RADIOIMMUNOLOCALIZATION OF MURINE MAMMARY-TUMOR VIRUS PROTEINS IN GELS

A procedure for the immunological detection of antigens on sodium dodecyl sulfate-polyacrylamide gels using iodinated antibodies combined with an immunoconcentration step to enrich for the desired antigen(s) is described. This selective enrichment is achieved by separation of the antigen-antibody complexes with formalin-treated cells of Staphylococcus aureus and is followed by radioimmunolocalization on gels. This method is particularly useful for the characterization of antigens present at low concentrations in complex biological fluids. Its usefulness is exemplified here by the successful identification of mouse mammary tumor virus antigens in extracts of murine mammary tumors and in plasmas of tumor-bearing animals. The procedure permits the ready determination that the gp52 protein detected in the plasmas of tumor-bearing animals is in fact present as a 52,000-dalton species and not as a higher MW precursor.