Presence of fibronectin in cold precipitates of patients with cryoimmunoglobulinemia.

Fibronectin (FN) has been implicated in the cryoprecipitation of fibrin-fibrinogen complexes. Preliminary observations have suggested that it may also play a role in cryoglobulinemia. In the present study 32 cryoprecipitates from patients with hepatitis, chronic active hepatitis, essential mixed cryoglobulinemia, and inflammatory bowel diseases were analyzed and screened for the presence of FN. Most cryoproteins of patients with essential mixed cryoglobulinemia and inflammatory bowel diseases were of the mixed IgM-IgG type and all contained FN. In contrast, most cryoproteins of patients with hepatitis were composed of polyclonal IgM and were devoid of FN. It is possible that FN characterizes and facilitates the formation of mixed cryoglobulins. However, its presence does not seem to be an absolute requirement for cryoprecipitation.