Flow Cytometric Characterization of T Cell Subsets and Microglia After Repetitive Mild Traumatic Brain Injury in Rats

Although, there is growing awareness in the progressive neurodegeneration of chronic traumatic encephalopathy, changes of immune reactions remain equivocal at best. Thus, in a clinically relevant rat repetitive mild traumatic brain injury (rmTBI) model, some immunologic cells (T cell subsets, microglia) in the injured brain and peripheral blood were analyzed by flow cytometry and immunofluorescence. In the injured brain, CD3(+) T cells showed a bimodal increase during 42 days post-injury (dpi). CD3(+)CD4(+) T cells firstly increased and then decreased, while CD3(+)CD8(+) T cells had reversed tendency. CD86(+)/CD11b(+) M1-like microglia increased at 42 dpi and CD206(+)/CD11b(+) M2-like microglia peaked at 7 dpi. In addition, peripheral immune suppression was implicated in the chronic phase after rmTBI. Taken together, the study provided useful information on long-term dynamic changes of some immune cells after rmTBI in rats.