FCGR2B and Autoimmunity: The production of autoantibodies by C57BL/6 mice in the absence of FcγRIIb suggests that FcγRIIb deficiency, besides modifying autoimmunity caused by other autoimmune susceptibility loci (e.g., Slamf129, Yaa), as discussed earlier, can result in loss of tolerance in the GC.