Wednesday, 23 December 2020

Microbiota linked to dynamics of human immune system


 

In recent years, the microbiota -- the community of bacteria and other microorganisms that live on and in the human body -- has captured the attention of scientists and the public, in part because it's become easier to study. It has been linked to many aspects of human health.

 

A multidisciplinary team from Memorial Sloan Kettering has shown for the first time that the gut microbiota directly shapes the makeup of the human immune system. Specifically, their research demonstrated that the concentration of different types of immune cells in the blood changed in relation to the presence of different bacterial strains in the gut. The results of their study, which used more than ten years of data collected from more than 2,000 patients.

 

The data that were used in the study came from people receiving allogeneic stem cell and bone marrow transplants (BMTs). After strong chemotherapy or radiation therapy is used to destroy cancerous blood cells, the patient's blood-forming system is replaced with stem cells from a donor. For the first few weeks until the donor's blood cells -- including the white blood cells that make up the immune system -- have established themselves, the patients are extremely vulnerable to infections. To protect them during this time, patients are given antibiotics.

 

But many of these antibiotics have the unwanted side effect of destroying healthy microbiota that live in the gut, allowing dangerous strains to take over. When the patient's immune system has reconstituted, the antibiotics are discontinued, and the gut microbiota slowly starts to grow back.

 

For more than ten years, members of MSK's BMT service have regularly collected and analyzed blood and fecal samples from patients throughout the BMT process. The bacterial DNA were processed by the staff at MSK's Lucille Castori Center for Microbes, Inflammation, and Cancer, which played a key role in creating the massive microbiota dataset.

 

This wider effort has been led by Marcel van den Brink, Head of the Division of Hematologic Malignancies, and a team of infectious disease specialists, BMT doctors, and scientists.

 

Previous research using samples collected from this work has looked at how the gut microbiota affects patients' health during the BMT process. A study published in February 2020 reported that having a greater diversity of species in the intestinal microbiota is associated with a lower risk of death after a BMT. It also found that having a lower diversity of microbiota before transplant resulted in a higher incidence of graft-versus-host disease, a potentially fatal complication in which the donor immune cells attack healthy tissue.

 

See:

 

Jonas Schluter, Jonathan U. Peled, Bradford P. Taylor, Kate A. Markey, Melody Smith, Ying Taur, Rene Niehus, Anna Staffas, Anqi Dai, Emily Fontana, Luigi A. Amoretti, Roberta J. Wright, Sejal Morjaria, Maly Fenelus, Melissa S. Pessin, Nelson J. Chao, Meagan Lew, Lauren Bohannon, Amy Bush, Anthony D. Sung, Tobias M. Hohl, Miguel-Angel Perales, Marcel R. M. van den Brink, Joao B. Xavier. The gut microbiota is associated with immune cell dynamics in humans. Nature, 2020; DOI: 10.1038/s41586-020-2971-8

 

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (http://www.pharmamicroresources.com/)

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