Which represents the main function of IgD?

Which represents the main function of IgD?

• A. Protection of the mucous membranes
• B. Removal of antigens by complement fixation
• C. Enhancing proliferation of B cells
• D. Destruction of parasitic worms

Answer: (C)

IgD’s main role is as the B cell receptor on naïve B cells. When an antigen binds to the IgD (along with IgM) on the B cell surface, it triggers signaling through the B cell receptor complex, activating the B cell and initiating its proliferation. This clonal expansion prepares the immune system to produce antibodies and to differentiate into antibody-secreting cells later in the response. IgD itself isn’t typically secreted in large amounts and doesn’t efficiently fix complement or directly destroy pathogens, which is why other isotypes handle those effector functions—IgA for mucosal protection, IgM and some IgG for complement activation, and IgE for defense against parasitic worms. Thus, the best description of IgD’s main function is to enhance activation and proliferation of B cells upon antigen binding.

IgD’s main role is as the B cell receptor on naïve B cells. When an antigen binds to the IgD (along with IgM) on the B cell surface, it triggers signaling through the B cell receptor complex, activating the B cell and initiating its proliferation. This clonal expansion prepares the immune system to produce antibodies and to differentiate into antibody-secreting cells later in the response. IgD itself isn’t typically secreted in large amounts and doesn’t efficiently fix complement or directly destroy pathogens, which is why other isotypes handle those effector functions—IgA for mucosal protection, IgM and some IgG for complement activation, and IgE for defense against parasitic worms. Thus, the best description of IgD’s main function is to enhance activation and proliferation of B cells upon antigen binding.