Association of polymorphisms in interleukin (IL)-12A and -B genes with rheumatoid arthritis in a Chinese population.

Rheumatoid arthritis (RA) is characterized by synovial infiltrates and progressive cell-mediated destruction of the joints, which results in significant disability and early mortality. Genetic factors may play an important role in the development of RA. The aim of this study was to investigate the association of common polymorphisms in interleukin (IL)-12A and IL-12B genes with RA in a Chinese Han population. Three single nucleotide polymorphisms (SNPs) in IL-12 genes were genotyped in 412 patients with RA and 279 control subjects using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Our data showed that IL-12B gene SNPs rs3212227 and rs6887695 were observed as a risk factor of RA. The minor allele (C) frequency of IL-12B gene rs3212227 and rs6887695 increased the risk of RA. Individuals carrying the rs3212227/rs6887695 C/C haplotype were associated with a significantly increased risk of RA. RA patients with the C allele of IL-12B gene rs6887695 was a protective factor to erosive arthropathy. Carriers of the C allele of IL-12B gene rs3212227 were significantly more likely to be RF-positive. No significant association was observed between rs2243115 in IL-12A and RA, due probably to the limited power. These results suggest that common variants in IL-12B may contribute to the development of RA in the Chinese population.