A recent investigation conducted by Christopher Hall, a researcher at the University of Auckland, alongside his collaborators, centered on neutrophils, a specific class of white blood cells integral to the body’s defense against bacterial pathogens.
Yi Du et al. identified a light-responsive cell-intrinsic timer that controls time-of-day variations in antibacterial activity. Image credit: Summerstock.
The scientific team utilized zebrafish as their experimental model. This choice was motivated by the fish’s genetic similarities to humans and their characteristic transparency, which facilitates real-time observation of physiological processes.
“Previous research had indicated that immune system responses reached their apex during the morning, coinciding with the initial active period for these fish,” stated Dr. Hall.
“Our hypothesis is that this phenomenon represents an evolutionary adaptation, whereby the host exhibits heightened activity during daylight hours, thereby increasing the probability of exposure to bacterial infections.”
Nevertheless, the investigators were keen to ascertain the precise mechanisms by which the immune response became synchronized with diurnal cycles.
The current study revealed that neutrophils possess an intrinsic circadian clock, which not only signals daytime but also enhances their capacity for bacterial eradication.
The majority of our cellular components are equipped with circadian clocks that dictate the time of day, thereby orchestrating various bodily functions.
External light sources exert the most profound influence on the recalibration of these biological clocks.
“Considering that neutrophils are among the initial immune cells mobilized to sites of inflammation, our discovery holds substantial implications for therapeutic interventions in a wide array of inflammatory conditions,” remarked Dr. Hall.
“This breakthrough opens avenues for the development of pharmaceutical agents designed to modulate the circadian clock within neutrophils, thereby augmenting their efficacy in combating infections.”
The findings from this research endeavor have been published in the esteemed journal Science Immunology.
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Lucia Yi Du et al. 2025. A light-regulated circadian timer optimizes neutrophil bactericidal activity to boost daytime immunity. Science Immunology 10 (107); doi: 10.1126/sciimmunol.adn3080
