Intensity of CTL degranulation capacity and cytotoxicity in Stx11^−/−, Rab27a^−/−, and Prf1^−/− mice. Spleen CD8 T cells from Stx11^−/−, Rab27a^−/−, Prf1^−/−, and control B6 mice were activated in vitro. (A) A representative FACS analysis for degranulation of CD8 T cells from control B6 (left panel), Stx11^−/− (left middle panel), Rab27a^−/− (right middle panel), and Prf1^−/− mice (right panel) on stimulation with medium (bottom row) or anti-CD3 antibody (top row). (B-C) Graphs show the mean ± SEM (n = 5) CD107 variation on control B6 (black squares), Stx11^−/− (open squares), Rab27a^−/− (gray triangles), and Prf1^−/− (gray circles) CD8 T cells after anti-CD3 stimulation over time (B) or with different concentrations of anti-CD3 antibody (C). *P < .05. **P < .01. ***P < .001. (D) Cytotoxicity was determined in activated CD8 T cells after incubation with target anti-CD3–loaded P815 cells for 3 hours. Data (mean ± SEM) are representative of 3 independent experiments performed in triplicate. *P < .05. **P < .01. ***P < .001.