Langerhans Cells: Functional aspects revealed by in vivo grafting studies

We performed 2 types of experiments to reveal aspects of Langerhans cell function. In the 1st type, tail skins (mice) and cheek pouches (hamsters) were grafted heterotopically to the thoracic wall of normal recipients and were subsequently painted with immunizing doses of a chemical contactant, dinitrofluorobenzene. In the 2nd type, corneal tissue and skin irradiated with ultraviolet light were grafted to recipients immunogenetically disparate for class I (murine K/D) or class II (Ia) antigens to determine the ability of these grafts to elicit allograft immunity. We found that the inability of intact murine tail skin to support the induction of contact sensitivity was a property of the skin itself, not the anatomical site. The inability to sensitize through cheek pouch was a property of the anatomical arrangement of the pouch in that an effective lymphatic drainage pathway did not exist. Although ultraviolet light apparently depleted body wall skin of ATPase-positive cells, it failed to rid skin of its capacity to express Ia antigens in a highly immunogenic way. Cornea grafts differing from their hosts across the I region alone of the major histocompatability complex succeeded neither in inciting their own rejection nor in prejudicing the host's subsequent response to body wall skin allografts bearing the same I region antigens. These results are strong circumstantial evidence that Langerhans cells are the important epidermal factors promoting induction of contact hypersensitivity. Ultraviolet light appears to be an effective way in which to transiently perturb Langerhans cell function, but is not an effective means of removing Langerhans cells from skin. The results of the cornea graft experiments offer hope that, when effective means of erasing Langerhans cells from skin have been found skin will be devoid of its capacity to promote contact hypersensitivity and to elicit allograft immunity directed at Ia antigens.