C5a anaphylatoxin is a major regulator of activating versus inhibitory FcgammaRs in immune complex-induced lung disease

J Clin Invest. 2002 Dec;110(12):1823-30. doi: 10.1172/JCI16577.


IgG Fc receptors (FcgammaRs, especially FcgammaRIII) and complement (in particular, C5a anaphylatoxin) are critical effectors of the acute inflammatory response to immune complexes (ICs). However, it is unknown whether and how these two key components can interact with each other in vivo. We use here a mouse model of the acute pulmonary IC hypersensitivity reaction to analyze their potential interaction. FcgammaRIII and C5aR are coexpressed on alveolar macrophages (AMs), and both FcgammaRIII and C5aR mutant mice display impaired immune responses. We find that recombinant human C5a (rhC5a) can control inverse expression of various FcgammaRs, and costimulation of ICs with rhC5a results in strong enhancement of FcgammaRIII-triggered cellular activation in vitro and in vivo. Moreover, we show here that early IC-induced bioactive C5a, and its interaction with C5aR, causes induction of activating FcgammaRIII and suppression of inhibitory FcgammaRII on AMs that appears crucial for efficient cytokine production and neutrophil recruitment in lung pathology. Therefore, C5a, which is a potent chemoattractant, has a broader critical function in regulating the inhibitory/activating FcgammaRII/III receptor pair to connect complement and FcgammaR effector pathways in immune inflammation.

Publication types

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

MeSH terms

  • Animals
  • Antigen-Antibody Complex / immunology*
  • Antigen-Antibody Complex / metabolism
  • Antigens, CD / metabolism
  • Bone Marrow Cells / cytology
  • Bone Marrow Cells / metabolism
  • Bronchoalveolar Lavage Fluid / chemistry
  • Bronchoalveolar Lavage Fluid / cytology
  • Cell Separation
  • Cells, Cultured
  • Chemotaxis / physiology
  • Complement C5a / immunology*
  • Complement C5a / metabolism
  • Disease Models, Animal
  • Flow Cytometry
  • Humans
  • Immune Complex Diseases / immunology*
  • Immune Complex Diseases / metabolism
  • Lung Diseases / immunology*
  • Lung Diseases / metabolism
  • Macrophages, Alveolar / cytology
  • Macrophages, Alveolar / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Ovalbumin / metabolism
  • Receptor, Anaphylatoxin C5a
  • Receptors, Complement / metabolism
  • Receptors, IgG / immunology*
  • Receptors, IgG / metabolism
  • Recombinant Proteins / immunology
  • Recombinant Proteins / metabolism


  • Antigen-Antibody Complex
  • Antigens, CD
  • Receptor, Anaphylatoxin C5a
  • Receptors, Complement
  • Receptors, IgG
  • Recombinant Proteins
  • Complement C5a
  • Ovalbumin