Cryoglobulinemia based on interaction between a gamma macroglobulin and 7S gamma globulin

A cryoglobulin is described, consisting of approximately equal quantities of 7S and 19S gamma globulins. The cold-precipitable protein was present in the serum as a soluble 22S complex. The property of cold precipitation resided in neither of the substituents of the cryoglobulin, but stemmed from the capacity of one of the constituents (the 19S component) to combine with 7S gamma globulin to form a complex insoluble at 4 °C and soluble at room temperature. The term “incomplete cryoglobulin” is suggested for this macrogammaglobulin. It was possible to prepare a cryoglobulin in vitro by addition of 7S gamma globulin from a normal subject to the 19S incomplete cryoglobulin obtained from the patient studied. The “incomplete cryoglobulin” gave a number of positive reactions for the rheumatoid factor, but was distinguished from it by its inability to agglutinate sensitized sheep erythrocytes. It could be readily detected, however, by a positive reaction with heat altered fraction II, the tanned cell test, the D cell test and the latex fixation test.