A monoclonal antibody (AB/3) reactive with human breast cancer

Monoclonal antibody AB/3 was produced from a fusion of spleen cells of a human breast cancer cell-primed BALB/c mouse with the murine myeloma cell line P3-NS1-Ag4-1. The antibody reacted strongly with the plasma membrane of human breast cancer cells. Tissue sections of both malignant and benign human mammary carcinomas and tumors of non-breast origin as well as apparently normal tissues were tested with immunoperoxidase. Ninety-six of 124 (77%) primary human breast cancers, 12 of 14 (86%) metastatic breast lesions, and 12 of 44 (27%) benign breast lesions reacted positively. Little or no appreciable reactivity was observed with apparently normal human tissues and carcinomas of non-breast origin, with the exception of colon carcinoma. Antibody AB/3 did not immunoprecipitate any identifiable protein from radiolabeled extracts of the immunizing cell line.