The search for tumor-associated proteins in pleural effusions by means of monoclonal antibodies and a dot blot assay.

Liquid moiety of 61 pleural effusions was tested for tumor-associated proteins (TAP) by means of a dot immunobinding (dot blot) assay (DIA) and a panel of monoclonal antibodies (Moabs). The sensitivity of the assay was checked using a purified, serially diluted carcinoembryonic antigen (CEA) preparation and an anti-CEA monoclonal IgG system. The latter was examined using both DIA and enzyme-linked immunosorbent assay ELISA solid phase assays in simulated conditions that mimicked the protein content of effusions. Finally, the results of DIA were compared to the immunohistochemistry carried out on cell sediments from the same effusions with similar Moabs. It was found that the prevalence of several TAPs, including CEA, epithelial membrane antigen (EMA), vimentin, tenascin, and Thomsen Friedenreich antigen, was significantly higher in the malignant effusions than in the nonmalignant ones. A total, larger than 2, of detected TAPs in a given fluid, was found almost exclusively in malignant effusions (p less than 0.0001). The detection limit of the DIA for a CEA was determined at 5 ng/ml, while for the ELISA it was 1 ng/ml. Several TAPs, especially the CEA, could be detected in parallel tests, carried out on the liquid moiety and the cell sediments of malignant effusions. The evaluation of selected TAPs in pleural effusions by dot blot assay may be of clinical value.