title: Immunological applications of type III Fc binding proteins. Comparison of different sources of protein G.
abstract: Protein G, a type III bacterial IgG Fc receptor isolated from certain group C or G streptococci, shows a wider range of species and subclass immunoglobulin reactivity than staphylococcal protein A and has been shown to be more useful than protein A for many immunochemical applications. Recently, two forms of wild type protein G and three forms of recombinant protein G have become commercially available. Each form of protein G was tested for reactivity with a variety of species of immunoglobulin and albumin. Additionally, one form of wild type protein G and two forms of the recombinant protein G were examined for their ability to stimulate in vitro proliferation of human peripheral blood leukocytes (PBL). Similar IgG species reactivity was observed for all forms of unlabeled protein G. By contrast, considerable variability in the relative IgG binding potentials of different protein G preparations was observed following radioiodination. Binding to human serum albumin was observed with one of the wild type protein G samples, however, the IgG binding activity of this protein was not affected by the presence of excess human serum albumin. In the human PBL proliferation assays, wild type protein G was weakly mitogenic and one form of recombinant protein G was shown to be a potent mitogen, while another form of recombinant protein G displayed no mitogenic potential. Differences in both functional and biological reactivities were observed among the various sources of protein G. These differences may lead to confusion if investigators consider all sources of protein G as a single entity with common properties.
authors.affiliation: Department of Microbiology, Medical College of Ohio, Toledo 43699.
authors.forename: E L
authors.initials: EL
authors.lastname: Faulmann
authors.forename: R A
authors.initials: RA
authors.lastname: Otten
authors.forename: D J
authors.initials: DJ
authors.lastname: Barrett
authors.forename: M D
authors.initials: MD
authors.lastname: Boyle
mesh_terms: D000936:Antigen-Antibody Complex / Q000378:metabolism; D000943:Antigens, Differentiation / Q000378:metabolism*; D001419:Bacteria / Q000276:immunology*; D001426:Bacterial Proteins / Q000378:metabolism*; D006801:Humans; D007118:Immunoassay / Q000379:methods; D066298:In Vitro Techniques; D008213:Lymphocyte Activation; D008214:Lymphocytes / Q000276:immunology; D008934:Mitogens; D011485:Protein Binding; D011961:Receptors, Fc / Q000378:metabolism*; D017452:Receptors, IgG; D011994:Recombinant Proteins / Q000378:metabolism; D012709:Serum Albumin / Q000378:metabolism
chemical_list: D000936:Antigen-Antibody Complex; D000943:Antigens, Differentiation; D001426:Bacterial Proteins; D008934:Mitogens; D011961:Receptors, Fc; D017452:Receptors, IgG; D011994:Recombinant Proteins; D012709:Serum Albumin