Immunoglobulin M (Ig M)
Immunoglobulin M is the largest of all isotypes with respect to size, and as such it has a low affinity for binding to antigens. It is usually intravascular, first to be produced in response to an attack on the body, before other immunoglobulins are called on. Immunoglobulin M activates the reactions of the complement system more readily than other antibodies, probably due its pentameric form. The population of Ig M antibodies rises rapidly in the early stages of an infection before the body had had time to produce enough Ig G for defense. Immunoglobulin M makes up 5-10 percent of total antibodies in the blood. [3]
