Detection of IL-20 and its receptors on psoriatic skin

The aim of this study was to investigate the expression of interleukin-20 (IL-20) and its receptors on psoriatic skin by immunohistochemical analysis and to evaluate the correlation of CD8-positive T lymphocytes with epidermal proliferation. Overexpression of IL-20 and its receptors was detected in the keratinocytes of the lesional skin of psoriasis and spongiotic dermatitis. The expression pattern of IL-20 spreads throughout the whole layer of epidermis, while IL-19 was expressed in up to three or four layers suprabasally. The serum level of IL-20 in psoriatic patients was significantly lower than that in healthy controls. IL-20 upregulated KGF transcripts on CD8-positive T cells. We hypothesize that overexpression of IL-20 is correlated with keratinocyte proliferation that acts through their receptor complex expressed by keratinocytes themselves. Furthermore, IL-20 can stimulate CD8-positive lymphocytes to produce KGF, which may contribute to sustaining the hyperproliferative status of the keratinocytes.