Types of Antibodies

Types of antibodies

Immunoglobulins (Ig) are categorized into five classes each with a characteristic type of heavy chain denoted asand µ types.

IgG : 70-75% of the total antibodies; smallest in size (monomeric); passes from mother to foetus through placenta as natural passive immunity.
IgA : 15%; as dimer; present in most of the external secretions like milk, saliva, sweat etc.      
IgM : 10%; largest size (pentamer) 5 molecules bound together as complex structure also called as millionaire antibodies; provides major immunity against bacteria and virus as secondary immune response and activates B-cell.
IgE : Least in number (about 0.2%); mediate allergic response as a complex on mast cell surface.
IgD : About 1%; mainly on the cell surface as receptors for activation of B-cell.
Notes : IgM is pentamer, IgA is dimer and the others are monomer.