The 5' untranslated region variant rs3811050 C/T of the interleukin-38 encoding gene is associated with susceptibility to rheumatoid arthritis in Iraqi women.

BACKGROUND

Interleukin (IL)-38, the latest member of the IL-1 cytokine family, is proposed to have a pathogenic role in rheumatoid arthritis (RA). It is encoded by the IL1F10 gene, which harbors single nucleotide polymorphisms (SNPs) that may predict the risk of autoimmune diseases. Among them are 5' untranslated region (UTR) SNPs, which play a key role in post-transcriptional control, but have not been studied in Iraqi RA patients.

METHODS

Two novel IL1F10 5'UTR SNPs (rs3811050 C/T and rs3811051 T/G) were explored in RA and control women (n = 120 and 110, respectively). SNPs were genotyped using TaqMan assay. An ELISA kit was used to measure serum IL-38 concentrations.

RESULTS

A reduced risk of RA was associated with rs3811050 T allele and CT genotype (corrected probability [pc] = 0.01 and < 0.001, respectively), while there was no significant association with rs3811051. Haplotype analysis demonstrated that C-T haplotype was associated with a 1.65-fold greater risk of RA, whereas a reduced risk was linked to T-G haplotype. IL-38 concentrations were higher in patients than in controls (p < 0.001). In addition, IL-38 showed acceptable performance in distinguishing between RA and control women (p < 0.001). When IL-38 concentrations were stratified according to SNP genotypes, no significant differences were found.

CONCLUSIONS

The rs3811050 variant was more likely to affect RA susceptibility in Iraqi women, and the T allele may play a role in reducing disease risk. IL-38 concentrations were elevated in RA patients, but were not affected by the rs3811050 and rs3811051 genotypes.