Structure and function of IgD

Several antibody responses include the production of specific IgD antibody [91], but the concentration of IgD in serum is very low. Since the antibody does not appear to activate any effector system, a possible protective role for IgD in serum has not been identified. However IgD, together with IgM, is a principal class of immunoglobulin found on the surface of B cells, where it is thought to act as an antigen receptor with an immunomodulatory role [92], 

The structure of human IgD is suggested to resemble fairly closely that of IgG, 

Recently, receptors for IgD have been described on T cells which may be important in immunomodulation [95]. 

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