Increased binding and killing of neuraminidase-galactose oxidase-treated tumor cells by normal macrophages.

The binding of Line 10 hepatoma cells to normal syngeneic guinea pig macrophages is increased when the tumor cells are treated with neuraminidase and galactose oxidase (NAGO) before they are added to the macrophage monolayers. The effect is abolished by exposure of the NAGO-treated tumor cells to sodium borohydride. Line 1 hepatoma cells treated with NAGO or with sodium periodate are killed to a greater extent than untreated tumor cells. This effect can also be reversed by sodium borohydride. Further, periodate-treated macrophages become cytotoxic for unmodified tumor cells. These results demonstrate that increased tumor cell killing occurs when artificial contacts (presumably via Schiff bases) are established between normal macrophages and tumor cells. They are consistent with the hypothesis that close cell to cell contact is necessary for macrophage-mediated cytotoxicity.