Immunoglobulins (antibodies) are special proteins that are secreted by the cells of the immune system to protect against foreign invaders (microorganisms, toxins). 

Depending on the function performed, there are 5 types of antibodies: A, D, E, G, M. IgM is the first to form in the blood in response to an acute infection. They play a key role in the defense against bacteria.

The principle of their action is as follows: immunoglobulin recognizes everything which protein structure is foreign to the body. Then it settles on the microbe and signals to the defense cells, which swallow and break down the object "marked" by immunoglobulin.

Therefore, the task of IgM is to stop the onset of disease as quickly as possible. IgM deficiency makes infectious diseases longer and more complicated. And an increased concentration indicates the presence of serious diseases that are difficult for the immune system to cope with on its own.