VMC 221: Veterinary Immunology and Serology (1+1)

STRUCTURE OF IMMUNOGLOBULINS

• The immunoglobulins are a large group of closely related heterogeneous glycoproteins.
• An immunoglobulin molecule is about 160 KDa and composed of 2 part of peptide chains of different sizes.
• The larger chains are called heavy (H) chains (50-60 KDa) and smaller chains are called light (L) chains (25 KDa).
• Both the light chains and both the heavy chains are identical.
• The carboxy (C) terminus domains of the heavy chains are inserted into the lipid bilayer of the B cells surface membrane.
• The light chains are only half the length of heavy chains and they are linked to heavy chains at its amino (N) terminus by disulphide (-S-S-) bonds, giving ‘Y’ shaped appearance.
• Two heavy chains are also joined together by disulphide bonds.
• The tail of ‘Y’ is F_C (crystalisable fragment can be crystallized in the cold) region is attached to the B cell and the arms called F_ab region which bind antigen.
• The antigen binding sites are formed by the groove created between light and heavy chains at their N-terminus.