FCGR2B and arthritic joint disease: When addressing the impact of the inhibitory FcγRIIB, it was first observed that mice lacking this receptor developed arthritis similar to wild-type (WT) mice (6); however, three later studies demonstrated an enhanced disease progression in FcγRIIB KO mice compared to WT mice, indicating that this inhibitory Fc receptor has an immunosuppressive role in the model (13, 17, 20).