PDCD1 and cancer: Pembrolizumab binds with high affinity to human PD-1, blocking receptor ligation by both PD-L1 and PD-L2 and leading to enhanced T-lymphocyte immune responses in preclinical models of cancer, with the modulation of key cytokines like interleukin (IL)-2, tumour necrosis factor (TNF)-α, and IFN-γ [100,101].