Immunoglobulin D

Immunoglobulin D (IgD) is one of the five major classes of immunoglobulins (antibodies) found in the immune system of mammals. It is primarily found on the surface of immature B cells and plays a crucial role in the initiation and regulation of immune responses.

Structure

Immunoglobulin D is a monomeric antibody, meaning it consists of a single unit. The structure of IgD is similar to that of other immunoglobulins, with two heavy chains and two light chains forming a Y-shaped molecule. The heavy chains in IgD are of the delta (_) type. The constant region of the delta heavy chain is what distinguishes IgD from other classes of immunoglobulins.

Function

The primary function of IgD is not completely understood, but it is known to be involved in the activation and regulation of B cells. IgD is expressed on the surface of B cells as a receptor that can bind antigens. This binding is thought to play a role in the activation of B cells and their differentiation into plasma cells and memory B cells.

IgD is also believed to be involved in the elimination of B cells that produce self-reactive antibodies, thus contributing to the maintenance of immune tolerance.

Distribution

IgD is found in very low concentrations in the blood plasma compared to other immunoglobulins such as IgG and IgM. It is primarily located on the surface of B cells in the lymphoid tissues.

Clinical Significance

Although IgD is not as well-studied as other immunoglobulins, abnormalities in IgD levels can be associated with certain immunodeficiency disorders and autoimmune diseases. Elevated levels of IgD can be seen in some cases of chronic infections and IgD myeloma, a rare form of multiple myeloma.

Related pages

• Immunoglobulin G
• Immunoglobulin M
• B cell
• Antibody
• Immune system

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  Mono and Polymers