Release of myeloperoxidase and lactoferrin by PMNs in response of chitosan. Degranulation was determined using the (a, b) myeloperoxidase (MPO) and (c, d) lactoferrin assay, as described in 'Materials and Methods'. Freshly isolated polymorphonuclear neutrophils (PMNs) resuspended in RPMI 1640 supplemented with 0.1% decomplemented fetal bovine serum were treated with cytochalasin B and further incubated with the indicated concentrations of 80% deacetylated (80 M; panels a and c) or 95% deacetylated (95 M; panels b and d) chitosan for 30 minutes at 37°C. The quantity of MPO released is expressed as '% MPO', which corresponds to the ratio of the amount of MPO released/total amount of cellular MPO. The amount of lactoferrin released is expressed in ng/ml. Results are presented as mean ± standard error. The difference from the negative control is statistically significant: *P < 0.001 (Tukey-Kramer test). The negative control = PMNs incubated in Hanks' Balanced Salt Solution supplemented with 0.1% decomplemented fetal bovine serum and incubated with cytochalasin B. This figure represents the results of at least three independent experiments. fMLP, N-formyl-methionyl-leucyl-phenylalanine.