T helper-2 cytokine/regulatory T-cell gene polymorphisms and their relation with risk of psoriasis in a South Indian Tamil cohort

Background: Psoriasis is known to be associated with an up-regulation of T-helper (Th)-1 & Th-17 cytokines and a relative down-regulation of Th-2 and T-regulatory (T-reg) cytokines. Certain allelic variants of these cytokine genes may alter Th1/Th17 and Th2/T-reg balance and may be associated with the risk of psoriasis. Hence we aimed to determine the association of IL-4 (rs2243250), IL-10 (rs1800871 and rs1800896) and FOXP3 (rs3761548) gene polymorphisms with risk of psoriasis in South Indian Tamils.

Methods: A total of 360 cases of psoriasis and 360 healthy controls were recruited. The polymorphism in IL-4 (rs2243250) & IL-10 (rs1800871) were typed by ARMS-PCR and IL-10 (rs1800896) & FOXP3 (rs3761548) were typed by TaqMan 5'allele discrimination assay.

Results: We observed that IL-4 (rs2243250) had a reduced risk of psoriasis, while the IL-10 (rs1800871) conferred an increased susceptibility to psoriasis, as compared with controls. However, IL-10 (rs1800896) and FOXP3 (rs3761548) gene polymorphisms were not associated with psoriasis risk. The plasma IL-4 levels was not different between the cases and controls, however the heterozygous CT genotype demonstrated significant high IL-4 levels. Plasma IL-10 levels were significantly increased in cases compared to controls, however none of the genotypes were associated with the plasma IL-10 levels.

Conclusion: Our results suggest that IL-4 (rs2243250) polymorphism is protective against psoriasis, while IL-10 (rs1800871) polymorphism confers increased risk of psoriasis in South Indian Tamils. Detection of these genetic variants as predictive risk factors may lead to the selection of patient-tailored therapy to maximize the effectiveness of therapy.