Induction of Malignant Lymphomas by Urethane in Adult Mice bearing Syngeneic Thymus Grafts

Abstract

IN recent years it has repeatedly been proved that neonatal or very young animals are very susceptible to carcinogenesis induced by different agents. One possible explanation is that tissues of new-born animals contain a large number of incompletely differentiated cells, particularly responsive to carcinogenic stimuli. It is relevant to this speculation that a close correlation has been noted between susceptibility of mice to develop malignant lymphomas and the presence in the thymus of a great concentration of immature cells, whether by reason of early age¹, genetic constitution², whole-body X-irradiation³, or regenerative changes in implanted thymus⁴. In thymectomized, virus-inoculated⁵ or X-irradiated⁴ mice, implantation of new-born thymus proved much more effective than adult thymus in restoring leukaemogenesis.