Immunoglobulin M (IgM)is an antibody produced by B cells, one of the cells that play a large role in the human immune system. When a foreign body, or antigen, infiltrates the body, IgM is the first antibody to appear.
Antibodies help the immune system identify possible dangers, such as bacteria or viruses. Though most antibodies have a similar base structure, each type has a distinct formation of amino acids at its tip. The unique tip configuration matches a similar formation of a specific antigen. If an antibody locks with its specific antigen, the body is alerted to the presence of a foreign body, prompting the immune system to move into action.
Immunoglobulin M (IgM) is useful in medicine because it can bind to many different antigens, even those of a disease that has never before appeared in the body. Typically, it appears during the initial stage of almost every infection. Doctors can take samples of a patient’s blood to test for this substance, therefore confirming an infection even if other symptoms are not present.
Another interesting property of IgM is that it cannot cross the wall of a human placenta. This trait is useful for doctors monitoring the growth of a fetus in the womb or a baby after it is born. If a sample of fluid from the womb is found positive for this antibody, it implies that the fetus has an infection. Being able to know the condition of a baby before birth is key to a healthy labor and delivery.
When there is too much IgM circulating in the body, it is known as hyper IgM syndrome. It is a rare genetic condition that can severely impair the immune system. When a person has the syndrome, his or her body produces too much immunoglobulin M, or may not be able to produce enough of other immunoglobulin classes. People with hyper IgM syndrome are more susceptible to infection as well as autoimmune disorders. The syndrome also might make the person more likely to develop cancer at an early age.
Research into antibodies began in 1890, but it took nearly 100 years for specific antibodies to be identified. During the 1960s, IgM was one of the first distinguished as unique, along with antibody G. In 1972, Rodney Porter and Gerald Edelman were awarded the Nobel Prize in Physiology or Medicine for their work discovering the chemical structure of antibodies.