Calprotectin-Mediated Zinc Chelation as a Biostatic Mechanism in Host Defence

The S-100 Ca²⁺ binding protein, calprotectin, isolated from neutrophil lysates, has been reported to exhibit zinc reversible biostatic activity in vitro . We verified these findings with C. albicans and investigated whether the growth inhibition resulted from zinc deprivation due to chelation by calprotectin. Calprotectin concentrations of 250 μg/ml significantly inhibited the growth of C. albicans . This was reversed by supplementing culture medium with 10 μM ZnSO₄. Incubation of calprotectin in culture medium for 24 h prior to inoculation significantly reduced the minimum inhibitory concentration. When this latter medium was ultrafiltered to remove the calprotectin and then inoculated with C. albicans , significant growth inhibition was still present: again it was reversed by zinc. These findings implicate zinc chelation as a novel, potentially important host defence function of an abundant neutrophil protein.