Plasmapheresis and cold sensitivity of immunoglobulin molecules. I. A study of hyperviscosity, cryoglobulinemia, euglobulinemia and macroglobulinemia vera.

There is a close connection between molecular changes of the Ig molecule with sinking temperature and the syndrome of hyperviscosity. The cryoglobulins are usually macroglobulins or complexes between IgM and other immunoglobulin classes. Many of these molecules can also be characterized as euglobulins. The connection between precipitation in the cold and in solutions with low electrolyte content is studied. Data on these connections are presented. The dependence of relative viscosity on the temperature has been investigated in a large number of sera from patients with different diseases. It is clear that most of these cold-sensitive globulins are macroglobulins (IgM). A number of viscosity curves at different temperatures in such sera are given. Also a few sera from patients with IgG myeloma have similar curves. The change in viscosity with lower temperatures implies that relative viscosity has to be determined at 37 degrees C in order to correspond to the condition in the living body. In practice, however, it is usually correct to state that IgM levels above 40 g/l are an indication that plasmapheresis should be considered. The best clinical sign is obtained by ophthalmoscopy. Difficulties with the counting of leukocytes and platelets in electronic counters may be caused by the presence of macroglobulins, usually but not always, cryoglobulins.