Mechanisms of Attachment of Neutrophils to Candida albicans Pseudohyphae in the Absence of Serum, and of Subsequent Damage to Pseudohyphae by Microbicidal Processes of Neutrophils In Vitro

Abstract

A B S T R A C T Mechanisms were studied that might explain the attachment and damage to Candida albicans pseudohyphae by neutrophils in the absence of serum. Attachment of neutrophils to pseudo hyphae was inhibited by Candida mannans (1-10 mg/ml), but not by mannose, dextran, chitin, conconavalin A, or highly charged polyamino acids. Contact was also inhibited by pretreatment of Candida before incubation with neutrophils with chymotrypsin, but not trypsin or several inhibitors of proteases. Similar results were obtained with pretreatment of neutrophils, except that trypsin was inhibitory. When pseudohyphae were killed with ultraviolet light, proteinpolysaccharide complexes of mol wt <10,000 were released which appeared to bind to the surfaces of neutrophils and inhibit contact between neutrophils and Candida, as well as other fungi.Damage to Candida by neutrophils was inhibited by agents known to act on neutrophil oxidative microbicidal mechanisms, including sodium cyanide, sodium azide, catalase, superoxide dismutase, and 1, 4 diazobicyclo (2, 2, 2) octane, a singlet oxygen quencher. Neutrophils from a patient with chronic granulomatous disease did not damage Candida at all. However, the hydroxyl radical scavengers mannitol and benzoate were not inhibitory. Cationic proteins and lactoferrin also did not appear to play a major role in this system. Low concentrations of lysozyme which Preliminary findings were presented in part at the Annual

Damage to Candida albicans Hyphae and Pseudohyphae by the Myeloperoxidase System and Oxidative Products of Neutrophil Metabolism In Vitro

“…In the presence ofmyeloperoxi- INTRODUCTION In previous studies in our laboratory, it was established that pseudohyphal and hyphal forms of Candida albicans could be damaged and probably killed by nonphagocytic mechanisms of human neutrophils in vitro (1). Experimental data indicated that Candida hyphae, though too large to be ingested, activated microbicidal mechanisms of neutrophils and caused specific release of neutrophil lysosomal enzymes (2). Indirect evidence supported the impression that oxidative mechanisms ofneutrophils were more important hian nonoxidative mechanisms in damaging hyphae.…”

“…In preliminary experiments, neutrophils from a single patient with chronic granulomatous disease failed to damage Candida hyphae (2). Moreover, inhibitors of potential nonoxidative microbicidal mechanisms, such as cationic proteins and lactoferrin, failed to alter damage to hyphae by normal neutrophils (2).…”

“…Furthermore, damage to Candida by neutrophils was inhibited by agents known to affect neutrophil oxidative microbicidal mechanisms. These include sodium cyanide and sodium azide (inhibitors of myeloperoxidase and of cell respiration in general), catalase (which degrades hydrogen peroxide), superoxide dismutase (which decomposes superoxide anion), and 1,4-diazobicyclo[2.2.2]octane (DABCO),1 a singlet oxygen quencher (2). In chronic granulomatous disease, neutrophils are deficient in microbicidal function because they are unable to generate normal amounts of hydrogen peroxide and other oxidative intermediates (3,4).…”

“…In chronic granulomatous disease, neutrophils are deficient in microbicidal function because they are unable to generate normal amounts of hydrogen peroxide and other oxidative intermediates (3,4). In preliminary experiments, neutrophils from a single patient with chronic granulomatous disease failed to damage Candida hyphae (2). Moreover, inhibitors of potential nonoxidative microbicidal mechanisms, such as cationic proteins and lactoferrin, failed to alter damage to hyphae by normal neutrophils (2).…”

“…Although oxidative intermediates appeared to be of critical importance in damage to Candida hyphae in vitro, neither the results with chronic granulomatous disease neutrophils nor the data obtained with inhibitors indicated which oxidative intermediates or pathways might be directly responsible for hyphal damage (1,2). For example, in addition to inhibition of myeloperoxidase, sodium azide and sodium cyanide may inhibit cell respiration (5) generally, whereas sodium azide in high concentrations acts as a quencher of singlet oxygen (6).…”