Peroxidase staining in elicited and nonelicited mononuclear peritoneal cells from BCG-sensitized and nonsensitized mice.

The peroxidase (PO) activity in nonelicited macrophages and in casein-elicited monocytes, obtained from peritoneal cavities of nonsensitized and BCG-sensitized mice and cultivated on glass for 1 or 2 h, was studied by light and electron microscopy, using the 3,3'-diaminobenzidine technique. These two types of glass-adherent peritoneal cells differed in PO activity. In macrophages, PO activity was predominantly in the nuclear envelope, rough endoplasmic reticulum, and occasionally in vesicles of the Golgi apparatus. In monocytes, PO activity was confined to cytoplasmic dense bodies resembling lysosomes, and was greater at 10 and 24 h after elicitation than at 96 h. The BCG sensitization did not significantly alter the proportion of cells with PO-positive granules in macrophages or monocytes from that observed in nonsensitized mice. From its lysosomal site, the PO in monocytes could come into contact with those microorganisms whose ingestion by these cells was followed by phagolysosome formation.