Antigen-antibody binding happens when an antibody is attracted to and attaches to an antigen. While it is attached, the antibody creates a chemical reaction that will eventually lead to the destruction of the antigen. Only specific antibodies can bind to the different types of antigens, though antigens that are similar in structure can be attacked by the same antibodies. The bond between an antigen and an antibody is reversible, so the antibody must attempt to make multiple connections to an antigen in order to stay connected until it eliminates the antigen.
There are many different types of antigens, though most are protein antigens, that can attract antibodies. Many antigens, such as viruses and bacteria, are harmful, while others, such as pollens or other allergens, are themselves, harmless. The antibodies involved in antigen-antibody binding are known as immunoglobulins. These are molecules that are manufactured by the immune system of an organism in order to destroy foreign bodies.
Immunoglobulins can have a high or a low affinity for certain antigens. When the affinity level is high, the antigen-antibody binding is strong. This strong link between the immunoglobulin and the antigen allows the immunoglobulin to set off a cascade of chemical reactions that eventually break down and destroy the antigen.
Even if the affinity of an antibody for an antigen is extremely high, antigen-antibody binding is not permanent. It is possible for the antigen to break off the connection with the antibody as a defense to its attack. In order to counter this, the antibody must attempt to bind to the antigen through a number of different connections.
Antigen-antibody binding usually relies on the use of weak electrical charges to pull the antigen and antibody together. Electron affinity on one side of the bond and a slight negative charge on the other is the most common cause for the binding of these two types of molecules. The types of bonds that hold the molecules together can be hydrophobic, electrostatic, or hydrogen bonds or Van der Waals forces.
All antigen-antibody binding is non-covalent, which means that they do not share electrons. They remain discrete molecules even while they are bound together. This means that when they come apart, each is intact.