CD274 and infection: Upregulation of the PD-Ls on activated CD4+ T cells in our series is consistent with the results of Mazerolles et al., who reported that PD-L1 expression on activated CD4 effector T cells is correlated with T-cell proliferation (25), and Trinchieri who observed that immunosuppressive mechanisms typical of the tumor microenvironment are observed in infected tissues during resolution of the immune response to infections (26).