Alkaline phosphatase-positive Langerhans cells in the epidermis of cattle.

Dendritic alkaline phosphatase-positive cells in the epidermis of cattle were studied. By light microscopy they were shown to occur in basal and suprabasal positions in the epidermis, with their dendrites reaching into outer layers of the stratum spinosum. They were also found in the external root sheaths of hair follicles. In separated epidermal sheets from ears of cattle these cells were found to be uniformly distributed with an average concentration of approximately 1,600 cells/mm2. Langerhans cells were identified in the epidermis by the presence of dendritic cells of Langerhans cell granules, a lobated nucleus and clear cytoplasm and the absence of desmosomes, tonofilaments, premelanosomes, and melanosomes. Alkaline phosphatase activity was associated with the plasmalemma of such cells and occasionally with cytoplasmic inclusions which may have been Langerhans cell granules. Enzyme activity was not associated with melanocytes or keratinocytes. It is confirmed that alkaline phosphatase activity is a feature of Langerhans cells, and possibly "indeterminate" cells in the normal epidermis of cattle.