Key Points Germline activating STAT3 mutations were detected in 3 patients with autoimmunity, hypogammaglobulinemia, and mycobacterial disease. T-cell lymphoproliferation, deficiency of regulatory and helper 17 T cells, natural killer cells, dendritic cells, and eosinophils were common.

Transfer of the whole microbiota may not reduce diabetes incidence despite a major change in gut microbiota, but single symbionts such as with beneficial metabolic and immune signalling effects may reduce diabetes incidence when administered as a probiotic.

Faecalibacterium prausnitzii is considered as one of the most important bacterial indicators 32 of a healthy gut. We studied the effects of oral F. prausnitzii treatment on high-fat fed mice. 33Compared to the High-fat Control mice, F. prausnitzii-treated mice had lower hepatic fat 34 content, AST and ALT, and increased fatty-acid oxidation and adiponectin signaling in liver.

Past sun exposure and vitamin D supplementation have been associated with a reduction in the risk of MS. We measured the serum concentration of 25-hydroxyvitamin D (25[OH]D) at the time of MS diagnosis in 40 MS patients and 40 controls. We found no difference in the serum levels of 25(OH)D between MS patients and controls when all samples or samples obtained during winter months were compared, but MS patients had significantly lower serum 25(OH)D concentrations in June to September than the controls. The vitamin D stores were adequate for bone metabolism (> 37 nmol/L) in 70% of MS patients throughout the year and within the hypovitaminosis level (< 37 nmol/L) in 30% of MS patients at some time of the year. During MS-relapses, 25(OH)D levels were lower than in remission, but mostly within the reference range observed in relation with normal bone metabolism. We conclude that the vitamin D stores in most MS patients are adequate for their normal bone metabolism. However, lower vitamin D levels during MS relapses than in remission suggest that vitamin D could be involved in the regulation of the clinical disease activity of MS. The optimal serum levels of vitamin D for the regulation of immune responses remain to be determined.

Leukocyte migration from the blood to tissues is a prerequisite for normal immune responses. We produced mice deficient in an endothelial cell-surface oxidase (amine oxidase, copper containing-3 [AOC3], also known as vascular adhesion protein-1 [VAP-1]) and found that this enzyme is needed for leukocyte extravasation in vivo. Real-time imaging shows that AOC3 mediates slow rolling, firm adhesion, and transmigration of leukocytes in vessels at inflammatory sites and lymphoid tissues. Absence of AOC3 results in reduced lymphocyte homing into lymphoid organs and in attenuated inflammatory response in peritonitis. These data alter the paradigm of leukocyte extravasation cascade by providing the first physiological proof for the concept that endothelial cell surface enzymes regulate the development of inflammatory reactions in vivo and suggest that this enzyme should be useful as an anti-inflammatory target.

Current knowledge of the phenotype of mononuclear cells accumulating in pancreatic islets in insulin-dependent diabetes (IDDM) and factors determining their homing into the pancreas is limited. Therefore, a pancreas obtained at the onset of IDDM was studied in detail. Cryostat sections were stained for mononuclear cell types, T cell receptor subtypes, and adhesion molecules of vascular endothelium and studied by immunofluorescence microscopy, and peripheral blood mononuclear cells were phenotyped using flow cytometry. Monocytes/macrophages (lysozyme-or CD 14-reactive cells) were identified among other mononuclear cell types in islet infiltrates. Vft

Vascular adhesion protein-1 (VAP-1) is an endothelial molecule that possesses both adhesive and enzymatic properties in vitro. So far, however, elucidation of its in vivo function has suffered from the lack of function-blocking reagents that are suitable for use in animal models. In this work we produced monoclonal antibodies against murine VAP-1 and characterized them using in vitro binding assays. We then examined whether the antibodies could prevent leukocyte migration in in vivo inflammation models, including two acute models (peritonitis induced with proteose peptone and interleukin-1 and air pouch inflammation enhanced by CCL21) and one chronic model (autoimmune diabetes in nonobese diabetic mice). Antibodies 7-88 and 7-106 inhibited migration of granulocytes and monocytes in both acute models of inflammation. Strikingly, antibody 7-88 significantly prevented diabetes in a subset of nonobese diabetic mice. The results show for the first time that in mouse models of inflammation, VAP-1 mediates leukocyte trafficking to sites of inflammation and thus is a potential target for anti-inflammatory therapies.

Aims/hypothesis Microbial factors influence the development of diabetes in NOD mice. Studies in germ-free animals have revealed important roles of microbiota in the regulation of Th17 and forkhead box P3 (FOXP3) + T regulatory (Treg) activation in the intestine. However, the effects of intestinal microbiota in immune regulation and diabetes development in NOD mice are still poorly understood. Methods A colony of germ-free NOD mice was established to evaluate the effects of intestinal microbiota on regulatory immunity in the gut, and on the development of insulitis and diabetes in NOD mice. Results Diabetes developed in roughly equal numbers in germ-free and specific pathogen-free NOD mice. Insulitis was accentuated in germ-free NOD mice; yet insulin preservation was unaltered. Germ-free NOD mice showed increased levels of Il17 (also known as Il17a) mRNA in the colon, and of Th17 and Th1 cells in the mesenteric and pancreatic lymph nodes, while Foxp3 mRNA and FOXP3 + Tregs were reduced. In the islet infiltrates, FOXP3 + CD4 + T cells were slightly increased in germ-free mice. B cells appeared less activated in the peritoneum and were less abundant in islet infiltrates. Conclusions/interpretation These results indicate that lack of intestinal microbiota promotes an imbalance between Th1, Th17 and Treg differentiation in the intestine. This imbalance is associated with accelerated insulitis, but intact recruitment of FOXP3 + Tregs into islets, suggesting: (1) a microbial dependence of local induction of Treg in the gut and draining lymph nodes; but (2) a potentially compensatory function of naturally occurring Tregs in the islets, which may help control diabetogenic T cells.