Immediate and short-, mid- and long-term effects of in vivo ionizing radiation exposure in BALB/c mice: I. Activation of lymphocytes and subpopulations.

BACKGROUND The main aim of this work was to study the effects of single whole-body irradiation (WBI) on the lymphoproliferative response in radiation-sensitive BALB/c mice. MATERIALS AND METHODS Mice were irradiated (0-5 Gy) and euthanized immediately afterward; other animals were subjected to WBI (4 Gy) and were analyzed after periods of 0-180 days. Splenic cell number, lymphoproliferative response and lymphocyte subpopulations were studied. RESULTS This study shows that immediately after exposure, an inhibition of the basal mitogen lymphoproliferative response was produced; furthermore, B-cells appear to be more radiosensitive than T-cells. However, up to 90 day's post-irradiation, mice spleens clearly show low cell numbers, and subpopulations and T-cell mitogens did not return to normal, while the basal response and B-cell mitogens peaked on day 15 post-WBI. CONCLUSION In our model, B-cells regenerate earlier than T-cells, while Th lymphocytes regenerate faster than Tc lymphocytes.