J CHAIN
J chain: translation
(= J-piece)
Polypeptide chain (15 kD), found in IgA and in IgM joining heavy chains (H chains) to each other to form dimers of IgA and pentamers of IgM. Disulphide bonds are formed between the J chain and H chains near the Fc ends of the heavy chains. Despite the similar name, it is not identical with the J region or coded for by the J gene.