The frequencies of haplotypes defined by three polymorphisms of the IL-31 gene: -1066, -2057, and IVS2+12 in Polish patients with atopic dermatitis.

Abstract

Severe pruritus is one of the cardinal symptoms of atopic dermatitis (AD). Recently, the interleukin (IL)-31 cytokine has been implicated in the induction and maintenance of severe pruritus and chronic skin inflammation in several pruritic skin diseases, including AD. We aimed to investigate the association of the IL-31 gene haplotypes with pruritus and severity of AD, as well as their correlation to the serum IL-31 levels. A total of 127 patients with AD and 96 healthy controls were analyzed for polymorphic variants of the IL-31 gene using an amplification refractory mutation system-polymerase chain reaction method. IL-31 haplotype frequencies were estimated with the use of tagging single nucleotide polymorphisms, expectation-maximization, and Excoffier-Laval-Balding algorithms. Serum IL-31 levels were measured using a standard enzyme-linked immunosorbent assay kit. The frequency of AAG, AGA, AGG, and GAA haplotypes of the IL-31 gene was higher in patients with AD than in controls. The mean IL-31 levels in serum were lower in controls than in the patients (P<0.00001) and were higher in those with severe vs. mild AD (P=0.008). No correlation was found between IL-31 and the severity of pruritus. The haplotype AAA was associated with a high IL-31 serum level (P=0.008) and with severe AD (high SCORing Atopic Dermatitis index) (P=0.013). The haplotype GAA was associated with a severe form of pruritus (P=0.016) and the haplotype GGG with the mild one (P=0.07). The results of this study suggest that the severity of AD in a Polish population is associated with some specific haplotypes of the IL-31 gene, which can indicate their prognostic role also renews the questions concerning the role of IL-31 in pruritus in AD.