OBJECTIVETo investigate the association of single nucleotide polymorphisms (SNPs) of the peptidylarginine deiminase IV (PADI4) and HLA-DRB1 shared epitope (SE) alleles with rheumatoid arthritis(RA) in a Chinese population.

METHODSFour exonic SNPs of the PADI4 gene (PADI 4_89*A/G, PADI 4_90*C/T, PADI 4_92*C/G and PADI 4_104*C/T) were genotyped in 67 unrelated patients with RA and 81 healthy controls, using cDNA sequencing and T vector cloning. HLA-DRB 1*01, *04 and *10 subtypes were determined by polymerase chain reaction with sequence specific primers (PCR-SSP).

RESULTSThe distributions of the 4 SNPs were different in the two groups, and increased RA susceptibility was significantly associated with the minor alleles of PADI 4_89*G (P was 0.023), PADI 4_90*T (P was 0.004), PADI 4_104*T (P was 0.003), and the haplotypes carrying the 4 minor alleles (P was 0.008). HLA-DRB1 SE alleles are composed of HLA-DRB 1*0101, *0102, *0401, *0404, *0405, *0408, *0409, *0410 and *1001. Individuals carrying the SE alleles were associated with increased RA susceptibility (P was 0.002). Individuals carrying both the SE alleles and minor alleles of the 4 SNPs were more susceptible to RA than individuals carrying neither the minor SNP alleles nor the SE alleles.

CONCLUSIONThe PADI4 SNPs and haplotypes are associated with RA susceptibility in Chinese. HLA-DRB1 shared epitope is also an important risky factor for RA. There may exist certain synergistic effect between the PADI4 minor alleles and the HLA-DRB1 shared epitope.