Long-Term Spontaneous Tumor Incidence in Neonatally Thymectomized Mice

Abstract

A number of workers have reported increased susceptibility of neonatally thymectomized mice to virally induced tumors (1–3). In this case, however, the response of the animal to the virus itself may be a critical factor, so that the effect of immunosuppression might be to reduce resistance to viral infection rather than to virally induced cell surface alteration.The effect of neonatal thymectomy on other forms of carcinogenesis is not at all clear. Trainin et al. (4) have reported a decreased latent period and an increased number of tumor nodules after urethane treatment of mice that had been subjected to thymectomy on the 3rd day of life. Miller and coworkers (5) reported a decreased latent period for tumor induction when early thymectomy was combined with exposure to chemical carcinogens. On the other hand, using a system similar to Miller's, Law (6) observed no effect of neonatal thymectomy on either tumor incidence or latency.