Neoplastic transformation of rat thymic cells induced in vitro by Gross leukemia virus.

Cultures of embryonal rat thymus infected initially with Gross leukemia virus have, at the present time, abundantly replicated infectious virus particles for 20 months. Cells from these cultures, after 3 months in vitro, displayed morphological changes and induced formation of tumors upon isotransplantation. The tumors were serially transplantable, and subsequent transplants continue to carry the initial Gross leukemia virus.