T reg cell–derived IL-10 and TGFβ mediate resolution of bacterial pneumonia. (A and B) Isolated T reg cells were coincubated with ADP-activated platelets and/or isolated macrophages and the concentration of (A) IL-10 and (B) TGFβ in the supernatant was analyzed (pooled data from three independent experiments with six samples in each group; Mann-Whitney test was used for statistical analysis, *, P < 0.05). Bacterial pneumonia was induced in WT mice by i.t. instillation of viable K. pneumoniae (1.5 × 10⁷ CFUs/mouse). (C) mRNA expression of Il10 and Tgfb1 in isolated alveolar macrophages and T reg cells was analyzed by qRT-PCT 5 d after induction of pneumonia. Mice received blocking antibodies against IL-10 (clone JES5-2A5, 50 µg/mouse) and TGFβ (clone 2G7, 100 µg/mouse) or isotype control 2 d after induction of pneumonia. (D–G) The number of (D) neutrophils in the BAL fluid, (E) the percentage of apoptotic neutrophils in the BAL, and the number of (F) T reg cells and (G) platelets was analyzed by flow cytometry (data pooled from two independent experiments with four mice in each group; Mann-Whitney test was used for statistical analysis, *, P < 0.05).