CD8A and viral infectious disease: In a preclinical model of an acute viral infection, the higher expression of PD-L1 on CD8+ T cells decreased the proliferation, functional maturation, and production of multiple granzymes of the effector CTL [89], similar to the model of graft-versus-host disease (GVHD), where Pdl1–/– CD8+ T cells diminished the production of inflammatory cytokines and enhanced the rate of CTL apoptosis [90].