The blockage of the PD-1/PD ligand 1 (PD-L1) pathway was found to restore effector function of T cells in some patients with CHB and in the woodchuck model of WHV-induced CH (Maier et al., 2007; Fisicaro et al., 2010; Liu et al., 2014; Balsitis et al., 2018). Here, PDCD1 is linked to cyclic hematopoiesis.