Ultrastructure of human skin by a rapid freezing technique: structural preservation and antigenicity

To investigate the natural fine structure of skin, human skin biopsies were studied by electron microscopy and immunoelectron microscopy using rapid freezing and freeze-substitution techniques. Well-preserved structures were observed within a depth of 20 microns from the slammed surface of the samples. Epidermal cells were always closely located with very narrow intercellular spaces. Keratin filaments were distributed densely and homogeneously without forming bundles in the cytoplasm of epidermal keratinocytes. Langerhans cell granules were composed of a flat vesicular portion and an oval rod portion. The most striking finding was in the dermal-epidermal junction, where the lamina densa was present but no lamina lucida was observed. Further, by immunoelectron microscopy with anti-keratin monoclonal antibody, the 20-microns-deep part of the samples revealed the most significant staining. These findings indicate that the ultrastructure of routinely processed skin samples may be modified during the procedure for conventional chemical fixation and dehydration and that the ultrastructurally most preserved specimens, reflecting the conditions close to natural in vivo structures of the skin, can be obtained by the techniques described in this paper.