Daylight can boost the immune system’s ability to fight infections

A breakthrough study, led by scientists at Waipapa Taumata Rau, University of Auckland, has uncovered how daylight can boost the immune system’s ability to fight infections.

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 makeup is similar to ours and the fish 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 lead researcher 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.”

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

In this new study, published in Science Immunology and led by two doctoral researchers, 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 says. “This finding paves the way for the development of drugs that target the circadian clock in neutrophils to boost their ability to fight infections.”

Current research is now focused on understanding the specific mechanisms by which light influences the neutrophil circadian clock.

A breakthrough study, led by scientists at Waipapa Taumata Rau, University of Auckland, has uncovered how daylight can boost the immune system’s ability to fight infections.

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 makeup is similar to ours and the fish 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 lead researcher 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.”

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

In this new study, published in Science Immunology and led by two doctoral researchers, 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 says. “This finding paves the way for the development of drugs that target the circadian clock in neutrophils to boost their ability to fight infections.”

Current research is now focused on understanding the specific mechanisms by which light influences the neutrophil circadian clock.