title: Mechanism of the antigen-independent cytokinergic SPE-7 IgE activation of human mast cells in vitro.
abstract: Release of pro-inflammatory mediators by mast cells is a key feature of allergic disease. The 'dogma' is that IgE molecules merely sensitise mast cells by binding FcεRI prior to cross-linking by multivalent allergen, receptor aggregation and mast cell activation. However, certain monoclonal IgE antibodies have been shown to elicit mast cell activation in an antigen-independent cytokinergic manner, and DNP-specific murine SPE-7 IgE is the most highly cytokinergic antibody known. We show that both monovalent hapten and recombinant SPE-7 IgE Fab inhibit its cytokinergic activity as measured by mast cell degranulation and TNF-α release. Using SPE-7 IgE, a non-cytokinergic human IgE and a poorly cytokinergic murine IgE, we reveal that interaction of the Fab region of 'free' SPE-7 IgE with the Fab of FcεRI-bound SPE-7 IgE is the basis of its cytokinergic activity. We rule out involvement of IgE Fc, Cε1 and Cλ/κ domains, and propose that 'free' SPE-7 IgE binds to FcεRI-bound SPE-7 IgE by an Fv-Fv interaction. Initial formation of a tri-molecular complex (one 'free' IgE molecule cross-linking two receptor-bound IgE molecules) leads to capture of further 'free' and receptor-bound IgEs to form larger clusters that trigger mast cell activation.
authors.affiliation: 1] Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom [2] MRC &Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom.
authors.forename: Heather J
authors.initials: HJ
authors.lastname: Bax
authors.affiliation: 1] Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom [2] MRC &Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom [3] NIHR Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trust and King's College London, London, United Kingdom.
authors.forename: Holly
authors.initials: H
authors.lastname: Bowen
authors.affiliation: 1] Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom [2] NIHR Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trust and King's College London, London, United Kingdom.
authors.forename: Tihomir S
authors.initials: TS
authors.lastname: Dodev
authors.affiliation: 1] Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom [2] MRC &Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Sutton
authors.affiliation: 1] Randall Division of Cell and Molecular Biophysics, King's College London, London, United Kingdom [2] MRC &Asthma UK Centre in Allergic Mechanisms of Asthma, London, United Kingdom [3] NIHR Biomedical Research Centre at Guy's and St Thomas' NHS Foundation Trust and King's College London, London, United Kingdom.
authors.forename: Hannah J
authors.initials: HJ
authors.lastname: Gould
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000941:Antigens / Q000276:immunology*; D015550:Cell Degranulation / Q000187:drug effects; D002460:Cell Line; D057809:HEK293 Cells; D006241:Haptens / Q000737:chemistry; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology / Q000473:pathology; D007073:Immunoglobulin E / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D007140:Immunoglobulin Fab Fragments / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D008407:Mast Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D008969:Molecular Sequence Data; D011485:Protein Binding; D051381:Rats; D017455:Receptors, IgE / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D000941:Antigens; D006241:Haptens; D007140:Immunoglobulin Fab Fragments; D017455:Receptors, IgE; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D007073:Immunoglobulin E