Plasma fibronectin and complement in surgical patients.

Plasma fibronectin and a fragment of the third component of complement (C3b) are both opsonins of the reticulo-endothelial system. Twenty patients undergoing uncomplicated gastro-intestinal surgery were studied. There was a significant reduction in plasma fibronectin and total haemolytic complement, but not C3, in the early postoperative period (days 1 to 3). In six surgical patients critically ill with severe sepsis both plasma fibronectin concentrations and C3 concentration were reduced significantly when compared with the early postoperative period of uncomplicated surgery. In addition, in the critically ill patients, direct evidence of complement activation was demonstrated. These studies show a transient reduction of humoral host defence mechanisms following surgery which may be permissive to bacteraemia and complement activation.