Figure 7.

Interchain disulfide linkage characteristics and structural isoforms of human IgG subclasses. (A) Schematic comparison of disulfide linkages and hinge amino acid sequences between the subclasses. The core hinge region sequences are displayed under each schematic. (B) Structural isoforms of IgG2 resulting from inter-chain disulfide shuffling: IgG2-A is the known classical form, IgG2-B is created by a symmetric disulfide linkage of both Fab regions to the hinge, and IgG2-A/B is an intermediate form with an asymmetric disulfide linkage of one Fab arm to the hinge. (C) Formation of a bispecific monovalent IgG4 molecule resulting from Fab arm exchange between 2 different monospecific bivalent IgG4 molecules. The non-covalently linked half molecule is created by the formation of intra-chain disulfide bonds as depicted in the insert. The C regions are shown in solid colors and the V regions are patterned.