A developmental study of murine epidermal Langerhans cells

Abstract

Prospective skin prior to invasion by neural crest cells was dissected from 10.5-day mouse embryos and cultivated in chick embryo hosts. The graft tissue was prepared for the demonstration of both mouse and chick cells, pigment cells, and Langerhans cells. Chick cells were not found in the graft mouse epidermis; however, ATPase-positive and osmium iodide-positive cells were present. Electron microscopic examination revealed that, in younger grafts, only indeterminate cells could be found among the keratinocytes. In older grafts, both indeterminate cells and Langerhans cells with granules were seen. The evidence affirms that epidermal Langerhans cells are not related to pigment cells. Based on the developmental nature of Birbeck (Langerhans) granules from the cytomembrane, it is proposed that the granule no longer be considered as specific to and characteristic of epidermal Langerhans cells. Rather, Langerhans cells should be defined as ATPase-positive, desmosome-free cells within stratified squamous, potentially keratinizing, epithelia. Thus epidermal, ATPase-positive indeterminate cells and such cells with Birbeck granules both should be considered as components of the Langerhans cell series. Normal chick skin does not show ATPase-positive cells. However, when 10.5-day mouse embryo ectoderm was inserted under the ectoderm of chick embryos, the resulting chimeric epidermis possessed ATPase-positive cells. It is proposed that epidermal Langerhans cells are of ectodermal origin.