Preliminary functional analysis of human epidermal T cells

The function of human epidermal T cells (ETC) is unknown, In the present st udy, dermal T cells (DTC), ETC and keratinocytes were cultured from normal human skin, DTC and ETC lines were expanded in medium containing interleuki n 2, The autologous keratinocytes were transfected with a human papillomavi rus 16 E6 and E7 plasmid to produce an immortal keratinocyte line "HEK001", Lymphocyte migration and adhesion to HEK001 was assessed in calcein fluori metric assays, ETC migrated towards HEK001 three to four times more than DT C, ETC adhered to HEK001 two to four times more than DTC, The proportion of ETC expressing the cutaneous lymphocyte-associated antigen was greater tha n that of DTC (26% and 1%, respectively), The keratinocyte line HEK001 expr essed ICAM-1 following stimulation with TNF-alpha or IFN-gamma and followin g coculture with autologous cutaneous T cells, A blocking anti-ICAM-1 antib ody reduced DTC and ETC adhesion to HEK001 by 30% and 50%, respectively, Th erefore, cutaneous T cells may upregulate keratinocyte ICAM-1 expression wh ich mediates adhesion to autologous keratinocytes. These results are consis tent with the hypothesis that the ETC and DTC populations are distinct, Bot h directed migration (epidermotropism) and selective retention may be invol ved in the development and maintenance of the ETC population in normal huma n skin.