Hematopoietic stem cells also fight infections

The human body has an effective system of preventing and fighting infections, which is managed by white blood cells. Research by scientists from the Institute of Molecular Genetics of the CAS has shown that in addition to these cells, hematopoietic stem cells also respond to acute threats. Experts have so far confirmed this in animal models. In the future, the findings could help us understand how to optimise immune responses and prevent sepsis.

The immune system is responsible for keeping the body healthy by producing white blood cells. Immune cells such as granulocytes, B-lymphocytes, and T-lymphocytes are responsible for eliminating and removing pathogens – germs or disease-causing agents. However, scientists have recently been asking whether the body's protection is mediated solely by mature immune cells or whether other cell types may also be involved.

Acute infections that are not dealt with quickly and effectively can lead to more serious conditions, such as sepsis. Sepsis is usually prevented by activating a rapid and acute response to the infectious agent, a process known as emergency granulopoiesis. Researchers at the Institute of Molecular Genetics have been studying emergency granulopoiesis for almost a decade and have confirmed that, in addition to the essential role of immune cells, hematopoietic stem cells are also activated in response to the presence of pathogens and have elucidated the mechanisms of this activation. The results of the study were published in The EMBO Journal.

Stem cells in bone marrow change their identity when threatened

"We knew that hematopoietic stem cells had all the tools to detect germs in our bodies, but we didn't understand why and how this would affect them," explains Meritxell Alberich Jorda, head of the Department of Haemato-oncology at the Institute of Molecular Genetics of the CAS (IMG CAS). Her team's results show that hematopoietic stem cells in the bone marrow are able to change their identity and thus promote the production of granulocytes, which are necessary to destroy the external pathogen.

"Hematopoietic stem cells choose to change their fate and compromise their daily tasks to help fight infections. We were surprised that cells whose job it is to maintain hematopoiesis throughout our lives would be so flexible and able to use such sophisticated mechanisms to destroy pathogens," says Karolina Vanickova, a scientist at the IMG CAS who conducted the research.

These discoveries were made in animal models and future experiments will need to test the findings in humans. "In the future, we hope that these findings will help us understand how to optimise our immune responses and develop strategies to prevent sepsis," says Meritxell Alberich Jorda.

Contact:

Dr. Meritxell Alberich Jorda
Institute of Molecular Genetics of the Czech Academy of Sciences
alberich@img.cas.cz

Publication: https://www.embopress.org/doi/full/10.15252/embj.2023113527

(Left) In healthy conditions, hematopoietic stem cells (HSCs) reside in the bone marrow and are rather dormant (not very active). In this situation, there is a low production of granulocytes, which are a type of immune cells that circulate in our blood.

(Right) When we face an infection, the HSCs detect the alarm signals and help produce granulocytes, which are responsible for attacking and destroying the pathogen.

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