Influence of 90Sr, adult thymectomy and antilymphocyteglobulin on haematopoietic tissues and peripheral blood leucocytes in CBA mice.

The role of long-time immune suppression in carcinogenesis induced by the long-lived internal emitter 90Sr, is investigated in an ongoing study. The experimental design is based on the assumption that impaired immune responsiveness, by other means than 90Sr, might increase the neoplastic response in exposed individuals, and thus reflect a protective function, if existing. Intercomparison is made of the tumour yield in mice exposed to different single doses of 90Sr and simultaneously subjected or not to long-term immune suppression by adult thymectomy (ATx) and/or antilymphocyteglobulin (ALG) treatment. Information on the general condition and responsiveness of the immune system, in the respective models, during tumour expectancy time, is essential for a conclusive evaluation of the results. To meet these demands the present paper reports on histopathologic alterations in immune organs and changes in white blood cell counts, induced by the different combinations of 90Sr, ATx and ALG treatment. The results confirm the prediction, that ATx + ALG is an efficient and, with respect to the purpose of the study, suitable treatment for additive long-term depression of the immune system in 90Sr irradiated mice, evidenced in particular by increased depletion of monomorphonuclear cells (MNC) in lymphoid organs and peripheral blood. Subsequent reports will deal with functional immune parameters.