30] IgG-binding factors

Abstract

This chapter provides an overview of IgG-binding factors. Immunoglobulin-binding factors (IBF) are a group of substances that regulate immunoglobulin (Ig) isotype production. IBF specific for IgG (IgG-BF), IgE (IgE-BF), and IgA (IgA-BF) are reported in the chapter. These factors share common properties: (1) they can be induced by the interaction of T cells with a given Ig isotype, (2) they bind to the Fc portion of the Ig isotype that they regulate, and (3) in general, they suppress the production of the isotype to which they bind. In the case of IgEBF, in addition to suppressor IgE-BF, a potentiating factor with affinity for IgE is also described. Subclass-specific mouse IgG-BF, suppressing IgG1, and IgG2 antibody production are induced by incubating T cells with murine monoclonal IgG1 and IgG2, respectively. They are isolated by affinity chromatography on IgG. They can be detected by a rosette inhibition assay. Their immunoregulatory activities are evaluated on in vitro secondary antibody responses. The chapter also discusses preparation of IgG-BF-producing cells.