Failure to detect immune deficiency in rats after prenatal or early postnatal irradiation

The authors looked for medium-term sequelae in the immune system of rats X-irradiated (0-2 Gy whole-body irradiation) during prenatal or early postnatal life. At an age of 8 weeks the histology of the spleen was normal, as was the distribution of B and T lymphocytes. Serum immunoglobulin levels were not significantly altered, even when different isotypes were considered. At 10 weeks, the rats were immunized with a T-dependent or T-independent dinitrophenylated-carrier antigen. Normal levels of specific antibodies were generated in all groups of animals injected with T-independent antigen. The T-dependent response, was higher in animals irradiated between day 6 and day 20 of gestation (but not in rats irradiated early after birth). This increase was significant only for IgM and IgG1 responses of some irradiated groups. Thus no medium-term immunodeficiency could be documented with methods used. The alteration in T-dependent response, points to a radiosensitive T regulatory mechanism. (author)