Langerhans Cells in Mouse Skin Experimentally Deprived of its Neural Crest Component

Abstract

Although a hundred years have passed since Paul Langerhans (1) first described the dendritic cells of the skin which now bear his name, their nature and significance remain uncertain. Langerhans considered the cells to be functional elements of the peripheral nervous system, a view that subsequently received support from many investigators (2, 3, 4). Other authorities, however, are of the opinion that they are in some way or other related to melanocytes, being either effete melanocytes (5, 6), postmelanin-synthetic cells (7), post-divisional stages of mature previously melanogenic melanocytes, or possibly melanocytes in an immature or arrested condition (8). Certainly, the evidence relating the two cells, though largely circumstantial, is impressive. Until very recently, this could be said to apply in particular to evidence arising from electron microscopic studies on normal skin, and on skin in depigmentary conditions such as vitiligo, human piebaldism, and white-spotting in rodents (9, 10, 11). However, the reported occurrence in nongranulomatous lesions of Histiocytosis-X of large numbers of cells identical in appearance with Langerhans cells (12, 13, 14), has revived lingering doubts that they do, in fact, belong to the melanocyte lineage. These doubts are reinforced by available and accumulating his-tochemical and electron-histochemical evidence (15, 16, 17), and by evidence which indicates that the epidermal Langerhans cell may have phagocytic or cytolytic functions which are not easy to reconcile with any of the hypotheses which relate it to the melanocyte (18).