Antibodies are glycoproteins, they have carbohydrate attached to them, and they each share a common Y-shaped structure composed
of four protein subunits. These subunits contain two identical light chains and two identical heavy chains. Each light chain
consists of about 200 amino acids, which compared to a heavy chains is only about half the size. The variable regions of the
antibody are located at the amino terminals, N-Terminals, and it is in this region where the first 100 or so amino acids vary
from antibody to antibody. The variable regions determine the antibody's antigen-binding specificity. The constant regions
are located on the light and heavy chains and only a few different amino acid sequences are found here. This region determines
antibodies' ability to activate other immune system components.
Humans make two different kinds of constant regions for their light chains producing: kappa and lambda light chains. Also
they produce five different kinds of constant regions for their heavy chains producing: mu chains (IgM antibodies), gamma
chains (IgG), alpha chains (IgA), delta chains (IgD), and epsilon chains (IgE). Each of these five kinds of heavy chains
appears to have no particular preference for pairing with the lambda or kappa light chains.