Viral antigen has been shown to induce the Treg cells in influenza virus–infected mice (58); in mice with BLIMP1-deficient T cells, following influenza infection, there was increased frequency of Treg cells and TEFF, with decreased IL-10 but enhanced IFN-γ production and increased IL-2 signaling in medLNs and lungs. Here, PRDM1 is linked to influenza.