For example, PDCD1 has been shown to be associated with lupus nephritis and anti-phospholipid antibodies in ethnic subgroups [4], and PTPN22 is primarily associated with anti-cyclic citrullinated peptide (anti-CCP) [22] and rheumatoid factor (RF) [23] autoantibody positive RA. This evidence concerns the gene PDCD1 and rheumatoid arthritis.