Daylight boosts immune power: Scientists uncover time-of-day link to infection defense

The discovery could lead to the development of drugs that enhance infection-fighting abilities by targeting the circadian clock in neutrophils, according to researchers at Waipapa Taumata Rau, University of Auckland.

New Delhi: A team of researchers has discovered how daylight can boost the immune system’s ability to fight infections.

The finding paves the way for development of drugs that target the circadian clock in neutrophils to boost their ability to fight infections, said the study led by scientists at Waipapa Taumata Rau, University of Auckland.

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The team focused on the most abundant immune cells in our bodies, called ‘neutrophils’, which are a type of white blood cell. These cells move quickly to the site of an infection and kill invading bacteria.

The researchers used zebrafish, a small freshwater fish, as a model organism, because its genetic make-up is similar to ours and they can be bred to have transparent bodies, making it easy to observe biological processes in real time.

“In earlier studies, we had observed that immune responses peaked in the morning, during the fish’s early active phase,” says Associate Professor Christopher Hall, from the Department of Molecular Medicine and Pathology.

“We think this represents an evolutionary response such that during daylight hours the host is more active so more likely to encounter bacterial infections,” Hall added.

However, the scientists wanted to find out how the immune response was being synchronised with daylight.

With this new study, published in Science Immunology, neutrophils were found to possess a circadian clock that alerted them to daytime, and boosted their ability to kill bacteria.

Most of our cells have circadian clocks to tell them what time of day it is in the outside world, in order to regulate the body’s activities. Light has the biggest influence on resetting these circadian clocks.

“Given that neutrophils are the first immune cells to be recruited to sites of inflammation, our discovery has very broad implications for therapeutic benefit in many inflammatory diseases,” Hall noted. Current research is now focused on understanding the specific mechanisms by which light influences the neutrophil circadian clock.