Everything about Antibody totally explained
Antibodies (also known as
immunoglobulins) 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 chain, 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.
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. 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.
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. 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.
Antibody forms
Antibodies occur in two forms: a
soluble form
secreted into the blood and
tissue fluids, and a
membrane-bound form attached to the surface of a
B cell that's called the
B cell receptor (BCR). The BCR allows a B cell to detect when a specific antigen is present in the body and triggers B cell activation. Activated B cells
differentiate into either antibody generating factories called
plasma cells that secrete soluble antibody, or into
memory cells that survive in the body for years afterwards to allow the immune system to remember an antigen and respond faster upon future exposures. Antibodies are, therefore, an essential component of the
adaptive immune system that learns, adapts and remembers responses to invading pathogens.
Isotypes
Further Information
Get more info on 'Antibody'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://antibody.totallyexplained.com">Antibody Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
