PDCD1 and leukemia: Zhang’s research revealed that a single TIGIT inhibitor upregulated only IFN-γ and TNF-α, but the combination of anti-TIGIT and anti-PD-1 inhibitors significantly upregulated IL-2, IFN-γ, and TNF-α in CD4+ or CD8+ T cells, which could enhance anti-leukemia immune response [64].