Immunoglobulin D (IgD), Serum

Immunoglobulin D (IgD) is a unique immunoglobulin with a concentration in serum far below those of IgG, IgA, and IgM but much higher than that of IgE. IgD represents about 0.25% of the total serum immunoglobulins and has a half-life of 2.8 days with a synthesis rate 10 times lower than that of IgA, IgM, and IgG. The long “hinge” region of IgD renders the molecule very susceptible to proteolytic degradation as well as making it flexible thus enhancing antigen binding. IgD does not bind to normal lymphocytes, neutrophils, or monocytes and does not cross the placenta. It binds bacteria (Neisseria catarrhalis and Haemophilus influenzae and weakly to streptococcal groups A, C, and G) nonspecifically through the Fc fragment on the one hand and has antibody activity to specific antigens on the other.

IgD is the major antigen receptor isotype on the surface of most peripheral B cells, where it is co-expressed with IgM. The majority of the cell-bound IgDs are of the k type (140kd). The role of IgD (especially the secreted form) is not fully understood. However, IgD can have a regulatory role, e.g., to enhance a protective antibody response of the IgM, IgG, or IgA isotype, or to interfere with viral replication (110kd). IgD can also participate in the generation and maintenance of B-cell memory and might have an important role in the transition from a stage of susceptibility to induction of B-cell tolerance to one of responsiveness.

1 ml Serum Stability: 2 Days at 2-8 °C

4.0 - 152.7 mg/L