Transplantation immunity of rats induced by hepatoma cells treated with heteroantibody.

Tumor cells from rat hepatomas, AH-414 and AH-64A induced by azo dye, were preincubated in vitro with different dilutions of rabbit anti-hepatoma serum. Then 10(6) cells were inoculated intraperitoneally into Donryu rats. After 6 weeks, rats surviving without tumors showed resistance to further challenge with the same tumor cells. The ratio of the number of surviving rats after challenge with 10(5) fresh tumor cells to those surviving after inoculation with serum-treated tumor cells was maximal using dilutions of antiserum of 1:240 with AH-414 tumor cells and of 1:400 with AH-64A cells. Pooled sera from AH-64A-resistant rats, 2 weeks after a 3rd challenge with 10(7) fresh tumor cells (RRS Lot III), had a cytotoxic effect on AH-64A cells at dilutions of up to 1:64 while sera isolated after the 1st or 2nd challenge (RRS Lot I or II) were weakly cytotoxic. The cytotoxicity was complement-dependent and stable on heating at 56 degrees for 30 min. RRS Lot III was active in the indirect immunofluorescence test. Rabbit anti-rat liver serum did not induce resistance to AH-64A in Donryu rats although the dilutions used had the same immune adherence or cytotoxic titer as rabbit anti-hepatoma serum. Rabbit anti-Donryu rat hepatoma serum failed to induce resistance to cells of a 3-methylcholanthrene-induced sarcoma, AMC 60, of ACI/N rats. The correlation between the immune adherence and cytotoxic titers of the rabbit antiserum and its effectiveness in sensitizing the animals against tumor cells is discussed.