Featured Research

from universities, journals, and other organizations

Source found for immune system effects on learning, memory

Date:
October 26, 2011
Source:
Duke University
Summary:
Immune system cells of the brain, which scavenge pathogens and damaged neurons, are also key players in memory and learning, according to new research by neuroscientists. Earlier studies had shown that laboratory rats experiencing an infection at an early age have an aggressive immune response to subsequent infections, which also harms their learning and memory. In a new study, researchers have identified the source of the learning difficulties and traces it back to the immune system itself.

Immune system cells of the brain, which scavenge pathogens and damaged neurons, are also key players in memory and learning, according to new research by Duke neuroscientists.

Related Articles


Earlier studies by Staci Bilbo, an assistant professor in psychology & neuroscience, had shown that laboratory rats experiencing an infection at an early age have an aggressive immune response to subsequent infections, which also harms their learning and memory.

In a study published in the Oct. 26 Journal of Neuroscience, Bilbo's team identifies the source of the learning difficulties and traces it back to the immune system itself.

The researchers found that specialized immune system cells in the brain called microglia release a signaling molecule called Interleukin-1, or IL-1, in response to an infection. IL-1 is also crucial to normal learning and memory in the hippocampus region of the brain. But too much IL-1 can impair learning and memory in laboratory animals.

"These same molecules go up in response to any brain infection. I don't really understand why you would build a brain that way, except that there are clearly benefits in other aspects of immunity, outside the brain," Bilbo said.

In a series of experiments she has been conducting for nearly a decade, very young rats are exposed to infection and then challenged again later with a second infection consisting of only harmless, dead bacteria. The "second hit" has been shown to affect learning and memory while these rats mount a highly effective immune response.

"The microglia remember that infection and respond differently," she said. "The infection itself wasn't doing permanent damage. It was changing the immune system somehow."

The second infection doesn't even have to be directly involved with the brain. A bacterial lesion on a limb produces enough of a signal to make the glia in the brain pump out extra IL-1. "These rats handle peripheral infection really well, but at a cost to the brain," Bilbo said.

To find out what had changed in the brains of the infected rats, the team used techniques borrowed from immunology to sort out one specific cell type from brain tissue rapidly enough that they could see what the cells had been doing.

The work adds to an emerging picture of glial cells acting in the brain much the same way immune system macrophages operate elsewhere in the body -- gobbling up other cells and tearing them apart. The glia also perform a pruning function to streamline the brain's neural architecture as it matures. But some brain disorders appear to be a case of dysfunctional pruning, Bilbo said.

To test how the immune response affected memory, Bilbo's team placed all the rats in a novel environment and exposed them to a sound and a mild shock through their feet. A normal rat remembers the environment after one trial, freezing in place immediately when they enter the familiar setting a second time.

But rats exposed to infection, who tend to overproduce IL-1, stroll through the previously painful experience as if they've never seen it before, Bilbo said.

Even without experiencing the second immune challenge, the rats infected as youngsters also seem to show cognitive declines earlier than their normal control counterparts. "This is intriguingly similar to what you see in Alzheimer's. It's really kind of scary," Bilbo said.

"These findings could help us understand why some humans are more vulnerable than others to cognitive impairments from chronic infections, aging and neurodegenerative diseases such as Alzheimer's disease," said Raz Yirmiya, a professor of psychobiology at the Hebrew University of Jerusalem, who was not involved in the research. "This might also lead to new approaches toward diagnostic, preventive and therapeutic procedures for these conditions."

Any illness that triggers an immune response tends to slow a person's cognition down as their body enters a recovery mode, but these animals have some sort of permanent change in their immune response, Bilbo said. The newborn rats exposed to infections in these experiments are roughly equivalent to a third-trimester human fetus, but it would be too soon to say what parallels these findings may have in humans, she said.

Bilbo believes the early infection triggers a permanent change in gene expression, and is now looking at the role of microglial cells in addiction, and the interactions between maternal care and immune function.

This research was supported by an ARRA stimulus grant from the National Institutes of Health.


Story Source:

The above story is based on materials provided by Duke University. Note: Materials may be edited for content and length.


Journal Reference:

  1. L. L. Williamson, P. W. Sholar, R. S. Mistry, S. H. Smith, S. D. Bilbo. Microglia and Memory: Modulation by Early-Life Infection. Journal of Neuroscience, 2011; 31 (43): 15511 DOI: 10.1523/JNEUROSCI.3688-11.2011

Cite This Page:

Duke University. "Source found for immune system effects on learning, memory." ScienceDaily. ScienceDaily, 26 October 2011. <www.sciencedaily.com/releases/2011/10/111026143803.htm>.
Duke University. (2011, October 26). Source found for immune system effects on learning, memory. ScienceDaily. Retrieved December 19, 2014 from www.sciencedaily.com/releases/2011/10/111026143803.htm
Duke University. "Source found for immune system effects on learning, memory." ScienceDaily. www.sciencedaily.com/releases/2011/10/111026143803.htm (accessed December 19, 2014).

Share This


More From ScienceDaily



More Health & Medicine News

Friday, December 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

The Best Tips to Curb Holiday Carbs

The Best Tips to Curb Holiday Carbs

Buzz60 (Dec. 19, 2014) It's hard to resist those delicious but fattening carbs we all crave during the winter months, but there are some ways to stay satisfied without consuming the extra calories. Vanessa Freeman (@VanessaFreeTV) has the details. Video provided by Buzz60
Powered by NewsLook.com
Sierra Leone Bikers Spread the Message to Fight Ebola

Sierra Leone Bikers Spread the Message to Fight Ebola

AFP (Dec. 19, 2014) More than 100 motorcyclists hit the road to spread awareness messages about Ebola. Nearly 7,000 people have now died from the virus, almost all of them in west Africa, according to the World Health Organization. Video provided by AFP
Powered by NewsLook.com
Researchers Test Colombian Village With High Alzheimer's Rates

Researchers Test Colombian Village With High Alzheimer's Rates

AFP (Dec. 19, 2014) In Yarumal, a village in N. Colombia, Alzheimer's has ravaged a disproportionately large number of families. A genetic "curse" that may pave the way for research on how to treat the disease that claims a new victim every four seconds. Duration: 02:42 Video provided by AFP
Powered by NewsLook.com
Double-Amputee Becomes First To Move Two Prosthetic Arms With His Mind

Double-Amputee Becomes First To Move Two Prosthetic Arms With His Mind

Buzz60 (Dec. 19, 2014) A double-amputee makes history by becoming the first person to wear and operate two prosthetic arms using only his mind. Jen Markham has the story. Video provided by Buzz60
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Health & Medicine

Mind & Brain

Living & Well

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins