CD11b-deficient mice exhibit an increased severity in the late phase of antibody transfer-induced experimental epidermolysis bullosa acquisita.

CD11b, the α-chain of ß2 integrin Mac-1, is involved in many activation processes of phagocytes. Depending on the respective autoimmune disorder, CD11b has been shown to exert pro-inflammatory functions or be dispensable in their pathogenesis. Here, we investigated the role of CD11b in the pathogenesis of experimental epidermolysis bullosa acquisita (EBA), an autoimmune skin blistering disease mediated by autoantibodies to type VII collagen. Unexpectedly, in an antibody transfer-induced model of EBA, CD11b-deficient mice developed more severe disease symptoms than wild-type mice in the late phase of the disease. Furthermore, as compared to wild-type controls, CD11b-deficient mice expressed increased levels of circulating IFN-γ and IL-4. Taken together, for the first time, our results suggest an anti-inflammatory role for CD11b in experimental autoimmune diseases.

Autoantibodies against C5aR1, C3aR1, CXCR3, and CXCR4 are decreased in primary Sjogren's syndrome.

BACKGROUND: Networks formed of numerous autoantibodies (aabs) directed against G-protein coupled receptors (GPCR) have been suggested to play important role in autoimmune disorders. In present study, we aimed to evaluate the association between anti-GPCR antibodies and primary Sjogren's syndrome (pSS) to determine the potential pathogenic factors. METHODS: By applying a cell membrane-based ELISA technique, which is capable of detecting aabs against conformational epitopes within GPCR, serum levels of fourteen GPCR were determined in well-characterized patients with pSS (n = 52) and gender-matched healthy controls (n = 54). Comparisons between groups were analyzed by two-tailed Mann-Whitney U test, Bonferroni correction was applied for multiple comparisons. Spearman`s rank correlation coefficients were calculated between variables and visualized by heat map. RESULTS: Compared to healthy subjects, sera of patients with pSS showed significantly higher binding to ß2AR and ETAR, but lower binding to C5aR1, C3aR1, CXCR3, and CXCR4. Autoantibodies against C5aR1, C3aR1, CXCR3, and CXCR4 were also decreased in patients with rheumatoid arthritis. In pSS patients, levels of anti-CXCR3 and anti-CXCR4 antibodies were negatively correlated with circulating lymphocyte counts. Furthermore, correlation signatures of anti-GPCR antibodies changed dramatically in the patients with pulmonary involvement. CONCLUSIONS: This study demonstrates an association between pSS and autoantibodies recognizing GPCR, especially those functionally involved in immune cell migration and exocrine glandular secretion.

Gene Expression Profiling of Lacrimal Glands Identifies the Ectopic Expression of MHC II on Glandular Cells as a Presymptomatic Feature in a Mouse Model of Primary Sjögren's Syndrome.

Ectopic expression of MHC II molecules on glandular cells is a feature of primary Sjögren's syndrome (pSS). However, the cause of this ectopic expression and its potential role in the pathogenesis of the disease remains elusive. Here, we report that ectopic expression of MHC II molecules on glandular cells represents an early presymptomatic event in a mouse model of pSS induced by immunization of Ro60_316-335 peptide emulsified in TiterMax® as an adjuvant. Ectopic expression of MHC II was induced by TiterMax® but not by complete freund's adjuvant (CFA). Furthermore, immunization with Ro60_316-335 peptide emulsified in TiterMax®, but not in CFA, induced a pSS-like disease in mice. Our results suggests that ectopic expression of MHC II molecules on glandular cells represents a presymptomatic feature of pSS and that such ectopic expression can be induced by exogenous factors. In addition, this study also provides a novel mechanism how adjuvants can amplify immune responses.

B Cells Are Indispensable for a Novel Mouse Model of Primary Sjögren's Syndrome.

Primary Sjögren's syndrome (pSS) is characterized by a panel of autoantibodies, while it is not clear whether B cells and autoantibodies play an essential role in pathogenesis of the disease. Here, we report a novel mouse model for pSS which is induced by immunization with the Ro60_316-335 peptide containing a predominant T cell epitope. After immunization, mice developed several symptoms mimicking pSS, including a decreased secretion of tears, lymphocytic infiltration into the lacrimal glands, autoantibodies, and increased levels of inflammatory cytokines. Disease susceptibility to this novel mouse model varies among strains, where C3H/HeJ (H2-k) and C3H/HeN (H2-k) are susceptible while DBA/1 (H2-q) and C57BL/6 (H2-b) are resistant. Depletion of B cells using anti-CD20 monoclonal antibodies prevented C3H/HeN mice from development of the pSS-like disease. In addition, HLA-DRB1*0803, a pSS risk allele, was predicted to bind to the hRo60_308-328 which contains a predominant T cell epitope of human Ro60. Therefore, this study provides a novel mouse model for pSS and reveals an indispensable role of B cells in this model. Moreover, it suggests that T cell epitope within Ro60 antigen is potentially pathogenic for pSS.

Autoantibodies against the Second Extracellular Loop of M3R Do neither Induce nor Indicate Primary Sjögren's Syndrome.

OBJECTIVES: Anti-muscarinic acetylcholine type-3 receptor (anti-M3R) autoantibodies have been suggested to be pathogenic for primary Sjögren's syndrome (pSS), and the second extracellular loop of M3R is suspected to carry a disease-promoting epitope. In this study, we aimed to evaluate the pathogenicity of autoantibodies against peptides derived from the second extracellular loop of M3R in mice and to determine whether those autoantibodies could be used as biomarker for pSS. METHODS: BALB/c mice were immunized with modified linear or cyclic peptides of the second extracellular loop of M3R. The function of exocrine glands was evaluated by measuring the secretion of saliva and tears. The histological evaluations were performed by using H&E staining or direct immunofluorescence staining. Autoantibodies against linear or cyclic peptides of the second extracellular loop of M3R in human and mice were determined using ELISA. RESULTS: Immunization induced mice to produce autoantibodies against the linear or cyclic peptides of the second extracellular loop of M3R, and those autoantibodies could bind onto salivary glands. However, those mice showed neither impairment in the secretion of tears or saliva nor histological abnormality in the exocrine glands. Furthermore, passive transfer of the IgG isolated from the immunized mice into healthy mice did not induced the dysfunction of the exocrine glands. The prevalence of autoantibodies against the peptides of the second extracellular loop of M3R was low in pSS patients, and it did not differ significantly from that in healthy controls. CONCLUSIONS: Our results suggest that the autoantibodies against peptides of the second extracellular loop of M3R are not pathogenic in vivo and they are not suitable as biomarkers for pSS diagnosis.

History and milestones of mouse models of autoimmune diseases.

Autoimmune diseases are a group of disorders mediated by self-reactive T cells and/or autoantibodies. Mice, as the most widely used animal for modeling autoimmune disorders, have been extensively used in the investigation of disease pathogenesis as well as in the search for novel therapeutics. Since the first mouse model of multiple sclerosis was established more than 60 years ago, hundreds of mouse models have been established for tens of autoimmune diseases. These mouse models can be divided into three categories based on the approaches used for disease induction. The first one represents the induced models in which autoimmunity is initiated in mice by immunization, adoptive transfer or environmental factors. The second group is formed by the spontaneous models where mice develop autoimmune disorders without further induction. The third group refers to the humanized models in which mice bearing humanized cells, tissues, or genes, develop autoimmune diseases either spontaneously or by induction. This article reviews the history and highlights the milestones of the mouse models of autoimmune diseases.