The decrease of anti-inflammatory
cytokine and increase of pro-inflammatory
cytokine was observed in
rheumatoid arthritis (RA).
Interleukin-10 (IL-10), a potent anti-inflammatory
cytokine, has been demonstrated to suppress joint swelling and deformation in RA animal model.
Interleukin-18 (IL-18), a widely distributed pro-inflammatory
cytokine, induces the production of IFN-γ, activate NK cells, and promote
inflammation. Recent studies demonstrated that the serum
IL-10 and
IL-18 levels may be influenced by genetics and related to susceptibility to several
autoimmune diseases. In the present study, using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and
DNA sequencing techniques, we analyzed the genotype and allele distributions of two single nucleotide polymorphisms (SNP) loci in the promoter region of
IL-10 and
IL-18 genes (IL-10-592 A/C and IL-18-607 A/C loci, respectively). Our results indicated that IL-10-592 allelic and genotypic frequencies were significantly different between the RA patients and normal subjects (P<0.05). In addition, significant differences of IL-10-592 allelic and genotypic frequencies were also detected between the patients with or without anti-
cyclic citrullinated peptide antibody (
anti-CCP) (P<0.05). In contrast, allelic and genotypic frequencies of IL-18-607 did not show significant difference between RA patients and normal subjects (P>0.05) or between
anti-CCP-positive and
anti-CCP-negative RA patients (P>0.05). Furthermore, ELISA detection of
IL-10 and
IL-18 serum levels revealed that the genotype of IL-10-592 was associated with
IL-10 serum level (P<0.05), but the genotype and allele frequency of IL-18-607 was not associated with
IL-18 serum level (P>0.05). Taken together, our findings provide new insight for the polymorphism of
IL-10 gene in the pathogenesis of RA.