Properties of a product of <i>Candida albicans</i> hyphae and pseudohyphae that inhibits contact between the fungi and human neutrophils <i>in vitro</i>.

Abstract

Abstract Killed or live, growing Candida hyphae liberated substances that inhibited attachment of neutrophils to live hyphae and also impaired other functions of neutrophils. Inhibitors also blocked attachment to bacteria (group B streptococci, Escherichia coli), as judged by direct microscopic observations and indirectly by inhibition of iodination of the particles by neutrophils. Iodination of soluble nonphagocytized proteins by neutrophils stimulated with phorbol myristate acetate was also inhibited. The normal respiratory burst of oxygen consumption in neutrophils after phagocytosis of particles such as zymosan was almost completely blocked, apparently due to inhibition of attachment of neutrophils to zymosan. Chemotaxis of neutrophils in response to zymosan-activated serum was reduced below that of unstimulated control neutrophils incubated without inhibitors. Inhibited neutrophils were viable, as judged by normal morphology in electron microscopic specimens, failure to release 51Cr, and absence of staining with trypan blue during incubation with the inhibitory supernatants. Incubation of neutrophils with Candida supernatants caused release of lysozyme but not lactate dehydrogenase from the cells, further evidence that supernatants caused functional changes without impairment of neutrophil viability. Elution behavior on an anion exchange resin indicated that the inhibitor was slightly charged, consistent with its amino acid composition, which showed an excess of glutamic and aspartic acids. With purification, inhibitory activity increased as protein content of samples increased and carbohydrate content decreased compared with unpurified samples. Gel chromatography on a Biogel P-6 resin revealed that inhibitory activity was concentrated in fractions containing peptides 2500 to 3000 daltons in size, which were rich in glutamic acid and contained minimal associated carbohydrates. This inhibitory substance or substances may have profound effects on neutrophils in vivo as well as in vitro.