Haemophilus influenzae and the complement system

Trends Microbiol. 2010 Jun;18(6):258-65. doi: 10.1016/j.tim.2010.03.007.


The respiratory tract pathogen Haemophilus influenzae is responsible for a variety of infections in humans including septicemia, bronchitis, pneumonia, and acute otitis media. The pathogenesis of H. influenzae relies on its capacity to resist human host defenses including the complement system, and thus H. influenzae has developed several efficient strategies to circumvent complement attack. In addition to attracting specific host complement regulators directly to the bacterial surface, the capsule, lipooligosaccharides, and several outer membrane proteins contribute to resistance against complement-mediated attacks and hence increased bacterial survival. Insights into the mechanisms of complement evasion by H. influenzae are important for understanding pathogenesis and for developing vaccines and new therapies aimed at patients with, for example, chronic obstructive pulmonary disease. Here we overview current knowledge on the different mechanisms by which H. influenzae evades attack by the host complement system.

Publication types

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

MeSH terms

  • Antibodies, Bacterial / immunology
  • Antibodies, Bacterial / metabolism
  • Antigens, Surface / immunology
  • Bacterial Capsules / immunology
  • Bacterial Outer Membrane Proteins / immunology
  • Complement Activation*
  • Complement System Proteins / immunology
  • Complement System Proteins / metabolism*
  • Haemophilus Infections / immunology
  • Haemophilus Infections / microbiology*
  • Haemophilus influenzae / immunology*
  • Haemophilus influenzae / metabolism
  • Haemophilus influenzae / pathogenicity*
  • Humans
  • Immune Evasion*
  • Lipopolysaccharides / immunology
  • Mucous Membrane / immunology
  • Mucous Membrane / microbiology
  • Polysaccharides, Bacterial / immunology
  • Respiratory System / immunology
  • Respiratory System / microbiology
  • Respiratory Tract Infections / immunology
  • Respiratory Tract Infections / microbiology*


  • Antibodies, Bacterial
  • Antigens, Surface
  • Bacterial Outer Membrane Proteins
  • Lipopolysaccharides
  • Polysaccharides, Bacterial
  • lipid-linked oligosaccharides
  • Complement System Proteins