The number of long-lived antibody-producing plasma cells is typically kept low, which has been interpreted as evidence suggesting extrinsic constraints on the niches that harbor such cells. In Science Signaling, Infantino et al. reveal that the tyrosine kinase Lyn exerts intrinsic control of plasma cell numbers by regulating their survival. Mice that lack B cell expression of Lyn accumulate a greater number of splenic IgM+ plasma cells by prolonging their survival. Lyn acts to suppress cytokine signaling that occurs by IL-6–STAT3 and IL-3–STAT5 pathways, both of which induce expression of the survival factor Mcl-1. Lyn does not alter signaling via other survival factors, including APRIL, BAFF and IL-21. These findings suggest that Lyn deficiency could contribute to some autoimmune diseases, such as systemic lupus erythematosus, that are characterized by excessive numbers of plasma cells.

Sci. Signal. (12 Aug 2014) 10.1126/scisignal.2005105