Tumor-associated
antigens (TAAs) expressed on
tumor cells from cattle with
enzootic bovine leukosis were divided into three groups by using 13
monoclonal antibodies: common TAA; partially common TAA; and individually distinct TAA. TAA was extracted from
tumor cells and purified by ion exchange chromatography on
diethylaminoethyl-cellulose and isoelectric focusing. The common TAA, which was detected on all
tumors tested, was eluted with 0.6 M KCl in ion exchange chromatography on
diethylaminoethyl-cellulose, and the isoelectric point of the
antigen was 6.8. The partially common TAA, which was detected on some (but not all) of the
tumors tested, was eluted with 0.4 to 0.8 M KCl, and the isoelectric points of the
antigen were 5.3, 5.8, and 6.4. The individually distinct TAA was present in the fractions eluted with 0.4 to 0.8 M KCl, and the isoelectric point of the
antigen was 5.5. Results of competitive binding assay and Western blot analysis showed that the common TAA was a
polypeptide with a molecular weight of 74,000; that it has at least two independent antigenic regions; that the partially common and individually distinct TAAs were a
polypeptide with a molecular weight of 64,000; and that the
antigenic determinants on the common TAA, partially common TAA, and individually distinct TAA existed independently from each other.