Lack of association between an interleukin-1 receptor antagonist gene polymorphism and ulcerative colitis

Abstract

Background - Recently, the association of a polymorphism in the gene coding for the anti-inflammatory cytokine interleukin-1 receptor antagonist with ulcerative colitis has been reported. This was interpreted as a possible genetic predisposition for severity of the inflammatory response. Aims - To examine this polymorphism in a southern German population. Subjects - The study included 234 healthy controls, 57 patients with ulcerative colitis, including 31 patients with pancolitis, 44 first degree healthy relatives of patients with ulcerative colitis, and 65 patients with Crohn's disease. Methods - Genotypes were determined by a polymerase chain reaction amplification of the intron 2 fragment harbouring a variable number of tandem repeat nucleotide sequences. Amplification products were separated on a 2% agarose gel. Results - The allele frequency for allele 2 was 27% in healthy controls, 28% in Crohn's disease, and 21% in patients with ulcerative colitis. The same allele frequency (21%) was found in a subgroup of patients with ulcerative colitis affecting the whole colon. Thus for allele 2 as well as for all other alleles, genotypes, or carriage rates no significant differences were found compared with controls. All allele frequencies in the control population were similar to those in earlier studies. Conclusions - No association of a polymorphism in the interleukin-1 receptor antagonist gene with ulcerative colitis could be identified in this southern German population. The findings of an earlier study reporting an increased frequency of allele 2, particularly in patients with pancolitis, could not be confirmed.