Release of immunoreactive human neutrophil proteinase 4, normally and in peritonitis

Abstract

A specific enzyme-linked immunoassay (ELISA) has been developed for the determination of neutrophil proteinase 4 (NP4) in human plasma/serum and tissue fluids. Comparison of the sequence for the first 20 N-terminal amino acids of NP4, neutrophil elastase and cathepsin G shows that NP4 is distinct from the other two proteases. However, all three show considerable homology. Neither elastase nor cathepsin G show any immunoreactivity when tested in the present ELISA. Normal human plasma contains about 38 μg/1 of NP4, identified as α₁ proteinase inhibitor complexes. This represents about 50% of the total amount of NP4 released in plasma. The remaining 50% is bound by α₂-macroglobulin. Blood coagulation leads to a rapid release of NP4 from the leukocytes. Peritonitis is accompanied by a pronounced release of NP4, as shown by a three-to 10-fold increase of NP4 plasma levels and by the NP4 level in peritoneal exudates, which reaches about 40 mg/1 in severe cases.

Key words:

• α₁-proteinase inhibitor
• α₂-macroglobulin
• leukocyte proteinases
• peritonitis