The expression 'antibody' is a relatively new term having its genesis in 1901. Before the 20th century, the word 'antibody' denoted a number of different substances that functioned as 'bodies' or foot soldiers who combated against contagions and its dire consequences.

Often an antibody is also referred to as immunoglobulin and is basically a gamma globulin protein present in blood or other fluids in the body of vertebrates. This special variety of protein possesses extraordinary receptors that enable them to identify and counteract alien objects or substances known as antigens, such as bacteria and viruses. The function of an antibody is to recognize and counteract antigens with a view to prevent them from affecting the host organism and making it sick. In fact, antibodies comprise the nucleus of the immune system in animals and function as surprise combatants that put down invasions by antigens promptly.

Antibodies are usually composed of fundamental structural elements - each of them comprising two heavy chains and two small light chains. These basic structural elements form monomers when they have a single unit, dimers with two elements or pentamers when they comprise five elements. Antibodies are generated by a sort of white blood cell known as plasma cell. In fact, there are various kinds of antibody heavy chains as well as numerous diverse types of antibodies that are categorized into separate isotypes depending on the kind of heavy chain they hold. So far, scientists have identified five different antibody isotypes in mammals that have different functions and aim in directing the proper immune reaction for every separate variety of foreign substance they come upon.

It may be noted that the immune system of our body manufactures antibodies as soon as it identifies detrimental objects known as antigens, which include microorganisms, such as viruses, bacteria, fungi and parasites, as well as different substances like chemicals. Ironically, the body also produces antibodies when the immune system erroneously deems even a hale and hearty tissue to be an injurious substance. Each form of antibody is distinctive and protects our body against one particular kind of antigen.

These antibodies are shaped like Y formations and make up concurrent chains of polypeptides called light or heavy chains. Antibodies enclose a series of amino acids that actually established the category or class they belong to. This also determines which specific antibody is able to attach or bind to a particular antigen. It may be noted here that each antibody is only able to attach to or counteract against only one antigen - an arrangement that is somewhat comparable to the lock and key system. In fact, each antibody has a receptor at its tip and this enables them to bind to only one specific antigen.

A number of antibodies produced by the B cells as and when required are able to drift without restraint in the blood. The membrane-bound antibodies that remain attached to the surface of the B cells continuously enable them to make out when then need to produce further antibodies. The membrane-bound antibodies sticking to the surface of the B cells actually function as radars that identify whenever there is an invasion by an antigen. These antibodies always keep the B cells on the alert and when they attach to an antigen they send a message to the B cells to produce more antibodies in order to efficiently combat the antigen incursion.

As mentioned earlier, bacteria, viruses and fungi comprise a few forms of antigens which attacks an organism and makes it fall sick. The body actually produces antibodies when it comes in contact with the antigen at the outset and stocks up these antibodies for use afterward. It is important to note that a number of antigens are so cunning that they are able to alter their genetic code sufficiently enough to enable their future generations to evade any interaction with antibodies, as their changed genetic code does not allow the lock and key to go with. However, most of the antigens are very familiar and staunch and can be encountered by vaccinating people against them.

There are times when the production of antibodies by our body turns out to be utter chaotic. In the instance of autoimmune disorder, the body begins to produce antibodies that work against it. In other words, when any individual is affected by this condition, his or her body will produce antibodies that will erroneously counteract with substances produced by their body thinking that these objects are harmful. Some people may also develop antibodies when they come in contact with a number of usually undamaging chemicals or compounds, such as food, pet scurf or even dust mites. When their body is exposed to these substances again, they will not only produce antibodies, but also set off an allergic reaction, as their bodies endeavor to combat the superficial antigens.

One of the most important functions of the immune system is to produce antibodies and, as discussed earlier, they are actually produced by a variety of white blood cells known as B cell or B lymphocyte. The antibodies produced by the B cells can be set off as well as directed against alien proteins, microorganisms or toxins. And some of the antibodies produced by the B cells are known as auto antibodies because they counteract with the tissues in our body, mistakenly considering them to be harmful substances.

Precisely speaking, all microorganisms are able to set off a counter action by the antibodies. Diversity is necessary among the antibodies in order to successfully identify as well as eliminate the different harmful microorganisms from the body and it is for this reason that the composition of the amino acids enclosed by the antibodies differ so that they can effectively tackle with different antigens. It is estimated that the human body is able to produce approximately 10 billion dissimilar antibodies and each one of them is proficient in binding a particular epitope of an antigen. Nevertheless, the fact remains that though a huge gamut of dissimilar antibodies is produced in the body of one individual, the number of genes available to produce these proteins is inadequate. Hence, scientists have invented many multifaceted genetic means to enable the B cells in animals to produce an assorted collection of antibodies with a comparatively small number of antibody genes.