Merck, G4386-5G, γ-Globulins from human blood

γ-Globulins are immunoglobulins and occur in five classes, namely: IgG, IgM, IgA, IgD, and IgE. These are glycoproteins that are antibodies produced by plasma cells. The immunoglobulins are heterogeneous molecules made up of four polypeptide chains (two light chains and two heavy chains) linked together by disulfide bonds. The antigen-binding site is present at the nitrogen terminal. 20% of the protein in plasma are immunoglobulins.