Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Appetite suppressant for scavenger cells

15.11.2012
Influenza curbs part of the immune system and abets bacterial infections

When infected with influenza, the body becomes an easy target for bacteria. The flu virus alters the host’s immune system and compromises its capacity to effectively fight off bacterial infections. Now, a team of immunologists at the Helmholtz Centre for Infection Research (HZI) and cooperation partners has discovered that an immune system molecule called TLR7 is partly to blame. The molecule recognizes the viral genome – and then signals scavenger cells of the immune system to ingest fewer bacteria. The researchers published their findings in the Journal of Innate Immunity.


A scavenger cell of the immune system ingests bacteria (shown in green). During an influenza infection, the macrophages’ appetite is curbed.
Manfred Rohde/HZI

The flu is not just a seasonal illness during the winter months. In the past, there have been several flu pandemics that have claimed the lives of millions. By now, we know that during the course of the disease, many people not only get sick from the flu itself but also from bacterial pathogens like the much-feared pneumococci, the bacteria causing pneumonia.

In many cases, such “superinfections” can cause the disease to take a turn for the worse. In fact, during the Spanish Flu of 1918 to 1920, they were responsible for the majority of deaths. Why an infection with the flu virus increases the risk for superinfections is still poorly understood. Now, a group of scientists from HZI, the University Hospital of the Otto von Guericke University Magdeburg, the Essen University Hospital, the Karolinska Institute in Stockholm, Sweden, as well as further research institutions have discovered one more detail on how the virus manipulates the immune system.

They focused on TLR7, a molecule that is found in different cells of the body. TLR7 is capable of recognizing viral genetic material. As it turns out, TLR7 has an unwanted side effect, too: During a flu infection, it appears to undermine the body’s innate ability to fight off bacteria, thereby increasing the chance of a superinfection. The researchers made their discovery when they examined how superinfected mice were dealing with the bacterium Streptococcus pneumoniae, the pneumonia pathogen. The scientists colored the bacteria and measured how many of them were taken up by scavenger cells of the immune system called macrophages. The macrophages of TLR7-deficient mice had a bigger appetite and eliminated larger numbers of bacteria when infected with the flu than those of mice with the intact viral sensor. “Without TLR7, it takes longer before influenza-infected mice reach the critical point where they are no longer able to cope with the bacterial infection,” explains Prof. Dunja Bruder, head of HZI’s “Immune Regulation Group” and professor of infection immunology at the University Hospital Magdeburg.

The scientists also have an idea about how TLR7 may be curtailing the scavenger cells’ appetite: Whenever the immune system recognizes a virus, it gets other immune cells to produce a signaling substance called IFN gamma. It is already known that this substance inhibits macrophages in the lungs, causing them to eliminate fewer bacteria. As part of their study, the researchers discovered another indication of this special relationship: In TLR7-deficient animals they found smaller quantities of the IFN gamma messenger substance. The consequence might be that macrophages have a bigger appetite and that therefore bacterial entry into the bloodstream is delayed.

“Our results confirm that in the long run the flu virus suppresses the body’s ability to defend itself against bacteria. Presumably, this is an unwanted side effect of the viral infection,” speculates Dr. Stegemann-Koniszewski, the study’s first author.

“Unfortunately, it is rather difficult to intervene therapeutically. At first glance, it seems obvious to inhibit TLR7 during influenza so that the macrophages are actually able to get rid of the bacteria. However, this could have unforeseen repercussions as TLR7 and IFN gamma are both part of a tightly regulated immunological network,” explains Prof. Matthias Gunzer, former research group leader at the HZI and currently a professor at Essen University Hospital.

Even if a lack of TLR7 cannot by itself ward off a bacterial superinfection, the researchers’ findings could still lead to highly promising potential clinical applications. “Missing TLR7 delays the spread of bacteria via the bloodstream,” says Bruder. “Even if we are only talking about a relatively brief window of time, this might be our critical opportunity for keeping a seriously ill patient alive. The more time doctors have to choose the right antibiotic for their patient, the better the chances of a successful treatment.”

Original Publication
Sabine Stegemann-Koniszewski, Marcus Gereke, Sofia Orrskog, Stefan Lienenklaus, Bastian Pasche, Sophie R. Bader, Achim D. Gruber, Shizuo Akira, Siegfried Weiss, Birgitta Henriques-Normark, Dunja Bruder*, Matthias Gunzer* (* These authors contributed equally to the study.)
TLR7 contributes to the rapid progression but not to the overall fatal outcome of secondary pneumococcal disease following influenza A virus infection
Journal of Innate Immunity, 2012
DOI: 10.1159/000345112
The research group "Immune Regulation" at the HZI explores the immune system under extreme situations. These can be parallel infections with different pathogens or the erroneous attack of parts of the own body by the immune system.
The Helmholtz Centre for Infection Research (HZI):
The Helmholtz Centre for Infection Research contributes to the achievement of the goals of the Helmholtz Association of German Research Centres and to the successful implementation of the research strategy of the German Federal Government. The goal is to meet the challenges in infection research and make a contribution to public health with new strategies for the prevention and therapy of infectious diseases.

http://www.helmholtz-hzi.de

Dr. Birgit Manno | Helmholtz-Zentrum
Further information:
http://www.helmholtz-hzi.de/en/news_events/news/view/article/complete/appetite_suppressant_for_scavenger_cells/

More articles from Life Sciences:

nachricht How brains surrender to sleep
23.06.2017 | IMP - Forschungsinstitut für Molekulare Pathologie GmbH

nachricht A new technique isolates neuronal activity during memory consolidation
22.06.2017 | Spanish National Research Council (CSIC)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>