Many patients in need of haematopoietic stem cell transplantation do not reach transplantation. An analysis on all unrelated donor searches for Dutch patients performed between 1987 and 2000 showed... Show moreMany patients in need of haematopoietic stem cell transplantation do not reach transplantation. An analysis on all unrelated donor searches for Dutch patients performed between 1987 and 2000 showed a significant decrease of the percentage of patients for whom no donor was available. Between 1996 and 2000, the efficiency of the donor search and transplantation process was the biggest constraint for patients of Northwest European origin. Thirty percent of patients became medically unfit for transplantation during the process, due to the duration of the process. Major Histocompatibility complex (MHC) differences between donor and patient can preclude successful transplantation. The assumption that highly diverged MHC class I molecules lead to more T cell alloreactivity was challenged. Single highly diverged (>=5alpha5beta) MHC class I molecules did not elicit an immune response by allogeneic CTL in vitro. I propose that in generating a T cell repertoire with a sufficiently narrow responsive for self-MHC, positive thymic selection limits the capacity to recognize allogeneic MHC molecules whose structure and sequence have diverged extensively. Its clinical relevance was evaluated. We could subdivide the donor-recipient pairs with a negative CTLp assay into a prognostic favourable and unfavourable group based on the (>=5alpha5beta) MHC mismatch category. Show less
