Swiss researchers have compiled studies that examined the connection between the so-called circadian rhythm and the immune system's defenses. The report was published last week in the journal “Trends in Immunology.” It turns out that the time of day can affect the strength of the immune response, from allergies to heart attacks.
Our biorhythm plays an important role in sleep, metabolism and other physiological processes. The researchers have found that the immune system fluctuates significantly throughout the day. This raises the question of whether it might one day be possible to optimize the immune system's response by using the human circadian clock.
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Various studies have compared the daily rhythm of immune cells under normal conditions, inflammation and disease. So it turned out that:
- Heart attacks in humans most often occur in the morning.In mice, the number of white blood cells that fight off bacteria, viruses and fungi (also called monocytes) is increased in the blood during the day. At night, monocytes in cardiac tissue are increased, resulting in reduced cardiac protection at this time of day compared to the morning.
- Parasitic infections depend on the time of day.Studies on mice, which were infected with the gastrointestinal parasite “Trichuris muris” in the morning, have shown that they can rid themselves of the worms significantly faster than mice that were infected in the evening.
- Allergic symptoms also follow a rhythm that depends on the time of dayand usually worsen between midnight and early morning. Therefore, the molecular clock may physiologically promote innate immune cell recruitment and the consequences of asthma in humans or airway inflammation in mice.
“Studying circadian rhythms in relation to innate and adaptive immunity is a great tool to understand the physiological interplay and time-dependent sequence of events in the generation of immune responses in general,” says co-author Christoph Scheiermann, an immunologist at the University of Geneva.
“The challenge is to translate our growing mechanistic understanding of circadian immunology into timed therapies for human patients.”
You can read the full report in the trade journal “Trends in Immunology” read in English.
