Reduction of the radiogenic tumor incidence by stimulation with lyophilized fetal cells

The effect of an immunization treatment with lyophilized xenogenic fetal cells was studied in 7 months old, female albino rats (strain Wistar). The tumor incidence was measured after a sublethal whole-body irradiation with 600 cGy. Furthermore, the spleen of the individual animals was histologically examined. 3,5 to 6 months after a whole-body irradiation with 600 cGy, the tumor incidence was 55%. The tumors found were tubular adenocarcinomas of the thyroid gland. A significant reduction of the tumor incidence can be achieved by an immunostimulation with xenogenic, lyophilized, fetal cells (connective tissue and bone marrow, respectively) administered twice, namely eight days before and four days after the whole-body irradiation. The tumor incidence measured after 3,5 months was 10% and 15%, respectively, and after 6 months 15% and 25%, respectively. No significant tumor protection is achieved, however, by a single stimulation before whole-body irradiation and by a stimulation performed one or two times after whole-body irradiation. Histologic examinations of the spleen show in the immunostimulized animals a strong regeneration of the immune system with a significantly increased number of follicles and a significant increase of lumphocytes in the red pulp. The authors stress the possible clinical importance for radio-oncology of an immunostimulation with lyophilized, xenogenic, fetal cells. (orig.)