Correlation between PD-1 and PD-L1 expression in DLBCL. (A) At a low cutoff for PD-L1 positivity on CD20⁺ lymphoma cells, the PD-L1⁺ group (95% of the cohort) had a significantly higher mean level of PD-1 expression than the PD-L1^– group. (B) At a 30% cutoff for PD-L1^high on CD20⁺ lymphoma cells (according to Kiyasu et al⁵⁷ ), the PD-L1^high group (12.9% of the cohort) had a significantly lower mean level of PD-1 expression than the PD-L1^low group. (C) PD-L1 levels on lymphoma cells were further stratified and correlated to PD-1⁺ levels (%) and absolute PD-1⁺ T cell numbers in the tumor microenvironment. (D) PD-L1 levels (%) on CD68⁺ cells were stratified and correlated to absolute PD-1⁺ T-cell numbers in the same tissues. (E) Dot plot for total PD-L1⁺ and PD-1⁺ cell counts in DLBCL tissues. Each dot represents the data for 1 patient.