IL-33 rapidly enhances platelet function for hemostasis. (A-F) Indicated mice were injected with PBS or IL-33. Platelet activities were assessed by flow cytometry 10 minutes after injection. Representative histograms of fluorescence intensity and quantification of geometric mean fluorescence intensity of CD62P and Jon/A for platelets treated with or without thrombin from WT (A-B), Vil1creIl33fl/fl (C-D), and ChgacreERIl1rl1fl/fl (E-F) mice. (G-H) Il33fl/fl and Vil1creIl33fl/fl (G) Il1rl1fl/fl and ChgacreERIl1rl1fl/fl (H) mice were injected with PBS or IL-33. Time to cessation of bleeding in response to tail injury was assessed 10 minutes after injection. (I) Representative histograms of fluorescence intensity of CD62P and Jon/A for platelets treated with or without thrombin between Tph1fl/fl and Vil1creTph1fl/fl mice. (J) Quantification of geometric mean fluorescence intensity in panel I. (K) Tph1fl/fl and Vil1creTph1fl/fl mice were injected with PBS or IL-33. Time to cessation of bleeding in response to tail injury was assessed 10 minutes after injection. Data are representative of 2 independent experiments (A,C,E,I) or are pooled from 2 independent experiments (B,D, F-H, J-K). *P < .05, **P < .01, ***P < .001 by Student t test. Error bars represent standard deviation. NS, not statistically significant.