TNF alpha expressing cells in epidermal tumors: correlation with ICAM-1 induction on keratinocytes and Langerhans...

TNF alpha may be a locally expressed immunomediator of cutaneous diseases. An immunohistochemical technique was used to study the expression of the cytotoxin in correlation with the intercellular adhesion molecule-1 (ICAM-1) and Langerhans cell (LC) distribution in viral-induced lesions, epidermal tumors and normal skin. In most cutaneous tumors, TNF alpha immunoreactivity localized to tumor cells and some cells of the histiocytic macrophage lineage including LC. In normal human skin only rare epidermal dendritic cells were found positive. TNF alpha expression by tumor cells did not correlate with a corresponding ICAM-1 induction but coincided with drastic LC depletion in the lesions except in condyloma acuminata. These results suggest that TNF alpha expression by keratinocytes under viral infection or transformation process may contribute to the self-limiting evolution of the lesions and to the modulation of the local immune reaction. Though the cytokine is not involved in the ICAM-1 induction on keratinocytes it may influence the LC depletion observed in these lesions.