Comparison of the effector functions of human immunoglobulins using a matched set of chimeric antibodies.

Abstract

The five Ig classes have distinct biological roles. The IgG subclasses also show marked differences in their ability to mediate a variety of effector functions. A detailed comparison of the properties of the human Ig classes and subclasses is not only of interest for relating the functions of antibodies to their structures but is also of great importance for the implementation of therapy based upon immunological intervention . Indeed, this second aspect has become particularly significant as the development of techniques for the production of chimeric antibodies (1-3) should ensure that immunological intervention is now likely to make use of mAbs that have human effector functions; several cell lines have already been established that secrete chimeric antibodies directed against human cancer cells (4-6).Much of our knowledge of the properties of human Igs has been obtained from the study of myeloma proteins (reviewed in references 7-9). However, generally myeloma proteins do not bind identified antigens and, moreover, different myeloma proteins differ not only in their heavy chain class/subclass but also in their light chains and variable regions. As the initiation of antibody effector activity is usually a consequence of antigen binding and is indeed influenced by the quality of that binding, previous studies on myeloma proteins, although valuable, may not provide a sufficient picture of antibody effector function for therapeutic purposes . To carry out a detailed and controlled comparison of the effector functions of the different human C regions, we have established a panel of cell lines that secrete a matched set of human chimeric antibodies . These antibodies are directed against the hapten 4-hydroxy-3-nitrophenacetyl (NP).' This specificity for a known hapten has allowed us to compare the effector functions of the IgG subclasses not only when interacting with soluble antigen but also when interacting with cell-bound antigen. This has enabled us to determine the efficacy with which different subclasses lyse their This work was supported by grants from the Medical Research Council and Wellcome Biotechnology .' Abbreviations used in this paper. ADCC, antibody-dependent cell-mediated cytotoxicity, NP, nitrophenacetyl ; NIP, 5-iodo-4-hydroxy-3-nitrophenyl .J. Exp. MED.

Mutations within a human IgG2 antibody form distinct and homogeneous disulfide isomers but do not affect Fc gamma receptor or C1q binding

“…1 This functional activity directly correlates with increased measured affinities of each IgG subclass to the effector proteins. Despite the large difference in observed effector function, IgG1 and IgG2 share significant sequence identity throughout the constant regions, including regions shown to interact with Fcc receptors and C1q.…”

Mapping of the C3b-binding site of CR1 and construction of a (CR1)2-F(ab')2 chimeric complement inhibitor.

“…Cells were distributed in cloning chambers and those secreting high amounts of (CR1)2-P(ab')a were identified by ELISA in which molecules binding NP were detected with anti-)~ mAb conjugated to horseradish peroxidase (Fisher Scientific Co., Pittsburgh, PA). These transfectants were batch cultured, and (CR1)2-F(ab')2 was purified from culture supematants by affanity chromatography on NP-sepharose (26,27).…”

Engineering an Improved IgG4 Molecule with Reduced Disulfide Bond Heterogeneity and Increased Fab Domain Thermal Stability

“…IgG1 and IgG3 are generally described as active isotypes because they perform antibody-dependent cellmediated cytotoxicity and complement-dependent cell-mediated cytotoxicity. This is because these isotypes have the greatest affinity to Fc␥ receptors (4 -6), whereas complement 1q binds strongly to C H 2 of these two isotypes (7,8). Conversely, IgG2 and IgG4 bind poorly to these effector molecules, resulting in relatively low effector function induction.…”