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

<i>Background:</i> 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. <i>Objectives:</i>The aim of this study was to evaluate an association between the <i>IL17A </i>(-197G>A; rs2275913) and <i>IL17F</i> (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. <i>Methods:</i> 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. <i>Results:</i> No statistically significant differences between psoriasis patients and controls were found in the frequency of the evaluated <i>IL17A </i>and<i> IL17F </i>genotypes and haplotypes. The <i>IL17A </i>or <i>IL17F</i>polymorphisms 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, <i>IL17F</i> 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. <i>Conclusion:</i> It can be stated that the <i>IL17A </i>and <i>IL17F</i> polymorphisms are not markers of susceptibility to psoriasis. However, the <i>IL17F</i> polymorphism may affect the response to NB-UVB therapy.