Studies of acute-phase infections in mice and humans (including acute HIV) suggest that an overwhelming majority of the CD8+ T cells that we identified as becoming activated in response to rebound (i.e., those expressing Ki67 +/− HLA-DR +/− CD38) are likely HIV-specific.42–44 Additionally, they preferentially occupy a T cell memory subset typical for HIV-specific CD8+ T cells (transitional memory, TTM). Here, MKI67 is linked to infection.