Immunoglobulin (Ig) Structure Immunology Review 381
2 heavy (H) chains & 2 light (L) chains held together by disulfide (S-S) bonds.g, a, m, d, e. Determine Ig class (IgG, IgA, IgM, IgD, IgE). 2 H chains in Ig always same.kor l. Both found in all classes of Igs, but only 1 type per molecule. Free L chains are known as Bence Jones
proteins.Fragment antigen binding. Consists of 1 L chain & 1/2 H chain held together by S-S bonds. 2 per Ig. Each can bind ag.Fragment crystallizable. Carboxy-terminal halves of 2 H chains held together by S-S bonds. Role in opsonization &
complement fixation.Carboxy-terminal ends of H & L chains where amino acid sequence is same for all chains of that type.Amino-terminal ends of H & L chains where amino acid sequence varies. Also known as antigen-recognition unit.
Responsible for Ig specificity.Flexible portion of H chain between 1st & 2nd constant regions. Allows molecule to bend so that 2 ag-binding
sites can operate independently.Glycoprotein that links Ig monomers in IgM & secretory IgA.Basic structure
Heavy (H) chains
Light (L) chains
Fab fragment
Fc fragment
Constant region
Variable region
Hinge region
Joining chain
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