IMMUNOGLOBULIN D (IgD)

Immunoglobulin D (IgD) is an antibody with the basic four polypeptide structure of an immunoglobulin (Figure 1); and IgD is mostly found attached to the membranes of B cell. IgD is a membrane bound immunoglobulin, and it has a molecular weight (MW) of about 180, 000 DA.

Immunoglobulin D is present in only trace amounts in serum; and in association with IgM, IgD is the main membrane-bound antibody commonly expressed on the surfaces of mature B cells or lymphocytes where they are believed to function as antigen receptors.

IgD does not fix complements, and it does not cross the placental barriers. IgD is absent from memory cells, and their full physiological function in the immune system is yet to be unraveled.    

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