Immunity stronger at night than during day

Dec 14, 2008

The immune system's battle against invading bacteria reaches its peak activity at night and is lowest during the day.

Experiments with the laboratory model organism, Drosophila melanogaster, reveal that the specific immune response known as phagocytosis oscillates with the body's circadian rhythm, according to Stanford researchers who presented their findings at the American Society for Cell Biology (ASCB) 48th Annual Meeting, Dec. 13-17, 2008 in San Francisco.

"These results suggest that immunity is stronger at night, consistent with the hypothesis that circadian proteins upregulate restorative functions such as specific immune responses during sleep, when animals are not engaged in metabolically costly activities," explains Mimi Shirasu-Hiza of Stanford University.

Shirasu-Hiza and her colleague David Schneider turned to the fruit fly, Drosophila melanogaster, as the model system to help them define the relationship between innate immunity and circadian rhythm, which is the oscillating protein clock or timing mechanism in cells.

Circadian rhythm paces the human body as well as the fruit fly through its days and nights, setting the rest/activity cycle that cues when to eat, sleep and mate over a 24-hour cycle.

In phagocytosis, the innate immune response targeted by the Stanford researchers, specific immune cells engulf and destroy the bacteria invading the body.

In humans, immune responses such as phagocytosis not only are involved in clearing bacterial infection but also are implicated in a growing number of human diseases, including cancer and neurodegenerative disorders.

In previous experiments, the researchers noted that flies sick with bacterial infection lost their circadian rhythm and that flies lacking circadian rhythm were highly susceptible to infection.

The flies were infected with two different bacterial pathogens, Listeria monocytogenes and Streptococcus pneumoniae.

To determine whether circadian proteins regulate immunity, the scientists infected flies with these pathogens at different times of day or night.

The flies infected at night had a better chance of surviving than did the flies infected during the day. In addition, the researchers also detected low phagocytic activity in some flies with a mutated circadian clock.

Source: American Society for Cell Biology

Explore further: In hot and cold water: The private lives of 'Hoff' crabs revealed

add to favorites email to friend print save as pdf

Related Stories

Evolving robot brains

10 hours ago

Researchers are using the principles of Darwinian evolution to develop robot brains that can navigate mazes, identify and catch falling objects, and work as a group to determine in which order they should ...

Facebook fends off telecom firms' complaints

10 hours ago

Facebook founder Mark Zuckerberg fended off complaints on Monday that the hugely popular social network was getting a free ride out of telecom operators who host its service on smartphones.

Scientists find clues to cancer drug failure

10 hours ago

Cancer patients fear the possibility that one day their cells might start rendering many different chemotherapy regimens ineffective. This phenomenon, called multidrug resistance, leads to tumors that defy ...

Glass coating improves battery performance

11 hours ago

Lithium-sulfur batteries have been a hot topic in battery research because of their ability to produce up to 10 times more energy than conventional batteries, which means they hold great promise for applications ...

Recommended for you

Sizing up cells: Study finds possible regulator of growth

9 hours ago

Modern biology has attained deep knowledge of how cells work, but the mechanisms by which cellular structures assemble and grow to the right size largely remain a mystery. Now, Princeton University researchers ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.