Hypodense eosinophilic granulocytes in normal individuals and patients with asthma: generation of hypodense cell populations in vitro.

Eosinophils from normal nonatopic healthy volunteers (195 +/- 106 cells per microliter) were isolated by centrifugation over a discontinuous Percoll gradient, under isotonic conditions, with a recovery of 46.5 +/- 26.2% from whole blood (n = 21; mean +/- SD). More than 90% of the eosinophils (purity greater than 93%) with a density between 1.095 to 1.105 gm/ml were defined normodense. Less than 10% of the eosinophils had a density less than 1.095 gm/ml and were defined hypodense. Isolation of eosinophils of patients with atopic asthma revealed a cell population with 65% to 70% hypodense cells that was independent of the total eosinophilic cell count. In vitro activation of normodense eosinophils, measured by an increase in superoxide production, induced quantities of hypodense eosinophils in the range found in patients with asthma. The amount of hypodense eosinophils induced by different stimuli was in the same order as the increase in superoxide production (antibiotic calcium ionophore A23187 greater than serum-treated zymosan greater than platelet-activating factor greater than N-formyl-methionyl-leucyl phenylalanine). During the stimulation of the normodense cells, no secretion of eosinophilic peroxidase or arylsulfatase B could be measured, even though hypodense eosinophils were produced. Enzymatic activity of arylsulfatase B within the eosinophils remained the same, before and after stimulation. The enzymatic activity of eosinophilic peroxidase in normodense eosinophils (16.6 +/- 9.7 micrograms/10(6) cells) did not change in the normodense fraction but was increased in the induced hypodense cells (34.0 +/- 8.4 micrograms/10(6) cells; n = 7; mean +/- SD; p less than 0.01) after stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)