Antibody is a protein that reacts against an antigen in an animal-type organism. Antibodies, which can be found in the blood or other body fluids, are used by the immune system to recognize and block viruses, bacteria, parasites or fungi. The most frequent antibody is formed by structural basic units that have four chains: two light and two heavy. The B lymphocyte is responsible for synthesizing the antibodies, which can be divided into five different classes in the case of mammals.
