Neutrophil degranulation of antibiotic proteins and peptides.

An activated neutrophil in the process of phagocytosis of gram-negative bacteria (yellow ovals) is demonstrated. As shown, specific (secondary) granules are more prone to degranulate their contents (including lactoferrin and cathelicidins) into the extracellular space. In contrast, azurophil (primary) granules, containing BPI and defensins, are predominantly degranulated into the phagolysosome. To a lesser extent, specific granules also degranulate into the phagolysosome and primary granules to the extracellular space (broken arrows). Neutrophil granule populations, including gelatinase granules and secretory vesicles, are demonstrated at the bottom of the figure.