Epidermal proliferation and accumulation of polymorphonuclear leukocytes in the psoriatic lesion

Biopsies were removed from the margin of plaques in 11 untreated psoriatic patients, and 8-microns sections prepared using the cryostat. Alternate sections were stained with H and E to assess the accumulation of polymorphonuclear leukocytes. The remaining sections were stained with the monoclonal antibody Ki67 in order to determine the number of cycling epidermal cells. In areas where polymorphonuclear leukocytes occurred in the stratum Malpighi the number of cycling epidermal cells was relatively low. In contrast, a positive correlation was shown between the density of microabscesses of Munro and the number of cycling epidermal cells. The clinically uninvolved skin of psoriatic patients shows a moderate enhancement of epidermal growth in the absence of any infiltrate. In the lesional skin the recruitment of cycling epidermal cells does not coincide with the invasion of polymorphonuclear leukocytes into the epidermis, but rather follows the penetration of these cells.