What is the main purpose of IgM antibodies?

The main purpose of IgM antibodies is to provide the first defense against pathogens in the blood. IgM is the first type of antibody produced in response to infection and plays a crucial role during the initial stages of the immune response. These antibodies are the largest in size and are effective in forming complexes with antigens, thereby promoting their neutralization and clearance from the bloodstream.

Additionally, IgM can activate the complement system, enhancing the ability to clear pathogens effectively. Its presence signals to the immune system that there is an active infection, prompting other immune responses to take place. Despite other immunoglobulins having important functions, IgM's primary role at the onset of infections is what distinguishes it in the immune response.