A new study published this week in the journal Immunity suggests that when our body clock is disrupted, it weakens the immune system. We already know that the circadian clock is a finely tuned genetic mechanism that regulates body functions that follow a 24-hour cycle, such as sleep patterns and metabolism. Now, researchers at Yale School of Medicine in the US show it may also influence our vulnerability to disease through its effect on the immune system.
Using lab mice, senior author Dr Erol Fikrig, a professor of epidemiology and microbial pathogenesis at Yale, and colleagues, found that the circadian clock controls the activity of Toll-like receptor 9 (TLR-9), an important gene in the immune system that reacts to the presence of DNA from bacteria and viruses.
They found that the mice’s immune system response to vaccination, and their ability to resist infection, were highest when expression levels of TLR-9 were at their highest point.
The findings suggest it could be the same for humans: disruption of our body clock makes us more vulnerable to illness. For example, jet lag could be a cause of illness. And there may be good and bad times of the day to get vaccinated.
The researchers also think the study could be clinically significant because we know that septic human patients are more likely to die between 2 and 6 am.
Fikrig, who is also an investigator for the Howard Hughes Medical Institute, told the press that:
“Sleep patterns of patients in intensive care are often disrupted because of the noise and prolonged exposure to artificial light.”
“It will be important to investigate how these factors influence immune system response,” he added.
Fikrig believes we know intuitively that when our sleep pattern is disturbed, we are more likely to fall ill.
“It does appear that disruptions of the circadian clock influence our susceptibility to pathogens,” he said.
He said the study not only uncovers a new, direct molecular link between the body clock and the immune system, but it offers a new point of view in biology about how the immune system works.
This could have important implications for how we prevent and treat disease: for instance it could lead to new therapies designed to optimize the immune response to protect patients when they are most vulnerable.
Written by Catharine Paddock PhD