IL1 gene polymorphisms in enthesitis related arthritis category of juvenile idiopathic arthritis (ERA-JIA)

Abstract

Cytokine gene loci are one of the potential susceptibility factors in immuno-inflammatory diseases. Interleukin1 (IL-1) is a major monocyte derived proinflammatory cytokine that mediates tissue damage and cartilage loss in chronic arthritis. IL-1 locus has been linked to various autoimmune diseases, but data on juvenile idiopathic arthritis (JIA) is limited. Ninety-four patients with enthesitis related arthritis (ERA) category of JIA (ILAR criteria) were included in the study. One hundred eighty-five healthy blood donors were used as controls. IL-1Ra VNTR polymorphism was done by PCR using specific primers, and allele assignment was done on product size obtained on 2% agarose gel. IL-1α-889 and IL-β-511 polymorphism was done using PCR–RFLP method. Among 94 patients, 87 were males, and the mean age at onset of disease was 11.8 + 1.8 years; 17 had history of uveitis, and 13 had positive family history. Forty-two had enthesitis, and 51 had inflammatory back pain; all had arthritis. Seventy-six were HLA B27 positive. All three loci genotypes were in the Hardy–Weinberg equilibrium in controls. There was no difference in genotype frequency among patients and controls for IL-1Ra, IL-1α-889 and IL-β-511. IL1*RN2 homozygosity was more common in patients, whereas carriage rate for IL1*RN1 was less frequent in patients. Haplotype frequencies were also similar in both groups. IL-1 gene cluster is not a susceptibility locus for ERA.