Xenogeneic neoplastic transplants in adult rats pretreated with thymic foetal extracts

The paper deals with the effect of thymic extracts from young foetal pigs and calves on the development of tumour xenografts, i.e. mouse ascites Ehrlich carcinoma and hamster malignant melanoma, in rats. The results of experiments showed that Ehrlich carcinoma developed in 4 out of 72 animals, i.e., in those animals which had received thymic extracts from young foetal pigs, Ehrlich carcinoma led to their death. Ehrlich carcinoma assumed a solid form and the cells changed in their shape. It developed normally, when retransplanted to mice. Hamster melanoma, when transplanted to rats given thymic extracts from young foetal calves, developed and survived for long periods of time (in one animal up to 190 days, and in the remaining animals much longer than in the controls and the animals injected with liver extracts from young foetal calves). The melanoma xenograft was not morphologically changed. A normal development of the malignant process occurred when melanoma was retransplanted to hamsters. Animals injected with thymic extracts from young foetal calves exhibited lymphopoenia and a fall in gamma globulin levels before tumour transplantation.