Regulation of type 1 diabetes development and B-cell activation in nonobese diabetic mice by early life exposure to a diabetogenic environment

Microbes, including viruses, influence type 1 diabetes (T1D) development, but many such influences remain undefined. Previous work on underlying immune mechanisms has focussed on cytokines and T cells. Here, we compared two nonobese diabetic (NOD) mouse colonies, NODlow and NODhigh, differing markedly in their cumulative T1D incidence (22% vs. 90% by 30 weeks in females). NODhigh mice harbored more complex intestinal microbiota, including several pathobionts; both colonies harbored segmented filamentous bacteria (SFB), thought to suppress T1D. Young NODhigh females had increased B-cell activation in their mesenteric lymph nodes. These phenotypes were transmissible. Co-housing of NODlow with NODhigh mice after weaning did not change T1D development, but T1D incidence was increased in female offspring of co-housed NODlow mice, which were exposed to the NODhigh environment both before and after weaning. These offspring also acquired microbiota and B-cell activation approaching those of NODhigh mice. In NODlow females, the low rate of T1D was unaffected by cyclophosphamide but increased by PD-L1 blockade. Thus, environmental exposures that are innocuous later in life may promote T1D progression if acquired early during immune development, possibly by altering B-cell activation and/or PD-L1 function. Moreover, T1D suppression in NOD mice by SFB may depend on the presence of other microbial influences. The complexity of microbial immune regulation revealed in this murine model may also be relevant to the environmental regulation of human T1D

Identification of Fc alpha receptor (CD89) isoforms generated by alternative splicing that are differentially expressed between blood monocytes and alveolar macrophages.

One of the hallmarks of mucosal-host defense is the clearance of inhaled Ags by alveolar macrophages (AM) through interactions of IgA Abs and IgA Fc receptors (Fc alpha R). AM constitutively expressed Fc alpha R at lower levels than freshly isolated and in vitro-differentiated monocytes as determined by immunofluorescence using four anti-Fc alpha R mAb. SDS-PAGE analysis of iodinated cell surface proteins revealed that Fc alpha R on AM has an Mr of 50 to 65 kDa, slightly lower than that on monocytes (55-75 kDa). Treatment of AM Fc alpha R by N-glycanase gave rise to a protein core of 28 KDa, smaller than the 32-kDa backbone of blood monocytes. AM Fc alpha R molecules were unaffected by phosphatidylinositol-phospholipase C treatment. Fc alpha R transcripts were analyzed by reverse transcription-PCR using primers in the 5' and 3' regions of a U937 Fc alpha R cDNA. Three transcripts were amplified, cloned, and sequenced from AM and/or monocyte mRNA, the full length Fc alpha R and two alternatively spliced products corresponding to deletions of 66 and 288 nucleotides in the portion coding for the extracellular domain; they were named Fc alpha R a.1, a.2, and a.3, respectively. These PCR products were transcribed and translated in vitro into three proteins (Mr 32, 30, and 22 kDa, respectively), in which the 32- and 30-kDa species were immunoprecipitated by an anti-Fc alpha R mAb. The predicted size of the protein encoded by the Fc alpha R a.2 transcript without the leader peptide is Mr approximately 27,400, a value that is consistent with the Mr of AM Fc alpha R backbone. These results indicate that AM express at their surfaces a protein product of an alternatively spliced Fc alpha R transcript, the Fc alpha R a.2 isoform, that might have physiologic relevance in IgA-mediated host defense at mucosal sites

Assessing immune responses in the nonobese diabetic mouse model of type 1 Diabetes

Type 1 diabetes is an autoimmune disease resulting in the loss of insulin production and, consequently, hyperglycemia. The nonobese diabetic (NOD) mouse develops spontaneous diabetes with considerable similarity to the disease in humans. Immunological studies using the NOD mouse model allow for the investigation of the natural history of the disease and leukocyte and lymphocyte pathogenic and regulatory functions, as well as testing potential therapies for intervention. The analyses of the cellular events leading up to diabetes may utilize different in vitro cellular assays, immunohistochemistry, and in vivo adoptive transfer, to study mechanisms of the disease and the effects of therapeutic intervention. In this chapter, we describe some common techniques for phenotyping and mechanistic analyses of function, particularly of CD8+ T cells

IRF5 governs liver macrophage activation that promotes hepatic fibrosis in mice and humans

Hepatic fibrosis arises from inflammation in the liver initiated by resident macrophage activation and massive leukocyte accumulation. Hepatic macrophages hold a central position in maintaining homeostasis in the liver and in the pathogenesis of acute and chronic liver injury linked to fibrogenesis. Interferon regulatory factor 5 (IRF5) has recently emerged as an important proinflammatory transcription factor involved in macrophage activation under acute and chronic inflammation. Here, we revealed that IRF5 is significantly induced in liver macrophages from human subjects developing liver fibrosis from nonalcoholic fatty liver disease or hepatitis C virus infection. Furthermore, IRF5 expression positively correlated with clinical markers of liver damage, such as plasma transaminase and bilirubin levels. Interestingly, mice lacking IRF5 in myeloid cells (MKO) were protected from hepatic fibrosis induced by metabolic or toxic stresses. Transcriptional reprogramming of macrophages lacking IRF5 was characterized by immunosuppressive and antiapoptotic properties. Consequently, IRF5 MKO mice respond to hepatocellular stress by promoting hepatocyte survival, leading to complete protection from hepatic fibrogenesis. Our findings reveal a regulatory network, governed by IRF5, that mediates hepatocyte death and liver fibrosis in mice and humans. Therefore, modulating IRF5 function may be an attractive approach to experimental therapeutics in fibroinflammatory liver disease