MBL-mediated opsonophagocytosis of Candida albicans by human neutrophils is coupled with intracellular Dectin-1-triggered ROS production

PLoS One. 2012;7(12):e50589. doi: 10.1371/journal.pone.0050589. Epub 2012 Dec 11.

Abstract

Mannan-binding lectin (MBL), a lectin homologous to C1q, greatly facilitates C3/C4-mediated opsonophagocytosis of Candida albicans (C. albicans) by human neutrophils, and has the capacity to bind to CR1 (CD35) expressed on circulating neutrophils. The intracellular pool of neutrophil Dectin-1 plays a critical role in stimulating the reactive oxygen species (ROS) generation through recognition of β-1,3-glucan component of phagocytized zymosan or yeasts. However, little is known about whether MBL can mediate the opsonophagocytosis of Candida albicans by neutrophils independent of complement activation, and whether MBL-mediated opsonophagocytosis influence the intracellular expression of Dectin-1 and ROS production. Here we showed that the inhibited phagocytic efficiency of neutrophils as a result of blockage of Dectin-1 was compensated by exogenous MBL alone in a dose-dependent manner. Furthermore, the expressions of Dectin-1 at mRNA and intracellular protein levels were significantly up-regulated in neutrophils stimulated by MBL-pre-incubated C. albicans, while the expression of surface Dectin-1 remained almost unchanged. Nevertheless, the stimulated ROS production in neutrophils was partly and irreversibly inhibited by blockage of Dectin-1 in the presence of exogenous MBL. Confocal microscopy examination showed that intracellular Dectin-1 was recruited and co-distributed with ROS on the surface of some phagocytized yeasts. The β-1,3-glucanase digestion test further suggested that the specific recognition and binding site of human Dectin-1 is just the β-1,3-glucan moiety on the cell wall of C. albicans. These data demonstrate that MBL has an ability to mediate the opsonophagocytosis of Candida albicans by human neutrophils independent of complement activation, which is coupled with intracellular Dectin-1-triggered ROS production.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Candida albicans / immunology
  • Candida albicans / pathogenicity
  • Cell Wall / immunology
  • Cell Wall / metabolism
  • Complement Activation / immunology
  • Humans
  • Lectins, C-Type* / antagonists & inhibitors
  • Lectins, C-Type* / immunology
  • Lectins, C-Type* / metabolism
  • Mannose-Binding Lectin / administration & dosage*
  • Neutrophils / drug effects
  • Neutrophils / immunology
  • Phagocytosis / drug effects*
  • Reactive Oxygen Species / metabolism*
  • Receptors, Complement 3b / immunology
  • Receptors, Complement 3b / metabolism
  • Zymosan / metabolism
  • beta-Glucans / pharmacology

Substances

  • CLEC7A protein, human
  • CR1 protein, human
  • Lectins, C-Type
  • Mannose-Binding Lectin
  • Reactive Oxygen Species
  • Receptors, Complement 3b
  • beta-Glucans
  • Zymosan
  • beta-1,3-glucan

Grants and funding

This study is supported by the grants from Wuhan Health Bureau (NO: [2011] 99) and Hubei Health Department (NO: JX3A25), China. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.