A DEVELOPMENTAL STUDY OF THE DISTRIBUTION AND FREQUENCY OF LANGERHANS CELLS IN RELATION TO FORMATION OF PATTERNING IN MOUSE TAIL EPIDERMIS

The structure of mouse tail epidermis has been investigated from day 15 of embryonic development and a qualitative and quantitative analysis of the localization of Langerhans cells has been carried out using the ATPase method.Langerhans cells occur exclusively in regions where a granular layer is present in the developing epidermis. The appearance of both a granular layer and evenly distributed Langerhans cells is noted for the first time at embryonic days 16 to 17. At postnatal day 3 the number of Langerhans cells as well as the thickness of the granular layer are increased although the characteristic scale-interscale pattern of adult mouse tail skin is not yet outlined. This occurs first around postnatal day 9 and is characterized by a gradual reduction of the granular layer in the regions surrounding the forming scales. Exactly the same areas are occupied by Langerhans cells.This pattern of distribution is maintained in the adult animal. Repeated treatment of adult mouse tail skin with vitamin A results in a conversion of the para-keratotic epidermis into an ortho-keratinizing one, so that a granular layer is present throughout the whole epidermis. Concomitantly, Langerhans cells can clearly be demonstrated in the scale regions