Activation of the alternative complement pathway by mannose-binding lectin via a C2-bypass pathway

Microbiol Immunol. 2011 Nov;55(11):817-21. doi: 10.1111/j.1348-0421.2011.00378.x.


MBL is a serum lectin that activates the lectin pathway of the complement system. MBL forms complexes with three types of MASPs. Upon binding to Salmonella serogroup C-specific oligosaccharide, MBL activates the alternative pathway via a C2-bypass pathway without involving MASP-2, C2 or C4. We demonstrate that mannan-bound MBL activates the alternative pathway via a C2-bypass pathway that requires MASP-2 and C4. Thus, depending on the ligands to which MBL binds, there may be two distinct MBL-mediated C2-bypass pathways.

MeSH terms

  • Complement Activation*
  • Complement C2 / immunology*
  • Complement C2 / metabolism*
  • Complement C4 / immunology
  • Complement C4 / metabolism
  • Complement Pathway, Alternative / immunology*
  • Humans
  • Mannose-Binding Lectin / immunology*
  • Mannose-Binding Lectin / metabolism*
  • Mannose-Binding Protein-Associated Serine Proteases / immunology
  • Mannose-Binding Protein-Associated Serine Proteases / metabolism
  • Salmonella / immunology


  • Complement C2
  • Complement C4
  • Mannose-Binding Lectin
  • MASP2 protein, human
  • Mannose-Binding Protein-Associated Serine Proteases