CD8A and COVID-19: PD-1 interaction with either of its ligands (PD-1L1, CD274 or PD-1L2, CD273, both members of theB7 family of T cell co-receptors that includes CD28) constitute significant negative immune checkpoints in the pathway responsible for blunting cell-mediated immune responses, specifically CD8+ responses,and for upregulating resulting pathologies (e.g., CoViD-19) and malignancies [9-11].