How bacteria trick our immune system

How bacteria trick our immune system

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Key bacterial defense strategy decoded

Our immune system can defend itself against pathogens through several defense mechanisms. Among other things, certain bacteria can be overridden via the so-called programmed cell death. Diarrhea pathogens of the Shigella genus can undermine this mechanism, as a recent study shows.

As part of a study, researchers from the University of Cologne found out how diarrhea bacteria of the genus Shigella manage to bypass the immune system's defense mechanisms. The results were recently presented in the renowned journal "Nature Microbiology".

Robbers and gendarmes in the organism

When bacteria enter our bodies, the immune system sends out killer cells to fight the invaders. However, various bacterial pathogens can hide from our immune system by staying inside body cells. There they can multiply unnoticed until the cell finally breaks down and releases a large number of pathogens, which can then infect other neighboring cells.

Self-destruction prevents reproduction

But the body also knows how to help itself against this strategy. Cells have some kind of self-destruction mechanism to prevent harmful effects. The cell becomes stressed by the infestation. This cellular stress situation causes the programmed cell death, the so-called apoptosis, to be triggered in order to prevent the undisturbed multiplication.

Bridged self-destruction mechanism

Apoptosis is mainly caused by the protein caspases. The team around Professor Dr. Hamid Kashkar has now been able to decipher how certain bacteria are able to prevent the cell from destroying itself. Using bacteria of the Shigella genus, the team showed that the outer membrane of the pathogen contains lipopolysaccharides (LPS). These LPS are able to bind the caspase proteins. Since the caspases are intercepted, they can no longer trigger the cell's self-destruction mechanism.

Shigella bacteria are typical pathogens of acute inflammatory diarrheal diseases. The latest research shows for the first time the molecular mechanism by which bacteria prevent the self-destruction of cells so that they can multiply undisturbed. The team around Kashkars thus decoded an important bacterial multiplication strategy. (vb)

Author and source information

This text corresponds to the specifications of the medical literature, medical guidelines and current studies and has been checked by medical doctors.

Graduate editor (FH) Volker Blasek


  • University of Cologne: Bacteria stop the cell's self-destruction program (accessed: December 28, 2019),
  • Saskia D. Günther, Melanie Fritsch, Jens M. Seeger, u.a .: Cytosolic Gram-negative bacteria prevent apoptosis by inhibition of effector caspases through lipopolysaccharide, Nature Microbiology, 2019,