CD38 and infection: The SFV-only infection induced CD8+ T cells with dominant phenotypes driven by the expression of KLRG-1, a marker of short-lived effector T cells (19), with significantly increased frequencies of KLRG1+, KLRG1+CD38+, KLRG1+CD38+PD1+ and KLRG1+CD38+CD25+ CD8+ T cell populations, compared to IAV→SFV infection (Fig. 4B).