CD4 and neoplasm: However, T cells exhibited a significant higher expression of PD-1 (mean on CD4+: 17% ± 12 SD; mean on CD8+: 27% ± 19 SD) on tumor infiltrating lymphocytes (TIL) compared to healthy donors or patient blood (Figure 1F; CD4+ = p = 0.004; CD8+ = p = 0.002).