Antigen presentation to T cells by MHC molecules is essential for adaptive immune responses. To determine the exact position of a gene affecting expression of MHC molecules, we finely mapped a previously defined rat quantitative trait locus regulating MHC class II on microglia in an advanced intercross line. We identified a small interval including the gene MHC class II transactivator (Mhc2ta) and, using a map over six inbred strains combined with gene sequencing and expression analysis, two conserved Mhc2ta haplotypes segregating with MHC class II levels. In humans, a -168A --> G polymorphism in the type III promoter of the MHC class II transactivator (MHC2TA) was associated with increased susceptibility to rheumatoid arthritis, multiple sclerosis and myocardial infarction, as well as lower expression of MHC2TA after stimulation of leukocytes with interferon-gamma. We conclude that polymorphisms in Mhc2ta and MHC2TA result in differential MHC molecule expression and are associated with susceptibility to common complex diseases with inflammatory components.

Innate immune mechanisms essential for priming encephalitogenic T cells in autoimmune neuroinflammation are poorly understood. Experimental autoimmune encephalomyelitis (EAE) is a IL-17-producing Th (Th17) cell-mediated autoimmune disease and an animal model of multiple sclerosis. To investigate how upstream TLR signals influence autoimmune T cell responses, we studied the role of individual TLR and MyD88, the common TLR adaptor molecule, in the initiation of innate and adaptive immune responses in EAE. Wild type (WT) C57BL/6, TLR-deficient and MyD88-deficient mice were immunized with myelin oligodendrocyte glycoprotein (MOG) in CFA. MyD88 -/-mice were completely EAE resistant. Purified splenic myeloid DC (mDC) from MyD88 -/-mice expressed much less IL-6 and IL-23, and serum and T cell IL-17 were absent. TLR4-/-and TLR9 -/-mice surprisingly exhibited more severe EAE symptoms than WT mice. IL-6 and IL-23 expression by mDC and Th17 responses were higher in TLR4 -/-mice, suggesting a regulatory role of TLR4 in priming Th17 cells. IL-6 expression by splenocytes was higher in TLR9 -/-mice. Our data suggest that MyD88 mediates the induction of mDC IL-6 and IL-23 responses after MOG immunization, which in turn drives IL-17-producing encephalitogenic Th17 cell activation. Importantly, we demonstrate that TLR4 and TLR9 regulate disease severity in MOGinduced EAE.

Multiple sclerosis (MS) is a chronic, inflammatory, demyelinating disease of the CNS, most frequently starting with a series of bouts, each followed by complete remission and then a secondary, progressive phase during which the neurological deficit increases steadily. The underlying molecular mechanisms responsible for disease progression are still unclear. Herein, we demonstrate that high mobility group box chromosomal protein 1 (HMGB1), a DNA-binding protein with proinflammatory properties, is evident in active lesions of MS and experimental autoimmune encephalomyelitis (EAE) and that HMGB1 levels correlate with active inflammation. Furthermore, the expression of the innate HMGB1 receptors--receptor for advanced glycation end products, TLR2, and TLR4--was also highly increased in MS and rodent EAE. Additionally, in vitro activation of rodent CNS-derived microglia and bone marrow-derived macrophages demonstrated that microglia were equally as capable as macrophages of translocating HMGB1 following LPS/IFN-gamma stimulation. Significant expression of HMGB1 and its receptors on accumulating activated macrophages and resident microglia may thus provide a positive feedback loop that amplifies the inflammatory response during MS and EAE pathogenesis.

