Antibodies

Antibodies (also called immunoglobulins or Ig's) are Y-shaped proteins that circulate through the blood stream and bind to specific antigens, thereby attacking microbes.

The antibodies are transported through the blood and the lymph to the pathogen invasion site.

The body contains millions of different B cells, each able to respond to one specific antigen.

There are 4 classes of antibodies (listed from most common to least common):

IgG
IgM
IgA
IgE
IgD
Each antibody is made of four polypeptide (protein) chains: 2 heavy chains and 2 light chains. Both heavy chains are identical to each other and both light chains are identical to each other. Each contains a constant region and a variable region. The constant region forms the main part of the molecule while the variable regions forms the antigen-binding site.Each antibody has 2 antigen-binding sites.