Macrophages activated as suspension cultures with lymphocyte mediators devoid of antigen become cytotoxic for tumor cells.

Normal peritoneal exudate cells (PEC) were activated as suspension cultures either in mediator-rich supernatants from o-chlorobenzoyl-bovine gamma-globulin (OCB-BGG) stimulated lymphocytes or in antigen-free Sephadex fractions from these supernants. After 24 hr incubation thration. The adherent cell fractions of PEC, recovered by trypsinization from monolayers and activated by this technique, were as cytotoxic as unfractionated PEC. Lymphocyte supernatants and antigen-free fractions of the supernatants induced comparable macrophage-mediated tumor cytotoxicity. Treatment of activated macrophages with trypsin did not alter their cytotoxic capacity.