B1-cell-produced anti-phosphatidylserine antibodies contribute to lupus nephritis development via TLR-mediated Syk activation

Autoantibodies produced by B cells play a pivotal role in the pathogenesis of systemic lupus erythematosus (SLE). However, both the cellular source of antiphospholipid antibodies and their contributions to the development of lupus nephritis (LN) remain largely unclear. Here, we report a pathogenic role of anti-phosphatidylserine (PS) autoantibodies in the development of LN. Elevated serum PS-specific IgG levels were measured in model mice and SLE patients, especially in those with LN. PS-specific IgG accumulation was found in the kidney biopsies of LN patients. Both transfer of SLE PS-specific IgG and PS immunization triggered lupus-like glomerular immune complex deposition in recipient mice. ELISPOT analysis identified B1a cells as the main cell type that secretes PS-specific IgG in both lupus model mice and patients. Adoptive transfer of PS-specific B1a cells accelerated the PS-specific autoimmune response and renal damage in recipient lupus model mice, whereas depletion of B1a cells attenuated lupus progression. In culture, PS-specific B1a cells were significantly expanded upon treatment with chromatin components, while blockade of TLR signal cascades by DNase I digestion and inhibitory ODN 2088 or R406 treatment profoundly abrogated chromatin-induced PS-specific IgG secretion by lupus B1a cells. Thus, our study has demonstrated that the anti-PS autoantibodies produced by B1 cells contribute to lupus nephritis development. Our findings that blockade of the TLR/Syk signaling cascade inhibits PS-specific B1-cell expansion provide new insights into lupus pathogenesis and may facilitate the development of novel therapeutic targets for the treatment of LN in SLE.

Prevalence, significance and predictive value of antiphospholipid antibodies in Crohn's disease

AIM: To assess the prevalence and stability of different antiphospholipid antibodies(APLAs) and their association with disease phenotype and progression in inflammatory bowel diseases(IBD) patients.METHODS: About 458 consecutive patients [Crohn's disease(CD): 271 and ulcerative colitis(UC): 187] were enrolled into a follow-up cohort study in a tertiary IBD referral center in Hungary. Detailed clinical phenotypes were determined at enrollment by reviewing the patients' medical charts. Disease activity, medical treatment and data about evolvement of complications or surgical interventions were determined prospectively during the follow-up. Disease course(development f complicated disease phenotype and need for surgery),occurrence of thrombotic events, actual state of diseaseactivity according to clinical, laboratory and endoscopic scores and accurate treatment regime were recorded during the follow-up,(median, 57.4 and 61.6 mo for CD and UC). Sera of IBD patients and 103 healthy controls(HC) were tested on individual anti-β2-Glycoprotein-I(anti-β2-GPI IgA/M/G), anti-cardiolipin(ACA IgA/M/G)and anti-phosphatidylserine/prothrombin(anti-PS/PT IgA/M/G) antibodies and also anti-Saccharomyces cerevisiae antibodies(ASCA IgA/G) by enzyme-linked immunosorbent assay(ELISA). In a subgroup of CD(n = 198) and UC patients(n = 103), obtaining consecutive samples over various arbitrary timepoints during the disease course, we evaluated the intraindividual stability of the APLA status. Additionally,we provide an overview of studies, performed so far, in which significance of APLAs in IBD were assessed.RESULTS: Patients with CD had significantly higher prevalence of both ACA(23.4%) and anti-PS/PT(20.4%) antibodies than UC(4.8%, p < 0.0001 and10.2%, p = 0.004) and HC(2.9%, p < 0.0001 and15.5%, p = NS). No difference was found for the prevalence of anti-β2-GPI between different groups(7.2%-9.7%). In CD, no association was found between APLA and ASCA status of the patients.Occurrence of anti-β2-GPI, ACA and anti-PS/PT was not different between the group of patients with active vs inactive disease state according to appropriate clinical, laboratory and endoscopic scores in CD as well as in UC patients. All subtypes of anti-β2-GPI and ACA IgM status were found to be very stable over time, in contrast ACA IgG and even more ACA IgA status showed significant intraindividual changes.Changes in antibody status were more remarkable in CD than UC(ACA IgA: 49.9% vs 23.3% and ACA IgG:21.2% vs 5.8%). Interestingly, 59.1% and 30.1% of CD patients who received anti-TNF therapy showed significant negative to positive changes in ACA IgA and IgG antibody status respectively. APLA status was not associated with the clinical phenotype at diagnosis or during follow-up, medical therapy, or thrombotic events and it was not associated with the probability of developing complicated disease phenotype or surgery in a Kaplan-Meier analysis.CONCLUSION: The present study demonstrated enhanced formation of APLAs in CD patients. However,presence of different APLAs were not associated with the clinical phenotype or disease course.