WORLD / Health
Immune system can alter body's clock
(Xinhua)
Updated: 2007-07-17 05:17
The sudden sleepiness that accompanies the onset of many illnesses occurs
when the immune system interferes with the body's circadian clocks, Swiss
researchers report on Monday.
The immune system cytokine, TNF-alpha, induces the fatigue associated
with some infections and autoimmune diseases, according to their papers
published in the online early edition of the U.S. journal Proceedings of
the National Academy of Sciences.
Like other body rhythms, sleep cycles are controlled by a circadian
clock. Previous research implicated the cytokine TNF- alpha in causing
sleepiness, so Gionata Cavadini and colleagues from University Hospital
Zurich investigated the effects of TNF- alpha on the genes involved
regulating circadian rhythms.
In cells, the cytokine suppressed the expression of several clock genes,
an effect that was duplicated in mice treated with TNF-alpha. In
addition, mice treated with TNF-alpha showed increased rest periods
during their activities.
Further investigation revealed that TNF-alpha only suppresses those clock
genes that have a specific element known as the E-box. While it is still
unclear whether increased rest is a boon to host defense mechanisms, the
researchers note that increased fatigue decreases quality of life in many
autoimmune diseases.
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