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Antibodies (also known as immunoglobulins[1], abbreviated Ig) are gamma globulin proteins that are found in blood or other bodily fluids of vertebrates, and are used by the immune system to identify and neutralize foreign objects, such as bacteria and viruses. They are typically made of basic structural units—each with two large heavy chains and two small light chains—to form, for example, monomers with one unit, dimers with two units or pentamers with five units. Antibodies are produced by a kind of white blood cell called a B cell. There are several different types of antibody heavy chains, and several different kinds of antibodies, which are grouped into different isotypes based on which heavy chain they possess. Five different antibody isotypes are known in mammals, which perform different roles, and help direct the appropriate immune response for each different type of foreign object they encounter.[2] Although the general structure of all antibodies is very similar, a small region at the tip of the protein is extremely variable, allowing millions of antibodies with slightly different tip structures to exist. This region is known as the hypervariable region. Each of these variants can bind to a different target, known as an antigen.[3] This huge diversity of antibodies allows the immune system to recognize an equally wide diversity of antigens. The unique part of the antigen recognized by an antibody is called an epitope. These epitopes bind with their antibody in a highly specific interaction, called induced fit, that allows antibodies to identify and bind only their unique antigen in the midst of the millions of different molecules that make up an organism. 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.[4] The large and diverse population of antibodies is generated by random combinations of a set of gene segments that encode different antigen binding sites (or paratopes), followed by random mutations in this area of the antibody gene, which create further diversity.[2][5] Antibody genes also re-organize in a process called class switching that changes the base of the heavy chain to another, creating a different isotype of the antibody that retains the antigen specific variable region. This allows a single antibody to be used by several different parts of the immune system. Production of antibodies is the main function of the humoral immune system.[6] Activated B cells differentiate into either antibody-producing cells called plasma cells that secrete soluble antibody or memory cells that survive in the body for years afterward in order to allow the immune system to remember an antigen and respond faster upon future exposures.[7] Antibodies are, therefore, an essential product of the adaptive immune system that learns and remembers responses to invading pathogens. Antibodies occur in two forms a soluble form secreted into the blood and other fluids in the body, and a membrane-bound form that is attached to the surface of a B cell.
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Antibody Subcategories
Antibody Articles
Diagnosing food intolerance
by Frann Leach
Jul 22, 2007
Food intolerance used to be called 'food allergies'. However, there is a world of difference between a true food allergy, such as the infamous peanut allergy, which can kill almost instantly, and an intolerance to, for example, gluten leading to g...
Allergic Rhinitis and Its Causes
by Alexander Chong
Dec 12, 2006
Allergic rhinitis is an atopic disease, which is inherited from the parent. If both your parents have allergic rhinitis or other respiratory diseases such as asthma, tuberculosis, and emphysema, the probability that you have these kinds of resp...
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