The Transmission of Lymphosarcoma in Xenopus laevis, the South African Clawed Toad1

The Xenopus lymphosarcoma agent is resistant to freezingthawing, freeze-drying, and antibiotics, but sensitive to heat, ether, and chloroform. It passes a 100-nui filter, and remains in the supernatant fluid following centrifugaron at 30,000 X g for 1 hr. The agent is passed from toad to toad through the water in which the Xenopus live. Phytohemagglutinin injection did not alter the latent period following tumor homogenate injection, but did encourage more extensive metastasis. Thymectomized Xenopus developed tumors following tumor homogenate injection at least as quickly as did nonthymectomized controls. Xenopus normal and tumor cells were cultured in vitro in a simple medium and in free gaseous exchange with the atmosphere. Cultured tumor cells retained the ability to induce tumors when injected into immature Xenopus, and cell-free medium from tumor tissue cultures also induced tumors.