Changes of lymphocytes and regulatory T cell subset of mice influenced by ^60Co y-ray irradiation

Objective To analyze the influence of ionizing radiation on the lymphocytes and its regulatory T cells in mice. Methods Mice were administered with whole body irradiation of γ-rays at different doses, and lymphocytes were separated from thymus and spleen, then the number of total cells were counted and the percentages of CD4＋T and CD4＋FOXP3＋CD25＋ Treg lymphocytes were analyzed by using FACS. Results The lymphocyte numbers in thymus and spleen decreased in dose-dependent manner and reached to the minimum at 4 d after irradiation （F=118.08,144.01,P〈0.05）. Exposure to higher dose（more than 1 Gy） decreased Treg number time-dependently in thymus, however increased it in spleen. On the contrary, exposure to lower dose（less than 0.75 Gy） increased Treg number in thymus. Besides, the percentage of Treg cells increased dose-dependently（in thymus, F=5.16,89.44,3.01,P〈0.05;in spleen, F=52.02,32.13,27.45,P〈0.05）. Conclusions The radiation responses of lymphocytes and their Treg subpopulation vary with the different doses. Treg cells are resistant to high dose irradiation, however, their differentiation could be induced by low dose irradiation. In addition, the different time-dependent responses of lymphocytes and their subpopulation to ionizing radiation indicate the difference of lymphocyte maturation, differentiation and emigration. Key words: Ionizing radiation;  Regulatory T cell;  Phenotype