The decreased expression of FcγRIIb on memory B cells or immediate plasma cell precursors which occurs in approximately 50% of SLE patients may be one mechanism which contributes uniquely to the observed diminished tolerance in antigen-experienced B cells as FcγRIIb inhibits the B cell response in post-germinal center compartments and regulates plasma cell homeostasis [44], [45], [46], [47]. The gene discussed is FCGR2B; the disease is systemic lupus erythematosus.