MRCP UK EXAMINATIONS

Detailed explanation-1: -Serum IgM exists as a pentamer in mammals and comprises approximately 10% of normal human serum Ig content. It predominates in primary immune responses to most antigens and is the most efficient complement-fixing immunoglobulin.

Detailed explanation-2: -IgM is the first antibody built during an immune response. It is responsible for agglutination and cyto-lytic reactions since in theory, its pentameric structure gives it 10 free antigen-binding sites as well as it possesses a high avidity.