Correlation Among Complement Activation, Protease Inhibitors, and Clinical Course in Acute Pancreatitis in Man

Abstract

Changes in complement levels and protease inhibitors were measured in plasma/ serum and peritoneal fluid during 15 attacks of acute pancreatitis. The abnormalities found in the complement system and the protease inhibitors were most pronounced in severe attacks, especially in the peritoneal fluid. Depressed levels of Clq, C3, properdin, and factor I were found in blood on admission in severe attacks. A decrease during the first days of illness was found for Clq, C3, C4, properdin, factor I, and factor H levels in blood. There was a discrepancy between the low Clq and the high Clr and Cls levels in blood. Complexes of inactivator and factor B conversion products were found, especially in the peritoneal fluid, denoting an activation of the complement system. High levels of trypsin in complex with α₁ protease inhibitor were found, both in blood and in peritoneal fluid, denoting the liberation of active trypsin in acute pancreatitis. The levels of the functional α₂-macroglobulin were low, especially in the peritoneal fluid. It is concluded that both classical and alternative complement activation take place in acute pancreatitis, starting in the peritoneal cavity. The magnitude of activation depends on the severity of the disease. Trypsin-induced activation of complement components may explain some of these changes.

Key Words:

• l-inactivator
• complement activation
• pancreatitis
• protease inhibitors
• trypsin