CD8A and Parkinson disease: To assess the mechanism of action of Treg expansion in hαSyn PD mice, we analyzed CD8+ brain T cell activation with the CD69 marker three days after CD28SA delivery and observed a slight suppression of CD8+CD69+ T cells in the brain T cells in hαSyn PD mice and, more strikingly, a suppression of early IL-2 expression in cervical lymph nodes and spleen of PD mice of ~ 30–45% three days after CD28SA injection.