Failure to confirm association between PDCD1 polymorphisms and rheumatoid arthritis in a Japanese population

Programmed cell death 1 (PDCD1) is a necessary negative regulator to maintain peripheral tolerance and is a key molecule in the development of autoimmune diseases. Although PDCD1 gene polymorphisms and haplotypes were reported to be associated with rheumatoid arthritis (RA), replication studies later on showed conflicting results. Here, we analyzed the association of PDCD1 with RA using a large series of Japanese RA patients and population-based controls. DNA samples were obtained from 1,504 RA patients and 449 sex-matched controls. All samples were genotyped for three SNPs on PDCD1 (PD-1.1, PD-1.3 and PD-1.5) using the TaqMan fluorogenic 5' nuclease assay. Chi-square testing was performed for a case-control study, and the PENHAPLO program was used for haplotype estimation. We could not observe any significant association of PD-1.1 or PD-1.5 polymorphisms between RA. PD-1.3, which was reported to be involved in susceptibility to RA in patients of European descent, was non-polymorphic in the Japanese population. We conclude that polymorphisms in the PDCD1 gene analyzed here are not associated with RA in a Japanese population.