Blood eosinophils from atopic donors express messenger RNA for the alpha, beta, and gamma subunits of the high-affinity IgE receptor (Fc epsilon RI) and intracellular, but not cell surface, alpha subunit protein.
BACKGROUND
Blood eosinophils from hypereosinophilic donors were previously reported to possess the functional high-affinity IgE receptor (Fc epsilon RI), so providing a potential mechanism to account for eosinophil degranulation in atopic allergic disease. Furthermore, tissue eosinophils from allergic tissue reactions were shown to be mRNA(+) for the alpha, beta, and gamma subunits of Fc epsilon RI and gave positive immunostaining with an anti-Fc epsilon RI-alpha antibody. Recent studies, however, revealed negative surface staining on peripheral blood eosinophils, but intracellular Fc epsilon RI-alpha protein was identified by Western blot analysis.


OBJECTIVE
Our purpose was to examine on peripheral blood eosinophils from atopic subjects (1) surface expression and mRNA for Fc epsilon RI-alpha, (2) up-regulation of Fc epsilon RI-alpha by allergy-associated tissue factors, and (3) Fc epsilon RI-alpha-dependent release of eosinophil peroxidase (EPO).


METHODS
We measured (1) Fc epsilon RI mRNA expression by in situ hybridization, (2) Fc epsilon RI-alpha by flow cytometry and immunocytochemistry (with use of nonpermeabilized and permeabilized cells), and (3) Fc epsilon RI-alpha-dependent release of EPO.


RESULTS
Eosinophils from atopic donors had negligible surface expression of Fc epsilon RI-alpha, which was not enhanced by culture with IgE, IL-3, IL-4, IL-5, GM-CSF, or fibronectin or coculture with fibroblasts. Permeabilization, however, revealed appreciable intracellular staining for Fc epsilon RI-alpha. The majority of eosinophils were mRNA(+) for the alpha, beta, and gamma subunits of Fc epsilon RI. Small but significant (P =.03) increases in alpha chain mRNA expression were observed after coculture of eosinophils with fibroblasts but not with IgE, IL-4, or fibronectin. Cross-linking of Fc epsilon RI on the surface of eosinophils from atopic donors did not lead to detectable EPO release.


CONCLUSIONS
Human blood eosinophils express negligible, nonfunctional membrane Fc epsilon RI-alpha but have intracellular Fc epsilon RI-alpha protein and mRNA expression for the alpha, beta, and gamma subunits.
Smith
S J
SJ
Department of Allergy and Clinical Immunology, Imperial College School of Medicine, National Heart and Lung Institute, London, United Kingdom.
Ying
S
S
Meng
Q
Q
Sullivan
M H
MH
Barkans
J
J
Kon
O M
OM
Sihra
B
B
Larché
M
M
Levi-Schaffer
F
F
Kay
A B
AB
D002462:Cell Membrane / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D002463:Cell Membrane Permeability / Q000187:drug effects; D002469:Cell Separation; D004804:Eosinophils / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism*; D004921:Erythropoietin / Q000378:metabolism; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000097:blood / Q000276:immunology* / Q000378:metabolism*; D007140:Immunoglobulin Fab Fragments / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis* / Q000097:blood; D017455:Receptors, IgE / Q000096:biosynthesis* / Q000097:blood; D012503:Saponins / Q000494:pharmacology
D007140:Immunoglobulin Fab Fragments; D012333:RNA, Messenger; D017455:Receptors, IgE; D012503:Saponins; D004921:Erythropoietin