title: Insoluble beta-glucan from the cell wall of Candida albicans induces immune responses of human THP-1 monocytes through Dectin-1.
abstract: BACKGROUND
  beta-glucan is the major structure component of Candida albicans (C. albicans) cell wall. It has been demonstrated that Dectin-1 as the principal C-type lectin pattern-recognition receptor (PRR) can recognize fungal beta-glucan and induce immune responses. In this study, we sought to clarify whether insoluble beta-glucan from the cell wall of C. albicans (CaIG) could induce immune responses in human THP-1 monocytes (a human acute monocytic leukemia cell line) and to determine the underlying mechanisms.
  
  
  METHODS
  Human THP-1 monocytes were challenged with CaIG in vitro. The mRNA expression of Dectin-1, Toll-like receptors (TLR2), proinflammatory cytokine (TNF-alpha) and chemokine (IL-8) was assayed by real-time reverse transcription polymerase chain reaction (RT-PCR). The secretion of TNF-a and IL-8 were measured by enzyme-linked immunosorbent assay (ELISA). H(2)O(2) release was determined by microplate fluorescent assay. Western blotting was used to analyze IkappaB-a phosphorylation and degradation.
  
  
  RESULTS
  Exposure of THP-1 monocytes to CaIG led to increased gene expression and secretion of TNF-alpha and IL-8. CaIG induced H(2)O(2) release in a time-dependent manner. CaIG hydrolyzed with zymolyase failed to induce gene expression and secretion of TNF-alpha, IL-8 and H(2)O(2) release. CaIG up-regulated the mRNA of Dectin-1, whereas the mRNA level of TLR2 was not altered. THP-1 monocytes challenged with CaIG resulted in the activation of NF-kappaB in a time-dependent manner. Dectin-1 inhibitor laminarin blocked the CaIG-induced production of TNF-alpha and H(2)O(2) in THP-1 monocytes, but no such effect was observed in pretreatment with anti-TLR2 neutralizing antibody and the LPS inhibitor (polymyxin B).
  
  
  CONCLUSIONS
  CaIG may play a role in activation of immune responses in human THP-1 cells through Dectin-1, not TLR2.
authors.affiliation: Department of Medical Mycology, Institute of Dermatology, Chinese Academy of Medical Science & Peking Union Medical College, Nanjing, China. minli08@gmail.com
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.forename: Ze-hu
authors.initials: ZH
authors.lastname: Liu
authors.forename: Qing
authors.initials: Q
authors.lastname: Chen
authors.forename: Wu-qing
authors.initials: WQ
authors.lastname: Zhou
authors.forename: Mei-wen
authors.initials: MW
authors.lastname: Yu
authors.forename: Gui-xia
authors.initials: GX
authors.lastname: Lü
authors.forename: Xue-lian
authors.initials: XL
authors.lastname: Lü
authors.forename: Yong-nian
authors.initials: YN
authors.lastname: Shen
authors.forename: Wei-da
authors.initials: WD
authors.lastname: Liu
authors.forename: Shao-xi
authors.initials: SX
authors.lastname: Wu