Fc?RIIB, Fc?RIIIB, and systemic lupus erythematosus
The autoimmune disease systemic lupus erythematosus (SLE) is characterized by the deposition of immune complexes in organs such as the kidney. This occurs as a result of multiple immunological abnormalities, including the production of high levels of autoantibody and dysregulated handling of immune complexes. Receptors for the Fc portion of IgG are critically involved in immune complex handling and clearance and in the regulation of B-cell activation. Polymorphisms in the low-affinity Fc? receptors have been associated with susceptibility to a number of autoimmune diseases, including SLE. We review the role of two such receptors in the pathogenesis of lupusthe inhibitory receptor Fc?RIIB and the glycosylphosphatidylinositol-linked activatory receptor Fc?RIIIB. Recent work has enhanced our understanding of the mechanism of action of the Fc?RIIB I232T polymorphism and the overall role of this receptor in SLE. The human neutrophil antigen-1 allotypes of Fc?RIIIB and the role of the receptor in SLE are discussed with regard to the recent determination of copy number variation in FCGR3B and the association of low copy number with SLE.
fc?riib fc?riiib systemic lupus erythematosus fcgr3b low-affinity fc receptors fcgr2b copy number variability