Antibody and Antigen

Since this is the largest of the antibodies, it is effective against larger microorganisms. Because of its large size (it combines 5 Y-shaped units), it remains in the bloodstream where it provides an early and diffuse protection against invading antigens, while the more specific and effective IgG antibodies are being produced by the plasma cells.

The ratio of IgM and IgG cells can indicate the various stages of a disease. In an early stage of a disease there are more IgM antibodies. As an typical infection progresses, many B cells shift from the IgM production to production of IgG antibodies. The presence of a greater number of IgG antibodies would indicate a later stage of the disease. IgM antibodies usually form clusters that are in the shape of a star.