title: Omalizumab reverses the phenotypic and functional effects of IgE-enhanced Fc epsilonRI on human skin mast cells.
abstract: The dramatic effects of the anti-IgE mAb omalizumab to lower free IgE levels and Fc epsilonRI levels on basophils contrast with more modest clinical effects. Accordingly, whether IgE modulates Fc epsilonRI levels and Fc epsilonRI-dependent mediator release in vitro on human skin mast cells (MC(TC) type) that had matured in vivo is of interest. IgE reversibly enhanced Fc epsilonRI levels on MC(TC) cells in a dose- and time-dependent manner (up-regulation t(1/2) of 4-5 days with 1-3 microg/ml IgE), without affecting cell proliferation. A molar ratio of omalizumab to IgE of 0.9 at baseline prevented receptor up-regulation by 50%, whereas adding omalizumab to MC(TC) cells already with IgE-enhanced Fc epsilonRI levels at molar ratios of 5, 12.5, and 31 reduced Fc epsilonRI levels to baseline with respective t(1/2) values of 8.7, 6.3, and 4.8 days. MC(TC) cells with IgE-enhanced Fc epsilonRI levels were more sensitive to stimulation with a low dose of anti-Fc epsilonRI mAb in terms of degranulation and production of PGD(2), GM-CSF, IL-6, IL-13, and TNF-alpha. Reducing up-regulated Fc epsilonRI levels with omalizumab also reduced mediator release to a low dose of anti-Fc epsilonRI mAb to baseline by 3-4 wk. Thus, reducing free IgE should decrease the hypersensitivity of allergic individuals to low naturally occurring concentrations of allergens.
authors.affiliation: Department of Internal Medicine, Division of Rheumatology, Allergy, and Immunology, Virginia Commonwealth University, Richmond, VA 23298, USA.
authors.forename: Gregorio
authors.initials: G
authors.lastname: Gomez
authors.forename: Sherryline
authors.initials: S
authors.lastname: Jogie-Brahim
authors.forename: Mika
authors.initials: M
authors.lastname: Shima
authors.forename: Lawrence B
authors.initials: LB
authors.lastname: Schwartz
mesh_terms: D018926:Anti-Allergic Agents / Q000494:pharmacology*; D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D061067:Antibodies, Monoclonal, Humanized; D015550:Cell Degranulation / Q000187:drug effects / Q000276:immunology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D006967:Hypersensitivity / Q000188:drug therapy / Q000276:immunology; D007073:Immunoglobulin E / Q000187:drug effects / Q000276:immunology*; D008407:Mast Cells / Q000187:drug effects* / Q000276:immunology; D000069444:Omalizumab; D010641:Phenotype; D017455:Receptors, IgE / Q000276:immunology*; D012867:Skin / Q000166:cytology / Q000187:drug effects / Q000276:immunology
chemical_list: D018926:Anti-Allergic Agents; D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D017455:Receptors, IgE; D000069444:Omalizumab; D007073:Immunoglobulin E