Epidermal Langerhans cells as accessory cells in con A stimulation of T lymphocytes in the guinea-pig.

Stimulation of guinea-pig T cells by concanavalin A (Con A) requires Ia-antigen expressing accessory cells. Such functional accessory cells were identified among the normal epidermal cells and could be fractionated and enriched by centrifugation on discontinuous Percoll density gradients. Epidermal cells collecting at a density of 1.08 g/ml were the most effective in mediating Con A-dependent T cell proliferation, induced the highest activity of T cell growth factors (TCGF) and were enriched fivefold for Ia antigen expressing cells. A monolayer immunosorbent technique yielded a 35-fold enrichment of Ia antigen expressing epidermal cells. This cell fraction induced high levels of TCGF in the culture supernatants. Since the only cells in the normal epidermis expressing Ia antigens are the Langerhans cells, we conclude that the Langerhans cells may act as accessory cells for Con A stimulation of T cells.