UPTAKE OF NEUTROPHILS AND NEUTROPHILIC COMPONENTS BY MACROPHAGES IN THE INFLAMED PERITONEAL-CAVITY OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

The interaction between neutrophils and macrophages in peritoneal infl ammatory exudates in rainbow trout injected intraperitoneally with sev eral bacterial and non-bacterial phlogistic agents was studied by ligh t and electron microscopic histochemistry. The transfer of neutrophili c components to macrophages was demonstrated by the presence in macrop hages of myeloperoxidase, an enzyme of the neutrophil not produced by rainbow trout monocytes and macrophages. Two mechanisms observed for t he transfer were phagocytosis of intact neutrophils and phagocytosis o f apoptotic bodies released from inflammatory neutrophils. Neutrophils with phagocytosed bacteria were also found to be ingested by macropha ges, with the consequent transfer of neutrophilic components and bacte ria to the macrophages. Two other mechanisms of transfer are considere d. One involves the intake by the macrophage of neutrophilic granules or granular molecules released by lysing or degranulating neutrophils, respectively. The other may be through gap junctions which were obser ved between adhering inflammatory neutrophils and macrophages. (C) 199 8 Academic Press.