Neutrophil interactions with the vascular endothelium

Neutrophils are a key mediator of the innate immune system and are pivotal in the inflammatory response to infection or tissue damage. Fundamental to the role that neutrophils play in host defence is their interaction with the vascular endothelium. From the initial mobilisation of neutrophils out of the bone marrow to their ultimate transmigration through the vasculature, endothelial cells are a vital component of the inflammatory process. This review focuses on the interactions that take place between neutrophils and the vascular endothelium during the various stages of the inflammatory response. The role of the vascular endothelium in detecting the initial episode of infection or tissue damage is explored and how this ultimately leads to mobilisation of the neutrophils from the bone marrow and into the bloodstream. The recruitment and adhesion of neutrophils to the vascular endothelium is also discussed, with particular emphasis on the various discrete stages of the adhesion cascade and what molecules mediate these steps. In addition, a novel role for the lipid kinase sphingosine kinase in neutrophil adhesion is examined. With the advent of improved imaging techniques and the development of new animal models, this is a dynamic area of research and this review aims to summarise some of the more recent findings.