Cytokine gene polymorphisms in psoriasis

Background Cytokine production is under genetic control, and certain alleli c variants of cytokine genes are associated with higher or lower cytokine p roduction in vitro and in vivo. Psoriasis is associated with an overexpress ion in the involved skin of T-helper cell type 1 (Th1) cytokines, e.g. inte rferon (IFN) -gamma and tumour necrosis factor (TNF) alpha and relative und erexpression of Th2 cytokines, e.g. interleukin (IL) -4 and IL-10. Objective We investigated the hypothesis that allelic variants of genes for a high production of Th1 cytokines or TNF-alpha, or conversely low product ion of Th2 cytokines might represent a risk factor for developing psoriasis . Methods Genotyping for IFN-gamma, IL-10, IL-4 and TNF-alpha was undertaken for 84 patients with psoriasis and compared with control data on file. Results Genotype frequencies showed no differences between patients and con trols for IFN-gamma, TNF-alpha or IL-4. For IL-10, patients with late onset psoriasis (over 40 years) were more likely to be heterozygous at position - 1082 (P = 0.02), corresponding to intermediate production of IL-10 in vit ro and in vivo. Conclusions Psoriasis is not determined by a genotype consistent with high production of Th1 cytokines or low production of Th2 cytokines. Thus, the T h1 cytokine profile found in psoriatic plaques is most likely a consequence of local factors.