Alveolar Macrophage Apoptosis–associated Bacterial Killing Helps Prevent Murine Pneumonia

What is it about?

Alveolar macrophages are the resident immune cell that ingest and kill bacteria in the lung, however the exact mechanisms by which they kill bacteria are unknown. We have generated a mouse in which macrophages are resistant to a form of cell death called apoptosis. Using this mouse we show that macrophage apoptosis is required for macrophages to kill those bacteria that remain alive after the initial first-wave of bacterial killing is completed. This process requires release of reactive oxygen species form organelles in the macrophage called mitochondria that are usually used to generate energy for the cell. We show that if this form of bacterial killing is prevented mice are more susceptible to pneumonia. When mice are more susceptible to pneumonia due to resistance to macrophage apoptosis we can enhance bacterial clearance in mice to limit pneumonia with medicines used for other medical indications that increase macrophage apoptosis. We are also able to show that human macrophages use the same killing mechanism.

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