Mismatched Bone Marrow Transplantation

In the United Kingdom, based on family size, the probability of a patient having a histocompatible sibling as a donor is only about 0,3 (1). Moreover, matched transplants are rarely successful for recipients over the age of 45 years. Thus for bone marrow transplantation to make any impact on the management of bone marrow disorders, particularly acute leukaemia, the availability of donors must be extended outside of those with complete identical inheritence of chromosome no, 6, HLA matched unrelated donors are being used to a limited extent to determine the feasibility of their use, but even with very large panels of normal donors the number of such transplants that have been undertaken is so small that no statement can be made on the efficacy of such a treatment, Seattle have previously reported a study in which donors were matched for one haplotype of chromosome no, 6, the other haplotype having antigenic similarities (2). These patients were given methotrexate as prophylaxis to prevent graft versus host disease (GvHD); many of them had active disease at the time of transplantation and in consequence there were many failures, but there were also some long term survivors. However, selecting patients whose donors are more than half identical at the MHC can only slightly extend the proportion of patients eligible for grafting.