J Clin Pathol 1987;40:221-225 Serum x-thiol protease inhibitor concentrations in health and disease

SUMMARY Serum a-thiol protease inhibitor (a-TPI) concentration was assayed by radial immuno-diffusion in normal subjects, pregnant women, and in a wide variety of diseases. The normal concen-tration (448 (SD 75) mg/1) increased significantly (p < 0 001) in pregnancy to 575 (89) mg/I, and in prostatic cancer treated by oestrogens to 666 (87) mg/l. Inconsistent changes were observed in inflammatory and malignant disease and in liver disease. A temporary pronounced fall of cx-TPI was seen after burn injury, and a sustained fall after bone marrow transplantation. Crossed immuno-electrophoresis showed that the serum cx-TPI occurred in two forms, with a2 and al electrophoretic mobilities. A heavy demand on this antiprotease may result in suppression of the al form. The control of proteolysis is of fundamental importance in maintaining normal tissue function, and the antiproteases in the blood provide a major system to oppose the activity of a wide diversity of proteolytic enzymes. The most widely studied in dis-ease are the serine antiproteases, such as a,-antitrypsin (alI-AT)