Objective:To observe the changes of CD3 +CD8 +CD28 - suppress T lymphocytes( Ts) and CD3 +CD8 +CD28 + cytotoxic T lymphocytes( Tc) subsets in peripheral blood of SD rats with spinal cord injury( SCI) . Methods:The SCI model of ten female SD rats were established using New York University Spinal Cord Contusion system. The changes of CD3 +CD8 +CD28 - and CD3 +CD8 +CD28 +T cell subsets in peripheral blood were evaluated using flow cytometry at the time points of pre-injury and days 1,3,5,7,14,21,28 and 56 post-injury. Results:The percentages of Ts and Tc in the CD3 + T cells of peripheral blood of healthy rats were(30. 27 ± 12. 09)%and(14. 75 ± 4. 29)%,respectively. The percentage of Ts was(22. 58 ± 12. 12)% at the first day of SCI. At the 5th day,it decreased to the lowest level(20. 86 ± 10. 41)%,it reached to the normal level from 7 to 21d after SCI. At 28th day,it increased to(37. 90 ± 12. 98)%. At 56th day(33. 79 ± 11. 44)%,it decreased to the normal level again(P>0. 05). The change trend of Tc was opposite to the Ts after SCI. The percentages of Tc at time points of days 1,5,21 and 28 post-injury were(17. 29 ± 7. 10)%,(20. 02 ± 6. 24)%, (23. 89 ± 6. 78)% and(13. 81 ± 11. 21)%,respectively. It didn't return to normal level,but decreased to(8. 71 ± 6. 44)% at the time points of 56 d(P0.05)。 Tc和Ts亚群的变化趋势相反,在损伤后1、5、21和28 d时其比例分别为(17.29±7.10)%、(20.02±6.24)%、(23.89±6.78)%和(13.81±11.21)%。但56 d时其比例没有恢复至术前水平,而是进一步下降至(8.71±6.44)%(P<0.01)。结论：在SCI后的早期阶段,SD大鼠外周血Tc占明显优势,提示Ts功能抑制、Tc功能增强是SCI免疫损伤机制之一。 SCI后5~21 d是进行免疫调节治疗的关键时间窗。
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