Novel interleukin-1 receptor antagonist exon polymorphisms and their use in allele-specific mRNA assessment.

A variable number of tandem repeats (VNTR) polymorphism has been described in intron 2 of the interleukin-1 receptor antagonist gene. Allele 2 of this polymorphism is associated with many chronic inflammatory diseases. Using direct sequencing of polymerase chain reaction products from individuals of known genotype for the VNTR, we have identified four single base change polymorphisms in exons 1ic and 2 and one upstream of exon 1ic, all of which are probably in linkage disequilibrium with the intron 2 VNTR. The exonic polymorphisms do not alter the encoded amino acid sequence. Using the exon 2 polymorphism as a marker for the intron 2 disease-associated allele, we have been able to analyse allele-specific mRNA in heterozygotic keratinocyte cell lines. The disease-associated allele shows no difference from other alleles in this cell type with respect to mRNA accumulation.

Interleukin 1 receptor antagonist gene polymorphism association with lichen sclerosus.

Cytokines play key roles in immune responses, inflammation and fibrosis. The balance between levels of cytokines, their receptors and specific inhibitors controls inflammatory reactions in tissues. The pathogenesis of lichen sclerosus is unknown but probably involves cytokine mediators such as interleukin 1 (IL-1) and interleukin 1 receptor antagonist (IL-1ra). The IL-1ra is a competitive inhibitor of IL-1 alpha and IL-1 beta, and therefore is a powerful endogenous anti-inflammatory molecule. The gene encoding IL-1ra (designated IL-1RN) has a variable number tandem repeat polymorphism in intron 2. There are five alleles of the gene corresponding to 2, 3, 4, 5 and 6 repeats of an 86-bp sequence. We have determined allele frequencies in a control population and a group of 78 patients with lichen sclerosus. The frequency of one of the alleles is related to increasing disease severity. Thus, IL-1RN may be a candidate gene or severity factor for lichen sclerosus or may possibly be a linked marker to another, as yet undefined, gene.

Severity of alopecia areata is associated with a polymorphism in the interleukin-1 receptor antagonist gene.

One of the most potent pro-inflammatory mediators is the early-acting cytokine interleukin-1. Its actions are regulated by a structurally related anti-inflammatory cytokine known as the interleukin-1 receptor antagonist. We have previously characterized a DNA polymorphism in this gene (IL-1rn) and have found associations between allele 2 and several chronic inflammatory diseases. In the present study, we tested the frequency of allele 2 of the IL-1rn gene in 90 patients with alopecia areata compared with 261 healthy controls. There was a significant association between allele 2 of the polymorphism and the severity of alopecia areata. The frequency of allele 2 increased from 24.1% in the control population to 25.9% in patchy alopecia areata, 36.1% in alopecia totalis, and 47.2% in alopecia universalis (p = 0.005). This severity association is similar to that found in other epithelial-related diseases, including inflammatory bowel disease, lichen sclerosus, and systemic lupus erythematosus.

Interleukin-1 receptor antagonist gene polymorphism as a disease severity factor in systemic lupus erythematosus.

OBJECTIVE: We have previously described associations between an allele of the interleukin-1 receptor antagonist gene (IL1RN) and several inflammatory diseases. In this study we tested the IL1RN gene as a possible marker in patients with systemic lupus erythematosus (SLE). METHODS: Eighty-one SLE patients and 261 ethnically matched control subjects were genotyped by polymerase chain reaction. RESULTS: We found an increase in both frequency and carriage rate of IL1RN*2 in the SLE group. This association strengthened with extensive disease and particularly with the presence of photosensitivity and discoid skin lesions. CONCLUSION: We describe a novel association between IL1RN*2 and SLE. Carriage of the allele seems to influence severity rather than susceptibility to SLE. We postulate that the association of this polymorphism with disease severity is a widespread feature of common inflammatory and autoimmune diseases.

Novel genetic association between ulcerative colitis and the anti-inflammatory cytokine interleukin-1 receptor antagonist.

BACKGROUND/AIMS: Ulcerative colitis and Crohn's disease have well-recognized familial tendencies, but the genetic basis of this clinical observation remains unknown. The cytokine interleukin-1 receptor antagonist is a potent anti-inflammatory protein that can prevent immune-mediated bowel inflammation in animals. We have previously characterized a polymorphism within the gene for this cytokine and others in the genes for the proinflammatory cytokines interleukin 1 alpha, interleukin 1 beta, and tumor necrosis factor alpha. The aim of this study was to determine whether inflammatory bowel disease was associated with particular alleles of these polymorphic cytokine genes. METHODS: The allelic frequencies of these polymorphic cytokine genes were determined in patients with ulcerative colitis (n = 113), Crohn's disease (n = 78), and healthy controls (n = 261). RESULTS: Allele 2 of interleukin-1 receptor antagonist was significantly over-represented in the ulcerative colitis patients: 35% versus 24% in controls (P = 0.007). Carriage of at least one copy of this allele gave an odds ratio of 2.0 for ulcerative colitis compared with controls. This association with allele 2 of interleukin 1 receptor antagonist was greatest in patients with total colitis and was not seen in Crohn's disease. There were no associations between UC and any of the other cytokine genes examined. CONCLUSIONS: This observation provides evidence that interleukin-1 receptor antagonist may have a role in determining the genetic susceptibility to and pathogenesis of ulcerative colitis.

Polymorphism in human IL-1 receptor antagonist gene intron 2 is caused by variable numbers of an 86-bp tandem repeat.

We have investigated the polymorphism in intron 2 of the interleukin-1 receptor antagonist gene and identified two new alleles of the system. We have shown that the polymorphism is caused by the variable copy number of an 86-bp sequence, by using the polymerase chain reaction and primers immediately flanking the repeat region, and by direct sequencing. The repeat region contains three potential protein-binding sites and therefore the variable copy number may have functional significance.