IMMUNOLOGY

Detailed explanation-1: -IgM is not only the first class of antibody to appear on the surface of a developing B cell. It is also the major class secreted into the blood in the early stages of a primary antibody response, on first exposure to an antigen.

Detailed explanation-2: -IgD is found in human serum at very low levels, and not at all in rodents. Therefore, secretory IgD does not play a significant role in the humoral immune defence of mammals. IgD is found in a membrane-bound form, with a classic transmembrane domain, but also as a GPI-linked molecule.

Detailed explanation-3: -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-4: -IgD (IgD) is a monomeric antibody isotype that is expressed in the plasma membranes of immature B-lymphocytes. IgD is also produced in a secreted form that is found in small amounts in blood serum. Secreted IgD is made up of two heavy chains of the delta class, and two light chains.

Detailed explanation-5: -In B cells, the function of IgD is to signal the B cells to be activated. By being activated, B cells are ready to take part in the defense of the body as part of the immune system. During B cell differentiation, IgM is the exclusive isotype expressed by immature B cells.