FCGR2A and autoimmune disease: It could point to lowered affinity of FcγRs to ICs due to polymorphism of FCGR genes, encoding Fcγ receptors from classes II and III (FCGR2A, FCGR2B, FCGR2C, FCGR3A, FCGR3B), and/or aberration in their copy number (CN), which has been revealed in many other autoimmune disorders, but not yet in SA.