Risk of donor lymphocyte infusions following allogeneic bone marrow transplantation.

Clinical data so far suggest that the resistance to induction of graft-vs.-host disease (GVHD) by donor lymphocyte infusions is less prominent in allogeneic bone marrow transplant patients than indicated by the limited results of experimental studies in animals published many years ago. To confirm this apparent discrepancy, graded numbers of donor type splenocytes were given at various intervals after bone marrow transplantation to mouse radiation chimeras. The results were closely similar to the previously published data, in that the chimeras developed a high degree of tolerance, equivalent to 2-3 log protection. It was also observed that this tolerance can be broken by prior treatment with a lethal dose of cyclophosphamide. It is postulated that the leukemic cells in relapsed patients reduce the suppressor cell population that is responsible for the resistance to re-induction of GVHD.