How circadian rhythm controls immunity discovered

Kathleen Blanchard's picture
Research finds direct link between circadian clock and immunity

We all know circadian rhythm, otherwise known as the body’s biological clock, controls a variety of metabolic functions. New research shows our internal circadian clock also governs immune function and is an important player when it comes to ability to fight disease.

The finding is significant because it shows sleep deprivation that is common, which also disrupts circadian rhythm, can make people more vulnerable to illness.

The new study, published in the Cell Press journal Immunity, found the “body clock” controls expression and function of Toll-like receptor 9 (TLR9) that senses DNA in viruses and bacteria.

The researchers found mice that were immunized when TLR9 was most active experienced enhanced immunity.


Dr. Erol Fikrig from Yale University School of Medicine said in a media release, "In our study, we were interested in investigating whether the ability of the immune system to detect a pathogen is under circadian control and whether there are timing-associated consequences for the subsequent immune response."

An important finding from the study was that mice induced to develop sepsis – an overwhelming infection that enters the bloodstream and can cause organ failure – fared better when TLR9 was most responsive.

Human patients who develop sepsis are most likely to die during 2:00 and 6:00 am. Dr. Fikrig explains patients in the intensive care unit of hospitals experience disrupted sleep patterns that could influence TLR9 expression levels and immune responses.

Fikrig says the finding opens new doors because it shows there is a direct link between circadian rhythms and immune response. The study could lead to new ways to boost immunity to protect patients who are vulnerable.

Immunity: DOI:10.1016/j.immuni.2011.12.017.
"The circadian clock controls tool-like receptor 9-mediated innate and adaptive immunity"
Silver A, et al
February 16, 2012

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