Morphological, histochemical, autoradiographic and topographical evidences of the origin of the Langerhans' cell from the melanocyte in the skin of the guinea pig.

The microscopic anatomy of the nucleus, Golgi substance, mitochondria, etc. of type 1, 2, 3 and 4 albino melanocytes, type 01 and 011 albino intermediate cells of Billingham and Medawar and type I, II, III and IV albino Langerhans' cells of the albino guinea pig, is presented in detail. The study has demonstrated that the albino melanocytes degenerate through sequential stages of intermediate cells of Billingham and Medawar, type I, II and III Langerhans' cells to ultimately from type IV Langerhans' cells. It has been shown that all the dendritic cells of the epidermis belonged to one class of cells. Autoradiographic techniques have shown that type 3 and type 4 melanocytes, respectively, bearing 6 and 5 round-tipped dendritic processes, divide by mitosis to form two daughter cells. One of these two daughter forms the intermediate cell of Billingham and Medawar. This cell, while transforming sequentially into type I, II, III and IV Langerhans' cells, moves up through the Malpighian and granular layers of cells, to the stratum corneum. This type IV Langerhans' cell is ultimately extruded out of the stratum corneum by exfoliation. The other daughter melanocyte remains at its place in the sub-basal zone to function as a mature melanocyte. The time for the passage of the daughter melanocyte to travel from the sub-basal zone to the stratum corneum layer was found to be 15 days.