Establishment of radioimmunoassay for human neutrophil peptides and their increases in plasma and neutrophil in infection.

Neutrophil peptide, also called defensin, is an antimicrobial peptide localized in azurophil granules in neutrophils. Using a synthetic human neutrophil peptide-1 (HNP-1), we prepared an antiserum against the peptide and established a highly sensitive radioimmunoassay (RIA). This RIA equally recognized HNP-1, -2, and -3 on a molar basis. Analyses of leukocyte and blood extracts obtained from normal individuals and patients with bacterial infection by reverse-phase high-performance liquid chromatography coupled with the RIA showed that the antiserum specifically detected HNP molecules. Concentrations of HNP 1-3 in total in normal human blood and plasma are 13.2 +/- 1.4 (mean +/- SEM) ng/mu 1 and 403.8 +/- 38.9 pg/mu 1, respectively. The values increased in infection and returned to within the normal levels after the recovery of the disorder. Granulocyte colony-stimulating factor (G-CSF) increased the plasma and blood concentrations of HNP 1-3. The RIA established here provides a useful tool to elucidate the pathophysiological significance of HNP and to evaluate the neutrophil functions in infection and inflammation.