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Study Tracks Immune Cell Regeneration After Stem Cell Therapy for MS
Memory T cells reappear immediately after blood stem cell transplantation in patients with multiple sclerosis (MS), according to a study published in Science Translational Medicine. The findings help shed light as to why stem cell transplants tend to be successful, according to the research team.
Researchers from the University of Zurich came to the discovery after analyzing immune system regeneration in 27 patients with MS who received stem cell therapy at the University Hospital Zurich in Switzerland.
As part of stem cell transplantation treatment, several chemotherapies are used to destroy the immune system, including a subset of T cells that mistakenly attack the myelin sheath of nerve cells in the brain and spinal cord of people with MS. Patients subsequently receive a transplant of their own blood stem cells harvested before chemotherapy, allowing the body to build a completely new immune system without autoreactive cells.
For the study, researchers analyzed patients’ immune systems before, during, and up to 2 years after treatment to track how different types of immune cells regenerated.
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Memory T cells ensure the body remembers pathogens, enabling it to react promptly when a new infection occurs, the research team explained. The memory T cells discovered in patients immediately after stem cell transplantation did not re-form, the team reported, but actually survived chemotherapy. However, the cells appear to pose no risk for a return of MS.
“They are pre-damaged due to the chemotherapy and therefore no longer able to trigger an autoimmune reaction,” explained corresponding author Roland Martin, MD.
In the months and years following stem cell transplant, patients’ bodies gradually recreated different types of immune cells, the study showed. The thymus gland played an important role as T cells learned to distinguish foreign structures, such as viruses, from the body’s own structures.
“Adults have very little functioning tissue left in the thymus,” said Dr Martin. “But after a transplant, the organ appears to resume its function and ensures the creation of a completely new repertoire of T cells, which evidently do not trigger MS or cause it to return. Eighty percent of patients remain disease-free long-term or even forever following an autologous hematopoietic stem cell transplant.”
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