Lack of persistent SLP-76–dependent TCR signals alters CD8⁺ Tcm differentiation. (A) Immunophenotyping of splenocytes from cHET and cKO mice 48 weeks after SLP-76 deletion. (Top) Contour plots gated on CD8⁺ T cells with a gate drawn around the CD44^hiH-2D^b:GP33⁺ population. (Bottom) Histograms of CD44^hiH-2D^b:GP33⁺-gated populations comparing cell-surface expression of CXCR3, CD122, CD127, and CD62L in cHET and cKO mice splenocytes. cHET cells are in solid gray; the black line represents cKO. (B) Representative histograms of CD62L expression on CD44^hiH-2D^b:GP33⁺–gated cells from cHET (top) and cKO (bottom) peripheral blood. The time after deletion is indicated in weeks. Relative percentages of cells within the indicated gated regions are shown. (C) Frequency of CD62L^hiYFP⁺CD44^hiH-2D^b:GP33⁺ T cells in peripheral blood. Averages and standard deviations from of cHET (black) and cKO (gray) cohorts are shown from infection with LCMV-Armstrong up to 48 weeks after deletion of SLP-76. Timing of LCMV and tamoxifen are indicated below the x-axis. Dotted vertical lines indicate the point at which 50% of each population was CD62L^hi. Asterisks show time points with statistical differences (P < .05).