Novel subunit in secretory IgA

Abstract

A new component, "J" (for joining), has been found in rabbit and human secretory IgA in addition to the S, α, and light chains already characterized. J has a molecular weight of approximately 23,000 and, by contrast with the S component, is disulphide-linked to the α chain. It is present in the dimer but not the monomer form of human IgA myelomas, and therefore seems to be responsible for the dimer structure characteristic of secretory IgA. © 1970 Nature Publishing Group.