IgM reassociation in the absence of J-chain

Human monoclonal IgM pentamers with different biophysical properties (euglobulin, pseudoglobulin or cryoglobulin) were reduced and reassociated in the absence of J-chain. Reassembly occurred for 50-82% of the monomers. The reassociated molecules consisted of covalent oligomers and pentamers. The deficiency of J-chain (estimated to be less than 0.17% of normal) was shown by alkaline-urea overloaded gel electrophoresis followed by silver staining. The addition of exogenous J-chain, from polymeric IgA or IgM, did not significantly modify the reassembly ratio. Thus J-chain does not seem to be an absolute requirement for IgM polymerization.