PDCD1 and tuberculosis: We thus evaluated the effect of BCG priming and PE/PPE boosting on immune responses and TB protection following immunization with PE/PPE epitopes, as detailed in the Fig 8A In the lungs of these mice, as determined ex vivo, we observed increased percentages of CD27- CD62L-, CCR6+ CXCR3+, CD27- PD-1+ (Fig 8B), and CD44hi (S7B Fig) cells, within the CD4+ T-cell compartment, as well as increased total numbers of CD4+ T cells (S8C Fig).