Recent studies: Immune system induces fungal spores in the lungs to commit suicide

Scientists discover protective mechanism of the immune system in the lungs
It is known that patients who suffer from an unstable immune system as a result of a serious illness are more likely to develop fungal infections. An international research team has discovered how the human immune system protects itself from fungal infections. The test results can be groundbreaking to free patients from fungal infections. Researchers from the University of Göttingen were involved in the study.

With every breath we take fungal spores into the lungs. There the fungi can cause life-threatening infections. Scientists from Germany, Israel and the United States have now found that the human immune system triggers a type of suicide mechanism in the lungs that causes the fungal spores to self-destruct. The results have been published in the journal Science.

Fungal infections in a weakened immune system
The intact immune system and a healthy colonized intestinal flora succeed without difficulty in breaking down invaded fungal cells or preventing overgrowth by (existing) populations in the body. However, if the immune system is weakened by previous illnesses or if the body's own defense mechanisms are reduced by the frequent use of medication, in particular antibiotics, the fungi can spread unhindered.

Every year as many people die from invasive fungal infections worldwide as from malaria or tuberculosis. In people with a weakened immune system, the spores can enter the blood via the lungs and from there into organs including the brain. This can lead to dangerous mycoses, which often end in death. The researchers now investigated why people with an intact immune system do not get sick more often, although we inhale up to ten billion fungal spores every day, and how an intact immune system prevents the fungal spores from spreading in the body.

"We found that our human neutrophil immune cells trigger a kind of suicide mechanism in the lungs of the fungal spores," explains Prof. Dr. Gerhard Braus, Head of the Molecular Microbiology and Genetics Department at the University of Göttingen.

Triggered suicide
Fungus spores have a protective protein against fungal suicide (Bir1). "If fungal spores get into the lungs, the immune cell sends out a signal that switches off the protective protein Bir1," says Braus. "As a result, the fungal spore destroys itself." If a fungus contains several genes for Bir1 and therefore more Bir1 protein than normal, the fungal spore remains protected and does not destroy. The results of the study could form the basis for new therapeutic strategies to cure patients with fungal infections. (sb)

Original publication: Neta Shlezinger et al. Sterilizing immunity in the lung relies on targeting fungal apoptosis-like programmed cell death. Science 2017. Doi: 10.1126 / science.aan0365

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