How Daylight Enhances the Immune System's Infection-Fighting Power

Recent research from the University of Auckland has revealed that exposure to daylight can significantly improve the immune system’s capacity to combat infections. Scientists concentrated on neutrophils, the most abundant type of white blood cells in the body, which are essential for quickly targeting and destroying bacteria at infection sites.

Using zebrafish as a model organism—chosen for their genetic similarities to humans and their transparent bodies that facilitate real-time observation—the team discovered notable variations in immune response tied to the time of day. Earlier studies indicated that immune responses peak in the morning during the fish’s active phase, suggesting an evolutionary adaptation to increased activity during daylight hours that raises the likelihood of encountering bacteria.

Further investigations led by doctoral researchers uncovered that neutrophils possess a circadian clock—an internal timer synchronized with the external light-dark cycle—that enhances their ability to fight bacteria during the day. Light plays a critical role in resetting these circadian clocks across various cells.

Associate Professor Christopher Hall explained that because neutrophils are the first immune cells to arrive at inflammation sites, understanding their circadian regulation could have broad implications. This insight paves the way for developing therapies targeting the circadian mechanisms within neutrophils to boost their infection-fighting efficiency.

Future research aims to delve deeper into the specific mechanisms through which light influences the neutrophil circadian clock, potentially leading to innovative treatments for inflammatory and infectious diseases.

Source: https://medicalxpress.com/news/2025-05-daylight-boost-immune-ability-infections.html