
<ArticleTitle>Mechanism of extracellular release of human neutrophil <prot>calprotectin</prot> complex.</ArticleTitle>
<AbstractText><prot>Calprotectin</prot> is an abundant cytosolic protein complex of human neutrophils with in vitro extracellular antimicrobial activity. Studies suggest that <prot>calprotectin</prot> may be actively secreted from intact HL-60 cells and that it can be translocated to polymorphonuclear neutrophil (PMN) cell membranes. To examine whether <prot>calprotectin</prot> is secreted extracellularly, we incubated soluble and particulate stimuli, including live and heat-inactivated Candida albicans, with whole blood and measured <prot>calprotectin</prot> levels in the plasma. We compared the release of <prot>calprotectin</prot> to that of <prot>lactoferrin</prot>, a protein known to be secreted by PMNs. Extracellular <prot>lactoferrin</prot> was detected after incubation with any of the particulate stimuli. In contrast, a significant increase in extracellular <prot>calprotectin</prot> was found only after incubation with live C. albicans. Specifically, the increase in extracellular <prot>calprotectin</prot> correlated directly with a proportional decrease in PMN viability. Our results indicate that human PMN <prot>calprotectin</prot> is not secreted extracellularly except as a result of cell disruption or death.</AbstractText>
