Skewed distribution of natural killer cells in psoriasis skin lesions.

Psoriasis is a hyper-proliferative disease of the skin in which immunological mechanisms play a direct pathogenetic role. There have been limited studies of natural killer (NK) cells in psoriasis. The aim of this study was to examine the phenotype of NK cells in skin biopsies and peripheral blood mononuclear cells from patients with psoriasis and healthy controls. CD56(+) CD16(-) and CD56(+) CD16(+) NK cells were isolated from lesional skin, unaffected skin and PBMC of psoriasis patients, and normal skin and PBMC from healthy controls. The expression of CD57, NKG2A and NKG2C was assessed by flow cytometry. NK cells in psoriasis skin lesions were skewed in their expression of CD57, a marker of NK cell maturity, with CD57 expression significantly reduced and NKG2A expression increased on NK cells in lesional and unaffected skin compared to controls. These data suggest that in this patient cohort, NK cells could be isolated from psoriasis lesions and exhibit an immature phenotype.