IMMUNOHISTOCHEMICAL REACTIVITY OF A MONOCLONAL ANTIBODY AGAINST CELL MEMBRANES OF HUMAN MAMMARY CARCINOMA CELLS (125B4) WITH RAT NORMAL TISSUES AND DMBA-INDUCED MAMMARY TUMORS

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Immunoperoxidase staining patterns with a monoclonal antibody against human breast cancer cell membrane, 125B4, were investigated in frozen sections of normal tissues from adult rats of both sexes and of various mammary tumors from 7, 12-dimethylbenz (α) anthracence (DMBA)-treated female rats. In normal tissues, 125B4 preferentially recognizes myoepithelial layers of the mammary, sweat and salivary glands, basally situated epithelial cells of the skin, vagina, esophagus, urethra, urinary bladder, seminal vesicle and epididymis, and endothelial cells of blood vessels. It does not react with luminal cells of the abovementioned organs, epithelial cells of the stomach, intestine, liver, pancreas and uterus, and mesenchymal cells. The reactivity in benign mammary tumors is comparable to that in normal mammary tissue, but it is observed on some adenoma cells scattered spottedly in proliferating fibroadenoma. In malignant mammary tumors, the reactivities are not restricted to the banally localized carcinoma cells and distributed abundantly in the carcinoma foci of squamous cells carcinoma, adenocarcinoma and carcinosarcoma. Neoplastic mesenchymal cells cannot be stained with 125B4, which stains endothelial cells within the tumor stroma. Except for the endothelium, therefore, our data indicate that this antibody may react to the antigens present in basal and myoepithelial cells of rat mammary parenchyma.