FCGR2B and systemic lupus erythematosus: In both human and murine SLE, susceptibility allele has been mapped to intervals linked to the Fc γ RII gene on chromosome I and it has been hypothesized that the Fc γ RIIB promotor polymorphism may possibly predispose through germinal center B cells abnormally down regulating Fc γ RIIB1 expression upon autoantigen stimulation and thus escaping negative signals for IgG production.