Release of lysosomal enzyme beta-glucuronidase from isolated human eosinophils

The human eosinophil contains lysosomal enzymes that can contribute directly to tissue injury and inflammation. Characterization of lysosomal-enzyme release from the eosinophil has been largely limited to isolates from patients with hypereosinophilia. Because eosinophils from such individuals may not demonstrate normal functional responses, we established a method to obtain purified, normal human eosinophils with a Percoll gradient. With this method, it is possible to isolate eosinophils (95.5 +/- 3.9%) and neutrophils (greater than 99%) in high purity from normal subjects. With these granulocyte isolates, we evaluated and compared release of the lysosomal enzyme, beta-glucuronidase (BG), after cell activation with opsonized zymosan particles. Neutrophils released 33.0 +/- 1.2% (mean +/- SEM; n = 5) of total BG (30 minutes of incubation with zymosan), whereas eosinophil secretion was 24.2 +/- 1.7% (n = 5). The fungal metabolite, cytochalasin B (CB), which inhibits microfilament activity, enhanced BG secretion from neutrophils (33.0 +/- 1.2% to 42.8 +/- 2.8% with CB; p less than 0.01). In contrast, CB had no effect on eosinophil BG release. Interestingly, BG content in eosinophils is 101.2 +/- 3.9 micrograms phenolphthalein per 10(6) cells per 18 hours, which compares to a neutrophil level of 51.0 +/- 3.2 (p less than 0.001). Thus, although eosinophils and neutrophils release a similar percentage of total cellular BG on stimulation with zymosan particles, the absolute amount of enzyme per cell is greater in the eosinophil than in the neutrophil. Study of eosinophil function promises to elicit a more complete insight into its contribution to tissue injury.