RESULTS

The procedure of fixation just described yielded a preservation of structural detail inferior to that usually obtained with osmium fixatives or glutaraldehyde but satisfactory enough to permit a correlation of enzymatic activity and fine structure. Langerhans cells were identified by the following criteria (3—5) relatively clear cytoplasm, polylobulated nucleus, typical rod-shaped Langcrhans-ccll profiles, and absence of tonofilaments, desmosomes, pre-melanosomes, and melanosomcs. Electron-dense material representing the his-tochemical reaction product, lead phosphate, and indicating nucleosidc-triphosphatase activity was found to be present in Langerhans cells. These deposits were observed to be localized within or at the surface of the cytomembranes of these cells (Figs. 1 to 3). The electron-dense material on the dendritic processes outlined very clearly the Langerhans cells within the mosaic of keratinncytcs, even at low magnifications (Fig. 4).

The enzymc-histochemical reaction product in most cases also appeared to fill the inter-cellular space between these cells and adjacent kcratinocytes and occasionally coated the surface of the latter cells (Figs. 2 and 3). The dee.-tron-dense material was never present between