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 Laser activated gold pyramids could deliver drugs, DNA into cells without harm
24.03.2017 | Harvard John A. Paulson School of Engineering and Applied Sciences

nachricht What does congenital Zika syndrome look like?
24.03.2017 | University of California - San Diego

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: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Argon is not the 'dope' for metallic hydrogen

24.03.2017 | Materials Sciences

Astronomers find unexpected, dust-obscured star formation in distant galaxy

24.03.2017 | Physics and Astronomy

Gravitational wave kicks monster black hole out of galactic core

24.03.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>