Differential expression of transforming growth factor-alpha (TGF-alpha) and EGF receptor in transitional area of psoriatic epidermis.

We investigated the localization of TGF-alpha and EGF receptor in psoriatic plaques, especially the clinically-determined transitional zone from uninvolved to involved psoriatic skin by immunohistochemistry. TGF-alpha was not increased in the transitional area compared with normal epidermis. It started to increase within the edge of psoriatic plaques. In contrast, EGF receptor increased up to the suprabasal layers even in the uninvolved skin adjacent to psoriatic plaques, compared with normal epidermis. Slight epidermal hyperplasia was also observed in the clinically-determined transitional area. This result suggests that the increase of EGF receptor precedes that of TGF-alpha in psoriatic plaque formation.