FCGR2B and systemic lupus erythematosus: However, the fact that only one defective variant is already associated with SLE indicates that these receptors have distinct functions in the development of autoimmunity.[7, 8] Recent findings indicate that Fc γ RIIB is important in the initiation of autoimmunity by modulating activation of B cells and subsequent antibody production, thus contributing to the breakdown of immune tolerance.