IgM -->
immunoglobulin M
medical dictionary

<immunology> An immunoglobulin M molecule (970 kD) is built up from five immunoglobulin G type monomers joined together, with the assistance of J chains, to form a cyclic pentamer.

Immunoglobulin M binds complement and a single molecule bound to a cell surface can lyse that cell. Immunoglobulin M is usually produced first in an immune response before immunoglobulin G.

The human red cell isoantibodies are immunoglobulin M antibodies. Heavy chain (mu chain) is rather larger than the heavy chains of other immunoglobulins.

Abbreviation: IgM

(30 Mar 1998)