Suboptimal Activation of Antigen-Specific CD4+ Effector Cells Enables Persistence of M. tuberculosis In Vivo
Figure 2
P25TCRTh1 cells produce IFN-γ in response to M. tuberculosis Ag85B peptide 25.
A. P25TCRTh1 cells were restimulated in vitro with C57BL/6 splenocytes in the presence or absence of peptide 25 and analyzed by flow cytometry for intracellular IFN-γ. B. CFP-P25TCRTh1 cells traffic to the lung parenchyma of M. tuberculosis-infected mice. Th1 effector cells were transferred on day 25, and lungs were harvested on day 28 postinfection. CFP-P25TCRTh1 cells (light blue-green) are found in interstitial regions with a high density of DAPI-stained nuclei, typical of the aggregates of macrophages, dendritic cells, and lymphocytes observed at this stage of infection. Scale bar: 50 µm. C. On day 18 post-infection, mice infected with either H37Rv (w.t.) or ΔAg85B M. tuberculosis received P25TCRTh1 cells by adoptive transfer. Lung cells were harvested 72 hours later (day 21). Transferred P25TCRTh1 (CD45.2+) cells were analyzed by flow cytometry for intracellular IFN-γ. One group of mice received intravenous treatment with Ag85B peptide 25 6 hours prior to lung cell harvest. Flow cytometry dot plots from in vivo experiments show a representative of four mice per group. D. Day 21 post-infection with either H37Rv or ΔAg85B: mean percentage from four individual mice of P25TCRTh1 or endogenous CD4+ T cells expressing IFN-γ with or without in vivo administration of Ag85B peptide 25.