Most living things have an internal body clock which regulates when they sleep and when they wake up. A complex set of genes turning on and off, make this body clock run over roughly 24 hours, and a gene known by the acronym BMAL1 is one of the master regulators of this clock, controlling many other body clock genes and pathways.
The internal body clock being out of alignment with the environment is why we get jet lag, but more recently, scientists have also found that the body clock affects immunity too.
We've previously found that the mice were worse at fighting off the pneumococcal bacteria that cause pneumonia when they got infected during the day, compared to infection at night. But we had no idea how this was happening. Oxford University's Professor David Ray, who led the study
To find out how the body clock might be influencing the body's infection fighting cells, Gareth Kitchen, a researcher at the University of Manchester, genetically engineered mice so that they didn't have the BMAL1 clock gene.
"We were really surprised to find that these mice, which had no clock in a set of immune cells, were more resistant to bacterial pneumonia,' said Professor Ray. 'Almost everything we've learnt about the body clock so far, whether it's studies in shift workers or experiments in mice, says that disrupting the body clock makes people and animals more likely to get ill, not less."
To find out what was making these mice pneumonia-resistant, the team focussed on a key immune cell, known as a macrophage. Macrophages are specialised cells in blood and tissue that detect, engulf and ultimately destroy bacteria and other harmful organisms that enter the body.
The researchers found that deleting the BMAL1 gene in the macrophages supercharged them, making them more mobile, and better able to engulf and destroy bacteria, both in a petri-dish, and inside the mice. The clock gene deletion set of a cascade of changes which ultimately triggered a switch which made the macrophages 'skeleton' (made up of a protein called actin) less rigid, making it easier for the cells to move and engulf bacteria. Related Stories
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