Changes

<p>Is found in high concentrations in blood plasma (below [[IgG]] conc.) and is the major Ig produced during primary immune response</p>

<p>Is found in high concentrations in blood plasma (below [[IgG]] conc.) and is the major Ig produced during primary immune response</p>

==Structure==

==Structure==

<p>IgM is the primordial antibody and, although a monomer, is secreted as a pentamer (five monomers joined by disulphide bonds with two monomers joined by a J chain). This gives it ten identical antigen binding sites although IgM usually has relatively low affinity for its antigen. Its heavy chain is type mu (µ ).</p>

<p>IgM is the primordial antibody and, although a monomer, is secreted as a pentamer (five monomers joined by disulphide bonds with two monomers joined by a J chain). This gives it ten identical antigen binding sites although IgM usually has relatively low affinity for its antigen. Its heavy chain is type mu (µ).</p>

 

==Production==

==Production==

<p>Produced by plasma cells in the spleen, bone marrow and lymph nodes. Since it is around five times larger than "normal" antibody it does not diffuse quickly or enter tissues readily and as such its concentration in extracellular fluid and lymph is very low.  

<p>Produced by plasma cells in the spleen, bone marrow and lymph nodes. Since it is around five times larger than "normal" antibody it does not diffuse quickly or enter tissues readily and as such its concentration in extracellular fluid and lymph is very low.