Antibodies

Antibodies are glycoproteins synthesized by B lymphocyte cells that share structural and functional characteristics. Functionally, they are characterized by their ability to bind to soluble antigens and other antigens bound to microorganisms or specialized cells. Antibodies are made up of two different polypeptides, one called the heavy chain and the other the light chain, which are encoded by different genes. Antibodies consist of two identical light chains (25 kDa each) and two identical heavy chains (50-75 kDa each). Antibodies are formed by three domains. Two of them are identical, formed by the heavy chain and the light chain, creating the Fab domain (antigen binding fragment), through which the antibody interacts with its specific antigen. The C-terminal end of both heavy chains gives rise to the Fc domain (fragment that crystallizes). The four chains are held together by disulfide bridges and non-covalent bonds. The different types of antibodies are distinguished by the type of heavy chain they contain, resulting in different classes or isotypes: IgG, IgM, IgA, IgE, and IgD.