Antibodies are a type of specialized protein generated by the immune system. Antibodies each contain two heavy chain proteins, which link to two smaller light chain proteins. The light chain contains a variable region that allows for an antibody to bind to one specific antigen. Upon exposure to a foreign material, or antigen, specialized immune system cells generate antibodies that bind to the antigen. Antibody binding to an antigen has many functions, both within the body and in laboratory testing.
Defense Against Infection
The major function of antibody-antigen binding within the body is to fight off infections. There are a number of different types of antibodies synthesized within the body, with the majority of the antibodies classified as immunoglobin G, or IgG. IgG antibodies produced by B-cell lymphocytes, a type of white blood cell, circulate throughout the body within the blood and bind to any available antigen. The antibody-antigen binding then stimulates the activation of other immune system cells, which engulf the foreign particle. Defects in antibody-antigen binding prevent the immune system from recognizing and attacking foreign particles within the body. Without proper antibody function, a person is left vulnerable to infection and disease.
Antibody-antigen binding also has a role in cancer therapy, and the use of antibody-based therapeutics allows for the selective targeting of cancer cells. Traditional chemotherapy drugs target proliferating cells thoughout the entire body, whether those cells are cancerous or not. This results in damage to a number of normal tissues throughout the body as a side effect of treatment, which may cause discomfort and pain over the course of chemotherapy treatment. Antibody-based therapies consist of antibodies designed to selectively bind proteins found on cancer cells. The antibody drug binds to its antigen on the surface of the cancer cell, and stimulates the body's natural immune system to attack and kill the cancer cell. Since the antibody binds selectively to cancer cells, healthy proliferative cell populations are largely unharmed by the therapy, decreasing the side effects experienced during treatment. The National Cancer Institute indicates that Herceptin, a breast cancer therapeutic, uses antibody-antigen binding to target and kill breast cancer cells.
Antibody-antigen binding also has a function in laboratory and medical testing. Since antibodies bind specifically to one antigen, the use of antibodies during laboratory testing can indicate the presence of a specific factor within a tissue sample. Antibody-antigen binding can be used to detect the presence of a specific protein within specific cells, a piece of biopsy tissue or the blood. NYU Langone Medical Center indicates that antibody-based tests are routinely used to characterize cancers and help distinguish between types of lymphoma. Antibody-antigen binding tests in the laboratory detect the presence of a specific protein by testing for the binding of an antibody. If a sample is positive for an antigen, the corresponding antibody will bind strongly to the sample, so the presence of the antibody acts as a marker for the presence of the antigen. If a sample is negative for an antigen, the antibody will not bind.