Immunoelectron microscopical location of the acid cysteine proteinase inhibitor in the lymphatic tissue of the tonsils.

Previous studies have shown the acid cysteine proteinase inhibitor (ACPI) to be a common characteristic of human squamous epithelial cells and dendritic reticulum cells (DRC) in lymphoid secondary follicles. In the present study, we used the PAP-preembedding technique for the immunoelectron microscopic identification of ACPI in DRC in palatine tonsillar tissue. ACPI appeared to be located in the cytoplasm of perikaryon and of dendritic processes of DRC on the membranes of the endoplasmic reticulum and the outer membrane of mitochondria. Further more, the tonofilaments and the desmosomal membranes exhibited a strong ACPI reactivity.