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Systemic lupus erythematosus (SLE) is an autoimmune disease. It is characterized by the production of various pathogenic autoantibodies and is suggested to be triggered by increased type I interferon (IFN) signature. Previous studies have identified increased plasmablasts in the peripheral blood of SLE patients. The biological characteristics of SLE plasmablasts remain unknown, and few treatments that target SLE plasmablasts have been applied despite the unique cellular properties of plasmablasts compared with other B cell subsets and plasma cells. We conducted microarray analysis of naïve and memory B cells and plasmablasts (CD38+CD43+ B cells) that were freshly isolated from healthy controls and active SLE (n = 4, each) to clarify the unique biological properties of SLE plasmablasts. The results revealed that all B cell subsets of SLE expressed more type I IFN-stimulated genes. In addition, SLE plasmablasts upregulated the expression of cell cycle-related genes associated with higher FOXM1 and FOXM1-regulated gene expression levels than that in healthy controls. This suggests that a causative relationship exists between type I IFN priming and enhanced proliferative capacity through FOXM1. The effects of pretreatment of IFNα on B cell activation and FOXM1 inhibitor FDI-6 on B cell proliferation and survival were investigated. Pretreatment with IFNα promoted B cell activation after stimulation with anti-IgG/IgM antibody. Flow cytometry revealed that pretreatment with IFNα preferentially enhanced the Atk and p38 pathways after triggering B cell receptors. FDI-6 inhibited cell division and induced apoptosis in activated B cells. These effects were pronounced in activated B cells pretreated with interferon α. This study can provide better understanding of the pathogenic mechanism of interferon-stimulated genes on SLE B cells and an insight into the development of novel therapeutic strategies.

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A 30‐year‐old man with severe hypoalbuminemia (serum albumin: 0.9 g/dL) was admitted with severe bilateral leg edema and unilateral pleural effusion. Serum anti‐SS‐A and SS‐B antibody levels were abnormally elevated, and his symptoms fulfilled the diagnostic criteria for Sjögren's syndrome. Technetium‐99m albumin scintigraphy revealed protein leakage from a large area of the small intestine. Immunohistochemistry revealed perivascular deposition of C1q, C3d, and immunoglobulin G in the duodenal mucosa. The patient was diagnosed with protein‐losing gastroenteropathy associated with Sjögren's syndrome. Within 2 months of treatment with oral prednisolone and mycophenolate mofetil, the clinical symptoms of hypoalbuminemia and Sjögren's syndrome disappeared completely.