Radiostrontium-induced oncogenesis and the role of immunosuppression. II. Influence of 90Sr dose, adult thymectomy and antilymphocyteglobulin treatment on the development of lympho-reticular and extraskeletal, neoplastic lesions in CBA mice.

The significance of depressed immune function for the development and progression of tumours induced by 90Sr (mainly osteosarcomas and malignant lymphomas) was investigated in a series of experiments by comparing the tumour responses in normal mice with those in immunocompromised mice. The present paper (part II) reports on lympho-reticular (LR) and extraskeletal neoplastic lesions in male CBA/SU mice after exposure to different single doses of 90Sr with or without additional immunosuppression by adult thymectomy (ATx) and/or prolonged antilymphocyteglobulin (ALG) treatment. Neoplastic lesions in bone were reported in part I. The status of the animal's immune system and responsive ability were examined in parallel experiments. The tumour yields were analysed in relation to the dosage of 90Sr and the immunosuppressive treatments employed. Although the incidences and latency times of induced tumours were clearly dose-dependent, they were never significantly influenced by ATx/ALG treatments. Thus, no substantial support was gained for the theory that the immune system plays a controlling or modifying role in 90Sr carcinogenesis. The results, which are in agreement with the bone tumour responses, suggest that 90Sr induced tumours either do not express the antigens necessary for immune rejection or that the decline in immune responsiveness induced by ATx/ALG was of little consequence for tumour development and spread. The pathogenesis of 90Sr induced malignant lymphomas (MLs) and their immunophenotypes are discussed.