Abstract
Peritoneal exudate macrophage monolayers (PEMM) from C57BL/6 and DBA/2 mice inoculated ip with tumor allografts were induced to release in vitro labile cell toxin(s), herein called "macrophage cytotoxin(s)" (MCT). Macrophages released MCT spontaneously for a short interval when initially established as monolayers, and they were reinduced to secrete MCT by exposure to allogeneic and syngeneic tumor cells (but not to normal cells) and by exposure to polyinosinic-polycytidylic acid (poly I . poly C) and lipopolysaccharide (LPS). PEMM from normal mice treated ip 3 days previously with thioglycollate were also induced to release toxins in vitro. These cells did not release MCT spontaneously before or after treatment with neoplastic cells but were induced to release MCT by exposure to poly I . poly C or LPS. Resident peritoneal macrophages did not release MCT either spontaneously or after treatment with tumor cells, poly I . poly C, or LPS. MCT released from alloimmune mice stimulated with syngeneic or allogeneic tumor cells were resolved by molecular sieving into a major peak at 140,000--160,000 daltons, called "alpha-MCT," and into a minor peak at 60,000 daltons, called "beta-MCT." However, supernatants from thioglycollate-induced PEMM, stimulated with poly I . poly C or LPS, appeared to be composed entirely of the alpha-class. alpha-MCT from poly I . poly C-stimulated PEMM caused 31--56% lysis of syngeneic EL-4 and allogeneic L-929, NS-1, and YAC-1 tumor cells in vitro but was not cytotoxic for normal cells. Secretion of the MCT by PEMM derived from thioglycollate-treated animals stimulated with poly I . poly C was inhibited by colchicine, emetine, iodoacetic acid, trypan blue, and cytochalasin B.
Highlights
The activated state of a murine PEM is characterized by increases in size, in motility, in phagocytic capacity, and in production of lysosome enzymes; by greater adherence to glass; and by an increased ability to nonspecifically destroy allogeneic and syngeneic neoplastic cells over normal cells in vitro [1,2,3,4,5,6,7,8]
Spontaneous MGT release in vitro from Peritoneal exudate macrophage monolayers (PEMM) obtained from G57ELI6 allograftedmice.-PEMM, from C57BL/6 mice that had received an ip injection ofP815 tumor, were established as described in "Materials and Methods." Samples of medium were removed at various intervals and tested for macrophage cytotoxin(s)" (MCT) actiVity on L-929 cells
The data shown in table 1 reveal that alloimmune macrophages released from 75-110 V MeT/ml in 4-6 hours when reexposed to EL 4 or P815 tumors for 1 hour
Summary
The activated state of a murine PEM is characterized by increases in size, in motility, in phagocytic capacity, and in production of lysosome enzymes; by greater adherence to glass; and by an increased ability to nonspecifically destroy allogeneic and syngeneic neoplastic cells over normal cells in vitro [1,2,3,4,5,6,7,8]. Several investigators [15] have suggested that tumor cell lysis subsequent to contact with the effector is mediated by materials derived from the activated macrophage lysosome system. It has been demonstrated that PEM from BCG-immune mice, obtained with or without purified protein derivative challenge, or that PEM from normal mice stimulated with LPS and poly I· poly C release cell toxins in vitro [16,17,18,19]. These toxins have not been well characterized; their involvement in the lytic event has been suggested. The present study describes an inducible system of cell lytic molecule(s) called "MCT" that are released by activated murine PEM in response to different in vitro stimuli
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