Immunoglobulins are glycoprotein molecules and a group of structurally similar but functionally apparently different proteins. The immunoglobulin "backbone" consists of heavy and light polypeptide chains. Five classes of immunoglobulins (IgA, IgG, IgM, IgE and IgD) have been distinguished on the basis of non cross-reacting antigenic determinants of their heavy chains.
The main function of immunoglobulins is to serve as antibodies that confer humoral immunity against bacterial, viral and other pathogens.
Application of antibodies in research and development, in vitro/in vivo diagnostics, or therapeutics requires antibodies with remarkable specificity.