Fig. 4

T cells from miR-155 ^−/− mice exhibited impaired antiviral effector function. WT and miR-155 ^−/− mice were immunized with DM-MHV via i.p. injection. a Animals were sacrificed 8 days p.i., and CD4⁺ and CD8⁺ T cells were isolated and pooled. The frequencies of total and virus-specific CD8⁺ T cells were determined by tetramer staining [96]. Equivalent numbers of virus-specific CTLs were added to target cells pulsed with either the immunodominant CD8⁺ T cell epitope within the spike (S) glycoprotein spanning residues 510-518 (S510-518, 50 μM) or control ovalbumin peptide (50 μM) at the indicated ratios, and lytic activity was determined as previously described [31, 96]. In addition, antigen recall responses to the immunodominant CD4 T cell epitope (M133-147) (b) or CD8 T cell epitope S510-518 (c) was performed, and IFN-γ levels were determined by ELISA as previously described [96]. Data are representative of at least two independent experiments, with at least five mice from each group. ^* p < 0.05; ^*** p < 0.001