IGG SUBCLASS VARIATION OF A MONOCLONAL ANTIBODY BINDING TO HUMAN FC-GAMMA RECEPTORS

Patel Patel

doi:10.3844/ajbbsp.2013.206.218

Abstract

The importance of human Fc receptors in immune regulation is well known. Their role is critical not on ly in the recruitment of cellular effector functions but also in regulating the balance in the periphery bet ween autoimmunity and tolerance. Despite their central i mportance, there is a dearth of literature on contr olled numeric comparisons in affinities of antibody subcl asses for gamma receptors. To date, no studies have directly compared humanized antibodies with the same variable region and differing Fc region subclasse s which would rule out any differences that may be at tributed to variations in the variable region. In t his study we characterized the interaction between four humanized monoclonal antibodies; IgG 1, G 2, G 3 and G4, each possessing an identical variable region and the repertoire of human Fc-gamma (Fc γ) receptors (Fc γRI, Fc γRIIA, Fc γRIIB, Fc γRIIIA and Fc γRIIIB). The studies were performed using both Surfa ce Plasmon Resonance (SPR) and Enzyme-Linked Immunosorbent-Assay (ELISA) formats. The affinities of the antibodies for their antigen molecule, an en dogenous human protein, were also analyzed by SPR. While the identity of the Fc-region had no signific ant effect on the binding to antigen, substantially different affinities for each of the Fc γ receptors, Fc γRI, Fc γRIIA, Fc γRIIB, Fc γRIIIA and Fc γRIIIB were observed across the various Fc-subclasses.

Highlights

Each consisting of one variable and 3 constant domains
In this study we characterized the interaction between four humanized monoclonal antibodies; IgG1, G2, G3 and G4, each possessing an identical variable region and the repertoire of human Fc-gamma (Fcγ) receptors (FcγRI, FcγRIIA, FcγRIIB, FcγRIIIA and FcγRIIIB)
While the identity of the Fc-region had no significant effect on the binding to antigen, substantially different affinities for each of the Fcγ receptors, FcγRI, FcγRIIA, FcγRIIB, FcγRIIIA and FcγRIIIB were observed across the various Fc-subclasses

Summary

Introduction

Each consisting of one variable and 3 constant domains. The two heavy chains are linked to each other and to a Monoclonal Antibodies (mAbs) are a rapidly light chain each by disulfide bonds. An IgG is inserted into the CH2 domain of a human IgG molecule increased its binding by approximately 10-fold to the comprised of two light chains each consisting of human neonatal receptor FcRn with almost a 4-fold variable and constant domains and two heavy chains, increase in serum half-life (Oganesyan et al, 2009). Three functionally and structurally distinct types of Fcγ-Receptors (FcγR) are expressed on human leukocytes, namely: FcγRI (CD64), FcγRII (CD32) and FcγRIII (CD16). The latter two classes are further divided into FcγRIIa, FcγRIIb, FcγRIIIa and FcγRIIIb. All FcγRs belong to the immunoglobulin superfamily and differ in their antibody affinities. FcγRs bind to the lower hinge region of IgG and in the case of IgG1, a common set of residues appears to be involved in the binding to all FcγRs (Sautes et al, 2003; Shields et al, 2001)

Methods

Results

Discussion

Conclusion