PDCD1 and viral infectious disease: Chronically stimulated T cells during aging, persistent viral infections, and cancer trigger an exhausted profile characterized by the expression of inhibitory receptors such as programmed cell death protein 1 (PD‐1) (Im et al. 2016; Lee et al. 2016), inducible costimulatory molecule (ICOS) (Im et al. 2016; Lee et al. 2016) and T‐cell immunoglobulin and immunoreceptor tyrosine‐based inhibitory motif domain (TIGIT) (Pieren et al. 2022).