Effect of D2O on the temperature-dependent solubility of cryoglobulin and noncryoglobulin IgM

Monoclonal cryoimmunoglobulins are immunoglobulins which become reversibly insoluble at low temperatures. These proteins are most often associated with various lymphoproliferative disorders. Non-cryoimmunoglobulins usually maintain their solubility in the cold at concentrations exceeding 200 mg/ml, while cryoglobulins precipitate from solution at these temperatures at concentrations as low as 0.1 mg/ml. Because cryoglobulins undergo a relatively large change in solubility over a narrow range of temperature and protein concentration (frequently a 103-104-fold change in solubility over a 10degC temperature range), their cold insolubility is generally assumed to arise from a major structural defect. In this report it is shown that the simple substitution of D2O for H2O as a solvent has not only a profound effect on the cold-dependent insolubility of a monoclonal, IgM-kappa cryoglobulin, but also imparts varying degrees of cold-dependent insolubility to a number of monoclonal non-cryoglobulin IgM proteins