Mouse monoclonal antibodies have been raised against human milk-fat globule membranes (HMFGM) to obtain reagents for mammary tumor diagnosis. A panel of 17 anti-HMFGM antibodies was selected for further investigation. Antibody-blocking studies indicated that with these antibodies at least nine different non-overlapping epitopes could be distinguished on six different molecules, MAM-1 to MAM-6. Electron microscopic studies of the cellular localization of the antigens detected by some of these antibodies revealed that they were present on the cell membrane mainly, on the microvilli, lining intercellular and intracytoplasmic lumina. The reactivity of the antibodies was studied on normal and tumor tissues and on in vitro cell lines. All antibodies reacted with the resting mammary gland while eight antibodies also bound to breast tumors. None of the antibodies was specific for the mammary gland or its tumors only, but most antibodies also reacted with other epithelial cells, especially of secretory tissues. When tested on a variety of cell lines a distribution reflecting the tissue distribution could be demonstrated. One of the antibodies reacted with nearly all carcinomas and their metastases and did not react with lymphomas, sarcomas, neuroblastomas, melanomas or nervous system tumors. The specificity of the antibodies, tested individually, was not sufficient for further differential diagnosis of the carcinomas, but when some of these antibodies were used in a panel they contribute to an important improvement of the diagnosis.

The development of the mouse mammary gland was studied immunohistochemically using monoclonal antibodies against cell surface and basement membrane proteins and a polyclonal antibody against keratin. We have identified three basic cell types: basal, myoepithelial, and epithelial cells. The epithelial cells can be subdivided into three immunologically related cell types: luminal type I, luminal type II, and alveolar cells. These five cell types appear at different stages of mammary gland development and have either acquired or lost one of the antibody-defined antigens. The cytoplasmic distribution of several of these antigens varied according to the location of the cells within the mammary gland. Epithelial cells which did not line the lumen expressed antigens throughout the cytoplasm. These antigens were demonstrated on the apical site in situations where the cells lined the lumen. One antigen became increasingly basolateral as the cells became attached to the basement membrane. The basal cells synthesize laminin and deposit it at the cell base. They are present in endbuds and ducts and are probably the stem cells of the mammary gland. Transitional forms have been demonstrated which developmentally link these cells with both myoepithelial and (luminal) epithelial cells.

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The immunoreactivity of a monosialoganglioside antigen defined by monoclonal antibody 116NS19-9 (19-9) was studied in neoplastic and normal glandular and mucosal epithelia using an indirect immunoperoxidase method. In neoplastic mucosae, the antigen was detected in the majority of colorectal and endometrial carcinomas, predominantly in a focal staining pattern. A substantial proportion of gastric and pancreatic tumors and an occasional breast carcinoma also reacted with the monoclonal antibody. Expression of the monosialoganglioside in normal colonic mucosa appeared to be restricted to areas adjacent to tumor tissue. In gastric mucosa, the antigen was confined to some areas showing intestinal metaplasia. The antigen was also detected in the epithelium of normal mucosa of the gall bladder and endocervix, as well as in some ductal epithelia of the pancreas and salivary glands. Most other mucosae were negative for antigen expression.

Cells from Burkitt lymphoma ( B L ) biopsies were examined for Epstein-Barr virus ( E B V)-associated antigens by complement fixation (CF) tests