CD4 and common variable immunodeficiency: In a murine lymphocytic choriomeningitis virus model, the synergistic use of IL-2 therapy and PD-1 blockade was able to reverse the exhausted immunophenotype of CD8 T cells and to regain control over the infection.16 Similar to the PKAI antagonist experience, Perreau et al17 showed that in vitro CD4 proliferation in patients with CVID may also be restored by blocking the programmed death ligand 1 and 2 axes (PD-L1/2).