The role of BLyS/BLyS receptors in anti-chromatin B cell regulation

Abstract

B lymphocyte stimulator (BLyS), also known as B cell-activating factor, is a key positive regulator of B cell homeostasis, and elevated levels of BLyS have been observed in systemic lupus erythematosus (SLE) patients. Given that anti-chromatin auto-antibodies are one of the hallmarks of SLE, we examined the role of BLyS and its receptors in the regulation of anti-chromatin B cells. We demonstrate that exogenous BLyS treatment leads to an increase in B cell numbers, particularly anti-chromatin B cells; yet, their localization in the spleen and auto-antibody production remain unaffected. We also examined transmembrane activator and CAML interactor (TACI), BLyS receptor 3 (BR3) and B cell maturation antigen expression on anti-chromatin B cells before and after receiving T cell help. Interestingly, in the absence of T cell help, TACI expression is greater on immature anti-chromatin B cells compared with immature Tg(-) B cells, whereas BR3 levels are comparable. After receiving T cell help, the anti-chromatin B cells that have differentiated into short-lived plasma cells no longer express BR3 but retain TACI. These data suggest a novel role for TACI in anti-chromatin B cell homeostasis and differentiation.