Featured Research

from universities, journals, and other organizations

Key Protein Keeps Chronic Infection In Check

Date:
May 10, 2009
Source:
University of California - Los Angeles
Summary:
A new study explains how a protein released by immune cells during chronic infection could restrict viruses like HIV and hepatitis C from spreading through the body.

Why is the immune system able to fight off some viruses but not others, leading to chronic, life-threatening infections like HIV and hepatitis C?

A new UCLA AIDS Institute study suggests the answer lies in a protein called interleukin-21 (IL-21), a powerful molecule released by immune cells during chronic infection. Published May 7 in the online edition of Science, the finding could explain how the immune system limits viral replication, restricting a virus's spread through the body.

The researchers looked at two types of T-cells — CD4 T-cells and CD8 T-cells — which are immune cells that play an important role in the body's response to infection. The CD4 T-cells help the immune system by producing IL-21 during chronic infection, bolstering the CD8 T-cells' ability to fight off the virus.

"The CD4 cells are the regulators — the generals, if you will," said principal investigator David Brooks, assistant professor of microbiology, immunology and molecular genetics at the David Geffen School of Medicine at UCLA. "The CD8 cells go out and kill the invaders; they're like the privates in the field."

To shed light on how CD4 T-cells help their CD8 counterparts clear viruses, the researchers infected mice with one of two strains of a virus. They knew that the first strain would generate a short-term infection and the second a chronic infection.

The scientists tested each strain on two groups of mice. One group was normal and the other was bred without IL-21 receptors.

In the normal mice, the first strain elicited a strong T-cell response that completely eliminated the virus in 10 days. The second strain caused a chronic infection that exhausted the T-cells, hampering their ability to fight the virus. The UCLA team detected high levels of IL-21 in these mice, suggesting that the protein plays a crucial role in sustaining the T-cells' ability to mount an immune response during long-lasting infection.

When the scientists infected the mice that lacked IL-21 receptors with the chronic infection strain, something curious happened. The majority of virus-fighting CD8 T-cells disappeared, preventing the immune system from containing the spread of the virus.

"IL-21 fuels CD8 T-cells' ability to function," Brooks said. "These immune cells are running a long-distance race to contain the virus before it spreads. If they don't get fed, they collapse on the track."

Without IL-21, the CD8 T-cells dwindled, even when the CD4 T-cells produced a robust response. The result indicates that the T-cells rely on IL-21 to resolve persistent infection.

"After the immune system loses CD8 T-cells, it's unable to clear the virus," Brooks said. "This tells us that IL-21 is a critical player in the body's fight against chronic infection."

The study was funded by the UCLA Center for AIDS Research, the Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research at UCLA, and the National Institutes of Health. Brooks' co-authors included Heidi Elsaesser of UCLA and Karsten Sauer of the Scripps Research Institute.


Story Source:

The above story is based on materials provided by University of California - Los Angeles. Note: Materials may be edited for content and length.


Cite This Page:

University of California - Los Angeles. "Key Protein Keeps Chronic Infection In Check." ScienceDaily. ScienceDaily, 10 May 2009. <www.sciencedaily.com/releases/2009/05/090508103842.htm>.
University of California - Los Angeles. (2009, May 10). Key Protein Keeps Chronic Infection In Check. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/2009/05/090508103842.htm
University of California - Los Angeles. "Key Protein Keeps Chronic Infection In Check." ScienceDaily. www.sciencedaily.com/releases/2009/05/090508103842.htm (accessed September 19, 2014).

Share This



More Health & Medicine News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

The Cost of Ebola

The Cost of Ebola

Reuters - Business Video Online (Sep. 18, 2014) As Sierra Leone prepares for a three-day "lockdown" in its latest bid to stem the spread of Ebola, Ciara Lee looks at the financial implications of fighting the largest ever outbreak of the disease. Video provided by Reuters
Powered by NewsLook.com
What HealthKit Bug Means For Your iOS Fitness Apps

What HealthKit Bug Means For Your iOS Fitness Apps

Newsy (Sep. 18, 2014) Apple has delayed the launch of the HealthKit app platform, citing a bug. Video provided by Newsy
Powered by NewsLook.com
U.S. Food Makers Surpass Calorie-Cutting Pledge

U.S. Food Makers Surpass Calorie-Cutting Pledge

Newsy (Sep. 18, 2014) Sixteen large food and beverage companies in the United States that committed to cut calories in their products far surpassed their target. Video provided by Newsy
Powered by NewsLook.com
Residents Vaccinated as Haiti Fights Cholera Epidemic

Residents Vaccinated as Haiti Fights Cholera Epidemic

AFP (Sep. 18, 2014) Haitians receive the second dose of the vaccine against cholera as part of the UN's vaccination campaign. Duration: 00:34 Video provided by AFP
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:
from the past week

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