Maisonneuve-Rosemont Hospital Université de Montréal

Limitation of complications

Hope for counteracting GVH

In graft-versus-host disease (GVH), the T lymphocytes contained in the transplant from a donor attack the body of the recipient, which cannot mount a defence since it is in a state of immune deficiency.

Until very recently, isolating the lymphocytes responsible for this reaction within the transplant was problematic. However, Dr. Denis Claude Roy and his team at MRH have developed a photodynamic process that eliminates the reactive T lymphocytes within the transplant. Stem cells from the donor and the lymphocytes contained within the transplant are put together with cells from the patient. A colourant that binds to anti-recipient reactive T lymphocytes is added to this cellular culture. The future transplant is then exposed to light, which transforms the colourant into a substance that is toxic for the anti-recipient reactive T lymphocytes, but safe for other cells.

The reactive T lymphocytes can then no longer function, which reduces the risk of a graft-versus-host reaction. As lymphocytes are also important in defending the body against viruses, such manipulation of the transplant is associated with an increased risk of a secondary viral infection, and preventive treatment to limit the complications related to infectious diseases will be needed.

Since it is now possible to isolate the T lymphocytes in the transplant and inactivate them, MRH researchers have posed the hypothesis that the process would enable transplants from only partially compatible donors to be performed.