Sputum processing for evaluation of inflammatory mediators

Neutrophil-dominated inflammation is prominent in the cystic fibrosis (CF) and chronic bronchitis (CB) airways. We assessed the degree of airway infla mmation by measuring the sputum concentrations of interleukin (IL)-8, myelo peroxidase (MPO), and deoxyribonucleic acid (DNA). We determined the relati onship among the concentrations of these mediators and investigated methodo logical problems that may be responsible for reported variability in measur ements. Sputa obtained from 31 patients were solubilized with phosphate-buf fered saline, dithiothreitol (DTT) (0.1 % or 1 %), or dornase alfa (0.2 mg/ mL). The sputum concentration of IL-8 and MPO was measured by enzyme-linked immunosorbent assay (ELISA), and DNA was measured using microfluorimetry. There was a significant relationship among sputum IL-8, MPO, and DNA. For M PO (means +/- SD), CF was 1,392 +/- 771 vs. CB at 75 +/- 65 mcg/mL; P < 0.0 001. For IL-8: CF was 239 +/- 154 vs. CB at 121 +/- 108 ng/mL; P= 0.0002. F or DNA, CF was 1.707 +/- 1.25 vs. CB at 0.184 +/- 0.272 mg/mL; P < 0.0001. The MPO concentration in CF sputum was approximately double after in vitro treatment with dornase alfa (P < 0.0001). There is a greater concentration of IL-8, MPC, and DNA in CF than in CB spu ta. There is a significant relationship among these inflammatory markers in sputum. DNA polymers bind myeloperoxidase in the sputum, and we speculate that treatment with dornase alfa may remove a source of MPO inhibition. (C) 2001 Wiley-Liss, Inc.