Analysis of the dynamics of cryoaggregation by light-scattering spectrometry

Cryoglobulins are proteins that precipitate at temperatures below 37 °C. Cold-induced precipitation of proteins may occur in vivo secondary to several important diseases, and lead to pathological manifestations involving different organs. Cryoprecipitation may be observed in vitro by exposing serum samples, supposed to contain cryoglobulins, to low temperatures, but this needs several days to occur. Protein-protein interactions leading to cryoprecipitation are still poorly understood and the knowledge of the underlying mechanism may be relevant to the understanding of the onset of pathological manifestations. Using light-scattering spectrometry, we studied cryoprecipitation occurring in vitro at different temperatures and cryoglobulin concentrations. We describe the kinetics of the cold-induced precipitation of mixed cryoglobulins, measured as increase in turbidity. The plots obtained demonstrate that the cryoprecipitation did not occur as a single-step reaction, but consisted of four distinct phases where both temperature and cryoglobulin concentration affected the immune complexes formation. Light scatter spectrometry may provide a simple, sensitive and rapid method for the detection of cryoglobulins.