DIFFERENCES IN PEROXIDASE LOCALIZATION OF RABBIT PERITONEAL MACROPHAGES AFTER SURFACE ADHERENCE

Abstract

Unlike resident peritoneal macrophages which contain peroxidase in the rough endoplasmic reticulum (RER) and perinuclear cisternae (PN), macrophages elicited into the rabbit peritoneal cavity by various stimulants lack the enzyme. Since it was previously found that such peroxidase reactivity rapidly appears in the RER and PN of blood monocytes after surface adherence in vitro, the question was raised as to whether the enzyme could be similarly produced in elicited macrophages by adherence. Cells from peritoneal exudates (96 h after endotoxin injection) were harvested, suspended in culture medium and allowed to adhere to fibrin-coated or plastic surfaces. Following culture for various intervals, they were fixed, incubated for peroxidase and examined by EM. These elicited cells, which initially contained no cytochemically detectable peroxidase, acquired peroxidatic activity in the RER and PN within 2 h after adherence in culture. Thus macrophages, like blood monocytes, may rapidly acquire peroxidase reactivity as a consequence of plasma membrane:external surface interaction. It seems unwise to use peroxidase localization as the basis for advocating the existence of 2 separate lines of peritoneal macrophages, as was previously proposed.