Navigation Links
Researchers discover how 'promiscuous parasites' hijack host immune cells
Date:9/21/2011

Toxoplasma gondii parasites can invade your bloodstream, break into your brain and prompt behavioral changes from recklessness to neuroticism. These highly contagious protozoa infect more than half the world's population, and most people's immune systems never purge the intruders.

Cornell researchers recently discovered how T. gondii evades our defenses by hacking immune cells, making it the first known parasite to control its host's immune system. Immunologists from the College of Veterinary Medicine published the study Sept. 8 in PLoS Pathogens, describing a forced partnership between parasite and host that challenges common conceptions of how pathogens interact with the body.

"Toxoplasma is an especially promiscuous parasite," said Eric Denkers, professor of immunology. "It infects nearly all warm-blooded species, most nucleated cell types and much of the human population. Although it lives in vital brain and muscle tissues, it usually causes no obvious reaction. Infection can seriously harm people with weak immune systems, yet most hosts experience no overt symptoms because Toxoplasma has found a way to coerce cooperation."

Famous for its manipulative powers, T. gondii has been shown to alter the brain chemistry of rodents so that they fearlessly pursue cats. Cats eat the rodents, delivering the parasites to their breeding ground in feline intestines. Similar manipulations have surfaced in human studies linking T. gondii infections to behavioral and personality shifts, schizophrenia and population variations, including cultural differences and skewed sex ratios. Denkers' study maps T. gondii's newfound ability to manipulate cells in the immune system at the molecular level.

"We found that Toxoplasma quiets its host's alarm system by blocking immune cells from producing certain cytokines, proteins that stimulate inflammation," said Denkers. "Cytokines are double-edged swords: They summon the immune system's reinforcements, but if too many accumulate they can damage the body they're trying to defend. An unregulated immune response can kill you."

When immune cells meet intruders, they release cytokines that summon more immune cells, which produce more cytokines, rapidly causing inflammation. T. gondii must allow cytokines to trigger enough of an immune response to keep its own numbers in check and ensure host survival. But too many cytokines cause an overwhelming immune response that could damage the host or eliminate the parasites.

"Toxoplasma hijacks immune cells to enforce a mutually beneficial balance," Denkers said. "Until recently we thought it walled itself away inside cells without interacting with its environment. It's now clear that the parasite actively releases messages into cells that change cell behavior."

To prove this, Barbara Butcher, a senior research associate working with Denkers, exposed immune cells in the lab to bacterial factors that typically stimulate the release of inflammatory cytokines.

"Cells infected with Toxoplasma produced no messages to trigger inflammation," Denkers said. "Our colleagues at Stanford University found that Toxoplasma produces a specific protein called ROP16 to suppress inflammatory responses. Collaborating with parasitologists at Dartmouth Medical School, we found that Toxoplasma sends ROP16 to infiltrate communication channels in immune cells, causing them to lower cytokine production.

"We are excited to have found the first non-bacterial pathogen able to exert this kind of control," said Denkers. "If Toxoplasma can do this, maybe other parasites can too. This is the first case where the whole process of immune system manipulation is close to being completely mapped out at the molecular level."

That map may help steer future investigations into how pathogens interact with hosts, unveiling the inner workings of a spectrum of infectious diseases.


'/>"/>

Contact: Joe Schwartz
Joe.Schwartz@cornell.edu
607-254-6235
Cornell University
Source:Eurekalert

Related medicine news :

1. Researchers map all the fragile sites of the yeast Saccharomyces cerevisiaes genome
2. UH Case Medical Center researchers publish promising findings for advanced cervical cancer
3. Researchers discover new way to kill pediatric brain tumors
4. Researchers Who Discovered First Genes for Stuttering will Present Findings to the National Stuttering Association
5. Researchers create drug to keep tumor growth switched off
6. Urine protein test might help diagnose kidney damage from lupus, UT Southwestern researchers find
7. GUMC researchers say flower power may reduce resistance to breast cancer drug tamoxifen
8. Clemson researchers develop hands-free texting application
9. Researchers find biomarkers in saliva for detection of early-stage pancreatic cancer
10. Researchers chart genomic map spanning over 2 dozen cancers
11. Researchers discover second protective role for tumor-suppressor
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:6/25/2016)... ... ... First Choice Emergency Room , the largest network of independent freestanding ... of its new Mesquite-Samuell Farm facility. , “We are pleased to announce Dr. ... James M. Muzzarelli, Executive Medical Director of First Choice Emergency Room. , Dr. ...
(Date:6/25/2016)... ... June 25, 2016 , ... On Friday, June 10, Van Mitchell, Secretary ... Work award to iHire in recognition of their exemplary accomplishments in worksite health promotion. ... Maryland Workplace Health & Wellness Symposium at the BWI Marriott in Linthicum Heights. iHire ...
(Date:6/24/2016)... ... June 24, 2016 , ... Those who have experienced traumatic events may suffer ... unhealthy avenues, such as drug or alcohol abuse, as a coping mechanism. To avoid ... healthy coping following a traumatic event. , Trauma sufferers tend to feel a range ...
(Date:6/24/2016)... ... 24, 2016 , ... The Pulmonary Hypertension Association (PHA) learned ... receive two significant new grants to support its work to advance research and ... by recognizing patients, medical professionals and scientists for their work in fighting pulmonary ...
(Date:6/24/2016)... ... June 24, 2016 , ... Comfort Keepers® of San Diego, CA ... the Road To Recovery® program to drive cancer patients to and from their cancer ... ensure the highest quality of life and ongoing independence. Getting to and from ...
Breaking Medicine News(10 mins):
(Date:6/24/2016)... , Belgium , June ... MKT: VNRX), today announced the appointment of Dr. ... of Directors as a Non-Executive Director, effective June ... Company,s Audit, Compensation and Nominations and Governance Committees.  ... Dr. Futcher will provide independent expertise and strategic ...
(Date:6/23/2016)... , June 23, 2016 Any dentist who ... challenges of the current process. Many of them do not ... the technical difficulties and high laboratory costs involved. And those ... offer it at such a high cost that the majority ... Dr. Parsa Zadeh , founder of Dental ...
(Date:6/23/2016)... , June 23, 2016 Research and ... Devices Medical Market Analysis 2016 - Forecast to 2022" ... The report contains up to date financial data derived ... Assessment of major trends with potential impact on the market ... of market segmentation which comprises of sub markets, regional and ...
Breaking Medicine Technology: