Current concepts about neutrophil granule physiology.

During the past decade it has become clear that neutrophil granules are not simple bags of proteolytic and microbicidal substances. Their membranes contain proteins of paramount importance for the neutrophil to carry out its function as the body's primary mobile phagocyte. It has recently become evident that the heterogeneity of neutrophil granules is much wider than previously thought and that a highly mobilizeable organelle, termed the secretory vesicle, may play a key role in modulating the neutrophil's surface protein profile in response to chemotactic factors. Clearly correct targeting of both membrane and matrix proteins into these different mobilizeable organelles is important for optimal function of the neutrophil. The expanding knowledge of protein targeting into granules and of control of their subsequent mobilization under the specialized conditions of rolling, adhesion, diapedesis, and phagocytosis is the subject of this review.