Practical Applications of Antibodies

Antibodies are substances found in the blood that help the body fight infection. They recognize foreign invaders and bind to chemicals on their surfaces called antigens. The process tags bacteria, viruses, infected cells or other foreign matter for destruction by other parts of the immune system. White blood cells called B-lymphocytes produce specific antibodies for every foreign antigen the body encounters. Because of this specificity, antibodies have numerous practical applications in the fields of medicine and research.

Types

• The site on an antigen that an antibody binds to is called an epitope. Any given antigen will likely have multiple epitopes against which B-lymphocytes produce antibodies. Polyclonal antibodies come from multiple B-lymphocytes and bind to a variety of epitopes. They are retrieved from the blood of an immunized animal such as a mouse, sheep or horse. The diversity of antibodies provided allows researchers to detect multiple epitope sites on a given antigen. In contrast, monoclonal antibodies come from one B-lymphocyte producing antibodies to one specific epitope. Researchers generate monoclonal antibodies by fusing a B-lymphocyte with an immortal type of cancer cell, or myeloma cell, from a mouse. Antibodies produced in this fashion are identical and specific for the epitope of interest.

Diagnostic Applications

• An antibody titer is a laboratory test that detects and measures the amount of specific antibodies in the blood. It can indicate if a person has or recently had an infection such as mononucleosis or viral hepatitis. Because vaccines stimulate antibody production against specific diseases, an antibody titer can indicate one's need for a booster shot or whether a recent immunization produced enough of an immune response to provide adequate disease protection. Sometimes the test is used to diagnose autoimmune diseases, conditions in which one's immune system produces antibodies to the body's own tissues. Antibodies can also detect small amounts of drugs, toxins and hormones. Those specific for human chorionic gonadotropin, or HCG, are used in pregnancy test kits.

Identification Applications

• Because different types of antibodies react specifically with antigens unique to a given organism, they can be used to identify it. Serology is the branch of medicine concerned with the role antibodies play in protecting the body from disease, including the use of antibody reactivity for microorganism identification. Antibodies of different organisms can be prepared in a laboratory. When antibodies against a specific organism are mixed with a suspension of that organism, the organisms stick together, a process known as agglutination. The test can identify not only the organism, but also its specific strain.

Treatment Applications

• Scientists have developed a variety of antibodies to treat specific conditions. Rituxan and Herceptin, drugs used to treat certain types of cancer, are based on antibody technology. Antibodies can be used to treat viral infections previously considered untreatable. Experts at Davidson College claim evidence exists suggesting that antibodies may lead to a cure for AIDS. Organ rejection is a major complication of transplant surgery. OKT3 is an antibody used to prevent organ rejection in transplant surgery patients.