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

A groundbreaking study, led by scientists at the University of Auckland (New Zealand), has discovered 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, a type of white blood cell. These cells quickly move to the site of an infection and eliminate invading bacteria. The researchers used zebrafish, a small freshwater fish, as a model organism because their genetic makeup is similar to ours and they can be bred to have transparent bodies, making it easier to observe biological processes in real time.

This discovery paves the way for the development of new drugs

“In previous studies, we had observed that immune responses peaked in the morning, during the fish's early active phase,” explains lead researcher Associate Professor Christopher Hall of the Department of Molecular Medicine and Pathology. “We believe this represents an evolutionary response: during daylight hours, the host is more active and therefore more likely to suffer from bacterial infections.”

However, scientists wanted to discover how the immune response synchronizes with daylight. In this new study, published in the journal Science Immunology, they discovered that neutrophils possess a circadian clock that alerts them to daylight and increases their ability to kill bacteria.

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“Because neutrophils are the first immune cells recruited to sites of inflammation, our discovery has broad implications for therapeutic benefit in many inflammatory diseases,” Hall says. “This finding paves the way for the development of drugs that target neutrophils’ circadian clock to enhance their ability to fight infections.”