Target role of Langerhans cells in mycosis fungoides: transmission and immuno-electron microscopic studies.

Langerhans cells of the epidermis are "special" macrophages, as indicated by their expression of Fc and C3 receptors and Ia antigen. Functionally, they can replace macrophages in presentation of antigens to T cells and in the MLR. Ultrastructural and immunologic studies were carried out on epidermal samples of mycosis fungoides. As in contact allergy, apposition of lymphocytes to Langerhans cells was noted. Destruction of Langerhans cells appeared to act as the focus for the development of Pautrier microabscesses. This destruction was accompanied by ingress of histocytic cells, probably related to the stem cell population for Langerhans cells. The target cell role of Langerhans cells appears to be similar in contact allergy and mycosis fungoides.