Abstract: Objective:To investigate the change of T lymphocyte subsets in peripheral blood of SD rats with acute spinal cord injury(SCI).Methods:Twenty two SD rats(11 each male and female) were used to establish SCI model using NYU Spinal Cord Contusion Impactor System.The CD3 +,CD3 + CD4 + and CD3 +,CD8 + T cells,and the proportion of CD3 + CD4 + to CD3+ CD8+ T cells of peripheral blood of all rats were evaluated using flow cytometry at the time points of preinjury and days 1,3,5,7and 14 postinjury.Results:The percentages of CD3+ CD8+ cells had no significant difference among before SCI,the 1st,7th and 14th day after SCI,butthe percentage of CD3+,CD8+ T cells at the 3rd,5th day was higher than at the 14th day after SCT and before SCI.The percentages of CD3+ and CD3+ CD4+ T cells,and ratio of CD3+ CD4+ to CD3+ CD8+ T cells at days 1,3,5 and 7 post-injury were significantly lowerthan those of at preinjury(P 0.01).After 14 days postinjury,all T lymphocyte subsets were restored to preoperative level,which wereno differences with preinjury(P 0.05).Conclusions:After acute SCI,the total of T cells and CD4+ T cells and the ratio of CD3+ CD4+ to CD3+ CD8+ T cells decrease,which suggest there may be T cell function abnormalities in the early stage of SCI in rat model.