PDCD1 and rheumatoid arthritis: In view of the pivotal role of PD-1/PD-L pathway in autoimmn immunology, it is worth considering of PDCD-1 functional SNPs, PDCD-1 −606A/G (rs36084323, also known as PD1.1) in promoter, PDCD-1 +7146A/G (rs11568821, also known as PD1.3) in intron 4, and PDCD-1 +7625G/A (rs2227982, also known as PD1.9) and PDCD-1 +7786G/C (rs2227981, also known as PD1.5) in exon 5 as prospective candidates for individuals susceptibility to RA in the Han Chinese population.