INDUCED SPUTUM CELL AND FLUID-PHASE INDEXES OF INFLAMMATION - COMPARISON OF TREATMENT WITH DITHIOTHREITOL VS PHOSPHATE-BUFFERED SALINE

Treatment of sputum with dithiothreitol (DTT) gives reliable measureme nts of cellular and fluid-phase markers of airway inflammation, We inv estigated the extent to which DTT treatment influences these measureme nts as compared with phosphate-buffered saline (PBS), Hypertonic salin e-induced sputum, collected from 20 asthmatic subjects, was examined w ithin 2 h. All portions which looked more solid (less fluid) than sali va were collected from the expectorate The selected sputum was then di vided into two portions: one treated with one volume of DTT and one vo lume of PES, the other with two volumes of PBS. The filtrates were ass essed blind for total and differential cell count, viability, and flui d-phase eosinophil cationic protein (ECP), fibrinogen, interleukin (IL )-5 and IL-8, Sputum treated with DTT compared with PBS had lower prop ortions of viable cells (median 66 versus 74%; p=0.003). In contrast, DTT-treated sputum had higher total cell counts (median 8.8 vs 2.8 x 1 0(6) mL(-1); p<0.001) and levels of ECP (median 1340 vs 584 mg.L-1; p< 0.001) The measurements were similar with respect to the proportion of eosinophils, neutrophils, lymphocytes, macrophages, and fluid-phase f ibrinogen, IL-5 and IL-8. We conclude that dithiothreitol disperses ce lls more effectively and that this might account for the higher levels of eosinophil cationic protein. Dithiothreitol may affect cell viabil ity, but the changes are not relevant with respect to cell counts. Add itionally, dithiothreitol does not seem to influence the other measure ments performed.