J chain



J chain is a protein component of the antibodies IgM and IgA.

Because IgM and IgA are the only two types of antibody that polymerize, it was initially thought that J chain was required for polymerization. However, it was subsequently found that IgM is able to polymerize in the absence of J chain as both a pentamer and a hexamer.

It is now believed that J chain is necessary to enable secretion of antibodies into mucosal tissues.