IL21 and influenza: However, upon further phenotypic characterization of CD4+ Tcm, we observed significantly elevated (P = 0.0061) frequencies of TIGIT-expressing CD4+ Tcm day 14 after B1 (Figure 3A), the same time point at which SIV+ IL-21–treated animals had significantly improved influenza HAI titers compared with SIV+ IL-21–untreated animals (Figure 1E).