Localization of eosinophil granule major basic protein in human basophils.
In experiments using an immunofluorescent method to localize human eosinophil granule major basic protein (MBP) in cells and tissues, a small number of cells stained for MBP that subsequently could not be identified as eosinophils. Because the Charcot-Leyden crystal protein, another eosinophil protein, was recently identified in basophils, we tested whether MBP might also be a constituent of blood basophils. Highly purified, eosinophil-free basophil suspensions were prepared using the fluorescence-activated cell sorter (FACS) to sort basophil-containing mononuclear cell preparations stained with fluorescein-conjugated sheep IgG anti-human IgE antibody. Using these FACS-purified basophils, we found that: (a) enrichment for surface IgE-positive cells (greater than 95% basophils) by FACS also enriched for cells staining for MBP by immunofluorescence; (b) MBP appeared to be localized in the histamine-, heparin-containing granules; (c) significant quantities of MBP were measurable by radioimmunoassay (RIA) in freeze-thaw detergent extracts of purified basophils; and (d) RIA dose-response curves for extracts of purified eosinophils and basophils had identical slopes. The MBP content of basophils from normal individuals averaged 140 ng/10(6) cells, whereas purified eosinophils from normal donors and patients with the hyper-eosinophilic syndrome averaged 4,979 and 824 ng/10(6) cells, respectively. MBP was also detected by immunofluorescence and RIA in cells obtained from a patient with basophil leukemia, although the MBP content for basophil leukemia cells was lower than that for normal basophils. We conclude that basophils contain a protein that is immunochemically indistinguishable from eosinophil granule MBP.
D001491:Basophils / Q000032:analysis* / Q000276:immunology; D001666:Binding Sites, Antibody; D001667:Binding, Competitive; D001798:Blood Proteins / Q000032:analysis* / Q000276:immunology; D002469:Cell Separation; D047091:Eosinophil Granule Proteins; D004804:Eosinophils / Q000032:analysis; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006801:Humans; D007073:Immunoglobulin E / Q000032:analysis; D007938:Leukemia / Q000032:analysis / Q000276:immunology; D011863:Radioimmunoassay; D012260:Ribonucleases
D001798:Blood Proteins; D047091:Eosinophil Granule Proteins; D007073:Immunoglobulin E; D012260:Ribonucleases