Introduction to Antibody Production
Why use antibodies?
Because antibodies bind with high affinity and specificity to a variety of molecules, most notably proteins and peptides, they are an unparalleled tool for use in biomedical research. They are used in assays where characterization, quantification, localization or verification of a protein is desired. Examples include diagnostic kits such as pregnancy tests, protein microarrays, immunohistochemistry, and common ELISA procedures. Given antibodies' ability to bind tightly to a desired molecule, much effort has been directed towards using antibodies for in-vivo therapeutic applications. Succesful 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, immunogens and epitopes?
The terms antigen and immunogen are often used interchangeably, and for most purposes, the difference is irrelevant. In essence, they describe two types of interactions between a molecule and the immune system. An immunogen refers to a molecule that is capable of eliciting an immune response by an organism's immune system, whereas an antigen refers to a molecule that is capable of binding to the product of that immune response. So, an immunogen is necessarily an antigen, but an antigen may not necessarily be an immunogen. Throughout this site, the term antigen will be used since it refers directly to the molecule that binds to the product of the immune response - the antibody. An epitope refers to the specific sequence of amino acids on an antigen to which the antibody binds. With any given antigen, there are likely to be multiple epitopes against which antibodies will be generated. In the context of antibody production, epitopes that are easily accessible for antibody binding are ideal. For more information, please visit our antigen design page.
How do antibodies fit into the immune response?
Although the mechanics of the immune response are beyond the scope of this site, 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 uniquely specific to that immunogen. Of even more importance, a separate B lymphocyte is responsible for generating an antibody to each individual epitope on the antigen's surface, meaning that 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 foreign object has been eliminated, the B cells that generated the antibodies remain in the blood stream, acting as a type of memory or adapted protection against further invasions from the same immunogen. For antibody production 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.