FCGR3B and systemic lupus erythematosus: Further, multiple studies have identified low FCGR3B CN (i.e., <2 copies) as a risk factor for systemic autoimmune diseases, such as systemic lupus erythematosus [9–11], rheumatoid arthritis [12, 13], primary Sjögren's syndrome [10, 11], and scleroderma [14], which is interpreted in terms of the important role that Fc receptors play in the clearance of immune complexes.