(A) Experimental scheme. CC042 mice were vaccinated or not vaccinated with BCG in the flank and rested for 9 weeks. A cohort from each vaccination group was treated with a combination of anti-CD4 and anti-CD8α mAbs for 3 weeks. Then, all mice were infected for 4 weeks with Rv.YFP. (B) Determination of CD4⁺ and CD8⁺ T cell depletion. Mice were treated with anti-CD4 and anti-CD8α mAbs after BCG vaccination as described in A. The location of the CD4⁺ and CD8β⁺ T cells was determined as described in Methods, and the populations are designated as either IV⁺ (intravascular) or IV^– (parenchymal). Representative flow plot of CD4 and CD8β expression of CD90⁺ T cells in the blood at 4 wpi of representative BCG-vaccinated CC042 mice with and without T depletion. These data are from the same experiment depicted in Figure 3F. (C) Frequency of IV⁺ or IV^– CD90⁺, CD4⁺, and CD8β⁺ T cells in the lung at the end of the depletion period but before MTBI of CC042 mice. (D and E) Enumeration of naive (CD44^–CD62L⁺, D) and antigen-experienced (CD44⁺CD62L^–, E) CD4⁺ (left) and CD8⁺ (right) T cells in the lungs of CC042 mice 4 weeks after infection. (F) BCG-elicited protection in the lung (left), mLN (middle), and spleen (right) is not affected by CD4⁺ and CD8⁺ T cell depletion. (C–F) One-way ANOVA with Šidák’s multiple-comparison test. Box-and-whisker plots indicate median (middle line), 25th and 75th percentiles (box), and minimum and maximum (whiskers). Each point represents an individual subject; n = 3–5 mice per group. The data are from 1 of 2 independent experiments with similar results.