Platelets and T reg cells drive macrophage polarization. (A and B) Isolated alveolar macrophages from untreated WT mice were incubated with (A) T reg cells alone or in combination with resting, ADP (10 µM)-, or human thrombin (0.1U ml-1)–activated platelets; or (B) the supernatant from cocultures of T reg cells alone or in combination with resting, ADP-, or thrombin-activated platelets and macrophage polarization was analyzed by by qRT-PCR (pooled data from three independent experiments with five samples in each group; Mann-Whitney test was used for statistical analysis, *, P < 0.05). (C and D) Isolated alveolar macrophages from untreated WT mice were incubated with (C) T reg cells alone or in combination with resting, ADP (10 µM)-, or human thrombin (0.1U ml−1)-activated platelets; or (D) the supernatant from cocultures of T reg cells alone or in combination with resting or ADP-activated platelets and the index of neutrophil efferocytosis was analyzed (pooled data from three independent experiments with five samples in each group; Mann-Whitney test was used for statistical analysis, *, P < 0.05).