These consist of antigen linked to antibody. Depending on ratio of antigen to antibody, these can be of varying size. When fixed at one site, they can be removed by phagocytic cells. They may also circulate prior to localization and removal, and can fix complement. Fab and Fc are involved.
Antibodies bind to organisms via their Fab region.
This is of great importance to the foetus in the first 3 months. The precise function of IgD is not known. It may serve as a maturation marker of B lymphocytes. When we are exposed to an antigen for the first time, there is a lag of several days before specific antibody becomes detectable. This antibody is IgM. After a short time, the antibody level declines.