Antitumor activity of macrophages grown in tumorous ascitic fluid.

Peritoneal macrophages from mice injected with glycogen proliferated in vitro in the presence of cell-free tumorous ascites. DNA synthesis of macrophages was also induced by ascitic fluid, but did not occur in the absence of the fluid. However, macrophage growth was inhibited at a higher concentration of ascitic fluid (greater than 20%). The growth stimulating activity of this fluid was stable on heat treatment. The adherent cultured cells that proliferated were typical macrophages, as indicated by nonspecific esterase staining, pinocytosis and phagocytosis. These macrophages showed cytolytic activity against a murine tumor in the presence of wheat germ agglutinin. However, their cytotoxicity with antitumor antibody decreased during the culture period. These results indicate that tumorous ascitic fluid contains a macrophage growth factor(s) and that macrophages cultured with, and induced to proliferate by, ascitic fluid can kill tumor cells in cooperation with lectin but not antibody.