NCIt synonyms : Immunoglobulin G Subclass 3; Immunoglobulin G3;
NCIt definition : Along with the immunoglobulin G4 subclass (IgG4), the IgG3 subtype makes up a minor
part of circulating antibodies in healthy individuals. The core hinge sequence contains
approximately four times the number of amino acids as the other subclasses; allotypes
of IgG3 can have up to 62 hinge residues and up to four interchain disulfide bonds.
The increased hinge size for IgG3 increases the separation between the Fc (constant
fragment) tail and Fab (antigen binding fragment) arms of antibodies of this subclass.
This enhances the relative flexibility of the molecule, which may modulate antigen-binding
capacity and immune complex formation, and may increase the affinity for binding to
both Fc receptors and complement component C1q.;