Interleukin-1 receptor antagonist gene polymorphism in patients with rheumatoid arthritis in India

Abstract

Background & objectives: Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring anti-inflammatory molecule that blocks action of IL-1. Polymorphism in IL-1Ra gene intron 2 results in differences in production of IL-1Ra. These polymorphisms are reportedly associated with autoimmune disease susceptibility in different studies. However, such data are lacking from India. We undertook this study to examine the IL-1Ra polymorphism as a susceptibility marker in patients with rheumatoid arthritis (RA). Methods: DNA samples from 107 patients with RA and 111 healthy controls were used to study genotypes of the IL-1RA gene by PCR. Allelic frequencies and carriage rates were calculated and compared in both the groups. Results: Among the 107 patients with RA, 93 were females and 75 per cent were seropositive for rheumatoid factor. The frequencies of IL-1RA alleles in controls were as follows: Allele 1 (IL-1RN*1) was 83.33 per cent, IL-1RA allele 2 (IL-1RN*2) was 16.21 per cent and allele 3 (0.46%). In RA patients the allele frequencies were 84.11 per cent for IL-1RN*1, 14.95 per cent for IL-1RN*2, 0.47 per cent each for IL-1RN*3 and IL-1RN*4. There was no difference in frequency of different alleles between the two groups. However, homozygosity for allele 2 was more frequent in controls (9.91%) as compared to patients (4.67%). Interpretation & conclusion: Our findings indicated that IL-1RA polymorphism was not a susceptibility marker in RA nor did it show any association with seropositivity, Sjögren’s syndrome or subcutaneous nodules. Further studies with large sample need to be done to confirm these findings.