The functional role of Langerhans cells.

Langerhans cells represent a subpopulation of mammalian epidermal cells. The recent findings that these cells are the only epidermal cells which express Fc-IgG receptors, C3 receptors and Ia antigens support the early suggestion that they are related to cells from the monocyte-macrophage-histiocyte series. In this report, evidence is presented that epidermal Langerhans cell can replace Ia-bearing macrophages in their capacity to induce antigen-specific and allogeneic T cell activation. The possible clinical implications of these findings are discussed with regard to the role of Langerhans cells as sensitizing factors in contact hypersensitivity and skin graft rejection.