General Description
Immunoglobulin G (IgG) belongs to the immunoglobulin family and is a widely expressed serum antibody. It consists of a γ heavy chain in the constant (C) region. The monomeric 150kDa structure of IgG constitutes two identical heavy chains and two identical light chains with molecular weight of 50kDa and 25kDa, respectively. The primary structure of this antibody also contains disulfide bonds involved in linking the two heavy chains, linking the heavy and light chains and residues inside the chains. IgG is further subdivided into four classes namely, IgG1, IgG2, IgG3, and IgG4 with different heavy chains, named γ1, γ2, γ3, and γ4, respectively. Limited digestion using papain cleaves the antibody into three fragments, two of which are identical and contain the antigen-binding activity. They are known as fragment antigen binding (Fab) fragments. These fragments contain light chains paired with the VH and CH1 domains of the heavy chains.
