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

Abstract

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 immuno-suppression by adult thymectomy (ATx) and/or prolonged antilymphocyteglobulin (ALG) treatment. Neoplastic lesions in bone were reported in part I (1). 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.

Key Words:

• Radiation carcinogenesis
• strontium-90
• immunosuppression
• lympho-reticular tumours
• extraskeletal tumours