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:10/13/2017)... , ... October 13, 2017 , ... ... be giving viewers the lowdown on sciatica in a new episode of "Success ... focuses on current events and innovation and investigates each subject in-depth with passion ...
(Date:10/12/2017)... ... 2017 , ... First Healthcare Compliance (FHC), an industry leader ... range of technology and learning solutions at the 68th Annual American Healthcare Association ... held October 14–18, 2017 at the Mandalay Bay Resort in Las Vegas, Nevada. ...
(Date:10/12/2017)... (PRWEB) , ... October 12, 2017 , ... IsoComforter, Inc. ... products, announced today the introduction of an innovative new design of the shoulder pad. ... so you get maximum comfort while controlling your pain while using cold therapy. By ...
(Date:10/12/2017)... LOS ANGELES (PRWEB) , ... October 12, 2017 ... ... of Parsa Mohebi Hair Restoration, has recently contributed a medical article to the ... doctors, on cosmetictown.com. Dr. Mohebi’s article spotlights the hair transplant procedure known as ...
(Date:10/12/2017)... Mich. (PRWEB) , ... October 12, 2017 , ... ... has been named one of Michigan’s 2017 Best and Brightest in Wellness® by ... Brightest in Wellness® awards program on Friday, Oct. 20 from 7:30 a.m. to ...
Breaking Medicine News(10 mins):
(Date:9/18/2017)... Pa. and KALAMAZOO, Mich. , Sept. 18, ... , and OptiMed Specialty Pharmacy of ... to offer a strategic hub service that expedites and ... sought-after personal spirometer, Spiro PD 2.0, and wellness management ... spirometer is a medical device used to measure lung ...
(Date:9/13/2017)... 13, 2017   OrthoAtlanta has been named the ... Host Committee (AFHC) for the 2018 College Football Playoff (CFP) ... at Mercedes-Benz Stadium in Atlanta, Georgia . ... "I,m In" campaign, participating in many activities leading up to, ... ...
(Date:9/12/2017)... N.J. , Sept. 12, 2017  Consumer reviews on the ... Hearing as the number one company for hearing aids, ranking ... and fifteen other brands. ... Embrace Hearing Named #1 by Consumers For Hearing Aids ... Embrace Hearing is an online store that provides high ...
Breaking Medicine Technology: