Immunoglobulin
(Ig) is a protein secreted by plasma cells, the differentiated B cells, and
binds with a particular antigen. Immunoglobulin is also called antibody. All
antibodies have the same Y-shaped structure and in their monomer form consists
of two identical heavy chains and two identical light chains.1 Immunoglobulin
is divided by five classes, namely IgG, IgM, IgA, IgD and IgE.2
Those classes are determined by the structure difference
in heavy-chain constant region. For this reason, those classes have no effects
towards the antibody specifity, whereas
the antibody specifity is determined by antigen binding sites.3
Immunoglobulins
belong to the group of glycoproteins called globulins. Immunoglobulin consists
of four polypeptides chains, that is two identical Heavy (H) chains and two
identical Light (L) chains. In every H and L chain are two distinct regions. In
the tips of the chain, there is V (variable) region as the sites of antigen
binding. It is V region that recognizes and attaches specifically to particular
antigen.3 The remainder L and H is the constant (C) region, nearly
the same to all antibodies in the same class, is responsible on the kind of
antigen-antibody reactions occurs.2
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