Platelet depletion during bacterial pneumonia and in Pf4iDTR mice. (A) Bacterial pneumonia was induced in WT mice and MIP2⍺ serum levels were measured at the indicated time points by ELISA assays (data pooled from two independent experiments with four to six mice in each group; Mann-Whitney test was used for statistical analysis, *, P < 0.05). (B) Systemic platelet and leukocyte count after injection of platelet-depleting antibody (clone R300, 2 µg/g body weight) or isotype control and in PF4+/+iDTR+DT, Mrp8+/+iDTR+DT, DEREG, and CD40L−/− mice (data pooled from two independent experiments with four to six mice in each group; Mann-Whitney test was used for statistical analysis, *, P < 0.05). (C) Scheme of platelet depletion in PF4−/−iDTR+DT and PF4+/+iDTR+DT (receiving DT) mice and corresponding platelet counts (data pooled from two independent experiments with six mice in each group; Mann-Whitney test was used for statistical analysis, *, P < 0.05). (D) Erythrocytes and white blood cell counts in peripheral blood of PF4+/+iDTR mice after control and DT treatment (data pooled from two independent experiments with four to six mice in each group; Mann-Whitney test was used for statistical analysis, *, P < 0.05). (E) Platelets were depleted by injection of a platelet-depleting antibody (clone R300, 2 µg/g body weight) 1 d before induction of bacterial pneumonia and survival was analyzed by Kaplan-Meier plot for the following 48 h (data pooled from three independent experiments with 8–10 mice in each group; Kaplan-Meyer survival analysis was used for statistical testing, *, P < 0.05). (F) Bacterial pneumonia was induced in WT or PF4-iDTR mice by i.t. instillation of viable K. pneumoniae (1.5 × 107 CFUs/mouse). Platelets were depleted 2 d after induction of pneumonia and the lung wet/dry ratio was analyzed (data pooled from two independent experiments with four to six mice in each group; Mann-Whitney test was used for statistical analysis, *, P < 0.05). Arrows in A and F indicate time point of platelet depletion.