Abstract
The relation with latent period (LP) of the antigenicity (AG) and growth rate (GR) of 7,12-dimethylbenz (a) anthracene-induced sarcomas have been studied in 3 experimental situations. In the first experiment, 36 primary BALB/c sarcomas showed a decrease of AG and an increase of GR when LP increased from 10 to 26 weeks. The tumors which appeared after a short latency grew slower and were more antigenic than tumors with longer latency. In the second experiment, one antigenic C3Hf fibrosarcoma was transplanted serially in immunodepressed and normal mice and tested for AG and GR at the 1st, 3rd, 6th, 8th and 10th transplant. The same relationship between AG and GR was observed in the two lines as AG decreased while GR increased during serial transplantations. In the third experiment, two monoclonal tumors isolated from the C3Hf fibrosarcoma of the previous experiment were tested at different transplant. A decline of antigenic strengh and an increase of GR during serial transplantation was observed in both tumors. The change of AG and GR observed in these experiments cannot be explained only by immunological surveillance, and nor by a clonal selection of high GR cells preexisting in the primary tumor. It seems rather that during proliferation the malignant cells gradually lose growth control leading to an increase of GR and, at the same time, to a diminution of AG.
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