The two weeks post infection time point was chosen since the majority of cells in the lung at that time point are recalled T cells and not yet newly infection-primed T cells (Non vaccinated showed <1% CD8 Ag85B or TB10.4 specific T cells and <0.2% CD4 T cells) [23], which enabled us to measure recruitment of the pre-existing CD4 and CD8 T cells. Here, CD4 is linked to infection.