The fundamental structure of IgG contains two identical heavy chains of about 50 kDa and two identical light chains of about 25 kDa, thus tetrameric quaternary structure. Light chain, which is usually same in a natural IgG molecule, includes κ chain and λ chain, but κ or λ antibody can exist in one body simultaneously. A heavy chain includes Fab- and Fc-Fragments. This antibody can recognize rabbit IgG Fc fragments of heavy chains.