Peroxidase and Catalase in Monocytes, Macrophages, Epithelioid Cells and Giant Cells of the Rat

Abstract

The cytochemical demonstration of peroxidatic (PO) activity is often used in studies on monocytes and macrophages. This reaction makes it possible to distinguish between resident (= tissue) macrophages on the one hand and monocytes and monocyte-derived cells on the other, since resident macrophages have PO activity in the rough endoplasmic reticulum (RER) and the nuclear envelope, monocytes only have PO-positive granules, and monocyte-derived cells either have PO-positive granules or are PO-negative (for a review, see Daems et al. 1979). It should be kept in mind in this connection that under cytochemical conditions a variety of compounds show PO activity: enzymes such as various peroxidases, catalase, and a number of cytochromes, but also hemoproteins such as hemoglobin, myoglobin, epinephrin, and lipofuscins. However, if the appropriate cytochemical conditions are chosen, the nature of the compound underlying the positive cytochemical reaction can be identified in most if not all cases (for reviews, see Fahimi 1975; Roels et al. 1975; Daems et al. 1979).