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Updated: May 11, 2026
Basophil Activation Test for Investigation of IgE-Mediated Mechanisms in Drug Hypersensitivity
Published on: September 16, 2011
Mass, charge, and subcellular localization of a unique secretory product identified by the basophil-specific antibody
A R McEuen1, J Calafat, S J Compton
1Immunopharmacology Group, Southampton General Hospital, UK.
Background:
BB1 is a basophil-specific mAb (Lab Invest 1999;79:27-38). The identity of the corresponding antigen has not been determined, but it gives a granular appearance on staining and is secreted on activation of basophils.
Objective:
We sought to further characterize the basophilspecific antigen identified by BB1.
Methods:
Intracellular localization was determined by flow cytometry and by immunogold labeling and electron microscopy. Physical chemical properties were investigated by gel filtration chromatography and preparative isoelectric focusing.
Results:
In flow cytometry, permeabilization of cells increased immunofluorescence 100-fold, confirming the predominantly intracellular localization of the antigen. It was further localized to the secretory granules by immunoelectron microscopy. Double labeling with a CD63-specific antibody demonstrated selective binding of BB1 to the granule matrix. Gel filtration chromatography indicated that the antigen is secreted as a complex of approximately 5 x 10(6) d, which was well resolved from the 210-kd supramolecular complex containing tryptase. The antigen was degraded by pronase. Isoelectric focusing indicated a highly basic protein with an isoelectric point of 9.6.
Conclusion:
With its granule localization, release on cell activation, and unique properties, the antigen identified by BB1 could be a novel mediator of allergic disease. We propose the name basogranulin for this novel basophil-specific protein.
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