Question

Which of the following statements are true regarding IgM ?

• A. IgM is a pentamer and is the largest immunoglobulin
• B. IgM exists as monomer on the B cell surface and secreted form is a pentamer
• C. IgM is involved in early primary immune response
• D. All of these

Answer 1

The correct option is D

All of these

IgM is the first antibody produced in a primary response to antigens. It exists as a monomer, similar in structure to IgG when bound to the B cell surface but its secreted form is a pentamer (H2L2)5, in which five monomer units are held together by disulphide bonds that link their heavy chain domains. The pentamer form makes it the largest immunoglobulin making it difficult for IgM to diffuse between intercellular spaces.