Psoriasis is a frequent multifactorial chronic inflammatory skin disease affecting approximately 2-3 % of the population. Th-17 and Th-22 T-cell subsets play a major role in the establishment of psoriasis. Th-17 lymphocytes are highly activated in psoriatic skin, releasing inflammatory cytokines involved in psoriasis plaques. Additionally, Th-22 secreted cytokines activate the proliferation and differentiation of keratinocytes, resulting in the specific hyperplasia of psoriatic epidermis.