Neutrophil Migration: Using All the Tricks of Mesenchymal and Amoeboid Cells to Navigate Many Environments

Humans encounter numerous pathogens every day and therefore rely heavily on the innate immune system that acts as the first line of defense against infectious agents. Neutrophils make up more than half of the circulating leukocytes in humans and are well equipped to neutralize invaders and thus are a crucial part of our defense system [Friedl and Weigelin (2008) Nat Immunol 9: 960; Rankin (2010) J Leukoc Biol 88: 241]. To get from the bloodstream to sites of insult, neutrophils often have to migrate through various tissues and cover distances much further than many other cells. Thus, it is not surprising that they use elements from both amoeboid and mesenchymal migration, allowing them to migrate efficiently through various environments as they navigate in the body. Here we will discuss the cellular properties of neutrophils that make them exceptional migrators in a variety of physiological contexts, along with the various signaling pathways that guide neutrophil migration.