Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Parasites that live inside cells use loophole to thwart immune system

04.11.2008
A study from St. Jude scientists shows how microbes can block nitric oxide production—a chemical key to the immune system -- and offers hints for fighting bacteria

St. Jude Children's Research Hospital scientists have discovered a mechanism by which intracellular pathogens can shut down one of the body's key chemical weapons against them: nitric oxide. The researchers found that the microbes block nitric oxide production by subverting the biochemical machinery used by immune cells called macrophages to produce the chemical.

Macrophages are the battle tanks of the immune system, attacking and consuming bacteria and parasites, shredding them with enzymes and poisoning them with nitric oxide. However, some pathogens, such as those that cause tuberculosis and toxoplasmosis, have evolved to live and proliferate within macrophages themselves. To do so, these intracellular pathogens deploy an arsenal of weapons to avoid and counterattack macrophage's own weapons.

In their study that appears in the advance online publication of the journal Nature Immunology, St. Jude researchers focused on the role the microbes play in activating the macrophages to make an enzyme called arginase. The arginase enzyme occurs naturally in macrophages, but is normally only expressed under very specific circumstances, including when macrophages might make too much nitric oxide.

"Although the findings are basic, they suggest that it might be feasible to develop drugs to block such pathogens' biochemical subversion, restoring nitric oxide production and empowering macrophages to attack the invaders," said Peter Murray, Ph.D., an associate member of the St. Jude departments of Infectious Diseases and Immunology.

Previously other researchers had shown that pre-activating arginase in macrophages grown in the culture dishes can block nitric oxide production in macrophages by breaking down the chemical arginine, which the macrophages need to make nitric oxide. "However, no one had really explored the possibility that intracellular pathogens could directly exploit arginase-activation as a defense until now," said Murray, the paper's senior author.

To discover whether pathogens could be induced to mount such a defense in macrophages, the St. Jude team studied the arginase-inducing activity of the microorganisms that cause tuberculosis and toxoplasmosis, as well as a relative of tuberculosis, Mycobacterium bovis, that is used as a live vaccine.

Studies in macrophages in the culture dish and in mice demonstrated that these microbes did trigger arginase production and that this triggering suppressed nitric oxide production in macrophages. The researchers also traced the biochemical mechanism by which the organisms triggered arginase—finding that the microbes hijack the machinery by which the macrophages recognize invading pathogens.

Also working with mice, the researchers tested whether shutting down arginase might enhance the ability to battle tuberculosis. They found that mice genetically engineered to lack arginase only in their macrophages showed superior resistance to tuberculosis and toxoplasmosis.

"Our findings reveal that these pathogens have evolved to exploit a biological loophole in the immune system," Murray said. "This discovery offers two important insights. It reaffirms the notion that pathogens have an incredibly diverse way of manipulating their hosts. And it reveals a new pathway by which a pathogen can induce an enzyme that is normally not present in those macrophages and use the induction of that enzyme to its advantage."

Murray emphasized that the findings are basic, and that the researchers can only speculate about possible clinical implications at the moment. "However, we believe it could be possible to develop targeted drugs to specifically inhibit pathogens' ability to induce arginase in macrophages," he said. Such drugs might suppress such diseases as tuberculosis and toxoplasmosis by increasing the ability of macrophages to make nitric oxide. Researchers believe that the drugs could work in combination with existing treatments for tuberculosis and parasites—dealing the diseases a therapeutic one-two punch.

Summer Freeman | EurekAlert!
Further information:
http://www.stjude.org

More articles from Life Sciences:

nachricht Researchers develop eco-friendly, 4-in-1 catalyst
25.04.2017 | Brown University

nachricht Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017
25.04.2017 | Laser Zentrum Hannover e.V.

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

NASA's Fermi catches gamma-ray flashes from tropical storms

25.04.2017 | Physics and Astronomy

Researchers invent process to make sustainable rubber, plastics

25.04.2017 | Materials Sciences

Transfecting cells gently – the LZH presents a GNOME prototype at the Labvolution 2017

25.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>