IgD

Definition

IgD is an immunoglobulin isotype that is expressed on the surface of mature, naive B cells. It acts as a receptor that helps initiate the humoral immune response by signaling the activation and differentiation of B cells upon antigen binding.

5 Must Know Facts For Your Next Test

1. IgD is co-expressed with IgM on the surface of mature, naive B cells and serves as a receptor that can bind to antigens.
2. Binding of antigen to the IgD receptor on B cells triggers their activation and differentiation into plasma cells and memory B cells.
3. IgD plays a role in maintaining B cell homeostasis and promoting the survival of mature, naive B cells in the periphery.
4. The concentration of IgD in the blood is typically much lower than other immunoglobulin isotypes, such as IgG and IgA.
5. Deficiencies or abnormalities in IgD production have been associated with certain immunodeficiency disorders and autoimmune conditions.

Review Questions

• Explain the role of IgD in the humoral immune response.
  • IgD serves as a receptor on the surface of mature, naive B cells and helps initiate the humoral immune response. When an antigen binds to the IgD receptor, it triggers the activation and differentiation of the B cell into plasma cells that secrete antibodies or memory B cells. This process is crucial for the recognition and elimination of pathogens through the production of antigen-specific antibodies.
• Describe the relationship between IgD and B cell homeostasis.
  • IgD plays an important role in maintaining the homeostasis of mature, naive B cells in the periphery. The co-expression of IgD and IgM on the B cell surface helps promote the survival and persistence of these cells, even in the absence of antigen stimulation. Disruptions in IgD production or signaling can lead to alterations in B cell numbers and contribute to the development of certain immunodeficiency disorders or autoimmune conditions.
• Analyze the significance of the relatively low concentration of IgD in the blood compared to other immunoglobulin isotypes.
  • The relatively low concentration of IgD in the blood, compared to other immunoglobulin isotypes like IgG and IgA, suggests that its primary function is not as a circulating antibody, but rather as a receptor on the surface of B cells. This low abundance in the blood may indicate that IgD plays a more specialized role in the initial activation and differentiation of B cells during the humoral immune response, rather than serving as a widespread effector molecule like other immunoglobulins. The precise regulation of IgD levels likely reflects its unique and targeted function in the immune system.

Related terms

Immunoglobulins:

Also known as antibodies, immunoglobulins are Y-shaped glycoprotein molecules produced by plasma B cells that recognize and bind to specific antigens.

B cells:

A type of lymphocyte that plays a central role in the humoral immune response by differentiating into antibody-secreting plasma cells and memory B cells.

Humoral Immune Response: The aspect of immunity that is mediated by secreted antibodies produced by plasma B cells, which neutralize pathogens and mark them for destruction.