Immunological studies on mouse mammary tumors. III. Surface antigens reacting with tumor-specific antibodies in immune adherence

Tumor-specific antibodies reacted with an isografted ascitic form of mouse mammary tumor, MM2, with a higher sensitivity in an immune adherence test than in an immune cytotoxicity test. Immune adherence and immune adherence inhibition tests were applied for the detection of surface antigens of MM2 tumor reacting with tumor-specific antibodies. After treatment with ether, ethanol, methanol, ethanol-ether mixture, acetone, chloroform-methanol mixture, deoxycholate, triton × 100, snake venoms, phospholipase A, or heating at 100° C for 15 minutes, the MM2 cells did not react with syngeneic antibodies in immune adherence. The reactivity of the cells was not suppressed by heating at 62° C for 15 minutes after treatment with deoxyribonuclease, ribonuclease, proteinases, neuraminidase, ultraviolet irradiation or freezing and thawing. In the immune adherence inhibition test, deoxycholate extract or triton × 100 extract of MM2 cells inhibited the immune adherence reactivity of syngeneic antibodies with MM2 cells, while the organic solvent extracts did not. This indicates that antigenic material was extractable in deoxycholate or triton × 100. After removal of surface antigens with 0.1% deoxycholate, fractions were prepared from treated MM2 cells. Fractions precipitated at 105,000 × g (microsomal fractions) as well as fractions precipitated at 11,000 × g (mitochondrial fractions) inhibited the immune adherence reactivity of tumor-specific antibodies with MM2, indicating that antigens were also present in these fractions.