Question

Immunoglobulin D:

1.Structure and functions

2. Evolutionary History

3. Unique Structures and components

4. roles in aspects of the metabolism of the organism

5. how does it interact with other organisms

Answer 1

Answer: Basically immunoglobulins are of five (5) different types: IgG, IgM, IgA, IgE and IgD. The name of these immunoglobulins based on the presence of heavy chains. Heavy chains of IgG (gamma “γ”),IgM (mu “µ”), IgA (alpha “α”), IgE (Episilon “ε”) and IgD (delta “δ”). All types of immunoglobulins are consists of light (2) and heavy chains (2).

1) Structure and function: The structure of IgD is similar to IgG immunoglobulin that is consists of two light and two heavy chains (dimmer of light and heavy chains). It consists of 0.2% of total immunoglobulins. It is one of the major type of membrane bound immunoglobulin on B cells (IgM is also a membrane bound immunoglobulin). It can activate basophils and mast cells.

2) Evolutionary history: Alternate RNA splicing and class switching recombination in B cells may produce diverse immunoglobulins. The alternate RNA splicing is present in all the jawed vertebrates but the class switching recombination is only present in higher vertebrates. So the diversity in higher vertebrates are more than the lower vertebrates.

3) Unique structure and components: Sedimentation coefficient of IgD is smaller (7S) than the other immunoglobulins. Molecular weight is 185kD consists of delta (“δ”) type of heavy chain with two antigenic valences. In serum the concentration of IgD is very less (0- 0.5mg/ml) compared with the others. It is like IgM, present with membrane bound state on mature B cells. It can activate basophils and mast cells.

4) Roles in aspects of the metabolism of the organisms: IgD gives the signal to B cells to activate, basophils and mast cells. The activated cells recruited at the site of infection and engulf the foreign particles or may form the cross chain structure that continuously activates the immune system to neutralise the invaders.

5) How does it interact with organisms: IgD immunoglobulins present in bound form on the surface of mature B cells. The antigen binding sites of IgD immunoglobulin interact with antigens (based on the homology) to activate the B cells for effector response simultaneously basophils and mast cells secreat the chemokines to attract the neutrophils, lymphocytes as well as other antigen presenting cells to engulf the invaders.