Mice that received the FcγRIIB−/−YaaIRF5+/+ bone marrow developed splenomegaly, antinuclear autoantibodies (ANAs), and kidney disease, whereas mice that received the FcγRIIB−/−YaaIRF5–/– bone marrow did not. This evidence concerns the gene FCGR2B and Splenomegaly.