Relation of alpha 2-macroglobulin and other antiproteases to the clinical features of acute pancreatitis.

alpha 2-macroglobulin is probably the most important of the antiproteases in plasma. In this study, the relationships of plasma alpha 2-macroglobulin to the clinical features of acute pancreatitis as well as to plasma levels of other antiproteases, immunoglobulins, and immunoreactive trypsin, were investigated in 55 patients with acute pancreatitis. The mean level of alpha 2-macroglobulin in 395 plasma samples from the patients was 2.12 g/liter compared with 2.41 g/liter in 29 healthy subjects and 2.93 g/liter in 17 patients with septicemia. Plasma levels were lower in 12 patients with severe pancreatitis than in 43 with mild attacks, and the lowest levels in three fatal attacks were less than half the mean of the normal range. Lowest levels were recorded at a mean time of 3 days after admission in the patients with mild attacks, at 5 days after admission in the patients with severe attacks, and 9 days after admission in those with fatal attacks. In contrast, plasma levels of the alpha 1-proteinase inhibitor antichymotrypsin and C-reactive protein increased to above normal levels during the attack, significantly more so in severe compared with mild attacks. Plasma levels of IgA, IgG, and IgM remained within the normal range or were increased. In patients with severe pancreatitis, plasma levels of immunoreactive trypsin remained elevated for longer than in those with mild attacks although there was little initial difference in the levels. These data suggest that decreasing levels of alpha 2-macroglobulin during the course of acute pancreatitis are due to a specific mechanism and unrelated, for the most part, to any generalized effect of pancreatitis on protein synthesis. The formation of rapidly cleared complexes between alpha 2-macroglobulin and active proteases is the most tenable explanation for the depletion of plasma levels, but the clinical significance of the changes remains unclear.