title: Association of all three types of Fc gamma R (CD64, CD32, and CD16) with a gamma-chain homodimer in cultured human monocytes.
abstract: Receptors for the Fc region of IgG (Fc gamma R) on mononuclear phagocytes have been shown to play an important role in the removal of IgG-opsonized particles from the circulation. We found that all three types of Fc gamma R (CD64, CD32, and CD16) in cultured human monocytes are associated with the gamma-chain homodimer that is also present in the high affinity receptor for IgE. Immunoprecipitates of each of these Fc gamma R, prepared from 1% digitonin lysates of cultured human monocytes, incorporated phosphate into a gamma-chain homodimer when incubated with [gamma-32P]ATP. Fc gamma RII immunoprecipitates also incorporated phosphate into Fc gamma RII itself. When human alveolar macrophages were used, similar results were obtained. Although to a minor extent, each anti-Fc gamma R immunoprecipitate from freshly purified monocytes also coprecipitated gamma-chains. These Fc gamma R and gamma-chains did not constitute one large complex, because anti-Fc gamma RI or anti-Fc gamma RIII immunoprecipitates did not coprecipitate Fc gamma RII. In addition, F (ab')2 fragments of anti-Fc gamma R mAb bound to intact cells were recovered in the anti-gamma-chain immunoprecipitates but not in immunoprecipitates made with anti-Fc gamma RIII or anti-Fc gamma RII mAb. When recovery of radioactivity in anti-gamma-chain immunoprecipitates was compared with that in anti-mouse-Ig immunoprecipitates, approximately 25% of the Fc gamma RI and 20% of the Fc gamma RII expressed at the cell surface were associated with gamma-chains. The gamma-chains may play an important role in signal transduction via Fc gamma R in human macrophages.
authors.affiliation: Central Laboratory of The Netherlands Red Cross Blood Transfusion Service, Amsterdam.
authors.forename: M
authors.initials: M
authors.lastname: Masuda
authors.forename: D
authors.initials: D
authors.lastname: Roos
mesh_terms: D000911:Antibodies, Monoclonal; D002478:Cells, Cultured; D006801:Humans; D007142:Immunoglobulin gamma-Chains / Q000737:chemistry / Q000378:metabolism*; D066298:In Vitro Techniques; D016676:Macrophages, Alveolar / Q000276:immunology / Q000378:metabolism; D009000:Monocytes / Q000276:immunology* / Q000378:metabolism; D010766:Phosphorylation; D011487:Protein Conformation; D017452:Receptors, IgG / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D007142:Immunoglobulin gamma-Chains; D017452:Receptors, IgG