ASSAY OF COMPLEXED ALPHA(1)-ANTICHYMOTRYPSIN IN PLASMA

We introduce an assay to measure complexed alpha1-antichymotrypsin in human plasma. The assay works on the principle that the target protein ase cathepsin G has a very high affinity to the surface of microtiter plates, even if these surfaces are blocked with albumin and Tween 20. alpha1-Antichymotrypsin, when complexed to cathepsin G, is thus immobi lized and can be detected with specific antibodies. The mean (SD) conc entration of alpha1-antichymotrypsin in 50 healthy individuals was 1.7 3 (0.58) nmol/L. The detection limit was 0.84 nmol/L. The results of t he assay are linear to at least 14 nmol/L. We propose to use this assa y for diseases in which increased turnover of alpha1-antichymotrypsin or cathepsin G can be expected to clarify further the function of this enzyme-inhibitor system.