The survival of long-lived plasma cells, which produce most serum immunoglobulin, is central to humoral immunity. We found here that the inhibitory Fc receptor FcgammaRIIb was expressed on plasma cells and controlled their persistence in the bone marrow. Crosslinking FcgammaRIIb induced apoptosis of plasma cells, which we propose contributes to the control of their homeostasis and suggests a method for therapeutic deletion. Plasma cells from mice prone to systemic lupus erythematosus did not express FcgammaRIIb and were protected from apoptosis. Human plasmablasts expressed FcgammaRIIb and were killed by crosslinking, as were FcgammaRIIb-expressing myeloma cells. Our results suggest that FcgammaRIIb controls bone marrow plasma cell persistence and that defects in it may contribute to autoantibody production.

Complementary DNA encoding the IgG1 induction factor, the first lymphokine directed to B lymphocytes, from a murine T-cell line has been cloned using a new strategy. The putative primary amino-acid sequence was deduced from the nucleotide sequence determined. The lymphokine synthesized by the direction of this cloned cDNA has many other functions, such as production of B-cell growth factor-1 and induction of Ia on B cells.