EAE, an animal model for MS, 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 plasmacytoid DC (pDC) in the initiation of autoimmune Th17-and Th1-cell responses and EAE, we depleted pDC with anti-pDC Ag-1 (anti-PDCA1) mAb prior to immunization of C57BL/6 mice with myelin oligodendrocyte glycoprotein (MOG). pDC-depleted mice developed less severe clinical and histopathological signs of EAE than control mice, which demonstrates a promoting role for pDC in the initiation of EAE. The levels of type I IFN were much lower in the sera from anti-PDCA1-treated mice. However, neutralization of type I IFN ameliorated the early phase of EAE but did not alter the severity of disease. Thus, only a minor part of the EAE-promoting effect of pDC appears to be mediated by IFN-a/b secretion. The numbers of MOG-specific Th17 cells, but not Th1 cells, were lower in spleen from anti-PDCA1-treated mice compared with controls. In contrast, pDC depletion a week after MOG immunization resulted in more severe clinical signs of EAE.In conclusion, we demonstrate that pDC promote initiation of MOG-induced Th17-cell responses and EAE.Key words: Autoimmunity . DC . EAE/MS . T cells . Type I IFN Supporting Information available online IntroductionEAE is an animal model for the human autoimmune demyelinating disease MS [1]. The pathological changes in the CNS during EAE are very similar to MS with perivascular infiltrates of T cells, B cells and macrophages [2]. Murine EAE is induced by injection of myelin autoantigens such as myelin oligodendrocyte glycoprotein (MOG) in CFA containing killed Mycobacterium tuberculosis and pertussis toxin. EAE was previously thought to be a purely IL-12-driven Th1-mediated autoimmune disease [3].However Langrish et al. demonstrated that proinflammatory IL-17-producing Th17 cells mediate EAE [4]. Murine-naïve CD4 CD251 6]. Recently it wasshown that different epitopes of MOG predominately induce a Th1 or Th17 response, which influences the lesion distribution and clinical symptoms of EAE and suggests a promoting role for both Th17 and Th1 cells in MOG-induced EAE [7]. DC are key actors when an adaptive immune response is initiated [8]. There are two major DC subsets in mice, which are characterized by differential expression of cell surface markers [9] . pDC also have a powerful ability to modify the adaptive immune response, e.g. T-cell differentiation [11,12]. The expression of costimulatory molecules differs between mDC and pDC, e.g. maturation leads to upregulation of B7 molecules on mDC, but downregulation of these molecules on pDC [13,14]. Moreover, mDC and pDC differ in their expression of TLR and response to TLR ligation. TLR7 and TLR9 ligation results in type I IFN production in pDC because of constitutive expression of IFN regulatory factor-7, whereas ligation of these receptors leads to IL-12 production in mDC [15,16]. We have previously shown that TLR9 a...

Neutralizing autoantibodies to type I, but not type II, interferons (IFNs) are found at high titers in almost every patient with autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED), a disease caused by AIRE gene mutations that lead to defects in thymic T-cell selection. Combining genome-wide expression array with real time RT-PCR assays, we here demonstrate that antibodies against IFN-α cause highly significant down-regulation of interferon-stimulated gene expression in cells from APECED patients' blood by blocking their highly dilute endogenous IFNs. This down-regulation was lost progressively as these APECED cells matured in cultures without neutralizing autoantibodies. Most interestingly, a rare APECED patient with autoantibodies to IFN-ω but not IFN-α showed a marked increase in expression of the same interferon-stimulated genes. We also report unexpected increases in serum CXCL10 levels in APECED. Our results argue that the breakdown of tolerance to IFNs in AIRE deficiency is associated with impaired responses to them in thymus, and highlight APECED as another autoimmune disease with associated dysregulation of IFN activity.

Regeneration of cells in the central nervous system is a process that might be affected during neurological disease and trauma. Because nitric oxide (NO) and its derivatives are powerful mediators in the inflammatory cascade, we have investigated the effects of pathophysiological concentrations of NO on neurogenesis, gliogenesis, and the expression of proneural genes in primary adult neural stem cell cultures. After exposure to NO, neurogenesis was downregulated, and this corresponded to decreased expression of the proneural gene neurogenin-2 and ␤-III-tubulin. The decreased ability to generate neurons was also found to be transmitted to the progeny of the cells. NO exposure was instead beneficial for astroglial differentiation, which was confirmed by increased activation of the Janus tyrosine kinase/signal transducer and activator of transcription transduction pathway. Our findings reveal a new role for NO during neuroinflammatory conditions, whereby its proastroglial fate-determining effect on neural stem cells might directly influence the neuroregenerative process.

Aims/HypothesisDiabetes mellitus is one of the most common endocrine disorders in dogs and is commonly proposed to be of autoimmune origin. Although the clinical presentation of human type 1 diabetes (T1D) and canine diabetes are similar, the aetiologies may differ. The aim of this study was to investigate if autoimmune aetiology resembling human T1D is as prevalent in dogs as previously reported.MethodsSera from 121 diabetic dogs representing 40 different breeds were tested for islet cell antibodies (ICA) and GAD65 autoantibodies (GADA) and compared with sera from 133 healthy dogs. ICA was detected by indirect immunofluorescence using both canine and human frozen sections. GADA was detected by in vitro transcription and translation (ITT) of human and canine GAD65, followed by immune precipitation. Sections of pancreata from five diabetic dogs and two control dogs were examined histopathologically including immunostaining for insulin, glucagon, somatostatin and pancreas polypeptide.ResultsNone of the canine sera analysed tested positive for ICA on sections of frozen canine or human ICA pancreas. However, serum from one diabetic dog was weakly positive in the canine GADA assay and serum from one healthy dog was weakly positive in the human GADA assay. Histopathology showed marked degenerative changes in endocrine islets, including vacuolisation and variable loss of immune-staining for insulin. No sign of inflammation was noted.Conclusions/InterpretationsContrary to previous observations, based on results from tests for humoral autoreactivity towards islet proteins using four different assays, and histopathological examinations, we do not find any support for an islet autoimmune aetiology in canine diabetes mellitus.

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...