Maisonneuve-Rosemont Hospital Université de Montréal

Rejection

When the recipient’s body attacks the transplant

A rare complication of allotransplantation is rejection. It comes about because of the capacity of the recipient’s immune cells to recognize donor cells as being foreign and eliminate them, thus destroying the transplant. Rejection therefore seldom occurs in myeloablative allogeneic transplants involving identical HLA, where its incidence is estimated at less than 5%.

Certain diseases, such as bone marrow aplasia and paroxysmal nocturnal hemoglobinuria (PNH) are associated with an increased risk of rejection resulting from heavy exposure to blood products (transfusions) during the pre-transplant period, as well as from the development of anti-HLA antibodies.

There are also other risk factors, such as genetic disparity between the donor and recipient (HLA incompatibility), transplant manipulation (decreasing T cells), small transplant infusion and non-myeloablative conditioning for allogeneic transplants. The risk of rejection is higher in such cases and may be as much as 10%.