Hemophagocytic macrophages in murine typhoid fever have an anti-inflammatory phenotype

Infect Immun. 2012 Oct;80(10):3642-9. doi: 10.1128/IAI.00656-12. Epub 2012 Aug 6.

Abstract

Histiocytes are white blood cells of the monocytic lineage and include macrophages and dendritic cells. In patients with a variety of infectious and noninfectious inflammatory disorders, histiocytes can engulf nonapoptotic leukocytes and nonsenescent erythrocytes and thus become hemophagocytes. We report here the identification and characterization of splenic hemophagocytes in a natural model of murine typhoid fever. The development of a flow-cytometric method allowed us to identify hemophagocytes based on their greater than 6N (termed 6N+) DNA content. Characterization of the 6N+ population from infected mice showed that these cells consist primarily of macrophages rather than dendritic cells and contain T lymphocytes, consistent with hemophagocytosis. Most 6N+ macrophages from Salmonella enterica serovar Typhimurium-infected mice contain intact DNA, consistent with hemophagocytosis. In contrast, most 6N+ macrophages from control mice or mice infected with a different bacterial pathogen, Yersinia pseudotuberculosis, contain damaged DNA. Finally, 6N+ splenic macrophages from S. Typhimurium-infected mice express markers consistent with an anti-inflammatory M2 activation state rather than a classical M1 activation state. We conclude that macrophages are the predominant splenic hemophagocyte in this disease model but not in Y. pseudotuberculosis-infected mice. The anti-inflammatory phenotype of hemophagocytic macrophages suggests that these cells contribute to the shift from acute to chronic infection.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Apoptosis
  • Disease Models, Animal
  • Flow Cytometry
  • Immunophenotyping
  • Inflammation / immunology*
  • Macrophages / classification
  • Macrophages / physiology*
  • Mice
  • Phagocytosis / physiology*
  • Salmonella typhimurium / immunology
  • Spleen / cytology
  • Spleen / immunology
  • Time Factors
  • Typhoid Fever / immunology
  • Typhoid Fever / pathology*
  • Yersinia pseudotuberculosis / immunology
  • Yersinia pseudotuberculosis Infections / immunology