Antigen presentation and allogeneic stimulation by Langerhans cells.

Isolated Langerhans cells were studied for 2 immunologic functions, the ability to present antigen to sensitized T lymphocytes and the ability to act as stimulator cells for mixed lymphocyte reactions. Langerhans cells can perform both of these functions. This fact, with the previous finding that Langerhans cells possess surface Ia antigens and Fc and C3 receptors, strongly suggests that Langerhans cells act as epidermal macrophages.