Vascular permeability is associated to platelet shedding of IL-1β–containing MPs. A-C show the percentage of (A) IL-1β–expressing platelets and (B) IL-1β–containing platelet-derived MPs and (C) the MFI of FLICA indicating caspase-1 activation in platelets isolated from healthy volunteers (control) or from DV-infected patients (dengue) that were positive (+) or negative (–) for signs of vascular permeability. The boxes indicate the median and interquartile ranges and the whiskers indicate 5 to 95 percentile. **P < .01 compared with healthy volunteers. ^#P < .05 between patients that were positive and negative for signs of increased vascular permeability. (D) Passive leakage of fluorescein isothiocyanate–conjugated albumin across endothelial cell layers was assessed after cell incubation with MPs recovered from mock- or DV-exposed platelets in the presence or absence of soluble IL-1Ra. The bars represent the mean ± SEM of 4 experiments using platelets from independent healthy donors. *P < .05 compared with mock MP-exposed endothelial cells layers. ^#P < .05 between endothelial cells layers that were incubated with sIL-1Ra or vehicle.