The importance of lysozyme for the viscosity of sputum from patients with chronic obstructive lung disease.

Addition of lysozyme (1 g/l) to sputum from patients with chronic obstructive lung disease increased the viscosity of the material significantly. The effect was prevented by addition of salt (LiCl) in the high concentration (0.25 mol/l). The sole addition of salt decreased the viscosity of native sputum. These results together with our earlier [5] studies of the interaction between the positively charged lysozyme and the negatively charged mucin molecules in model systems, indicate that lysozyme acts as a cross-linking agent in mucus by an electrostatic mechanism. Lysozyme is thus, at least partly, responsible for building up a macromolecular network giving mucus its characteristic gel-like properties.