Immunological and physicochemical studies of IgA1 (delta) cryogelglobulinaemia.

Cryogelglobulinaemia in a patient with multiple myeloma and hyperviscosity syndrome was caused by an IgA(λ) protein. The M component circulated mainly in the form of a monomer, although a small portion of the IgA molecules were in a polymeric form. It was found that both purified monomer and polymer gelled promptly when cooled, although the limiting concentration producing a gel with the polymer was approximately one-half that required for gelation of the monomer, It was also found that the isolated (Fab') fragment gelled on cooling. The property of cryogelation was reversibly abolished by high and low pH, high salt concentrations, high concentrations of urea, and was irreversibly abolished by mild reduction and alkylation. It seems to be the first case of IgA(λ) cryogelglobulinaemia in which gelation was definitely associated with monomeric IgA and the (Fab') portion of the molecule.