Galectin-3 reduces the severity of pneumococcal pneumonia by augmenting neutrophil function

Am J Pathol. 2008 Feb;172(2):395-405. doi: 10.2353/ajpath.2008.070870. Epub 2008 Jan 17.


The Gram-positive Streptococcus pneumoniae is the leading cause of community-acquired pneumonia worldwide, resulting in high mortality. Our in vivo studies show that galectin-3(-/-) mice develop more severe pneumonia after infection with S. pneumoniae, as demonstrated by increased bacteremia and lung damage compared to wild-type mice and that galectin-3 reduces the severity of pneumococcal pneumonia in part by augmenting neutrophil function. Specifically, we show that 1) galectin-3 directly acts as a neutrophil-activating agent and potentiates the effect of fMLP, 2) exogenous galectin-3 augments neutrophil phagocytosis of bacteria and delays neutrophil apoptosis, 3) phagocytosis of apoptotic neutrophils by galectin-3(-/-) macrophages is less efficient compared to wild type, and 4) galectin-3 demonstrates bacteriostatic properties against S. pneumoniae in vitro. Furthermore, ad-back of recombinant galectin-3 in vivo protects galectin-3-deficient mice from developing severe pneumonia. Together, these results demonstrate that galectin-3 is a key molecule in the host defense against pneumococcal infection. Therapeutic strategies designed to augment galectin-3 activity may both enhance inflammatory cell function (by directly affecting neutrophil responsiveness and prolonging neutrophil longevity) and have direct bacteriostatic activity, improving clinical outcomes after severe pneumococcal infection.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / immunology
  • Flow Cytometry
  • Galectin 3 / immunology*
  • Galectin 3 / metabolism
  • Humans
  • Macrophages / immunology
  • Macrophages / metabolism
  • Mice
  • Mice, Mutant Strains
  • Neutrophil Activation / physiology
  • Neutrophils / immunology*
  • Neutrophils / metabolism
  • Phagocytosis / immunology
  • Pneumonia, Pneumococcal / immunology*
  • Pneumonia, Pneumococcal / metabolism
  • Streptococcus pneumoniae / immunology


  • Galectin 3