INHIBITION OF CANDIDA-ALBICANS GROWTH BY CALPROTECTIN IN THE ABSENCE OF DIRECT-CONTACT WITH THE ORGANISMS

Calprotectin is a calcium- and zinc-binding protein that is present in neutrophil cytoplasm and abscess fluid supernatants. This protein app ears to inhibit microbial growth through competition for zinc; however , experiments to show that calprotectin can inhibit growth of microorg anisms across filter membranes have yielded conflicting results to dat e. To prevent recontamination of the filtrate by zinc in this type of experiment, Candida albicans was cultured on filter membranes placed o n top of an agarose gel containing calprotectin. In these studies, cal protectin in the gels underneath did suppress growth on top of the fil ters, an effect reversible by 30 mu M ZnSO4. In other experiments, the protein did not adhere to the organisms and later suppress their grow th. These results indicate that calprotectin inhibits C. albicans grow th in the absence of direct contact with the organisms; the findings s upport a zinc-deprivation mechanism of antimicrobial activity for this protein.