Is our immune system also a question of time?

Time of day affects the immune system's defenses
Our defenses are affected by a variety of factors. Here our biorhythm seems to play a bigger role than previously thought. Researchers from the Ludwig Maximillians University (LMU) in Munich found in a recent study that the lymphocytes, which have a significant influence on the response of the immune system, circulate through the body in a certain rhythm. So the immune response fluctuates during the day.

Depending on the time of day, the lymphocytes "stimulate the immune response, sometimes stronger, sometimes weaker," reports the LMU. This is due to the fact that they circulate through the body in a so-called circadian rhythm, which lasts about 24 hours. The results of the current study could also have an impact on vaccine administration, the researchers report. In the future, the time of day of a vaccination may be specifically adapted to the circadian rhythm of the immune response.

The immune defense is subject to considerable fluctuations during the day, which is due to the circulating lymphocytes. (Image: ag visuell /

Adaptive immune response significantly stronger at certain times
According to the researchers, the lymphocytes play an important role in the defense against pathogens such as bacteria and viruses. The analysis of the migration of lymphocytes through the body during the day makes it clear that extremely different immune reactions can be expected at different times of the day. As the LMU physiologists Dr. Christoph Scheiermann and David Druzd report in the current issue of the journal "Immunity", the adaptive immune response turns out to be significantly stronger at certain times.

In the blood during the day, in the lymph nodes at night
Using the mouse model as an example, the researchers were able to demonstrate in the current study that the time of day determines where the lymphocytes are located in the body. This has a lasting impact on the immune response. "During the day, the lymphocytes circulate heavily in the blood, and when night falls they collect in lymph nodes," reports Dr. Scheiermann. This rhythm of lymphocyte distribution has far-reaching effects, according to the doctors. This also applies to vaccinations. "The time of day of the immunization has a lasting influence on the immune response," Scheiermann continues. Depending on the time of day, the immune response was very different. (fp)

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