In vitro measurement of cytotoxic antibodies in mouse-immune sera against mouse ascites tumor cells.

Abstract

Previous studies reported that nontumorigenic 6C3HED tissue-culture cells induced strong tumor-specific immunoprotection against 6C3HED tumors. However, in the in vitro test, sera from C3H mice immunized with nontumorigenic 6C3HED tissue-culture cells failed to lyse 6C3HED ascites tumor cells when fresh guinea pig serum was incorporated as the complement source. A number of serum samples from different animal species were assayed as a complement source. With the exception of fresh rabbit serum, all other sera were either by themselves toxic to 6C3HED ascites tumor cells, or did not function as a complement source. The rabbit serum, by itself, was not toxic to 6C3HED tumor cells, but when incorporated with the isogeneic mouse-immune serum, killed more than 95% tumor cells. The facilitating activity exhibited by rabbit serum was characterized as classical complement and was not due to the presence of heterophile antibodies in the rabbit serum. By using this immunolytic testing system, the sera from mice bearing 6C3HED, S-180, TA-3, and Ehrlich solid tumors for an extensive time were found toxic to homologous ascites tumor cells. The cross-reactivity of the sera from tumor-bearing animals suggests that these four murine tumors, 6C3HED, S-180, TA-3, and Ehrlich, share some common tumor-specific antigen(s).