PHAGOCYTOSIS OF POLYMORPHONUCLEAR LEUKOCYTES BY GUINEA-PIG PERITONEAL-MACROPHAGES - EFFECTS OF SERUM AND TEMPERATURE INVITRO

The regulation of phagocytosis of neutrophils by peritoneal macrophages was studied in vitro. Peritoneal exudate cells (PECs) of guinea pigs were lavaged 15 h after the i.p. injection of thioglycollate medium and were cultured in chamber-slides. When PECs were cultured in RPMI 1640 medium in the absence of serum, approximately 20% of the macrophages phagocytized autologous neutrophils during 48-72 h of culture. Addition of guinea pig serum to the culture (2.5-20% v/v) suppressed the extent of the phagocytosis. The suppression was induced by globulin-rich ammonium sulfate fractions of the serum. Sera from rat, mouse, hamster, horse or calf also suppressed the phagocytosis, but fetal bovine serum (FBS) supported the phagocytosis, which was inhibited by globulin-rich Cohn fractions of bovine serum. The rate of neutrophil-phagocytosing macrophages was proportional to the rate of the pyknotic change of neutrophils. At a high temperature (42-degrees-C), the autophagocytosis took place at 12 h of culture when fresh, but not heat-inactivated, autologous serum was added, implying that complement components may play a role in the hyperthermia-induced phagocytosis of neutrophils by macrophages. At 42-degrees-C, ingested neutrophils did not show the pyknotic changes, indicating that intact neutrophils were ingested by macrophages.