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: A touching story: The ancient conversation between plants, fungi and bacteria

add to favorites email to friend print save as pdf

Related Stories

Airlines on alert as eruption begins in Iceland

7 hours ago

Iceland's Bardarbunga volcano burst forth with a small eruption Saturday under the ice of Europe's largest glacier, scientists said, prompting the country to close airspace over the area.

Two Galileo satellites lose their way

10 hours ago

Two European Galileo satellites launched as part of a navigation system designed to rival GPS have failed to locate their intended orbit, launch firm Arianespace said Saturday.

Volcanic eruption begins under Iceland glacier

10 hours ago

Iceland's Bardarbunga volcano began erupting Saturday under the country's largest glacier after a week of seismic activity rattled the area with thousands of earthquakes, the country's Meteorological Office ...

Recommended for you

Wolves susceptible to yawn contagion

3 hours ago

Wolves may be susceptible to yawn contagion, according to a study published August 27, 2014 in the open-access journal PLOS ONE by Teresa Romero from The University of Tokyo, Japan, and colleagues.

Walking fish reveal how our ancestors evolved onto land

4 hours ago

About 400 million years ago a group of fish began exploring land and evolved into tetrapods – today's amphibians, reptiles, birds, and mammals. But just how these ancient fish used their fishy bodies and ...

User comments : 0