Leukocyte-endothelial cell interactions evoked by mast cells.

In this review we have summarized some of the evidence to support the view that mast cells play a critical role in leukocyte recruitment to sites of inflammation. Initially, data using a pharmacological tool, compound 48/80, which directly activates mast cells, is reviewed, demonstrating that this reagent can induce the multi-step recruitment of leukocytes (rolling, adhesion and emigration) to sites of inflammation. The adhesive mechanisms and pro-inflammatory mediators implicated in mast cell-induced leukocyte recruitment are discussed. Additionally, data are presented to implicate mast cells in delayed-type hypersensitivity reactions as they pertain to leukocyte recruitment. There is a growing body of evidence to suggest that mast cells also recruit leukocytes in IgE-independent leukocyte recruitment. Ischemia/reperfusion- and bacterial toxin- (Helicobacter pylori and Clostridium difficile) induced leukocyte recruitment is at least in part mast cell dependent. Future directions including preliminary work highlighting the role of nitric oxide as a modulator of mast cell function and subsequent leukocyte recruitment is also discussed.