When mice were infected with lymphocytic choriomeningitis virus (LCMV)–Armstrong or influenza A-PR8 viruses, there was a surge of Ly49+CD8+ T cells in the blood of wild-type mice (Fig. 6, A and E), consistent with our previous observations of increased KIR+CD8+ T cells in patients with acute SARS-CoV-2 or influenza infection. Here, KIR3DL1 is linked to influenza.