Paralytic autoimmune myositis develops in nonobese diabetic mice made Th1 cytokine-deficient by expression of an IFN-gamma receptor beta-chain transgene

BATF2 balances the T cell-mediated immune response of CADM with an anti-MDA5 autoantibody

OBJECTIVES

Clinically amyopathic dermatomyositis (CADM) is a subtype of dermatomyositis (DM) characterized by low-grade or absent muscle inflammation but frequent and rapidly progressive interstitial lung disease (RP-ILD) and skin ulcers with anti-melanoma differentiation-associated gene 5 (anti-MDA5) autoantibodies. Basic leucine zipper transcription factor ATF-like 2 (BATF2) is thought to function as an inhibitor of tumours and inflammation. Here, we aimed to investigate the roles of BATF2 in Th cell differentiation of CADM with an anti-MDA5 autoantibody (anti-MDA5⁺ CADM).

METHODS

Naive CD4⁺ T cells from human peripheral blood mononuclear cells (PBMCs) of healthy controls (HCs) were isolated and then cultured with IL-12, TGF-β or TGF-β plus IL-6 following anti-CD3 and anti-CD28 stimulations. The expression of BATF2 was measured by real-time PCR. The percentages of Th1, Th17 and Treg CD4⁺ T cells were detected by flow cytometry. BATF2 knockdown of CD4⁺ T cells was performed using small interfering RNAs (siRNAs).

RESULTS

The expression of BATF2 in PBMCs was higher in anti-MDA5⁺ CADM patients than in healthy controls. The BATF2 mRNA expression was increased under Th1 and Treg polarization but decreased under Th17 polarization. Th17 cell activation-associated genes were possibly increased while Th1 and Treg cell differentiation-associated genes were inhibited by posttranscriptional gene silencing of BATF2 in CD4⁺ T cells.

CONCLUSIONS

BATF2 promoted Th1 and Treg cell differentiation but suppressed Th17 cell activation in anti-MDA5⁺ CADM.

T Cells from NOD-PerIg Mice Target Both Pancreatic and Neuronal Tissue

It has become increasingly appreciated that autoimmune responses against neuronal components play an important role in type 1 diabetes (T1D) pathogenesis. In fact, a large proportion of islet-infiltrating B lymphocytes in the NOD mouse model of T1D produce Abs directed against the neuronal type III intermediate filament protein peripherin. NOD-PerIg mice are a previously developed BCR-transgenic model in which virtually all B lymphocytes express the H and L chain Ig molecules from the intra-islet-derived anti-peripherin-reactive hybridoma H280. NOD-PerIg mice have accelerated T1D development, and PerIg B lymphocytes actively proliferate within islets and expand cognitively interactive pathogenic T cells from a pool of naive precursors. We now report adoptively transferred T cells or whole splenocytes from NOD-PerIg mice expectedly induce T1D in NOD.scid recipients but, depending on the kinetics of disease development, can also elicit a peripheral neuritis (with secondary myositis). This neuritis was predominantly composed of CD4⁺ and CD8⁺ T cells. Ab depletion studies showed neuritis still developed in the absence of NOD-PerIg CD8⁺ T cells but required CD4⁺ T cells. Surprisingly, sciatic nerve-infiltrating CD4⁺ cells had an expansion of IFN-γ^- and TNF-α^- double-negative cells compared with those within both islets and spleen. Nerve and islet-infiltrating CD4⁺ T cells also differed by expression patterns of CD95, PD-1, and Tim-3. Further studies found transitory early B lymphocyte depletion delayed T1D onset in a portion of NOD-PerIg mice, allowing them to survive long enough to develop neuritis outside of the transfer setting. Together, this study presents a new model of peripherin-reactive B lymphocyte-dependent autoimmune neuritis.

Distinct effector mechanisms in the development of autoimmune neuropathy versus diabetes in nonobese diabetic mice

NOD mice deficient for the costimulatory molecule B7-2 (NOD-B7-2KO mice) are protected from autoimmune diabetes but develop a spontaneous autoimmune peripheral neuropathy that resembles human diseases Guillain-Barre syndrome and chronic inflammatory demyelinating polyradiculoneuropathy. Similar observations have now been made in conventional NOD mice. We have shown previously that this disease was mediated by autoreactive T cells inducing demyelination in the peripheral nervous system. In this study, we analyzed the molecular pathways involved in the disease. Our data showed that neuropathy developed in the absence of perforin or fas, suggesting that classic cytotoxicity pathways were dispensable for nerve damage in NOD-B7-2KO mice. In contrast, IFN-gamma played an obligatory role in the development of neuropathy as demonstrated by the complete protection from disease and infiltration in the nerves in NOD-B7-2KO mice deficient for IFN-gamma. This result was consistent with the inflammatory phenotype of T cells infiltrating the peripheral nerves. Importantly, the relative role of perforin, fas, and IFN-gamma appears completely different in autoimmune diabetes vs neuropathy. Thus, there are sharp contrasts in the pathogenesis of autoimmune diseases targeting different tissues in the same NOD background.

