Antigens associated with canine spontaneous mammary carcinoma

Soluble proteins were prepared from canine spontaneous mammary carcinoma (CSMC) cells by extraction with 3M KCl or limited hydrolysis of isolated cell membranes with papain. These preparations were assayed for tumour-associated antigens by inhibition of fully absorbed rabbit antisera. Organ-specific reactivity was demonstrated and antigenic specificity indicated the possible involvement of fetal components. Exclusion chromatography showed that antigenic activity was associated with macromolecules of different sizes in each of the protein preparations which allowed partial purification of tumour-associated antigens. Antigens were also prepared from circulating immune complexes in the serum of tumour-bearing animals. These studies provide a basis for the development of serological markers of malignancy in CSMC.