Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Helicobacter pylori - the key behind its recognition is somewhere else

01.11.2004


The first step against infection is the detection of microorganisms capable of causing disease. This is done through the recognition of molecular structures not shared by the host, but also present in other harmless or even useful microbes. A question that has puzzled scientists for many years is how the host knows exactly against which microbes to mount an immune response. But now, in the November issue of Nature Immunology, scientists describe for the first time an ingenious bacteria-recognition mechanism by epithelial cells, which allows the distinction to be made between dangerous and innocuous bacteria.

The innate immune system is the mammals’ first line of defence as it can be mobilised almost immediately, and so has a crucial role in the prevention and/or fight of infection. Key players in the recognition of bacteria are two families of receptors: Toll-like receptors (TLR), which are normally expressed in cell membranes, and the nucleotide-binding oligomerization domain (Nod) family, found in the cytoplasm.

A simple system by which the innate immune system can differentiate between pathogenic (disease-inducing) and non-pathogenic bacteria is by selective expression of these receptors. For example, TLR and Nod receptors, specific for bacterial molecular components, are expressed in sterile areas of the body like the internal organs, the bloodstream or the cytoplasm. The logic behind this is that if bacteria are found at those locations it would be as result of an infection and consequently an immune response should be mounted. This differential receptor expression however, can not explain how in places like the digestive system, where a varied population of both pathogenic and non-pathogenic extracellular bacteria exist, we are still able to discriminate and attack only the those which can induce disease.



But now Jérôme Viala , Catherine Chaput, Ivo G. Boneca, Richard L. Ferrero and colleagues at the Institute Pasteur in Paris, the National University of Ireland and the Millenium Pharmaceuticals in Cambridge, Massachusetts, USA while working on the mechanism of recognition by epithelial cells of a pathogenic variant of Helicobacter pylori (H. pylori) which is associated with ulcers and stomach cancer, found one such mechanism of discrimination between “good” and “bad” bacteria.

The team of scientist discovered that the inflammatory reaction of epithelial cells in response to H. pylori was triggered through Nod1, a member of the Nod receptor family, localised in the cytoplasm of the epithelial cells. This was very interesting, as H. pylori does not enter the cells during infection and until now was thought to be recognised through a member of the TLR family, which are normally localised on the cell surface.

In addition, Viala , Ferrero and colleagues also show that the activation of Nod1 and subsequent inflammatory response against infection, was dependent of a bacterial syringe-like structure called type IV secretion system.

Further experiments led to the discovery that H. pylori induces an inflammatory response in gastric epithelial cells by injecting peptidoglycan, a component of the bacterial cell wall, into these cells through a type IV secretion system. The peptidoglycan is then recognised in the cytoplasm by Nod1 leading to the production of pro-inflammatory molecules, which will start an immune response against the pathogenic bacteria. It is not clear why bacteria have conserved such a mechanism if, as it seems, it can be harmful for their survival but one hypothesis is that it might have advantages not yet discovered.

These results are extremely interesting when considering the fact that while most pathogenic bacteria present this type of syringe-like secretion systems, non-pathogenic bacteria, on the other hand, generally do not have such systems of interaction. A good example is non-pathogenic variants of H. pylori which have no secretion system.

Viala , Ferrero and colleagues’s work is very important for the understanding of how the body deals with infection not only because it shows that an intracellular receptor (Nod1) can recognise an extracellular bacterium without this entering the cytoplasm, but also because it describes for the first time a bacterial recognition system that is able to discriminate between dangerous and innocuous microorganisms and mount a response only when necessary.

Piece researched and written by: Catarina Amorim (catarina.amorim@linacre.ox.ac.uk)

Catarina Amorim | alfa
Further information:
http://www.nature.com
http://www.oces.mcies.pt

More articles from Health and Medicine:

nachricht The genes are not to blame
20.07.2018 | Technische Universität München

nachricht Targeting headaches and tumors with nano-submarines
20.07.2018 | Universitätsmedizin der Johannes Gutenberg-Universität Mainz

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

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

Im Focus: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>