EAE, an animal model for multiple sclerosis, is a Th17-and Th1-cell-mediated autoimmune disease, but the mechanisms leading to priming of encephalitogenic T cells in autoimmune neuroinflammation are poorly understood. To investigate the role of dendritic cells (DCs) in the initiation of autoimmune Th17-and Th1-cell responses and EAE, we used mice transgenic for a simian diphtheria toxin receptor (DTR) expressed under the control of the murine CD11c promoter (CD11c-DTR mice on C57BL/6 background). EAE was induced by immunization with myelin oligodendrocyte glycoprotein (MOG) protein in CFA. DCs were depleted on the day before and 8 days after MOG immunization. The mean clinical EAE score was only mildly reduced in DC-depleted mice when DCs were ablated before EAE induction. The frequency of activated Th cells was not altered, and MOGinduced Th17 or Th1-cell responses were not altered, in the spleens of DC-depleted mice. Similar results were obtained if DCs were ablated the first 10 days after MOG immunization with repeated DC depletions. Unexpectedly, transient depletion of DCs did not affect priming or differentiation of MOG-induced Th17 and Th1-cell responses or the incidence of EAE. Thus, the mechansim of priming of Th cells in EAE remains to be elucidated. Keywords: Autoimmunity r Dendritic cells r EAE/MS r T cells r Th cells See accompanying Commentary by Becher and Greter Supporting Information available online IntroductionDendritic cells (DCs) are key actors of adaptive immune responses against infections [1][2][3]. There are several DCs subsets in mice which are characterized by differential expression of cell surface markers and their location; e.g. myeloid DCs (mDCs), plasmacytoid DCs (pDCs), dermal DCs, CD11b + DCs, and CD11b − DCs [4,5]. Ly6C hi monocytes are considered to be precursors of inflammatory DCs (inflDCs) which are recruited to site of Correspondence: Dr. Anna Lobell e-mail: Anna.Lobell@medsci.uu.se inflammation [4]. InflDCs express intermediate to high levels of CD11c and MHC class II (MHC II). mDCs are highly specialized in priming naïve T cells in vitro [3]. In vivo depletion of murine CD11c + mDCs by diphtheria toxin (DTx)-based transgenic systems has demonstrated an indispensible role for DCs during priming of CD8 + T-cell responses to viruses, intracellular bacteria and malaria parasites [1,6]. Priming of Th1 responses and Th2 responses to parasites also depends on DCs [2,7]. Furthermore, ablation of DCs leads to dissemination of * These authors contributed equally to the work. Results Efficiency of DC depletionCD11c-DTR mice on C57BL/6 genetic background were immunized with MOG protein in CFA and pertussis toxin to induce EAE. First, the efficiency of DC depletion was assessed after DTx injection of CD11c-DTR mice. An analysis of DC depletion in the skin, skin-draining inguinal LN and spleen was performed both before and after MOG immunization. All results are presented in Supporting Information Table 1 and the most relevant results are presented in Figure 1. Dermal Langerin − DCs w...

Loss of tolerance to neutrophil myeloperoxidase (MPO) underlies the development of ANCA-associated vasculitis and GN, but the mechanisms underlying this loss of tolerance are poorly understood. Here, we assessed the role of the thymus in deletion of autoreactive anti-MPO T cells and the importance of peripheral regulatory T cells in maintaining tolerance to MPO and protecting from GN. Thymic expression of MPO mRNA predominantly localized to medullary thymic epithelial cells. To assess the role of MPO in forming the T cell repertoire and the role of the autoimmune regulator Aire in thymic MPO expression, we compared the effects of immunizing Mpo 2/2 mice, Aire 2/2 mice, and control littermates with MPO.Immunized Mpo 2/2 and Aire 2/2 mice developed significantly more proinflammatory cytokine-producing anti-MPO T cells and higher ANCA titers than control mice. When we triggered GN with a subnephritogenic dose of anti-glomerular basement membrane antibody, Aire 2/2 mice had more severe renal disease than Aire +/+ mice, consistent with a role for Aire-dependent central deletion in establishing tolerance to MPO. Furthermore, depleting peripheral regulatory T cells in wild-type mice also led to more anti-MPO T cells, higher ANCA titers, and more severe GN after immunization with MPO. Taken together, these results suggest that Aire-dependent central deletion and regulatory T cell-mediated peripheral tolerance both play major roles in establishing and maintaining tolerance to MPO, thereby protecting against the development of anti-MPO GN.

Autoimmune polyendocrine syndrome type 1 (APS-1) is a multiorgan autoimmune disease caused by mutations in the autoimmune regulator (AIRE) gene. Chronic mucocutaneous candidiasis, hypoparathyroidism and adrenal failure are hallmarks of the disease. The critical mechanisms causing chronic mucocutaneous candidiasis in APS-1 patients have not been identified although autoantibodies to cytokines are implicated in the pathogenesis. To investigate whether the Th reactivity to Candida albicans (C. albicans) and other stimuli was altered, we isolated PBMC from APS-1 patients and matched healthy controls. The Th17 pathway was upregulated in response to C. albicans in APS-1 patients, whereas the IL-22 secretion was reduced. Autoantibodies against IL-22, IL-17A and IL-17F were detected in sera from APS-1 patients by immunoprecipitation. In addition, Aire-deficient (Aire 0/0 ) mice were much more susceptible than Aire 1/1 mice to mucosal candidiasis and C. albicansinduced Th17-and Th1-cell responses were increased in Aire 0/0 mice. Thus an excessive IL-17A reactivity towards C. albicans was observed in APS-1 patients and Aire 0/0 mice.

Autoimmune polyendocrine syndrome type 1 (APS-1) is caused by mutations of the autoimmune regulator (AIRE) gene. Mouse studies have shown that this results in defective negative selection of T cells and defective early seeding of peripheral organs with regulatory T cells (Tregs). Aire deficiency in humans and mice manifests as spontaneous autoimmunity against multiple organs, and 20% of patients develop an autoimmune hepatitis (AIH). To study AIH in APS-1, we generated a murine model of human AIH on a BALB/c mouse background, in which Aire is truncated at exon 2. A subgroup of 24% of mice is affected by AIH, characterized by lymphoplasmacytic and periportal hepatic infiltrates, autoantibodies, elevated aminotransferases, and a chronic and progressive course of disease. Disease manifestation was dependent on specific Aire mutations and the genetic background of the mice. Though intrahepatic Treg numbers were increased and hyperproliferative, the intrahepatic CD4/CD8 ratio was decreased. The targets of the adaptive autoimmune response were polyspecific and not focussed on essential autoantigens, as described for other APS-1-related autoimmune diseases. The AIH could be treated with prednisolone or adoptive transfer of polyspecific Tregs. Conclusion: Development of AIH in APS-1 is dependent on specific Aire mutations and genetic background genes. Autoimmune response is polyspecific and can be controlled by steroids or transfer with Tregs. This might enable new treatment options for patients with AIH. (HEPATOLOGY 2015;61:1295-1305 A utoimmune polyendocrine syndrome type 1 (APS-1) is a rare monogenetic recessive disorder caused by mutations in the autoimmune regulator (Aire) gene. The disease manifests in early childhood, and APS-1 patients suffer from at least a triad of mucocutaneous candidiasis, Addison's disease, and hypoparathyroidism. In addition, patients also exhibit Sj€ ogren's syndrome, premature ovarian/gonad failure, anemia, diabetes, alopecia, vitiligo, gastritis, and autoimmune hepatitis (AIH), 1 the latter affecting up to 20% of APS-1 patients. 2