Immunoglobulin G (IgG) is the main potentiator of humoral immunity in the host extracellular fluids including blood, lymph and saliva. Immunoglobulin G (IgG) is the simplest, most abundant antibody class in vertebrates constituting some 75% of total immunoglobulin in humans. These molecules are glycoproteins formed of four polypeptide chains, consisting of two identical copies of each of two kinds of polypeptide chain: light (L) (which may be of either the κ or λ class), and heavy, gamma (γ) (which may be of one of four subclasses), linked together by disulfide bonds and noncovalent forces in the form L-H-H-L.