Loss of control of bacterial burden and disrupted granuloma morphology in the absence of TLR2 during chronic stages of Mtb infection.

<p>Bacterial burden in the lungs following aerosol infection with Mtb at doses of 100 CFU (A), 150 CFU (B), or 10 CFU (C) was compared between WT and TLR2KO mice. The numbers of viable bacilli were determined by plating serial dilutions of lung homogenates onto 7H11 agar plates. CFU were counted after 21 days of incubation at 37°C. Each time point includes 4–5 mice per group, except for the 15 week time point in (A), which includes 2 mice per group, and the 18 week time point in (C), which includes 4 WT and 3 KO mice. Panel (A) is representative for 1 of 3 independent experiments. Data are presented as mean CFU counts ± SEM. Asterisks represent statistically significant differences between WT and KO at a particular time point. * = p<0.05, ** = p<0.01, *** = p<0.001. Formalin-fixed, paraffin-embedded lung tissue was obtained at 4 weeks (D–E), 7 weeks (F–G), and 12 weeks (H–I) following infection. Sections were stained using a standard H&E protocol. Photomicrographs were taken at 5× (D–G) and 10× (H–I) magnification. Representatives of sections from 4–5 mice per group are shown.