Histiocytic and dendritic reticulum cells shown by a zinc iodide-osmium technique.

Structures corresponding to histiocytic and dendritic reticulum cells have been shown in human tonsillar tissue, "reactive" lymph nodes and spleens by means of a zinc iodide-osmium technique. These cell types have been shown in various locations in these tissues using paraffin and resin embedded sections produced after fixation/staining of the tissue in zinc iodide-osmium. The quality of morphology attained by this procedure is much improved compared with the demonstration of the two cell types by means of alpha-naphthyl acetate esterase reactions performed on frozen sections. The zonal architecture of the lymphoid follicle is emphasised by this technique. In lymph nodes, sinus lining cells are also shown. Lymphoid cells, polymorphs, fibroblasts, and endothelial cells are negative with the zinc iodide-osmium method. In addition, interdigitating cells are not stained. The results of this procedure are compared with those with those of other methods for the demonstration of histiocytic and dendritic reticulum cells.