Specificity of tumour associated transplantation antigens (TATA) of different clones from the same tumour

The TATA of two clones from the same murine methylcholanthrene-induced fibrosarcoma have been investigated by immunizing syngeneic mice with irradiated cells of one or both clones and challenging them 14 days later with viable cells. The tumour had been induced in a female backcross CBA mouse heterozygous for the A and B alloenzymes of phosphoglycerate kinase-1 (PGK-1). One clone expressed A and the other B, and both A and B hosts were used in the experiments. Each clone was found to possess strong TATA but there was no demonstrable cross reactivity. The clonal composition of tumours produced by inoculating mice with a mixture of the two clones was profoundly altered by prior immunization with one of them. A second experiment was performed with 3 clones from another tumour, these expressed PGK-1 A, B and AB respectively. Again, there was no evidence of immunological cross reactivity between the A and B clones, but there was some cross reactivity between the A clone and AB clone. These results, coupled with previous observations of changes in the clonal composition of pleoclonal murine fibrosarcomas in culture and on transplantation, suggest that the antigenic specificity of these tumours is less stable than is commonly supposed.