Platelet interactions with the vessel wall at sites of increased permeability and neutrophil transmigration. (A) A platelet bound to an emigrating neutrophil squeezing between 2 adjacent endothelial cells in an inflamed rat mesenteric venule. Adapted from Marchesi and Florey9 with permission. (B, upper left) A platelet can be seen adherent to the surface of the inflamed endothelium. Adapted from Marchesi8 with permission. (Upper right) A single platelet that seems to be sealing an open endothelial junction in an inflamed venule of the rat cremaster muscle. The white asterisks indicate the subendothelial accumulation of intravenously injected colloidal mercuric sulfide particles used as a marker of endothelial permeability. (Bottom) A single platelet filling an endothelial gap. Note that this platelet has lost its discoid shape, molding the interendothelial space. Adapted from Majno and Palade65 with permission. B, basement membrane; En, endothelial cell; G, endothelial gap; J, junction; L, lumen; Plt, platelet; R, red blood cell.
