Dynamics of Inter-heavy Chain Interactions in Human Immunoglobulin G (IgG) Subclasses Studied by Kinetic Fab Arm Exchange

Abstract

Background: Fab arm exchange requires weak interactions between CH3 domains, such as in human IgG4.Results: CH3-CH3 interactions differ >1,000,000-fold between human subclasses and allotypes due to variations Lys/Asn-392, Val/Met-397, and Lys/Arg-409.Conclusion: For IgG2 and IgG3, but not IgG1, hinge disulfide bonds are essential to prevent half-molecule dissociation.Significance: Subclass/allotype variation in the CH3 domain can alter antibody stability and functionality.

The FcγR of Humans and Non-human Primates and Their Interaction with IgG: Implications for Induction of Inflammation, Resistance to Infection and the Use of Therapeutic Monoclonal Antibodies

“…The extent to which the interaction of IgG2 and IgG4 with FccR follows the ''canonical rules'' of IgG1 binding is not clear (Table 3) Table 3) suggests it cannot interact with the critical tryptophans of the ''Trp sandwich'' in FccRII or FccRIIIb, which is absolutely essential for the binding of IgG1 and IgG3 Rispens et al 2014). Note that the Fab fragment in chain B has been removed for clarity and the structure shown is based on the FccRIIa structure of (Ramsland et al 2011) and similar interactions are apparent for Fc: FccRIII (Sondermann et al 2000;Radaev et al 2001) (Ramsland et al 2011) and hFccRIIIb (Radaev et al 2001) and (Sondermann et al 2000).…”

Cross-reactive and pre-existing antibodies to therapeutic antibodies—Effects on treatment and immunogenicity

“…101 The interaction involves (partial) dissociation and re-association of CH3 domains, 102 which is most efficient for IgG3 and IgG4. 103 Association of IgG4 is also observed to various degrees to immobilized IgG from other species, 104 and is easily confused for e.g., rheumatoid factor activity. 105 A similar association could be envisaged involving dissociation and re-association of light and heavy chains from certain antibody molecules, especially since interactions between VH and VL domains may greatly differ in association strength for different antibodies.…”

The S228P Mutation Prevents in Vivo and in Vitro IgG4 Fab-arm Exchange as Demonstrated using a Combination of Novel Quantitative Immunoassays and Physiological Matrix Preparation

“…6,7,25). While half-molecules have been shown to exist by various direct and indirect methods (6,(27)(28)(29), their precise involvement in FAE remains unclear and a focus of ongoing investigation. In this report, two differently configured MSD assay formats were used to characterize and quantify IgG4 FAE in physiologically relevant in vitro matrices.…”