The study focuses on the impact of “social jet lag,” a condition where people’s natural sleep-wake cycles do not match their daily schedules. This misalignment, common among night-shift workers and those with irregular sleep patterns, has been linked to weakened immunity.
The Role of Circadian Rhythms
Circadian rhythms are natural 24-hour cycles that influence biological processes. They evolved billions of years ago to help organisms adapt to the Earth’s day-night cycle. Most cells, including immune cells, have their own internal clocks.
However, scientists still don’t fully understand how these clocks work in different cell types, especially in the immune system.
Studying Zebrafish to Understand Immunity
To explore this, researchers used larval zebrafish, which are genetically similar to humans and have transparent bodies ideal for microscopic observation. The team focused on neutrophils, a type of white blood cell that quickly responds to bacterial infections.
Experiments showed that neutrophils are more effective at killing bacteria during the day. The researchers believe this may be an evolutionary adaptation, since both humans and zebrafish are more active — and more likely to encounter bacteria — in daylight hours.
Internal Clocks Help Neutrophils Fight Infection
By filming neutrophils at different times, researchers discovered these cells were more efficient at killing bacteria during the day. When scientists genetically turned off the internal clocks in the neutrophils, the cells lost this advantage.
This revealed that neutrophils have their own internal, light-sensitive clocks. These clocks act like alarms, telling the cells when it’s daytime and enhancing their bacteria-fighting power.
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