Expression of a Rat Ovary‐independent Mammary Tumor‐associated Antigen Defined by a Monoclonal Antibody, TAK‐B1

A monoclonal antibody, TAK‐B1, was produced by immunization of BALB/c mice with mammary carcinoma induced in inbred Sprague‐Dawley rats by treatment with 7,12‐dimethylbenz[a]anthra‐cene. TAK‐B1 reacted with ovary‐independent mammary carcinoma cells which had been transformed from ovary‐dependent mammary carcinoma cells, but did not react with original mammary carcinoma cells or with cells from mammary glands exhibiting fibrocystic changes or normal mammary glands. However, TAK‐B1 reacted not only with basal cells of the epidermis and epithelial cells of the bottom portion of crypts of the small intestine in adult rats, but also with basal cells of epidermis in skin and mesenchymal cells around developing hair follicles in fetuses. We therefore classify TAK‐B1 as an ovary‐independent rat mammary tumor‐associated antigen. Immunoelectron microscopic examinations revealed that the antigen recognized by TAK‐B1 was localized in the cell surface membrane of ovary‐independent mammary carcinoma cells. Immunoprecipitation assay revealed that the antigen recognized by TAK‐B1 was composed of M 220,000 protein and four other minor proteins.