ANATOMY

Detailed explanation-1: -Immunoglobulin D (IgD) is an antibody isotype that makes up about 1% of proteins in the plasma membranes of immature B-lymphocytes where it is usually co-expressed with another cell surface antibody called IgM.

Detailed explanation-2: -Expression of the membrane-bound form of the immunoglobulin (Ig) as part of the antigen receptor is indispensable for both the development and the effector function of B cells. Among five known isotypes, IgM and IgD are the common B cell antigen receptors (BCRs) that are co-expressed in naïve B cells.

Detailed explanation-3: -Immunoglobulin D (IgD) is primarily found on the surface of B lymphocytes where it functions as a receptor for antigen. IgD does not bind complement or cells through the Fc receptor. A small amount of IgD is secreted accounting for about 0.25 per cent of the total serum immunoglobulins (Vladutiu, 2000).

Detailed explanation-4: -Prior to mounting an immune response, B cells carry two closely related versions of the B cell receptor on their surface: IgM and IgD. Both IgM and IgD perform many of the same roles and can largely substitute for one another.

Detailed explanation-5: -Mature B cells have both immunoglobulin M (IgM) and IgD types of BCRs, which have identical antigen-binding sites and are both associated with the signaling subunits Ig and Ig, but differ in their membrane-bound heavy chain isoforms.