Interleukin 1 Receptor Antagonist(IL-1ra) Gene Polymorphism in Children with Henoch-Schonlein Purpura Nephritis

ABSTRACT

PURPOSE: Interleukin 1 receptor antagonist(IL-1ra) is an endogenous antiinflammatory agent that binds to IL-1 receptor and thus competitively inhibits the binding of IL-1alpha and IL-1beta. Allele 2 in association with various autoimmune diseases has been reported. In order to evaluate the influence of IL-1ra gene VNTR polymorphism on the susceptibility to HSP and its possible association with disease severity, manifested by severe renal involvement and renal sequelae, we studied the incidence of carriage rate and allele frequency of the 2 repeats of IL-1ra allele 2(IL1RN*2) of the IL-1ra gene in children with HSP with and without renal involvement. METHODS: The IL-1ra gene polymorphisms were determined in children with HSP with(n= 40) or without nephritis(n=34) who had been diagnosed at Busan Paik Hospital and the control groups(n=163). Gene polymorphism was identified by PCR amplification of the genomic DNA. RESULTS: The allelic frequency and carriage rate of IL1RN*1 were found most frequently in patients with HSP and in controls. The allelic frequency of IL1RN*2 was higher in patients with HSP compared to that of controls(4.7% vs. 2.5%, P=0.794). The carriage rate of IL1RN*2 was higher in patients with HSP compared to that of controls(8.1% vs. 6.8%, P= 0.916). The allelic frequency of IL1RN*2 was higher in patients with HSP nephritis compared to that of HSP(6.3% vs.2.9%, P=0.356). The carriage rate of IL1RN*2 was higher in patients with HSP nephritis compared to that of HSP(10.0% vs. 5.9%, P=0.523). Among 13 patients with heavy proteinuria(>1.0 g), 11 had IL1RN*1, 1 had IL1RN*2 and the others had IL1RN*4. At the time of last follow up 4 patients had sustained proteinuria and their genotype was IL1RN*1. CONCLUSION: The allelic frequency and carriage rate of IL1RN*1 were found most frequently in patients with HSP and in controls. Our study suggests that the carriage rate and allele frequency of the 2-repeats of IL-1ra allele 2(IL1RN*2) of the IL-1ra gene may not be associated with susceptibility and severity of renal involvement in children with HSP.