Supplementary Material for: IL17A and IL17F Gene Polymorphism Association with Psoriasis Risk and Response to Treatment in a Polish Population

Background: Recent studies have revealed the pivotal role of Th17 cells and interleukin-17 (IL-17) in plaque psoriasis development and treatment outcome. The IL-17 family consists of 6 structurally related cytokines (IL-17A, IL-17B, IL-17C, IL-17D, IL-17E, IL-17F), of which IL-17A and IL-17F mediate similar biological effects. Objectives:The aim of this study was to evaluate an association between the IL17A (-197G>A; rs2275913) and IL17F (rs763780: T>C; rs11465553: G>A; rs2397084: T>C) polymorphisms with psoriasis susceptibility as well as response to topical and combined topical with narrow-band ultraviolet B (NB-UVB) therapy in a Polish population. Methods: Association study involving 407 psoriasis patients and 205 healthy controls. Treatment efficacy was analyzed in 207 patients with mild psoriasis (Psoriasis Area and Severity Index; PASI 3-12) and moderate psoriasis (PASI 12-18), who were randomly subjected to topical or combined topical and NB-UVB treatment. The polymorphisms were evaluated by RT-PCR. Results: No statistically significant differences between psoriasis patients and controls were found in the frequency of the evaluated IL17A and IL17F genotypes and haplotypes. The IL17A or IL17Fpolymorphisms were not associated with treatment outcome measures: efficacy of treatment at the eighth week of the study and PASI change after topical or combined topical and NB-UVB therapy. However, IL17F rs2397084 variant allele C carriers required a significantly higher number of NB-UVB irradiations in comparison to TT homozygotes (15.5 ± 11.4 vs. 11.1 ± 11.9, p = 0.047) to produce a positive clinical response. Conclusion: It can be stated that the IL17A and IL17F polymorphisms are not markers of susceptibility to psoriasis. However, the IL17F polymorphism may affect the response to NB-UVB therapy.