Absence of a genetic association between IL-1RN and IL-1B gene polymorphisms in ulcerative colitis and crohn disease in multiple populations from northeast England

Inflammatory bowel disease (IBD) is a chronic inflammation of the gastroint estinal tract of unknown aetiology, phenotypically categorized into ulcerat ive colitis (UC) and Crohn disease (CD). Genetic factors are of considerabl e importance in both. The genetic relationship between IBD and the interleu kin-1 receptor antagonist and interleukin-1 beta genes (IL-IRN, and IL-1B, respectively) has been extensively studied. However, the quality and outcom e of the genetic association studies, in particular the association with IL -1RN*2, have been variable and these associations remain controversial. The aim of the present study was to re-investigate these two candidate genes i n a large series of IBD patients from a genetically homogeneous population with low levels of population admixture, and provide a definitive answer to this question. Methods: A total of 529 northern European Caucasoid patient s with IBD (347 UC. 182 CD) and 289 racially and geographically matched hea lthy controls were studied. The IL-IRN and IL-IB genotypes, allele frequenc ies and most probable haplotypes were determined by standard PCR protocols. Results: There were no significant differences in the distributions of the IL-IRN and IL-IB genotypes, allele frequencies or haplotypes in either pat ient series compared to healthy controls or between clinical subsets. Genot ype distribution and frequency data for allele 2 (IL-1RN*2) in particular s howed no significant differences across all patient groups for all three se ries. Conclusion: The findings of this study lead us to reject the IL-IRN*2 association with IBD.