A one-step sandwich enzyme immunoassay using monoclonal antibodies for detection of human neutrophil elastase

A one-step sandwich enzyme immunoassay (EIA) system for human neutrophil elastase (hNE) was established with monoclonal antibodies to quantify the hNE levels in body fluids. hNE in samples was allowed to simultaneously react with both solid-phase and peroxidase-labeled antibodies. The EIA system required 75 min for the reactions (immunoreaction for 60 min and color reaction for 15 min), and the sensitivity for standard hNE was 0.2 ng/ml (4 pg/assay, 2 S.D.s above the zero point). Linearity was obtained from 0.2 400 ng/ml (4 pg 8 ng/assay). The EIA system recognized free and α₁-proteinase inhibitor complexed forms of hNE, whereas the α₂-macroglobulin-complexed form was not detected. The hNE levels in the synovial fluids from patients with rheumatoid arthritis were higher than those in the fluids of those with osteoarthritis or traumatic arthritis. Saliva from patients with periodontal diseases also contained significantly increased amounts of hNE compared with that of healthy subjects.