TIGIT and neoplasm: PD-1+ CD4+ (p < .0001) and CD8+ (p < .0001) T cells that do not co-express TIGIT were more abundant in the tumor than in the spleen while no significant changes in the frequency of PD-1+ TIGIT− subset were observed in the Treg compartment (Figure 1b-d, quantified in Figure 1f).