Changes and significance of CD4 + CD25 + regulatory T cells in γ-ray irradiated mice / 中华放射医学与防护杂志

ABSTRACT

Objective To observe the effect of γ-ray irradiation on CD4 + CD25 + regulatory T cells (Tregs),and to investigate the mechanism of immune injury induced by irradiation.Methods The thymus and spleen of C57BL/6 mice were taken and weighted 1-28 d after γ-ray irradiation,and the organ coefficients were calculated.The amount of mouse peripheral WBC measured,CD4 + T cells and Tregs in peripheral and splenic were analyzed by flow cytometry.Results Coefficients of mouse thymus and spleen decreased significantly 1 d post irradiation,and reached to the bottom at 7 d.Coefficients did not recover to control level 28 d after radiation.Peripheral WBC continuously decreased and reached the bottom at 7 d,and did not recover to control level up to 28 d postirradiation.Peripheral CD4 + T lymphocyte temporally reduced at 1 d,while it increased at 7 d,and it approached to control level at 28 d after radiation.Splenic CD4 + T cells slightly reduced at 7 d however,they basically maintained as the same level as control 14 d and 28 d after radiation.Peripheral Tregs ascended at 1 d and reached the peak at 7 d,and reduced at 14 d and 28 d postirradiation,although they still were significantly higher than those of control group.At the same time,splenic Tregs increased significantly and achieved peak value at 1 d,and then gradually decreased and reached the minimum at 28 d after irradiation,which were significantly lower than those of control group( t =2.731,P ＜ 0.05).Conclusions Mouse thymus and spleen were injured severely,and the number of immunocytes decreased after 6 Gy whole body γ-ray irradiation.However,Tregs with immunosuppressive action increased significantly postirradiation,revealing that Tregs were closely correlated with immune function depression and immunomodulation imbalance induced by ionizing radiation.