Antibody From Wikipedia,the free encyclopedia An antibody(Ab).also known as an immunoglobulin(Ig).is a large,Y-shaped protein produced mainly by plasma cells that is Antigens the pathogen,called an ar region.Each tip of the"Y"of an antibody contains a paratope (analogous to a lock)that is specific for one particular epitope (similarly anal ogous to a key)on an antigen. allow ing these two gen-bind ing s el for attack by other parts of the immune system,or can neutralize its target directly (for example,by blocking a part of a microbe that is for its invasi ial).Depending on antigen, the foreign substance.The ability of an antibody to communicate with the other components of the immune system is mediated via its Fc region(located at the e of th on site h )which a con 0nn尚n bodies9 Antibo小y mmune syste ntibodies re secrete adaptive toa lock and key immune system, E sty by sical fo that is from the celtobe freen the.and a membrane-bound form that is attached to the surface of a B cell and is referred to as the B-cell ceptor(BCR).The BCR is found only on the surface of B cells and to either antibody fact ,61 of the B cel to produce full activation of the B cell and,therefore,antibody generation follow ing an n binding.Soluble antibodies are released into the blood and tissue fluids,as well as many secretions to continue to survey for invading microorganisms. Antibodies are gly coproteins belonging to the immunoglobulin superfamily4]They constitute most of the amma globulin fraction of the blood proteins.They are typically made of basic structural units-each with two large heavy chains and two small light chains.There are several different types of antibody heavy chains that def e five different types of fragments(Fc)that may be a ach d to the antige inding able to hind to its ep which is essentially the BCR).thus alowng the complex to mediate different role dependingon he ycn)preet at comerdThe ftbdibind The ability of antibodies to bind to ect th or eacn c rent type of ey histamine release a's Fab parat binds to all raic antigon for 黑高Re欧gan0 Though 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,or antigen-binding sites,to exist.This region is known as the hypervariable region.Each of these variants can bind to a different