title: Fc gamma-receptor activity of isolated human placental syncytiotrophoblast plasma membrane.
abstract: Fc gamma-receptor activity of isolated human placental syncytiotrophoblast microvillous plasma membrane (StMPM) vesicle preparations has been determined in an immunoradiometric assay using Sepharose-immobilized protein A to separate free 125I-labelled human IgG from membrane-bound 125I-IgG. This receptor assay has been optimalized in terms of buffer pH and molarity, and used to demonstrate that prior 60 min washing of isolated membranes in 3 M KCl to remove extrinsic membrane-bound protein substantially increases the membrane-binding capacity for IgG. Inhibition studies have determined the syncytiotrophoblast Fc gamma-receptor equilibrium constant for association (Ka) as 4.0 x 10(7) M-1 at 37 degrees and the number of available Fc gamma-receptor sites as 1.5 x 10(14) per mg membrane protein.
mesh_terms: D000918:Antibody Specificity; D002462:Cell Membrane / Q000276:immunology; D004306:Dose-Response Relationship, Immunologic; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007074:Immunoglobulin G / Q000276:immunology; D011247:Pregnancy; D011961:Receptors, Fc / Q000032:analysis*; D013205:Staphylococcal Protein A; D014327:Trophoblasts / Q000276:immunology*
chemical_list: D007074:Immunoglobulin G; D011961:Receptors, Fc; D013205:Staphylococcal Protein A