Cryoprecipitogogue from normal serum: mechanism for cryoprecipitation of immune complexes.

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Abstract
The relationship of cryoglobulins to immune complexes in sera of patients with rheumatic or infectious diseases was examined. Polyethylene glycol was used to precipitate large proteins from normal serum and then was dialyzed away. The precipitated proteins were soluble in warm phosphate-buffered saline; at 4.degree. C they reversibly reprecipitated. As they reprecipitated, they selectively coprecipitated cold-soluble immune complexes. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, these normal, nonIg cryoproteins were similar to the nonIg constituents of washed cryoIg from patients with rheumatic or infectious diseases. Cryoprecipitability probably is a property not of immune complexes themselves but of a group of large normal serum proteins. In inflammatory diseases, the concentrations of some of these proteins, responding as acute-phase reactants, may increase to the point where intermolecular attractive forces become prominent, particularly in the cold. Cold-augmented molecular aggregation between these nonIg proteins and immune complexes could then act to decrease their collective solubility and result in the cryoprecipitation of otherwise cold-soluble immune complexes.