Cold insoluble globulin: relationship with lymphocytotoxins in autoimmune diseases.

Lymphocytotoxic activity is known to better occur at low temperatures and to be relatively enriched in cryoglobulins. As the cold insoluble globulin, Fibronectin, is a main component of cryoglobulins, experiments were carried out to find out whether Fibronectin was involved in the mechanism of cytotoxicity or not. No direct or indirect (complement-mediated) effects were seen. A significant association was observed between lymphocytotoxic activity and circulating immune complexes and between Fibronectin positivity and cytotoxicity in PEG-precipitates of sera from three groups of patients affected with SLE, RA and Ps.A. respectively. As Fibronectin is a cryoprecipitagogue protein, possible implications of these findings are discussed.