Antibody, also called Immunoglobulin, is a large Y globulin secreted by Effector B cell which is used in identifying and neutralizing the outsiders like bacterial and virus. Antibody is only found in blood ,body fluid and cytomembrane’s surface of Vertebrate. In addition, antiboy can identify one characteristics of specific outsiders. The specific outsider is antigen. Antibody is a symmetrical structure containing four Polypeptide chains. Two of these chains are heavy chains which are longer and contain bigger relative moleculars and the others are shorter light chains containing smaller relative mileculars.

Antibody’s main funcion is to bind with antigens including the outside and the inside to eliminate the microorganism and oarasite which intrude the host’s body. Antibody is also a protein produced by reaction of antigen and binding with specificity of antigen. Thus every kinds of antibody can bind with Epitope of specific antigen. These binds can inactivat antigens but it doesn’t work and even cause the Pathological damage of the host somtimes.