PGAP3 and rheumatoid arthritis: BANK1 is primarily expressed in CD19+ B cells and is a known SLE and RA susceptibility gene [34, 35]; in animal studies, the PGAP3 gene knockout has been associated with reduced apoptotic cell clearance, a causal pathway for autoimmunity [36]; PLCL2 is known to encode a negative regulator of B cell receptor signalling important in controlling immune responses and is a known susceptibility gene for RA [37].