Antibodies are an unparalleled tool for use in biomedical research because they bind with high affinity and specificity to a variety of molecules - most notably proteins and peptides. They are used in procedures where characterization, quantification, localization or verification of a protein is necessary.
Due to an antibodies' ability to bind tightly to a desired molecule, they have been used for in-vivo therapeutic applications. Successful applications have included Genentech's Herceptin? drug for specific types of breast cancer and IDEC Pharmaceutical's Rituxan? for use against certain B-cell non-Hodgkin's lymphomas.

What are antigens and immunogens?
The terms antigen and immunogen are often used interchangeably, and for nearly all purposes the difference is immaterial. In essence, they describe two forms of interactions between a molecule and the immune system. An immunogen refers to a molecule that elicits an immune response in an organism's immune system, whereas an antigen refers to a molecule that is able to bind to the product of that immune response. So, an immunogen is always an antigen, but an antigen may not necessarily be an immunogen.
What are epitopes?
An epitope is the specific sequence of amino acids on an antigen to which the antibody binds. For any given antigen, there are likely to be multiple epitopes against which antibodies will be produced. For antibody production, epitopes that are easily accessible for antibody binding are preferable.
In general, most ideal antigenic epitopes are hydrophilic, surface orientated and flexible. This is recommended because in most natural environments, hydrophilic regions tend to be located on the surface of proteins, whereas hydrophobic regions tend to reside in the interior of the protein. Similarly, can only bind to epitopes found on the surface of proteins and tend to bind with greater affinity when those epitopes are flexible enough to move into accessible positions.

Antibodies and the immune response
It is useful, in the context of antibody production, to understand the role that antibodies play and some of the mechanisms surrounding their use. After an organism's immune system recognizes a molecule as foreign, B-lymphocytes begin generating antibodies that are unique to that immunogen.
More important, a separate B lymphocyte generates an antibody for each individual epitope on the antigen's surface; thus there will be several different antibodies that bind with high affinity to any given immunogen.
In some cases, such as with viruses, the binding action of the antibody is sufficient to disable the pathogen. In other cases, such as with bacteria, the antibodies bind to surface proteins on the bacterium's surface, thereby signaling to other components of the immune system that the pathogen should be destroyed.
After the pathogen has been disabled, the B cells that generated the antibodies remain in the blood stream, acting as a type of memory protection against further invasions from the same immunogen.
For purposes, it is important to remember that each B cell generates exactly one highly specific antibody, and that any given antigen is likely to have several antibodies that bind to the various epitopes on its surface.

About the Author
With 35 years of experience in generating , Pacific Immunology Corp. is a leading global provider of services. Through continual refinement of techniques, protocols and reagents, Pacific Immunology has developed the capacity to consistently generate high affinity Peptide and at reasonable prices.