| In this study, the effects of CD3 McAb, CD28 McAb, PHA and low-dose gamma-rays irradiation on T lymphocytes were investigated to explore factors influencing T cell signals transduction and discover molecular mechanism of irnnune effects stimulated by ionzing radiation, and offer theoreatic basis of early measures for decrease in harmful effects and increase in favourable effects of irradiation, and provide experimental data for combination of tumor radiotherapy with inmunotherapy. Using C03 McAb and CD28 McAb as the first and the second signals, and using PHA and low-dose gamma-rays irradiation as stimulatory factors in T cell activation, the influences of these factors and the two signals on human lymphocyte proliferation response were studied with 3H-thymidin(3H-TdR) incorporation. The effects of gamma-rays irradiation on CD3, CD4 and CD8 molecule expression of human lymphocytes irradiated with 0. 5, 2, 4 and 8 Gy gamma-rays or with 0.5, 2, 4 and 8Gy(D2) gamma-rays 4h after 10 cGy irradiation(DD were investigated in normal donor. 24h or 48h after final irradiation the changes of CD3+ CD4+ and CD8+ molecules were measured by flow cytometry (FCM) with indirect inmunofluorescence technique. The functional interplay between Fas and CD28 and the effects of different dose gamma-rays irradiation on CP28 and Fas molecules expression in human T cells were measured by FCM with direct irrmunofluorescence technique. Before and after irradiation the T cells DNA fragmentation and apoptosis were determined by JAM test and FCIvI technique respectively. The effects of different dose gamma-rays irradiation on B7. 1 molecule expression in human tumar cells was investigated at different time. After exposured the changes of B7. 1 niilecule were measured by FQvI with indirect inmunofluorescence technique. The expression of B7.1 messenger RNA on SMMC-72 irradiated with 50 Gy was examined by reverse-transcription polymerase chain reaction (RT? PCR). Natural killer activity on tunrj)r target cell irradiated with gamma-rays was determined by 2H-TdR release method. The results show as follow: 1. Lymphocytes proliferation response were occured when CD3 McAb and CD28 McAb were treated costimulaneously or within certain intervals between two McAb (20h and 40h). P1-IA and lOcGy gamma-rays irradiation can also activate lymphocytes to proliferate. The results show that I cell activation and proliferation requirs interaction on two signals induced by TCR/CD3 complex and CD28/B7. 1, which is an important aspect in cellular inmune regulation. 2. The CD3+, CD4+ and CD8+ nnlecules expression in the groups of high dose irradiation decreased with increasing dose (p<0.01), while the CDW, CD4+ and CD8+ irolecules privously exposed to lOcGy irradiation could reduce this influence. The expression of CD3 on lymphocyte in radiotherapy tiimjr with lOcGy, over lOGy and 2OGy were lower than that of normal conrol, and the expression of CIA and CD8 with over 2OGy were lower than that of nomal control. The results indicate that high dose irradiation influence the expression of the first signals on iirmune cells. 3. CD28 melecule expression was down-regulated and Fas receptor expression was up-regulated in CD3?T cells, and T cell EM fragmentation and apoptosis increased (p<0. 01) by gamma-ray irradiation with increasing irradiation dosage, which could affect...
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