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American Journal of Pathology, Vol 91, 217-227, Copyright © 1978 by American Society for Investigative Pathology

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Effects of whole-body irradiation on neonatally thymectomized mice. Incidence of benign and malignant tumors

RE Anderson, JL Howarth and GM Troup

The individual and combined effects of neonatal thymectomy and whole- body irradiation on the prevalence of benign and malignant tumors in germ-free female mice of the Charles Rivers line were studied to determine if a portion of the tumorigenic effects of irradiation can be attributed to injury of the thymic-dependent component of the immune response. Neonatal thymectomy increased a) the incidence of benign and malignant tumors and b) the prevalence of multiple primary neoplasms in an individual mouse. Whole-body exposure to 700 rad at 6 weeks of age further increased th incidence of tumors, but the relative magnitude of this increase was less pronounced than in sham-operated controls. Thus, the cumulative effects of thymectomy plus irradiation are less pronounced than the sum of the individual effects. One of several possible explanations for this observation is that a portion of the carcinogenic effects of whole-body irradiation is mediated by suppression of the thymic-dependent component of the immune response.