CD8A and tauopathy: Interestingly, Chen et al. also observed CXCR6 and PD-1 expression in brain T cells that promoted tauopathy in TE4 mice, and reported that anti-PD-1 treatment increased the activity of PD-1+ CD4+ Tregs but did not alter the activity of detrimental PD-1+ CD8+ T cells [6].