Abstract:

Abstract:Objective
To observe the changes of the regulatory T cells（Treg）and the expression of TGF-β1 in mouse spleen induced by different doses of X-ray irradiation at different time and study the effects of the X-ray on the Treg and TGF-β1. Methods The male ICR mice were irradiated with different doses of  X-ray (low dose:0,0.050 Gy,0.075 Gy,0.100 Gy,0.200 Gy;high dose: 0,0.500 Gy,1.000 Gy,2.000 Gy,4.000 Gy,6.000 Gy) respectively by the XSS205 (FZ)-type stationary X-ray deep therapy machine all over the body. Then the mice were killed 16 h after irradiation and the  Treg and the expression level of TGF-β1 in the mouse spleen were detected by flow cytometry,RT-PCR and Western blotting.Results Compared with  sham-irradiation group,the percentage of  Treg had no significant changes in mouse spleen in low dose irradiation groups (P<0.05); in  high dose irradiation groups,the percentage of  Treg was increased as the dose rose from 1.000 Gy to the higher levels(P< 0.05,P< 0.01),which showing a dose-dependent phenomenon. Compared with  sham-irradiaton group,the level of TGF-β1 mRNA in mouse spleen had a trend to increase sustainedly as the dose was increased from 0.500 Gy to the higher doses,and then was increased to 2.000 times higher in  2 Gy group,following with a slight decrease. The level of TGF-β1 protein in mouse spleen  in 0.100 Gy group was significantly higher than that in sham-irradiation group,and had an increasing tendency   in  high dose irradiation groups.There were significantly differences of the expression of TGF-β1 protein between 4.000 Gy group,6.000 Gy group and sham-irriadiation group(P<0.05).Conclusion The percentage of  Treg is increased after induced by  high dose X-ray,as well as the increasing secretion of the TGF-β1,which might be another reason for  high and low dose X-rays inducing different immune responses.

Key words: ionizing radiation;regulatory T cells;transforming growth factor;immune response