Neither WT nor Ifnar1^−/− T reg cells are GP_66-77 specific during LCMV infection. Left: representative histograms showing I-A^b/GP_66-77 tetramer staining among gated WT (left) or Ifnar1^−/− (right) CD4⁺Foxp3⁻ T cells (top) and CD4⁺Foxp3⁺ T cells (bottom) from spleens of the same mixed bone marrow chimeric mouse 7 dpi with LCMV-Armstrong. Numbers represent frequency of tetramer-positive cells among the indicated populations. Right: absolute number of the indicated tetramer-positive populations in spleens of chimeric mice 7 dpi with LCMV-Armstrong. Statistical significance was determined using two-tailed paired Student’s t test. n = 4 per group. Data are representative of 2 independent experiments with 3–4 mice per group. *, P < 0.05, P < 0.0001. All data are presented as the mean values ± SEM.