Pathologic studies of friend virus leukemia and the development of a transplantable tumor in balb/c mice.

Summary The pathology of Friend virus infection in BALB/c mice was studied and was found to be similar to that seen in other highly susceptible strains. In attempts to develop a transplantable tumor variant, 328 BALB/c mice received grafts of either liver or spleen from other BALB/c mice given inoculations of Friend virus 43–124 days previously. Two tumor lines were established from the liver and spleen, respectively, of a single mouse. Both grew rapidly and were readily transplantable. The incubation period fell from 46 to 7 days. Virtually all the mice that developed a tumor showed signs of generalized Friend disease. Microscopically, the two tumor lines were identical and were classified as reticulum-cell sarcomas. They appeared to have arisen from the same primitive reticulum cells that proliferate in Friend virus infection. The spleens and livers of tumor-bearing animals showed, in addition to the microscopic changes of generalized Friend disease, nodules composed of reticulum cells closely resembling those comprising the tumor. The microscopic impression that these were true tumor metastases was confirmed by showing that some of the cells in the spleens of tumor-bearing animals would themselves give rise to tumors identical histologically and genetically to the original tumor. The tumor could be produced only by injecting living cells. Friend virus was consistently associated with the tumor; no increase in the potential of the virus for tumor induction could be demonstrated.