Langerhans Cells as Stimulator Cells in the Murine Primary Epidermal Cell-Lymphocyte Reaction: Alteration by UV-B Irradiation

Abstract

I region dependent functions of immunocompetent cells, i.e., induction of antigen specific, allogeneic and syngeneic T cell activation, have been reported to be highly UV susceptible. Since the epidermis is the only tissue which is naturally exposed to UV-irradiation, we conducted experiments to investigate whether murine epidermal cells (EC), particularly Ia-positive Langerhans cells (LC), could induce syngeneic and allogeneic T cell activation and, if so, whether these functions could be altered by UV-irradiation. Epidermal cell-lymphocyte cultures (ELR) were established using either nonirradiated or irradiated (1–40 mJ/cm 2 UV-B) Balb/c (H-2 d ) EC as stimulator cells and either Balb/c or C57B1/6 (H-2 b ) purified T lymphocytes as responders. Balb/c EC not only induced a vigorous proliferative response in C57B1/6T cells (peak response: day 5–6) but also substantially stimulated syngeneic T cells (day 7–9). Pretreatment of EC with specific anti-Ia serum plus complement abolished their stimulatory capacities which demonstrates that LC are of critical importance in these reactions. UV-B irradiation of EC resulted in a dose-dependent reduction of their ELR-stimulatory capacities. UV-B doses which virtually abolished the ELR stimulatory capacity of LC did not affect EC viability and only marginally reduced the protein synthesizing capacity of EC. The finding that I region dependent LC functions are particularly UV-susceptible may provide a useful tool for the modulation of the afferent limb of the immune response.