Have recent immunogenetic investigations increased our understanding of disease mechanisms in the idiopathic inflammatory myopathies?

PURPOSE OF REVIEW

The idiopathic inflammatory myopathies (IIM) continue to provide a challenge given the variable effectiveness of the available treatments, and immunogenetic studies are ongoing to further elucidate IIM disease mechanisms. This review examines how recent research has improved our understanding of the mechanisms that lead to IIM.

RECENT FINDINGS

HLA-DRB1 studies in a large homogenous cohort of UK Caucasian patients have confirmed that polymyositis (PM) and dermatomyositis (DM) are not genetically identical diseases while other studies have shown that tumor necrosis factor alpha is genetically implicated in disease susceptibility. Some remarkable results from an international collaboration, correlating gene-environment interactions, clearly suggest that ultraviolet light is capable of modulating both clinical and immunologic features of IIMs. Studies on microchimerism are unraveling interesting associations in juvenile DM patients, and bolstering the hypothesis that myositis may be an 'allo-immune' disease. mRNA gene expression profiling is helping to increase our understanding of myositis pathogenesis, whilst animal models have provided new information on the roles of Th1 responses and nitric oxide synthase in muscle disease. New candidate genes have been examined in inclusion body myositis (IBM), and a novel gene transfer experiment has been conducted, which led to significant changes in expression of the IBM phenotype.

SUMMARY

Improving the understanding of the immunogenetics and immunopathogenesis of the IIMs may in the future provide novel therapeutic targets, and thus improve outcomes in these difficult diseases.

Individual nonobese diabetic mice exhibit unique patterns of CD8+ T cell reactivity to three islet antigens, including the newly identified widely expressed dystrophia myotonica kinase

Spontaneous autoimmune diabetes development in NOD mice requires both CD8(+) and CD4(+) T cells. Three pathogenic CD8(+) T cell populations (represented by the G9C8, 8.3, and AI4 clones) have been described. Although the Ags for G9C8 and 8.3 are known to be insulin and islet-specific glucose-6-phosphatase catalytic subunit-related protein, respectively, only mimotope peptides had previously been identified for AI4. In this study, we used peptide/MHC tetramers to detect and quantify these three pathogenic populations among beta cell-reactive T cells cultured from islets of individual NOD mice. Even within age-matched groups, each individual mouse exhibited a unique distribution of beta cell-reactive CD8(+) T cells, both in terms of the number of tetramer-staining populations and the relative proportion of each population in the islet infiltrate. Thus, the inflammatory process in each individual follows its own distinctive course. Screening of a combinatorial peptide library in positional scanning format led to the identification of a peptide derived from dystrophia myotonica kinase (DMK) that is recognized by AI4-like T cells. Importantly, the antigenic peptide is naturally processed and presented by DMK-transfected cells. DMK is a widely expressed protein that is nonetheless the target of a beta cell-specific autoimmune response.

Pathogenic T-cell clones in autoimmune diabetes: more lessons from the NOD mouse

T-cell clones that can efficiently transfer diabetes to prediabetic nonobese diabetic (NOD) mice provide a powerful approach to dissecting the autoimmune disease process and for investigating immunoregulation. Diabetogenic T-cell clones carried in culture allow for detailed analysis of T-cell effector function and in vivo activity, and thus the contribution of a single clonotype to pathogenesis can be studied. As T cells comprising most or all of the repertoire in T-cell receptor transgenic (TCR-Tg) mice, diabetogenic T-cell clones have led to new variations on the NOD mouse model of autoimmune disease. T-cell clones are being used to screen peptide libraries and proteomic arrays to identify the autoantigens that drive these clones in vivo and to extend our knowledge of the processes that give rise to these antigens. With the identification of peptide agonists and natural ligands, the development of MHC-peptide multimers has been possible. These reagents can track T cells in vivo and thus provide new approaches for disease diagnosis and therapy as well as a versatile set of tools for basic research on how T cells contribute to autoimmune disease.