Immunoglobulin M (IgM) is one of several antibody isotypes (also known as immunoglobulins) produced by vertebrates. IgM is the largest antibody and it is the first antibody to appear in response to initial exposure to antigen. [1] [2] In humans and other mammals studied, plasmablasts present in the

Initially expected to be important for the formation of polymeric immunoglobulins, the J chain is in fact strongly (but not exclusively) dependent on the J chain for polymerization of IgA. [16][17] In contrast, aggregated IgM is formed efficiently in the absence of the J chain. [18][19]The major for