A Low molecular weight BAFF receptor antagonist inhibits differentiation of human peripheral B cells into plasma blasts/plasma cells in vitro.

Abstract

Abstract Backgrounds and Purpose We have demonstrated that the elevated expression of BAFF receptor (BR3) on monocytes is involved in the overproduction of IgG by B cells in patients with primary Sjögren’s syndrome (pSS) which is often accompanied with hypergammaglobulinemia. We discovered a low molecular weight compound, BIK13, which inhibits binding of BAFF to BR3, by our original high-throughput screening system. We found that BIK-13 suppressed IL-6 production by BAFF-stimulated pSS monocytes. In this study, we investigated inhibitory effects of BIK-13 on B cell functions. Methods PBMCs were cultured with a B cell-stimulants cocktail, such as anti-IgM and CD40 antibodies, human IL-21 and human BAFF, in the presence of BIK-13. B cell-differentiation was monitored through analysis of the expression levels of CD19/CD38/IgD and activation-induced cytidine deaminase (AID) by FACS and qPCR, respectively. The amounts of IL-6 and IgG produced in vitro by the cells were measured by ELISA. Results Increased production of IgG and IL-6 by PBMC upon stimulation with B cell-stimulants was suppressed by BIK13 in a dose dependent manner. FACS analysis indicated that differentiation of B cells into plasma blasts and/or plasma cells was inhibited by BIK-13. In addition, the expression level of AID was also suppressed by the compound, suggesting that the IgG class switching was impaired. Conclusion These data collectively suggest that BIK-13 suppresses the B cell functions and may provide a novel therapeutic possibility to treat autoimmune diseases such as pSS.