OBJECTIVETo investigate the relation between CD4(+) and CD8(+) T lymphocyte infiltration and apoptosis of the neurons in the local traumatic brain tissue after brain trauma in rats.

METHODSIn rat models of brain trauma, the changes in the number of CD4(+) and CD8(+) T lymphocytes and the apoptosis of neurons in the local traumatic brain tissue were observed by immunohistochemistry at different time points after brain trauma.

RESULTSTwenty-four hours after brain trauma, a significant increase in the number of CD4(+) and CD8(+) T lymphocytes occurred in the injured brain tissue, both reaching the highest levels on day 10, at the point of which the number of CD4(+) cells increased by about 15 folds and that of CD8(+) cells by about 20 folds compared with the control groups. The CD4(+) and CD8(+) T lymphocytes both began to decrease 30 days after the injury. A similar pattern of alterations was found in the apoptosis of neurons in the local brain tissue. Correlation analysis demonstrated a close positive correlation between the changes in CD4(+) and CD8(+) lymphocyte numbers and the number apoptotic neurons in the injured brain tissue.

CONCLUSIONSBrain trauma induces obvious increases in CD4(+) and CD8(+) T lymphocytes and enhanced cellular immune response in the injured brain tissue to mediate neuronal apoptosis and further exacerbate the brain tissue injuries.