Effect of immune complex-containing sera from patients with rheumatic diseases on thromboplastin activity of monocytes.

Monocytes isolated from peripheral blood of patients with various rheumatic diseases and circulating immune complexes (IC) developed a significantly higher thromboplastin (tissue factor) activity than normal cells when cultured in vitro without inducers, but normal cells responded more strongly with thromboplastin production upon stimulation with IC or phytohaemagglutinin (PHA). Sera from patients with rheumatic diseases and circulating IC induced a significant increase in the thromboplastin activity of normal monocytes. Lysozyme release from patient monocytes was significantly lower than the release from control cells when stimulated with IC. Patient sera contained higher amounts of lysozyme than normal sera, indicating lysozyme release in vivo. These data suggest that activation of monocytes in vivo by IC may take place. The increased expression of thromboplastin in monocytes/tissue macrophages may be important for the development of microvascular thrombosis and fibrin deposition seen in chronic inflammatory lesions.