Figure 1.

IgG4 antibody has a distinctive structure. (A). Two heavy chains and two light chains make up the IgG4 antibody. (B). The Fc fragment of one IgG4 molecule can react with the Fc fragment of another. (C). When half-molecules are exchanged (called a Fab-arm interchange), IgG4 combines two distinct specificities into a unique molecule (bispecific antibody). Reproduced from [41]. This is an open-access article distributed under the terms of the Creative Commons CC-BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.