A<unk>  is the small polypeptide subunit of an antibody (or immunoglobulin); a typical antibody is composed of two immunoglobulin (Ig) heavy chains and two Ig<unk> s.
Light chain
Immunoglobulin heavy chain
Immunoglobulin G
Immunoglobulin A
Immunoglobulin D
Immunoglobulin M
Antibodies
Gamma globulin