Immunoglobulin D

Immunoglobulin D (IgD) is an antibody isotype that plays a complex role in the immune system. It is present on the surface of many B cells where it functions as an antigen receptor.

Structure

Immunoglobulin D, like all antibodies, is a protein structure composed of two heavy chains and two light chains. Each heavy chain has one variable domain followed by three constant domains, while each light chain has one variable domain and one constant domain. The variable domains of the heavy and light chains together form the antigen-binding site.

Function

The primary function of IgD is as an antigen receptor on the surface of B cells. When an antigen binds to the IgD molecule, it triggers the B cell to proliferate and differentiate into a plasma cell, which produces large amounts of antibodies to fight the invading pathogen.

Clinical significance

Abnormal levels of IgD can be indicative of various health conditions. Elevated levels of IgD may be seen in certain types of leukemia and lymphoma, as well as in some autoimmune diseases. Low levels of IgD can be seen in individuals with selective IgA deficiency, a condition in which the body does not produce enough of the antibody IgA.

See also

• Immunoglobulin
• B cell
• Antibody
• Immune system

References

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