Assessment of T Cell Activation in a Mouse Model of Traumatic Facial Nerve Injury

Objective To investigate T cell activation following facial nerve axotomization and latent neuroimmunologic mechanisms in traumatic facial paralysis. Methods A murine model of facial nerve transaction was used. Lymphocytes from cervical and mesenteric lymph nodes in BABL/c mice at specific times were collected and expression rates of CD69 on T cells were assessed by flow cytometry. Results Infiltrating T cells were detected around the facial neurons in the facial nerve nucleus in mice whose facial nerve was transected. Immunofluorescent staining showed recruitment of activated T cells. Three days post-facial nerve transection, the expression rate of CD69 on T cells from cervical draining lymphoid nodes (CDLNs) was significantly different from that on T cells from mesenteric lymph nodes (MLNs)(P=0.0457), whereas the latter was similar to that in animals undergoing sham surgeries and that in blank control animals (p=0.2817 and 0.2724, respectively). Two weeks post-nerve transection, the T cell CD69 expression rate from CDLNs remained at a higher level and than that in the sham-operation animals (p=0.0007). At two weeks, CD69 expression rate on T cells from MLNs was also up-regulated and different compared with the sham-operation animals and with itself at three days post-operation (p=0.0082 and 0.0133, respectively). Conclusion T cells appear to be activated and up-regulated in CDLNs following facial nerve transection. There is even evidence of T cell activation in MLNs at 2 weeks post-nerve transection. This suggestes an alteration of immune response from local to general immunity in the acute stage of facial nerve trauma, which may help coordinating and controlling the scales and orientation of the neuroimmune response during the pathogenesis and progression of facial nerve trauma.