Figure 6. Rescue of WT phenotype in TLR2KO mice following intra-tracheal instillation of WT macrophages.

TLR2KO mice were intra-tracheally instilled with 2.5×10⁶ WT peritoneal macrophages (WT→KO) or TLR2KO peritoneal macrophages (KO→KO) one day prior to infection with a low-dose of Mtb. Single cell suspensions were prepared at week 7 post-Mtb infection. Lung cells were stained with antibodies against CD4 and Foxp3, followed by flow cytometric analysis. Expression of Foxp3 is presented as a percentage of the gated CD4⁺ cell population (A). Percentage of CD4⁺ cells was determined by gating on CD4⁺ cells from total lymphocytes gated (B). Total number of viable cells in the lungs was determined by trypan blue exclusion method (C). Percentage of involved lung area was quantitated by superimposing a grid overlay onto photomicrographs of H&E stained lung sections taken with a 5× objective lens. One representative section per mouse was used for quantitation (D). Bacterial burden in the lungs (E) and spleen (F) was determined by plating serial dilutions of tissue homogenates onto 7H11 agar plates. Data include 5–6 mice per group and are presented as mean ± SEM. _*, p<0.05; _****, p<0.0001.