Figure 2.

Binding events that lead to vasculature occlusion on inflamed endothelium. (A) Neutrophil rolling is mediated by P-selectin and E-selectin binding PSGL-1 and L-selectin. Signaling through E-selectin/L-selectin bonds results in (1) release of MRP8/14 and endogenous activation of surface TLR4 which primes integrin for activation and (2) direct signaling of transition to a high-affinity integrin state capable of binding ligand. High affinity integrin is capable of stable bond formation to VCAM-1 and ICAM-1 on endothelial to mediate neutrophil arrest. (B) Secondary capture of sRBC to adherent neutrophils is mediated via Mac-1. The mechanism of capture is an active area of research. (C) Secondary capture of platelets to adherent neutrophils is mediated through platelet surface P-selectin and its binding to PSGL-1 and L-selectin. (D) Direct engagement of sRBC to the surface of endothelial cells has been attributed to P-selectin, similar to secondary capture via Mac-1.