Pulmonary collectins in innate immunity of the lung

Cell Microbiol. 2007 Aug;9(8):1871-9. doi: 10.1111/j.1462-5822.2007.00953.x. Epub 2007 May 8.


Pulmonary collectins, hydrophilic surfactant proteins A and D (SP-A and SP-D), have been implicated in the regulation of pulmonary host defence and inflammation. SP-A and SP-D directly interact with a variety of microorganisms including bacteria and viruses, and attenuate the growth of Gram-negative bacteria, Histoplasma capsulatum and Mycoplasma pneumoniae. The collectins are thought to contribute to bacterial clearance. These lectins augment the phagocytosis of the bacteria by macrophages. SP-A serves as an opsonin and stimulates the uptake of bacteria and bacillus Calmette-Guérin through a C1q receptor- and an SP-R210-mediated processes. The collectin also stimulates FcR- and CR1-mediated phagocytosis by activating the macrophages. In addition, SP-A and SP-D directly interact with macrophages and enhance the phagocytosis of Streptococcus pneumoniae and Mycobacterium by increasing cell surface localization of the phagocytic receptors, scavenger receptor A and mannose receptor. The collectins also modulate pulmonary inflammation. SP-A and SP-D bind to cell surface receptors including Toll-like receptors, SIRPalpha and calreticulin/CD91, and attenuate or enhance inflammation in a microbial ligand-specific manner. In this article we review the immunomodulatory functions of SP-A and SP-D and their possible mechanisms in direct actions on microbes, macrophage phagocytosis and modulation of inflammation.

Publication types

  • Review

MeSH terms

  • Animals
  • Collectins / immunology*
  • Humans
  • Immunity, Innate*
  • Lung / immunology*
  • Lung / microbiology
  • Macrophages / immunology
  • Macrophages / microbiology
  • Phagocytosis
  • Pneumonia / immunology*
  • Pneumonia / microbiology
  • Pulmonary Surfactant-Associated Protein A / immunology
  • Pulmonary Surfactant-Associated Protein D / immunology


  • Collectins
  • Pulmonary Surfactant-Associated Protein A
  • Pulmonary Surfactant-Associated Protein D