Local effect of MCs on the vasculature during acute inflammation. In this diagram, activated MCs release inflammatory mediators, which then induce changes along vascular endothelium. Some of these mediators directly act on ECs and smooth muscle cells to promote vasodilation and vascular leakiness. In addition, vascular ECs up-regulate many adhesion molecules and release WPBs to promote the rolling and extravasation of leukocytes into the inflamed tissue. Concurrently, increased vascular leakiness promotes the loss of fluid and blood proteins into the tissue, or edema. Additional MC-derived mediators can limit clotting and these responses cumulatively act to increase vascular flow through the site of inflammation. Presumably, the compromised barrier function of the vascular ECs would also facilitate the dissemination of MC products systemically.