Natural and perturbed distributions of Langerhans cells: responses to ultraviolet light, heterotopic skin grafting, and dinitrofluorobenzene sensitization.

Epidermal Langerhans cells exhibit many features of macrophages/monocytes. Both bear surface receptors for the Fc portion of immunoglobulin molecules and the C3b complement component. Both take up, process, and present antigens to reactive lymphocytes in an effective fashion, and they display on their cell surfaces the alloantigenic determinants encoded by the I region of the major histocompatibility complex. In view of these facts, we explored the extent to which cutaneous sites with unusual immunologic attributes might correspondingly have maldistributions or decreased surface densities of Langerhans cells. Common body sites such as the ear, back, and abdominal wall skin in hamsters, mice, and guinea pigs had regularly distributed ATPase-positive Langerhans cells in surface densities between 500 and 1,500 cells/mm2. In contrast, hamster cheek pouch epithelium had fewer than 200 Langerhans cells/mm2 and murine tail skin exhibited both a decreased density and an unusual gridlike distribution of the cells. Langerhans cells were never demonstrated in corneal epithelium. Perturbation of body wall skin with ultraviolet light and with dinitrofluorobenzene temporarily depleted the skin of ATPase-positive Langerhans cells. Heterotopic grafts of hamster cheek pouch and murine tail skin tended to accumulate Langerhans cells and to become more like body wall skin. The concordance of Langerhans cell aberrations and unusual immunologic features of corneal cheek pouches and tail skins suggests the possibility that intentional perturbations of surface Langerhans cells, as with UVL, might achieve unusual immunologic reactions within normal body wall skin.