Related Experiment Videos
Deficient intracellular killing of bacteria by murine alveolar macrophages
P H Nibbering1, M T van den Barselaar, J S van de Gevel
1Department of Infectious Diseases, University Hospital, Leiden, The Netherlands.
Abstract:
Microbiologic methods were used to assess the in vitro phagocytosis and intracellular killing of various species of bacteria by freshly isolated murine peritoneal and alveolar macrophages. Peritoneal macrophages showed effective phagocytosis of opsonized Streptococcus pneumoniae, Streptococcus pyogenes, Pseudomonas aeruginosa, Staphylococcus epidermidis, and Listeria monocytogenes, and moderate ingestion of Staphylococcus aureus and Escherichia coli. Alveolar macrophages were poor in phagocytosing opsonized S. pyogenes, S. aureus, and E. coli; ingestion of S. pneumoniae, P. aeruginosa, and S. epidermidis was moderate. Peritoneal macrophages killed 40 to 80% of these bacteria intracellularly, but alveolar macrophages showed almost no intracellular killing of bacteria. To find out whether there is a correlation between the poor bactericidal activity of alveolar macrophages and the oxygen-dependent microbicidal mechanisms of these cells, we determined the uptake of oxygen and the release of superoxide anion and hydrogen peroxide by macrophages at rest and after stimulation with phorbol myristate acetate (PMA) or opsonized S. aureus. Upon exposure to these stimuli, peritoneal macrophages, but not alveolar macrophages, showed an increased uptake of oxygen and release of superoxide anion and hydrogen peroxide. Because alveolar macrophages contain surface active material (SAM), we investigated the phagocytosis and intracellular killing of bacteria and the release of hydrogen peroxide by peritoneal macrophages pretreated with SAM. The results showed reduced phagocytosis and impaired intracellular killing of S. epidermidis by these macrophages. The release of hydrogen peroxide by SAM-pretreated peritoneal macrophages upon stimulation with PMA or opsonized S. aureus was equal to that of the control peritoneal macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Murine peritoneal macrophages effectively phagocytose and kill bacteria, unlike alveolar macrophages which show poor bacterial killing. Surface active material impairs macrophage phagocytosis and killing, suggesting a role in reduced microbicidal activity.
Area of Science:
- Immunology
- Cell Biology
- Microbiology
Background:
- Macrophages are crucial immune cells involved in phagocytosis and intracellular killing of pathogens.
- Peritoneal and alveolar macrophages exhibit distinct functional characteristics and roles in host defense.
- Understanding macrophage microbicidal mechanisms is vital for developing strategies against bacterial infections.
Purpose of the Study:
- To compare the in vitro phagocytosis and intracellular killing capabilities of murine peritoneal and alveolar macrophages against various bacterial species.
- To investigate the role of oxygen-dependent microbicidal mechanisms in the bactericidal activity of these macrophages.
- To determine the effect of surface active material (SAM) on macrophage function.
Main Methods:
- Microbiologic assays were employed to assess phagocytosis and intracellular killing of opsonized bacteria by isolated macrophages.
- Oxygen uptake and the release of superoxide anion and hydrogen peroxide were measured in response to stimuli.
- Peritoneal macrophages were pretreated with SAM to evaluate its impact on phagocytosis, killing, and reactive oxygen species production.
Main Results:
- Peritoneal macrophages demonstrated effective phagocytosis and intracellular killing of multiple bacterial species, while alveolar macrophages showed significantly reduced capabilities.
- Alveolar macrophages exhibited poor phagocytosis of certain bacteria and almost no intracellular killing.
- Peritoneal macrophages showed increased oxygen uptake and reactive oxygen species release upon stimulation, a response absent in alveolar macrophages.
- SAM pretreatment of peritoneal macrophages led to reduced phagocytosis and impaired intracellular killing of Staphylococcus epidermidis.
Conclusions:
- Murine peritoneal macrophages possess superior phagocytic and bactericidal functions compared to alveolar macrophages.
- The impaired microbicidal activity of alveolar macrophages may be linked to deficient oxygen-dependent mechanisms.
- Surface active material present in alveolar macrophages can inhibit their phagocytic and bactericidal capacity, potentially contributing to their reduced effectiveness against bacteria.