What is a Binding Antibody?

J. Banfield

A binding antibody is a protein molecule manufactured by the body as an immune response. Antibodies, also known as immunoglobulins, are generated by the immune system to find and attack foreign organisms within the body. These organisms — or parts of them — are called antigens. A binding antibody is an antibody that has a reaction when combined with an antigen, locking the antigen to it before working to eliminate or neutralize it.

The body produces many different antibodies to help protect against invasion by foreign antigens.
The body produces many different antibodies to help protect against invasion by foreign antigens.

Antibodies are able to detect and react to the invading microorganisms known as antigens; however, B-cell receptor (BCR) antibodies may require the aid of other cells for full activation. Antigens are macromolecules with at least one antigenic determinant or part of the antigen that the immune system recognizes. They are also called immunogens because they cause an immune response. These invaders can be anything from a bacteria or a virus to pollen.

The binding antibody reacts with foreign organisms during a humoral immune response. A humoral immune response occurs when antibodies are secreted from within the body fluids. This differs from cellular immunity, which relies on special types of white blood cells to attack foreign organisms.

Antibodies are made up of four polypeptides. Two heavy chains and two light chains join together to form a Y-shaped molecule. An amino acid sequence is at the tip of each Y branch, and is known as a paratope. Similar to a lock, a paratope is designed to fit one specific epitope.

The surface of every antigen contains an epitope. An epitope is roughly equivalent to a key, is specific to each antigen, and is recognized by the corresponding paratope of the antibody. When the paratope and the epitope fit together, the binding antibody attaches to the antigen. This interaction is referred to as antibody binding.

Once bound, there are two ways a binding antibody can remove the microbe. The antibody can mark the infected cell for attack by other components of the immune system. When this occurs, other cells such as T helper cells, are activated to help destroy invading organisms. Alternately, the binding antibody can neutralize the antigen directly. The organism can be eliminated by blocking the area that is crucial for the its ability to invade and survive.

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