The PD1/PDL1 signaling pathway, comprised of the programmed cell death protein 1 (PD1) and programmed cell death ligand 1 (PDL1) expressed on the surface of T lymphocyte cells, can inhibit the proliferation of T lymphocyte cells and down-regulate specific T lymphocyte immune function to limit immune-mediated host tissue damage and promote the persistence of infection (Francisco et al., 2010; Noack and Miossec, 2014). Here, PDCD1 is linked to infection.