IgG (immunoglobulin G) antibody is enriched in mother milk. IgG is a major class of immunoglobulin. It contributes to 10A20% of plasma protein and is regarded as one of the most abundant serum protein. It consists of four subclasses IgG1 IgG2 IgG3 and IgG4. The IgG structure possesses four polypeptide chains containing two identical³ heavy (H) chains and two identicalº or» light (L) chains of 50kDa and 25kDa respectively. The chains are interlinked with a disulfide bond. Both the L and the H chains consist of a variable domain at the N-terminal. The C-terminal bearsAE constant domains three in H chain with a hinge region and one in the L chain. The variable region of IgG antibody is specific to antigens and is highly conserved.