CD4 and infection: Analysis of T cell numbers in the lungs 14 days post-inoculation via flow cytometry (Fig. S3)71,72 revealed that infection with wild-type RB50 did not significantly increase CD4+ T cell numbers in the lungs (Fig. 4A), and only modestly increased CD8+ T cells (Fig. 4B) compared to the non-infected control, while challenge with the ΔbtrS mutant resulted in more than twice as many CD4+ and CD8+ T cells in the lungs.