Marrow Graft Failure

Abstract

To achieve sustained marrow engraftment the patient’s own immune cells must be eliminated or suppressed in order to allow donor-derived cells to replace the patient’s lymphohemopoietic system. Under controlled experimental conditions it is possible to distinguish between graft rejection due to a memory response following preceding sensitization, and failure of sustained engraftment in a nonsensitized recipient on the basis of genetic (hybrid, allogeneic) resistance. It is more difficult to separate these two mechanisms in man. Sometimes it is not certain whether a patient has been transfused or not, sometimes transfusions are given in the peri-transplant period, i.e. while the patient is receiving immunosuppressive therapy. Furthermore, factors other than allosensitization and resistance, e.g., defects of the microenvironment, can contribute to graft failure. In any event graft failure can manifest itself either as primary engraftment failure or as initial engraftment followed by secondary graft loss, generally within weeks, occasionally later. Graft failure may or may not be associated with reappearance of recipient cells, i.e. there may be cellular and occasionally humoral evidence of a host response to the attempted graft, or the graft may be lost for other reasons without there ever being an active host response. The latter certainly applies in patients given autologous grafts.