Enzyme-linked immunosorbent assays for human tissue kallikrein and analysis of immunoreactive kallikrein in the plasma by them.

Abstract

In order to study immunoreactive tissue kallikrein (TK) in human plasma, three kinds of enzyme-linked immunosorbent assay (ELISA) systems for human urinary kallikrein (HUK) were developed. All three types of TK in the plasma, i.e., active kallikrein, prokallikrein and kallikrein-alpha 1 antitrypsin (alpha 1 AT) complex, could be measured by the competitive ELISA (C-ELISA). However, the sandwich ELISA (S-ELISA) showed more strict specificity. Namely, both active and prokallikreins were able to be measured by the S-ELISA, while kallikrein-alpha 1 AT complex was hardly measurable. Measurement of this kallikrein-alpha 1 AT complex was made possible by using horseradish peroxidase (HRP)-labeled anti-alpha 1 AT IgG instead of HRP-labeled anti-HUK Fab' as the second antibody (HS-ELISA). Using these ELISAs we studied TK in plasma and the following observations were made. 1) The greater part of TK in the plasma was found in a form of a complex with alpha 1 AT. 2) The amount of free type TK was very small and the most part of this type TK in normal plasma was prokallikrein.