The body contains hundreds of thousands of different white blood cells called B lymphocytes (also known as B cells). Each B-cell is capable of producing one type of antibody. Antibody proteins are produced by the immune system in response to the presence in the body of antigens. These antigens can be foreign proteins or polysaccharides such as bacteria, bacterial toxins, viruses, or other cells or proteins. The antibody substance is made of four polypeptide chains – these are known as two identical light and two identical heavy chains – joined by disulfide bridges. Though the general structure of all antibodies is very similar, a small region at the tip of the protein is extremely variable. This feature allows millions of antibodies with slightly different tip structures, or antigen binding sites, to exist. This also allows each antibody bearing a site on its membrane that will bind with a specific antigen. The specific binding property of antibodies with antigens is a key feature used in the Enzyme-Linked ImmunoSorbent Assay, or ELISA kit technique. It allows the ELISA kit method to detect specific molecules with high specificity and sensitivity because of the discriminatory capabilities of the antibodies and antigens used.
Antibodies which are identical with each other at every amino acid (because they have all been produced by the descendants of a single B cell) are called monoclonal antibodies. Serum antibodies are polyclonal antibodies, because they are produced by the descendants of several B cells that recognize different epitopes on the same antigen. The huge diversity of antibodies allows the immune system to recognize an equally wide diversity of antigens. Antigens are characteristically defined as any foreign substance that causes an immune response. The unique part of the antigen recognized by an antibody is called an epitope. Each epitope binds with their antibody in a highly specific interaction, called induced fit or lock and key. This process allows antibodies to identify and bind only their unique antigen in the midst of the millions of different molecules that make up an organism. The ELISA kit test has been developed to screen large numbers of samples using multi-well plates, making it one of the first high throughput assays.
Recognition of an antigen by an antibody tags it for attack by other parts of the immune system. Antibodies can also neutralize targets directly by, for example, binding to a part of a pathogen that it needs to cause an infection. Antibodies combine with some antigens, such as bacterial toxins, and neutralize their effect. They remove other substances from circulation in body fluids. They bind certain antigens together, a process known as agglutination. They activate complement, blood serum proteins that cause the destruction of invading cells. Humans and higher primates also produce “natural antibodies” which are present in serum before viral infection. Natural antibodies have been defined as antibodies that are produced without any previous infection, vaccination, other foreign antigen exposure or passive immunization.
Biological scientists have used antibodies for many years to study proteins. The substances detected by ELISA kit method include hormones, bacterial antigens and antibodies. ELISA kit technology is widely utilized to detect substances that have antigenic properties, primarily proteins. ELISA kit procedure is highly sensitive to specific antibodies and provides an analytical system capable of detecting very low levels of antibodies and antigens. The ways antibodies are produced and used has led to an increasingly powerful technology. Antibodies are also very important tools used in medicine and science. Scientists can use antibody binding activity to identify an organism – in order to decide what kind of medical treatment we may need. For antibodies to play their role in the defence mechanism, they must be extremely diverse and yet highly specific. They also need the diversity to defend against a large number of unexpected and unknown possibilities.