PPP1R18 and autoimmune disease: Among these 14 novel genes identified, CYP21A2, MSH5, PPP1R18, and MMEL1 are found in or near the human major histocompatibility complex (MHC) region on chromosome 6, where these genes play a crucial function in immune response and immunological regulation and are implicated in several inflammatory and autoimmune diseases (37–42).