A new type of temperature-dependent serum M protein: a case of IgG-lambda type multiple myeloma.

Background: We report a rare case of temperature-dependent serum M protein (thermoprotein), monoclonal IgG(1)-lambda protein isolated from 90-year-old female with advanced multiple myeloma.

Methods: M protein was identified in the blood plasma of the patient by immunoelectrophoresis (IEP). To evaluate the types of bonds, the properties of the protein after reduction and chemical treatment were examined.

Results: This protein was irreversibly precipitated at or above room temperature when exposed in the air. This protein was redissolved by 30 mmol/l dithiothreitol, 4 mol/l urea, or 8 mmol/l EDTA.

Conclusions: Unlike other immunoglobulins reported to date, this data suggests that hydrogen, disulfide, and ionic bonds are involved in the temperature-dependent precipitation of this M protein.