The immunoglobulin molecule

Antibodies, or immunoglobulins, have been used for many years in immunohematology and yet the complexity of these molecules is rarely considered. This review concentrates on IgG and IgM molecules, as these are most usually found in transfusion laboratories. The basic structure and function of the immunoglobulin molecule are addressed at both the protein and the gene level, and isotypes, allotypes, and idiotypes are introduced. Although the antibody molecules secreted by each B cell have a unique binding site, a diverse array of immunoglobulin is produced not only by random recombination of the genetic components during assembly of the molecules but also due to somatic mutation. These events, as well as gene restriction, which is often seen in IgM antibodies to blood group antigens, are discussed and some of the differences between monoclonal and polyclonal antibodies are addressed.