title: A soluble form of the high affinity IgE receptor, Fc-epsilon-RI, circulates in human serum.
abstract: Soluble IgE receptors are potential in vivo modulators of IgE-mediated immune responses and are thus important for our basic understanding of allergic responses. We here characterize a novel soluble version of the IgE-binding alpha-chain of Fc-epsilon-RI (sFcεRI), the high affinity receptor for IgE. sFcεRI immunoprecipitates as a protein of ∼40 kDa and contains an intact IgE-binding site. In human serum, sFcεRI is found as a soluble free IgE receptor as well as a complex with IgE. Using a newly established ELISA, we show that serum sFcεRI levels correlate with serum IgE in patients with elevated IgE. We also show that serum of individuals with normal IgE levels can be found to contain high levels of sFcεRI. After IgE-antigen-mediated crosslinking of surface FcεRI, we detect sFcεRI in the exosome-depleted, soluble fraction of cell culture supernatants. We further show that sFcεRI can block binding of IgE to FcεRI expressed at the cell surface. In summary, we here describe the alpha-chain of FcεRI as a circulating soluble IgE receptor isoform in human serum.
authors.affiliation: Division of Gastroenterology and Nutrition, Department of Pediatrics, Harvard Medical School, Children's Hospital Boston, Boston, Massachusetts, United States of America.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Dehlink
authors.forename: Barbara
authors.initials: B
authors.lastname: Platzer
authors.forename: Alexandra H
authors.initials: AH
authors.lastname: Baker
authors.forename: Jessica
authors.initials: J
authors.lastname: Larosa
authors.forename: Michael
authors.initials: M
authors.lastname: Pardo
authors.forename: Peter
authors.initials: P
authors.lastname: Dwyer
authors.forename: Elizabeth H
authors.initials: EH
authors.lastname: Yen
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Szépfalusi
authors.forename: Samuel
authors.initials: S
authors.lastname: Nurko
authors.forename: Edda
authors.initials: E
authors.lastname: Fiebiger
mesh_terms: D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007073:Immunoglobulin E / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D020033:Protein Isoforms / Q000097:blood / Q000378:metabolism; D017455:Receptors, IgE / Q000097:blood* / Q000378:metabolism
chemical_list: D020033:Protein Isoforms; D017455:Receptors, IgE; D007073:Immunoglobulin E