Immune System Clocks Respond to Daylight

Immune System Clocks Respond to Daylight

While no one denies that our bodies operate on a circadian rhythm of day and night cycles, you should know about the potential effects of daylight on our immune system.  In today’s article, researchers report findings in zebrafish immune cells that could impact how we handle infections in our own bodies and maybe someday in how we treat infections.  They don’t just demonstrate higher activity of immune cells called neutrophils during daylight hours but also identify the likely mechanisms for the increased anti-infection activity.

Prior research, the type easily found in internet searches or in everyday life understanding, tells us that disrupting our normal circadian rhythms with things like shift work can increase our risk of infections.  Many propose that immune systems adapted to provide a more robust anti-infection response during the active hours of an organism’s daily life.  The potential for harnessing this immune boosting mechanism drives medical researchers to better understand what genes and pathways are involved so that one day, we can translate that understanding into therapies for human disease.

Without getting into the confusing details, abbreviations, and scientific methods, the study demonstrates how the neutrophils (one of primary immune cells in animals) become more active during daylight exposure than during darkness.  The neutrophills make more reactive oxygen species- molecules used to kill bacteria, parasites, and viruses.  During these times, the zebrafish showed a stronger response to experimentally introduced bacteria.

Going deeper into the mechanisms, they identified several genes and their protein products which changed in response to the daylight exposures.  They then connected these genes and proteins with other genes and proteins involved with producing the ROS in the neutrophils.  These findings helped demonstrate not only the larger picture of a stronger immune response but also daylight’s connections to that response.

Of course, very few of us (besides the aquarium enthusiasts) care much about the health of zebrafish.  However, as this line of research continues, we will hopefully find both simple ways to optimize this effect for humans and ways to better target therapies (supplements or pharmaceuticals) to increase our chances against infections we face daily.  In the meantime, in helping our patients restore and enjoy healthier, more abundant lives, we pay attention to their circadian rhythms and encourage appropriate amounts of exposure to sunlight.  Even without full mechanistic understanding or expensive pharmaceuticals, we can help our patients today with what we already know about the benefits of daylight and stable daily sleep/wake patterns.

 

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Original Article:

Lucia Yi Du, Pramuk Keerthisinghe, Leah Rolland, Yih Jian Sung, Hannah Darroch, Tanja Linnerz, Elina Ashimbayeva, Matthew J. Grant, Purvi M. Kakadia, Annasuya Ramachandran, Alexander Tups, Herman P. Spaink, Stefan K. Bohlander, James Cheeseman, Philip S. Crosier, Jonathan W. Astin, Guy Warman, Christopher J. Hall. A light-regulated circadian timer optimizes neutrophil bactericidal activity to boost daytime immunity. Science Immunology, 2025; 10 (107) DOI: 10.1126/sciimmunol.adn3080

 

Thanks to Science Daily:

University of Auckland. “Daytime boosts immunity, scientists find.” ScienceDaily. ScienceDaily, 23 May 2025. <www.sciencedaily.com/releases/2025/05/250523141912.htm>.

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Sanctuary Functional Medicine, under the direction of Dr Eric Potter, IFMCP MD, provides functional medicine services to Nashville, Middle Tennessee and beyond. We frequently treat patients from Kentucky, Alabama, Mississippi, Georgia, Ohio, Indiana, and more... offering the hope of healthier more abundant lives to those with chronic illness.