Daylight Found To Boost Immune Response, Study Reveals

A team of scientists from Waipapa Taumata Rau, University of Auckland, has uncovered how daylight strengthens the immune system’s ability to fight infections.

Their research further highlights the vital role of the body’s internal clock in immune defence and could pave the way for novel treatments that enhance the performance of key immune cells.

Neutrophils: The Body’s First Responders

The researchers focused their attention on neutrophils, the most abundant white blood cells in the human body.

These cells further play a crucial role in immune defence, quickly travelling to sites of infection to kill invading bacteria.

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To better understand neutrophil behaviour, the scientists turned to an unlikely helper: the zebrafish.

This small freshwater species shares a significant portion of its genetic code with humans and can be bred to have transparent bodies, allowing researchers to observe biological processes in real time.

Immune Activity Peaks In Daylight

Associate Professor Christopher Hall, from the Department of Molecular Medicine and Pathology, explained that previous studies revealed a curious trend: immune responses in zebrafish peaked during the morning, coinciding with the fish’s early active phase.

“We believe this represents an evolutionary adaptation,” said Hall. “During daylight hours, the host is more active and therefore more likely to encounter harmful bacteria.”

Uncovering The Circadian Clock In Neutrophils

While these earlier observations suggested a link between light and immune function, the precise mechanism remained unclear.

This new study, published in Science Immunology, has now revealed that neutrophils possess a circadian clock—an internal mechanism that allows them to sense the time of day.

This internal clock further appears to prime neutrophils during daylight, enhancing their ability to destroy bacteria when the host is most active.

Light As A Regulator Of Immunity

Circadian clocks exist in most of the body’s cells, helping to synchronise internal processes with external cues such as light.

Among these, light plays the most significant role in resetting the body’s biological rhythm.

“Given that neutrophils are the first immune cells to respond to inflammation, this discovery could have broad implications for the treatment of inflammatory diseases,” Hall stated.

Next Steps: Understanding The Mechanism

The research team is now working to identify the specific pathways through which daylight influences the neutrophil clock.

Their goal is to develop new therapies that harness this natural rhythm, potentially leading to drugs that optimise immune performance at specific times of day.