Insights into how the biological clock and time of day influence immune responses are revealed in a mouse study published in Nature Communications. Understanding the effect of the interplay between circadian rhythms and 24-hour day-night cycles may help inform drug-targeting strategies to alleviate autoimmune disease.
The circadian rhythm describes the biological clock that modulates the activities of life forms on Earth according to a 24-hour cycle. Maintaining a good circadian rhythm is generally believed to lead to good health for humans, and disrupting the circadian rhythm (for example, working night shifts) has been associated with immune diseases such as multiple sclerosis; however, the underlying molecular links have been unclear.
Kingston Mills, Annie Curtis and colleagues show that the induction of immune responses and regulation of autoimmunity are affected by the time-of-the-day when the immunization is performed. Using mice as the model organism, they show that a master circadian gene, BMAL1, is responsible for sensing and acting on the time-of-the-day cues to suppress inflammation. Loss of BMAL1, or immunization at midday instead of midnight, causes more severe experimental autoimmune encephalomyelitis, a mouse model of multiple sclerosis.
Although further investigations are needed to understand how to precisely modulate circadian rhythm or time-of-the-day cues for beneficial immunity, the findings in this article serve well to remind us the importance of ‘keeping the time’ when dealing with the immune system.