Studies on the inhibition of proteolytic enzymes by serum. III. Physiological aspects of variations in proteolytic inhibition. The concurrence of changes in fibrinogen concentration with changes in trypsin inhibition.

Variation in the inhibition of trypsin, chymotrypsin, and plasmin by serum was studied in 65 normal individuals and in 117 patients with a variety of diseases. It was shown that elevated inhibition for trypsin and chymotrypsin is associated with disease processes that bring about cellular destruction. Changes in the inhibition of trypsin and chymotrypsin were closely correlated with changes in the erythrocyte sedimentation rate and fibrinogen concentration that occur in association with disease. Intravenous typhoid vaccine was found to produce parallel changes in the inhibition of trypsin and chymotrypsin and in the fibrinogen concentration in human beings. It was concluded that the diagnostic significance of increased trypsin or chymotrypsin inhibition is the same as that of increased fibrinogen concentration; it is a common, non-specific response to a variety of pathological conditions and has no value as a specific diagnostic test. Increased plasmin inhibition occurred too infrequently to permit detailed study.