title: Allelic polymorphism in IL-1 beta and IL-1 receptor antagonist (IL-1Ra) genes in inflammatory bowel disease.
abstract: Recent reports have shown that allele 2 of the IL-1 receptor antagonist (IL-1Ra) gene is over-represented in ulcerative colitis (UC). Healthy individuals carrying allele 2 of this gene have increased production of IL-1Ra protein. Since the final outcome of the biological effects of IL-1 beta may depend on the relative proportion of these two cytokines, we have studied if a TaqI polymorphism in the IL-1 beta gene, which is relevant to IL-1 beta protein production, may be involved in the genetic susceptibility to UC and Crohn's disease (CD), in association with the established IL-1Ra gene polymorphism. Polymorphisms in the closely linked genes for IL-1 beta and IL-1Ra were typed in 100 unrelated Dutch patients with UC, 79 with CD, and 71 healthy controls. The polymorphic regions in exon 5 of the IL-1 beta gene and in intron 2 of the IL-1Ra gene, were studied by polymerase chain reaction (PCR)-based methods. The IL-1 beta allele frequencies in UC and CD patients did not differ from those in healthy controls. In order to study if the IL-1 beta gene polymorphism might participate synergistically with the IL-1Ra gene polymorphism in susceptibility to UC and CD, individuals were distributed into carriers and non-carriers of allele 2 of the genes encoding IL-1 beta and IL-1Ra, in each of the patient groups and controls. Results indicated a significant association of this pair of genes, estimated by the odds ratio (OR) after performing Fisher's exact test, in the UC group (P = 0.023, OR = 2.81), as well as in the CD group (P = 0.01, OR = 3.79). Thus, non-carriers of IL-1 beta allele 2 were more often present in the subgroup of patients carrying the IL-1Ra allele 2. By contrast, no association of these alleles was detected in the group of healthy controls (P = 1.00, OR = 0.92). These results suggest that the IL-1 beta/IL-1Ra allelic cluster may participate in defining the biological basis of predisposition to chronic inflammatory bowel diseases.
authors.affiliation: Department of Gastroenterology, Free University Hospital Amsterdam, The Netherlands.
authors.forename: G
authors.initials: G
authors.lastname: Bioque
authors.forename: J B
authors.initials: JB
authors.lastname: Crusius
authors.forename: I
authors.initials: I
authors.lastname: Koutroubakis
authors.forename: G
authors.initials: G
authors.lastname: Bouma
authors.forename: P J
authors.initials: PJ
authors.lastname: Kostense
authors.forename: S G
authors.initials: SG
authors.lastname: Meuwissen
authors.forename: A S
authors.initials: AS
authors.lastname: Peña
mesh_terms: D000483:Alleles; D001483:Base Sequence; D003093:Colitis, Ulcerative / Q000235:genetics*; D003424:Crohn Disease / Q000235:genetics*; D017931:DNA Primers / Q000737:chemistry; D005787:Gene Frequency; D006801:Humans; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1 / Q000235:genetics*; D008969:Molecular Sequence Data; D012795:Sialoglycoproteins / Q000235:genetics*
chemical_list: D017931:DNA Primers; C507763:IL1RN protein, human; D053590:Interleukin 1 Receptor Antagonist Protein; D007375:Interleukin-1; D012795:Sialoglycoproteins