PDCD1 and B-cell chronic lymphocytic leukemia: The percentage of PD-1 and PD-L1 on CD4+ (Fig. 5A and D), CD8+ (Fig. 5B and E) T cells, and CD19 + B (Fig. 5C and F) cells was highest in the SID EBV + and CLL EBV + groups, indicating the activation of immunosuppressive pathways in response to EBV reactivation.