The presence of unconventional T cells may explain the link between diverse intestinal microbiomes and better outcomes after stem cell transplants. A new study, published in Science Translational Medicine, suggests that improving gut microbiome diversity could support blood cancer patients receiving stem cell transplants.
“Strategies to support intestinal microbial diversity may therefore be beneficial for transplantation patients because of a positive effect on unconventional T cell populations,” the authors note.
Current dangers of stem cell transplants
Stem cell transplants can be lifesaving for patients with blood cancers, but the procedure carries a high risk of serious side effects.
Complications such as graft-versus-host disease are often life threatening. Graft-versus-host disease is a condition that might take place following an allogeneic transplant. In graft-versus-host disease, the donated bone marrow or blood stem cells view the recipient’s body as foreign, and the donated cells or bone marrow attack the body.
Transplant recipients unfortunately still have a poor 3-year mortality rate approaching 50%.
A gut feeling
Research shows that patients with more diverse intestinal microbiomes tend to have more promising transplant outcomes. They also have lower rates of infections, relapse, and graft-versus-host disease.
To understand why, the researchers gathered 174 patients undergoing stem cell transplants. They analysed these populations using both single-cell transcriptomics and flow cytometry. Patients’ immune cells were profiled 30 and 100 days after transplantation.
The study discovered that patients with more diverse microbiomes at day 30 had higher numbers of two unconventional types of T cells. T cells are a group of white blood cells that help to manage the human immune system.
The first type were innate-like mucosal-associated invariant T cells. These are derived from vitamin B biosynthesis and have important roles in defence against bacterial and viral infections. The other type were Vd2 cells which exert anti-tumour effects.
Higher survival rates
The study linked both cell types to higher survival rates and a lower risk of acute graft-versus-host disease in the patients. Further work demonstrated that the T cells relied on metabolic products from the intestinal microbiome to persist after transplant.
The findings suggest that diverse microbiomes help maintain T cells that reduce the likelihood of dangerous transplant complications such as graft-versus-host disease.
The authors caution that larger, multicentre studies are needed to confirm the link between T cell populations and outcomes in recipients of stem cell transplants.
Written by Poppy Jayne Morgan, Front Line Genomics
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