Demo SD, Masuda E, Rossi AB, Throndset BT, Gerard AL, Chan EH, Armstrong RJ, Fox BP, Lorens JB, Payan DG, Scheller RH, Fisher JM. Quantitative measurement of mast cell degranulation using a novel flow cytometric annexin-V binding assay.
Cytometry 1999;
36:340-8. [PMID:
10404150 DOI:
10.1002/(sici)1097-0320(19990801)36:4<340::aid-cyto9>3.0.co;2-c]
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Abstract
BACKGROUND
Mast cells are primary mediators of allergic inflammation. Antigen-mediated crosslinking of their cell surface immunoglobulin E (IgE) receptors results in degranulation and the release of proinflammatory mediators including histamine, tumor necrosis factor-alpha, and leukotrienes.
METHODS
Mast cells were stimulated to degranulate by using either IgE crosslinking or ionophore treatment. Exogenously added annexin-V was used to stain exocytosing granules, and the extent of binding was measured flow cytometrically. Release of the enzyme beta-hexosaminidase was used for population-based measurements of degranulation. Two known inhibitors of degranulation, the phosphatidylinositol 3 kinase inhibitor wortmannin and overexpression of a mutant rab3d protein, were used as controls to validate the annexin-V binding assay.
RESULTS
Annexin-V specifically bound to mast cell granules exposed after stimulation in proportion to the extent of degranulation. Annexin-V binding was calcium dependent and was blocked by phosphatidylserine containing liposomes, consistent with specific binding to this membrane lipid. Visualization of annexin-V staining showed granular cell surface patches that colocalized with the exocytic granule marker VAMP-green fluorescent protein (GFP). Wortmannin inhibited both annexin-V binding and beta-hexosaminidase release in RBL-2H3 cells, as did the expression of a dominant negative rab3d mutant protein.
CONCLUSIONS
The annexin-V binding assay represents a powerful new flow cytometric method to monitor mast cell degranulation for functional analysis.
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