Neutrophil Cell Shape Change: Mechanism and Signalling during Cell Spreading and Phagocytosis

Perhaps the most important feature of neutrophils is their ability to rapidly change shape. In the bloodstream, the neutrophils circulate as almost spherical cells, with the ability to deform in order to pass along narrower capillaries. Upon receiving the signal to extravasate, they are able to transform their morphology and flatten onto the endothelium surface. This transition, from a spherical to a flattened morphology, is the first key step which neutrophils undergo before moving out of the blood and into the extravascular tissue space. Once they have migrated through tissues towards sites of infection, neutrophils carry out their primary role—killing infecting microbes by performing phagocytosis and producing toxic reactive oxygen species within the microbe-containing phagosome. Phagocytosis involves the second key morphology change that neutrophils undergo, with the formation of pseudopodia which capture the microbe within an internal vesicle. Both the spherical to flattened stage and the phagocytic capture stage are rapid, each being completed within 100 s. Knowing how these rapid cell shape changes occur in neutrophils is thus fundamental to understanding neutrophil behaviour. This article will discuss advances in our current knowledge of this process, and also identify an important regulated molecular event which may represent an important target for anti-inflammatory therapy.