The amazing shrinking laboratory.

A new monoclonal antibody to epithelial membrane antigen (EMA) E29. A comparison of its immunocytochemical reactivity with polyclonal anti-EMA antibodies and with another monoclonal antibody, HMFG-2. Summary Two polyclonal rabbit antibodies to epithelial membrane antogen (EMA), two mouse monoclonal antibodies (E29 and HMFG-2), and a "cocktail" of these two monoclonals have been compared using an indirect immunoperoxidase technique. Sections from 25 tissues (17 malignant and 8 benign), were examined. The distribution of staining with each of these reagents was similar, but the polyclonal antibodies produced stronger staining in colorectal carcinomas and lactating breast, whereas staining with the monoclonal antibodies was stronger in non-neoplastic pleural mesothelium and in pulmonary alveolar cells. When the two monoclonals were mixed there was no increase in staining intensity. E29 gave a "cleaner" result than HMFG-2, with better discrimination between cells and stroma, and is highly suitable for routine diagnostic histopathology. Antibodies to human milk fat globule membranes (HMFG) (Ceriani et al., 1977), have been shown to react with normal and neoplastic epithelium in a wide variety of sites (Heyderman et al. Heyderman et al., 1984a,b). The glycoprotein with which these antisera react has been termed epithelial membrane antigen (EMA), since the staining in normal epithelial tissues, as well as in well-to-moderately differentiated adenocarcinomas, is mainly on the luminal or plasma membrane. The antigen has been partially purified, and shown to consist of a heterogeneous glycoprotein(s) of high mol. wt. It has been suggested that carbohydrate forms the major antigenic determinant, the principal sugars being galactose and N-acetyl-glucosamine (Ormerod et al., 1983). All the breast carcinomas in the published series, and the majority of adenocarcinomas from a variety of sites, have been positive for EMA, while sarcomas and neural tumours have been reported to be negative. A few lymphomas (Sloane et al., also show positivity. The presence of EMA in a tumour is highly suggestive of epithelial derivation, while its absence virtually excludes breast origin. In tissue sections from some patients, staining of the membrane of plasma cells has also been seen (Dearnaley et al., 1983; Delsol et al., 1984; Heyderman et al., 1984a). Antisera to EMA have been used for the detection of bone marrow and lymph node metastases from breast carcinoma (Heyderman et The value of EMA in tumour pathology has been established by these investigations, but further studies have been limited by shortage of sufficient antisera suitable for immunocytochemistry. Two monoclonal antibodies were …