PDCD1 and classic Hodgkin lymphoma: Particularly, in contrast with the high responsiveness of anti-PD-1 therapy in patients with cHL, the HLA class I cell surface expression is lost in up to 70% of cHL cases (Oudejans et al., 1996; Liu et al., 2014; Nijland et al., 2017; Liang et al., 2019).