Anti‐tumor activity in human serum: Antibodies detecting blood‐group‐A‐like antigen on the surface of tumor cells in culture

Abstract

Abstract Sera from many patients with tumors showed demonstrable cytotoxic antibody activity against selected human tumor cells in culture. The antibody activity detected in the present study was not found to be specific for tumors, but was shown to be directed against an antigen that is serologically related to blood group A. Direct cytotoxicity and absorption analyses, blocking tests, and erythrocyte adherence tests confirmed this conclusion. Antibody activity was found, as expected, frequently in sera from patients with blood‐groups O and B phenotypes, and not in patients belonging to blood‐groups A or AB. In view of the ubiquitous occurrence of blood‐group antibodies, their possible role in some human tumor serological studies should not be ignored.