The effects of occlusion of the skin on the Langerhans' cell and the epidermal mononuclear cells.

Clinically normal skin was occluded for 3, 6, 24, and 48 hours with aluminium cups used for patch testing. Electron microscope sections from occluded skin showed morphological alterations in the Langerhans' cells and apposition of mononuclear cells. After occlusion an increased number of mononuclear cells were found in the epidermis, compared with normal skin.