γδ T Cells Express Activation Markers in the Central Nervous System of Mice with Chronic-relapsing Experimental Autoimmune Encephalomyelitis

In this study, we assessed the expression of activation markers on γδ T cells in central nervous system (CNS) lesions of SJL mice adoptively sensitized to develop experimental autoimmune encephalomyelitis (EAE) using myelin basic protein-reactive T cells. Although disease expression is known to be dependent upon T cells that express the αβ T cell receptor (TCR), a role for γδ T cells has been implicated in some studies but not in others. Using three-color flow cytometric analysis of both total and γδ T cells in spleen and CNS, the data showed that expression of CD69 (early activation marker), CD62L (lymphocyte homing receptor), CD25 (IL-2Rα), CD122 (IL-2Rβ) and CD95/CD95L (Fas/FasL), fluctuated on γδ T cells in EAE lesions in a disease-related fashion. Furthermore, the pattern of expression for these markers on γδ T cells was distinct from that found on the total lymphocyte population. Cytokine analysis of γδ T cells in the CNS demonstrated a bias towards a Th1-like cytokine profile. From these data, we conclude that γδ T cells in EAE lesions display an activated phenotype and form a dynamic component of the total lymphocyte population in the CNS, supporting a contributory role for these cells.