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.

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Objective. We have previously described associations between an allele of the interleukin-1 receptor antagonist gene (ILlRN) and several inflammatory diseases. In this study we tested the ILlRN 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 ILlRN*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 ILlRN*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.

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