Background: Eosinophils and neutrophils take part in the pathogenesis of bronchial asthma. Cellular adhesion through β
2 integrins is crucial for subsequent effector functions in both cell types. We compared α
Mβ
2 expression, cellular adhesion and superoxide anion (O
2-) release of human eosinophils and neutrophils under uniform conditions.
Methods: Eosinophils and neutrophils from normal volunteers were purified by a magnetic cell-separation system and a one-step gradient method, respectively. Cells were stimulated with platelet-activating factor (PAF) or complement 5a (C5a) on human serum albumin (HSA)-coated surfaces. Expression of α
Mβ
2 was measured by flow cytometry with phycoerythrin-conjugated anti-CD11b monoclonal antibody. O
2- release was assayed by chemiluminescence using a
Cypridina luciferin analogue as the amplifier. Cellular adhesion was assessed by measuring fluorescence intensity of calcein-AM, which was preincorporated in the cell cytoplasm. Cellular morphology was observed with a light microscope.
Results: α
Mβ
2 expression on the neutrophil cell surface was greater than that on eosinophils, both at rest and on stimulation. In contrast, eosinophils exerted significantly greater cellular adhesion and O
2- release on HSA-coated surfaces than neutrophils. Morphologically, eosinophils showed marked flattening and deformity, while neutrophil shape change was minimal.
Conclusions: Eosinophils and neutrophils showed different activation profiles with stimulation of PAF or C5a on HSA-coated surfaces. In eosinophils the intensity of cellular adhesion and O
2- release paralleled the upregulation of α
Mβ
2, while in neutrophils the amount of α
Mβ
2 surface expression appeared to be less associated with the degree of cellular adhesion and O
2- release.
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