NK cells and CD8 T cells of Stx11^−/− mice display impaired effector functions. (A) Degranulation and cytotoxicity of NK cells from Stx11^+/− (○), Stx11^−/− (●), PKO (), and wild-type B6 () mice analyzed 24 hours after intraperitoneal injection of poly I:C on YAC-1 target cells. Degranulation is shown as increase of CD107a expression on NK1.1⁺CD3⁻ cells after restimulation with YAC-1 cells or medium control. Statistical analysis shows delta CD107a, which is calculated as percentage of CD107a expression after YAC-1 stimulation minus percentage of CD107a after medium exposure (background). (B) Degranulation ability of CD8 T cells on day 12 after LCMV infection measured by surface expression of CD107a after 4 hours of in vitro restimulation with GP33 peptide. (C) Antiviral cytotoxic activity of Stx11^+/− (○), Stx11^−/− (●), PKO (), and B6 () spleen cells toward target cells loaded with the immunodominant LCMV epitopes GP33-41 or NP396-404 or an irrelevant adeno peptide in a 5-hour ⁵¹Cr release assay. (D) Spontaneous (ex vivo, without restimulation) IFN-γ expression of CD8 T cells and serum levels of IFN-γ. (E) Viral titers were determined 12 days after LCMV infection in spleen, liver, lungs, and kidney. FACS illustrations are representative for the respective mouse groups; graphs beneath each FACS plot represent data for individual mice. Horizontal lines in graphs represent mean values. Data are (mean ± SEM) representative for 3 independent experiments with at least 3 mice per group. *P < .05 (Student unpaired t test). ***P < .001 (Student unpaired t test). n.s. indicates not significant; and n.d., not detectable.