FCGR2A and AIDS: The FCGR2A gene encodes an activating receptor expressed on macrophages and neutrophils, and a coding polymorphism (rs1801274 c.497AG [p.His131Arg]) has been associated with susceptibility to perinatal HIV infection [15] and variation in HIV progression to AIDS [16], with His131 homozygotes showing increased perinatal transmission and more rapid progression to AIDS.