Immunochemical studies on an IgG lambda cryoglobulin in cold-induced urticaria

A type I cryoglobulinaemia associated with cold-induced urticaria was demonstrated in a 64-year-old woman without primary disease. The cryoglobulin contained only IgG lambda as disclosed by immunofixation technique. Different physicochemical studies indicated that the IgG lambda component was monomeric at temperatures above 35 degrees C, but became polymerized below 35 degrees C. In addition crossed immunoelectrophoresis of plasma fibronectin from the patient showed a heterogeneous precipitate at low temperatures but a homogeneous precipitate at 25 degrees C indicating a complex formation at low temperature between IgG lambda and fibronectin. Fibronectin, however, was not essential for the cold precipitation of the cryoglobulin. The precipitation phenomenon at low temperatures was found to be a result of the physicochemical properties of the cryoglobulin itself unrelated to the antibody specificities tested. The importance of performing the immunochemical and physicochemical techniques at low temperature (7 degrees C) and at high temperature (35 degrees C) to gain knowledge of the nature of the protein, is emphasized. We conclude that only results obtained by relevant laboratory procedures might lead to correct classification and understanding of cryoglobulinaemia.