Effect of UVA and PUVA on alloactivating and antigen-presenting capacity of human epidermal Langerhans cells.

Human epidermal cell suspensions (EC), obtained with a suction blister technique and enzyme digestion, were irradiated with various doses of UVA with (PUVA) or without previous incubation with 8-methoxypsoralen (8-MOP). EC were then cocultured with allogeneic T cells or pulsed with the soluble antigen purified protein derivative of tuberculin (PPD) for 90 min before being cocultured with autologous T cells. While low doses of UVA induced a small but significant increase in the PPD-specific T-cell response, both PUVA and higher doses of UVA induced dose-dependent reductions. The allogeneic T-cell responses were reduced with PUVA, as well as with UVA, in a dose-dependent fashion. PUVA was far more effective than UVA in reducing both allogeneic and antigen-specific T-cell responses. There were no differences between numbers of DR-positive cells in EC before, immediately after or 24 h after PUVA or UVA radiation, and quantitative determination of EC HLA-DR molecules using an indirect radioimmunoassay (RIA) technique did not reveal any difference between PUVA-treated and non-irradiated cells.