-) bone marrow cells. The pathogenic TRAF2(-/-)TNFα(-/-) T cells showed constitutive NFκB2p52 activation and produced elevated levels of T-helper 1 and T-helper 17 cytokines. Our results suggest that a regulatory circuit consisting of TRAF2-NFκB-induced kinase-NFκB2p52 is essential for the proper control of effector T-cell polarization and that loss of T-cell TRAF2 function induces constitutive NFκB2p52 activity that drives fatal autoimmune inflammation independently of TNFα signaling. The involvement of this regulatory circuit in controlling autoimmune responses highlights the delicate balance required to avoid paradoxical adverse events when implementing new targeted anti-inflammatory therapies.
Fatigue is common in multiple sclerosis (MS); it significantly impairs quality of life, and treatment options are limited. A randomized controlled trial of Elevida, a self-guided, online German fatigue intervention, showed significant benefit. We tested an English version of Elevida with people with MS in Australia. Participants were volunteers with MS who self-reported at least mild fatigue (≥ 43 on the Fatigue Scale for Motor and Cognitive Functions scale), some mobility (Expanded Disability Status Scale < 8), and no or mild cognitive difficulties (≤ 32 on the Multiple Sclerosis Neuropsychological Questionnaire). Participants completed the 9-week English Elevida program, commenting on and rating its acceptability. The Chalder Fatigue Scale was completed at baseline, end-of-program, and 2 months later. We undertook qualitative (thematic analysis) and quantitative (before/after differences, tested using paired t test) analyses. Thirty-eight people with MS expressed an interest in the study; 26 were eligible; 20 began the study. Fifteen participants (75%) completed the program (mean [SD]: 58.9 [10.5] years of age, 67% women, 9 with relapsing MS, 6 with progressive MS). Over 90% of completing participants rated acceptability as good or very good, and approximately 70% found the program helpful. Three themes were identified: Positive or negative comments on program features, incorrect assumptions in program content, and personal experiences and reflections. Significant improvement (P < .01) in fatigue scores from baseline to program completion was maintained 2 months after program completion. Elevida was acceptable and effective for MS-related fatigue. Identified themes will guide further development of the program to satisfy users' sense of autonomy, competence, and relatedness.
Abstract The mechanisms of type-1 and type-2 diabetes induction are different, yet the two diseases are tightly linked to excessive inflammation. Studies with mice lacking soluble IgM have implicated a protective role of IgM against inflammation and autoimmune progression. Recently, both human and mouse studies have demonstrated Toso/FAIM3, a type one transmembrane protein, to be the receptor for IgM. In our study, we investigated the role of Toso in both type I and type 2 diabetes models in mice. Toso has only been reported to be expressed on B cells and activated T cells. In a type 1 diabetes model, we found that Toso on dendritic cells is required for breaking T cell tolerance and diabetes induction. In a type 2 diabetes model which is induced by 12-14 weeks of high fat diet feeding, WT mice became obese and developed glucose intolerance and insulin resistance. Interestingly, although Toso-deficient mice had similar weight gain, they had improved glucose tolerance and insulin sensitivity compared to the WT mice. Furthermore, Toso-/- mice were found to have decreased B cell number and proinflammatory macrophages in the adipose tissues. In contrast to the protective role of IgM in autoimmune disease progressions, our findings demonstrate a novel and pathogenic role of Toso in both type 1 and type 2 diabetes induction, and suggest that Toso respresents a potential therapeutic target against both autoimmune and type 2 diabetes.
The paracaspase MALT1 plays an important role in signaling pathways leading to NF-kB activation. To investigate the contribution of its proteolytic activity to overall pathway regulation we generated MALT1 protease-deficient mice (Malt1PD/PD) and compared them to MALT1 KO animals (Malt1-/-). Malt1PD/PD mice displayed defects in multiple cell types including Treg, IL10-producing B cells and mature T and B cells. Immune defects were more pronounced in Malt1-/- animals. Both mouse lines showed abrogated B cell responses upon immunization and were protected in a Th17-dependent EAE model. Surprisingly, Malt1PD/PD animals developed a multi-organ inflammation characterized by Th2-type responses and enhanced IgG1 and IgE levels which was prevented by reconstitution with WT Treg. These data uncover a previously unappreciated key function of MALT1 protease activity in immune homeostasis and its relevance in human health and disease.
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