Immunoglobulin M, an antibody.

Immunoglobulin M

A type of immunoglobulin, or antibody, that exists mostly as a pentamer (five monomers joined together). It is the first immunoglobulin to be made by a B cell when it is exposed to an antigen.

(n) one of the five major classes of immunoglobulins; involved in fighting blood infections and in triggering production of immunoglobulin G

Immunoglobulin M (IgM), which is found mainly in the blood and lymph fluid, is the first antibody to be made by the body to fight a new infection. Source: KidsHealth

IgM is the first immunoglobulin synthesised in an antibody response. An immunoglobulin (or antibody) is a protein which is involved in immune responses. It is a strong activator of the complement syst [..]

A class of Immunoglobulin bearing mu chains (Immunoglobulin mu-Chains). IgM can fix Complement. The name comes from its high Molecular Weight and originally being called a macroglobulin.

the first antibodies made in response to initial exposure to an antigen

One of many antibodies present in blood serum which is usually indicative of an acute infection.

Abbreviation for the International Grandmaster Chess Title, which is an old term. These days, most just refer to this title as Grandmaster, which carries the GM abbreviation and goes before the player's name, e.g. GM Jon Doe.

Immunoglobulin gamma M - The class of antibodies found circulating in the blood, and first to appear in initial response to exposure to an antigen (before IgG). IgM is highly efficient in stimulating complement activity. The human red cell isoantibodies which control the A, B, O blood groups are IgM antibodies. IgM has a very high molecular weight [..]