Immunoaffinity isolation of ductal carcinoma antigen using monoclonal antibody F36/22

Monoclonal antibody (McAb) F36/22, raised against a human breast tumor line, identifies an antigen found in the circulation of cancer patients. Antigen was purified from malignant effusions using McAb-affinity chromatography followed by adsorption-desorption from immobilized wheat germ lectin. Electrophoretic analysis demonstrated the isolation of a single high mol. wt glycoprotein exhibiting an isoionic point near pH 4.2 and a density of approx. 1.45 g/ml. Although highly reactive with wheat germ lectin, a negligible or weak interaction was observed with concanavalin A, lentil and peanut agglutinin. The antigen was immune-precipitable, indicating the occurrence of multiple McAb-binding sites, and was resistant to heat and acid treatments. Antigenicity was not perturbed following protease or neuraminidase treatments, but was affected upon exposure to alkaline conditions. Taken together, these data suggest that McAb F36/22 recognizes a high mol. wt component occurring in circulation as a mucin-like glycoprotein.