Complement activation by CpG in a human whole blood loop system: mechanisms and immunomodulatory effects

J Immunol. 2009 Nov 15;183(10):6724-32. doi: 10.4049/jimmunol.0902374. Epub 2009 Oct 28.

Abstract

Phosphorothioate oligodeoxynucleotides can activate complement, and experimental murine studies have revealed differential effects upon simultaneous TLR stimulation and complement activation compared with either event alone. We set out to investigate the immune stimulatory effects of CpG 2006 in fresh non-anticoagulated human blood with or without presence of active complement. We also sought to elucidate the mechanism behind complement activation upon stimulation with phosphorothioate CpG 2006. In a human blood loop system, both backbone and sequence-specific effects by CpG were counteracted by selective inhibition of C3. Furthermore, DNA backbone-mediated CD40 and CD83 expression on monocytes and sequence-specific IL-6 and TNF production were reduced by complement inhibition. CpG-induced complement activation occurred via either the classical or the alternative pathway and deposits of both IgM and properdin, two activators of complement, were detected on CpG after incubation with EDTA plasma. Quartz crystal microbalance with dissipation monitoring demonstrated alternative pathway convertase build-up onto CpG as a likely pathway to initiate and sustain complement activation. Specific inhibition of C3 suppressed CpG 2006 uptake into monocytes indicating that C3 fragments are involved in CpG internalization. The interplay between complement and TLR9 signaling demonstrated herein warrants further investigation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adjuvants, Immunologic / pharmacology*
  • Antigens, CD / immunology
  • Antigens, CD / metabolism
  • CD40 Antigens / immunology
  • CD40 Antigens / metabolism
  • Complement Activation / drug effects*
  • Complement Activation / immunology
  • Complement Pathway, Alternative / drug effects
  • Complement Pathway, Alternative / immunology
  • Complement System Proteins / drug effects
  • Complement System Proteins / immunology
  • Complement System Proteins / metabolism
  • Cytokines / drug effects
  • Cytokines / immunology*
  • Cytokines / metabolism
  • Humans
  • Immunoglobulin M / immunology
  • Immunoglobulin M / metabolism
  • Immunoglobulins / immunology
  • Immunoglobulins / metabolism
  • Interleukin-6 / immunology
  • Interleukin-6 / metabolism
  • Membrane Glycoproteins / immunology
  • Membrane Glycoproteins / metabolism
  • Monocytes / cytology
  • Monocytes / drug effects
  • Monocytes / immunology*
  • Monocytes / metabolism
  • Oligodeoxyribonucleotides / pharmacology*
  • Peptides, Cyclic / pharmacology
  • Phosphorothioate Oligonucleotides / pharmacology*
  • Properdin / immunology
  • Properdin / metabolism
  • Tumor Necrosis Factor-alpha / immunology
  • Tumor Necrosis Factor-alpha / metabolism

Substances

  • Adjuvants, Immunologic
  • Antigens, CD
  • CD40 Antigens
  • CD83 antigen
  • CPG-oligonucleotide
  • Cytokines
  • IL6 protein, human
  • Immunoglobulin M
  • Immunoglobulins
  • Interleukin-6
  • Membrane Glycoproteins
  • Oligodeoxyribonucleotides
  • Peptides, Cyclic
  • Phosphorothioate Oligonucleotides
  • Tumor Necrosis Factor-alpha
  • compstatin
  • Properdin
  • Complement System Proteins