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Current concepts implicate the cytokines IL-17 and IL-22 in the pathogenesis of psoriasis. These two cytokines are produced by T cells that infiltrate psoriatic plaques. However, other cells also produce IL-17 and IL-22. This study was conducted to determine whether non–T cells contribute to the abundance of IL-17 and IL-22 in psoriatic skin lesions.
Skin biopsies from 30 patients with plaque-type psoriasis and 6 patients with atopic dermatitis were evaluated. Over 75% of the bone marrow–derived cells in the cutaneous lesions were T cells, and about 10% were mast cells. Interestingly, only about 1% of T cells were found to produce IL-22, compared with nearly 90% of mast cells. In other words, there were eight times as many IL-22-producing ma…