A tumor-specific cytotoxic and neutralizing factor in rats immunized with ascites hepatoma induced by azo dyes.

Abstract

Transplantation immunity of Donryu rats against ascites hepatoma AH-64A induced by azo dye was demonstrated by intraperitoneal injection of tumor cells pretreated with heteroantibodies in vitro. Hyper-immunity was induced by successive challenges with fresh tumor cells. The cytotoxic effect of the serum of resistant rats (RRS) against AH-64A tumor cells was not reduced after absorption with normal rat liver cells, but was slightly reduced after absorption with normal rat spleen cells. The cytotoxicity was absorbed completely with 5 times 10(6) AH-64A tumor cells. AH-64A, -B, -C, and -D are ascites hepatoma cell lines originating from a single Donryu rat. AH-64A and AH-64B cross-reacted with RRS while AH-64C and AH-64D, chemically induced DBLA-6 leukemia cells and normal lymph node cells of rats, did not react with RRS in indirect immunofluorescence and cytotoxicity tests. A neutralization test was carried out by treating 2 times 10(5) tumor cell with either RRS or immune spleen cell in vitro and then injecting them subcutaneously into irradiated rats (400 R). It was found that 1:20 dilution of RRS protected the rats against AH-64A tumor cell growth while 1:40 and 1:80 dilutions of RRS caused some protection. A subcutaneous tumor mass developed after transplantation of tumor cells treated with RRS, but after about 2 weeks this began to decrease in size and disappeared completely within 6 weeks after transplantation. Treatment of AH-64A tumor cells with immune spleen cells at cell-to-cell ratios of 1:200 and 1:100 caused complete neutralization while normal spleen cells at a ratio of 1:200 had slight effect. Treat;ent with immune spleen cells prevented tumor growth from t;e start. Most of the surviving animals were resistant to c,allenge with 1 times 10(5) fresh AH-64A cells. RRS was fractionated by cellulose acetate membrane electrophoresis and the amounts of beta1- and gamma-globulin fractions were found to be 48 and 42% more than in normal rat serum. The immunoelectrophoretic pattern of resistant rat serum showed a stronger IgM precipitin line than that of normal rat serum.