IRAK1 and miR-499 play an important role in the etiology of rheumatoid arthritis. Few studies to date have focused on the influence of the IRAK1 rs3027898 C/A and hsa-mir-499 rs3746444 T/C polymorphisms in the susceptibility of the Chinese population to rheumatoid arthritis. We hypothesized that these polymorphisms may contribute to rheumatoid arthritis susceptibility. We studied IRAK1 rs3027898 C/A and hsa-mir-499 rs3746444 T/C gene polymorphisms in 214 rheumatoid arthritis cases and 478 controls in a Chinese population. Genotyping was performed by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). When the IRAK1 rs3027898 CC homozygote genotype was used as the reference group, the AA genotype was associated with significantly increased risk of rheumatoid arthritis (odds ratio (OR) = 1.91, 95 % confidence interval (CI) = 1.12-3.26, p = 0.017). A significantly increased risk of RA associated with the IRAK1 rs3027898 AA genotype was more evident among females, younger patients, CRP negative patients and both anti-CCP positive and negative patients compared with the IRAK1 rs3027898 CC/CA genotypes. The hsa-mir-499 rs3746444 T/C single nucleotide polymorphism (SNP) was not significantly associated with the risk for rheumatoid arthritis. Our findings suggest that the functional SNP IRAK1 rs3027898 C/A variant allele is associated with the development of rheumatoid arthritis. However, the hsa-mir-499 rs3746444 T/C polymorphism may not be associated with susceptibility to rheumatoid arthritis.

Macrophage migration inhibitory factor (MIF) is a key pro-inflammatory mediator. It plays an important role part in the pathogenesis of several inflammatory and immune diseases. A functional single nucleotide polymorphism (SNP) of MIF -173 G/C is known to influence MIF promoter activity in T lymphoblast cell lines and is associated with a higher serum MIF level. The CD40 is also crucial for some relevant functions of the immune system and may be related to rheumatoid arthritis (RA). And CD226 is an important cell-surface receptor molecule involved in the adhesion and activation of T-cell. We hypothesized that these polymorphisms may contribute to RA susceptibility. We studied MIF -173 G/C, CD40, and CD226 gene polymorphisms in 214 patients with RA and 478 controls in a Chinese population. Genotyping was done by using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). When the MIF -173 GG homozygote genotype was used as the reference group, the CC genotype was associated with a significantly increased risk for RA. In the recessive model, when the MIF -173 GG/GC genotypes were used as the reference group, the CC homozygote genotype was associated with a significant 1.56-fold increased susceptibility to RA. None of the CD40 rs1883832 C/T and CD226 rs763361 C/T polymorphisms achieved a significant difference in genotype distributions between cases and controls. In the stratification analyzes, a significantly increased risk for RA associated with the MIF -173 CC genotype was evident among CRP-negative patients compared with the MIF -173 GG/GC genotype. For the CD40 rs1883832 C/T variant, the risk effects of CD40 rs1883832 TT versus CD40 rs1883832 CC/CT were significant in men. These findings suggested that the functional SNP MIF -173 G/C variant allele was associated with the development of RA. However, CD40 and CD226 gene polymorphisms may not be associated with RA susceptibility. Due to the limitation of sample size, this study should be considered preliminary.

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