miR-17∼92 acts in a CD8 T-cell–intrinsic manner to regulate memory differentiation. (A) 10⁵ naïve CD8^CKO (Thy1.2⁺) or CD8^CTg (Thy1.2⁺) P14 cells were adoptively transferred along with equal numbers of wild-type D^bGP33-specific P14 (Thy1.1⁺) cells into naïve C57Bl/6 mice (Ly5.1⁺) that were subsequently infected with LCMV. (B) Splenocytes were isolated at days 7 or >30 after infection, and frequencies of antigen-specific CD8^WT, CD8^CKO, and CD8^CTg cells were determined by flow cytometry using CD8, Ly5.1, Thy1.1, and Thy1.2 markers. Absolute numbers of antigen-specific CD8 T cells at the effector and memory phases are presented as bar graphs. Percentage contraction of CD8 T cells from peak to memory is shown at top of the respective groups. (C) Representative FACS plots of CD127 and KLRG-1 expression on CD8^WT-, CD8^CKO-, and CD8^CTg-gated populations are shown in spleen (SPL), inguinal lymph node (iLN), lung (LNG), liver (LIV), and blood (PBL) at day 7 after infection. Mean ± SEM of %MPECs (CD127^hi KLRG-1^lo) and %SLECs (CD127^lo KLRG-1^hi) at indicated times after infection are plotted as bar graphs. Results are representative of at least 4 independent experiments with n ≥ 3 in each group. Unpaired Student t test was used for statistical significance. (D) CD8^WT, CD8^CKO, and CD8^CTg donor cells were analyzed for Bcl-2 expression in SPL and PBL at the peak of CD8 T-cell expansion. Histogram plots with mean fluorescence intensity (MFI) of Bcl-2 expression are shown. (E) Histogram plots of l-selectin (CD62L) expression on CD8^WT, CD8^CKO, and CD8^CTg cells in SPL and PBL are presented at memory. Numbers represent frequencies of CD62L^hi antigen–specific CD8 T cells. (F) Bar graphs represent mean ± SEM values for %localization of CD8^WT, CD8^CKO, and CD8^CTg cells at the memory phase in indicated tissues. %localization in each tissue was calculated by dividing the number of CD8^WT, CD8^CKO, or CD8^CTg donor cells in the tissue by total number of respective donor cells in all tissues.