Structure and biology of complement protein C3, a connecting link between innate and acquired immunity

Immunol Rev. 2001 Apr;180:35-48. doi: 10.1034/j.1600-065x.2001.1800103.x.


Complement protein C3 is a central molecule in the complement system whose activation is essential for all the important functions performed by this system. After four decades of research it is now well established that C3 functions like a double-edged sword: on the one hand it promotes phagocytosis, supports local inflammatory responses against pathogens, and instructs the adaptive immune response to select the appropriate antigens for a humoral response; on the other hand its unregulated activation leads to host cell damage. In addition, its interactions with the proteins of foreign pathogens may provide a mechanism by which these microorganisms evade complement attack. Therefore, a clear knowledge of the molecule and its interactions at the molecular level not only may allow the rational design of molecular adjuvants but may also lead to the development of complement inhibitors and new therapeutic agents against infectious diseases.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Amides / chemistry
  • Amino Acid Sequence
  • Animals
  • Autoimmunity
  • Complement Activation
  • Complement C3 / chemistry
  • Complement C3 / immunology*
  • Complement Inactivator Proteins / physiology
  • Consensus Sequence
  • Esters / chemistry
  • Evolution, Molecular
  • Graft Rejection / immunology
  • Humans
  • Immune System / physiology
  • Ligands
  • Molecular Sequence Data
  • Phagocytosis
  • Protein Binding
  • Protein Conformation
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Structure-Activity Relationship
  • Viruses / immunology


  • Amides
  • Complement C3
  • Complement Inactivator Proteins
  • Esters
  • Ligands