fcgr2b regulates b cell activation by increasing the bcr activation threshold and suppressing b cell mediated antigen presentation to t cells through the itim-dependent inhibitory mechanism. ligation of fcgr2b on b cells downregulates antibody production, prevents the membrane organization of bcr and cd19 and promotes apoptosis. co-ligation of fcgr2b on dendritic cells inhibits maturation and blocks cell activation. the negative regulatory role of the fcgriib molecule is not limited to bcr-induced b-cell activation, but is also functional on other b-cell activation pathways mediated by cd40 and il-4.