The release of lysosomal enzymes from human polymorphonuclear leukocytes by human C3e

C3e is a leukocytosis-inducing peptide of degraded C3 that has the electrophoretic behavior of prealbumin and a MW of 10-12,000. Using a homogeneous preparation, the ability of C3e to promote lysosomal enzyme release from human polymorphonuclear leukocytes (PMNs) was examined by incubation of various concentrations of C3e with cytochalasin B-treated (5 μg/ml) human PMNs for 60 min at 37°C. Amounts of extracellular β-glucuronidase, myeloperoxidase, and lysozyme were determined in the cell-free supernatants and it was found that all three enzymes were released in significant amounts without concomitant release of the cytoplasmic enzyme lactate dehydrogenase (LDH). At a concentration of 25 μg/ml of C3e, 25 ± 1.1% (SD) of lysozyme, 20 ± 0.9% β-glucuronidase, and 24.3 ± 0.9% myeloperoxidase were released into the supernatant while the release of LDH remained within the 4-7% range throughout these studies. Furthermore the supernatants were found to contain a substance which was capable of a generating chemotactic fragment from isolated C5. The same range of C3e concentrations (5-25 μg/ml) was, however, incapable of effecting histamine release from basophils. These results suggest that generation of C3e in vivo may serve as a potent stimulus for the generation of the C5-cleaving enzyme from PMNs which in turn may function to recruit more neutrophils by a positive feedback mechanism.