BACKGROUND Myeloablative allogeneic hematopoietic stem-cell transplantation is curative in children with sickle cell disease, but in adults the procedure is unduly toxic. Graft rejection and graft-versus-host disease (GVHD) are additional barriers to its success. We performed nonmyeloablative stem-cell transplantation in adults with sickle cell disease. METHODS Ten adults (age range, 16 to 45 years) with severe sickle cell disease underwent nonmyeloablative transplantation with CD34+ peripheral-blood stem cells, mobilized by granulocyte colony-stimulating factor (G-CSF), which were obtained from HLA-matched siblings. The patients received 300 cGy of total-body irradiation plus alemtuzumab before transplantation, and sirolimus was administered afterward. RESULTS All 10 patients were alive at a median follow-up of 30 months after transplantation (range, 15 to 54). Nine patients had long-term, stable donor lymphohematopoietic engraftment at levels that sufficed to reverse the sickle cell disease phenotype. Mean (±SE) donor–recipient chimerism for T cells (CD3+) and myeloid cells (CD14+15+) was 53.3±8.6% and 83.3±10.3%, respectively, in the nine patients whose grafts were successful. Hemoglobin values before transplantation and at the last follow-up assessment were 9.0±0.3 and 12.6±0.5 g per deciliter, respectively. Serious adverse events included the narcotic-withdrawal syndrome and sirolimus-associated pneumonitis and arthralgia. Neither acute nor chronic GVHD developed in any patient. CONCLUSIONS A protocol for nonmyeloablative allogeneic hematopoietic stem-cell transplantation that includes total-body irradiation and treatment with alemtuzumab and sirolimus can achieve stable, mixed donor–recipient chimerism and reverse the sickle cell phenotype.

Delayed donor red cell engraftment and pure red cell aplasia (PRCA) are wellrecognized complications of major ABOincompatible hematopoietic stem cell transplantation (SCT) performed by means of myeloablative conditioning. To evaluate these events following reducedintensity nonmyeloablative SCT (NST), consecutive series of patients with major ABO incompatibility undergoing either NST (fludarabine/cyclophosphamide conditioning) or myeloablative SCT (cyclophosphamide/high-dose total body irradiation) were compared. Donor red blood cell (RBC) chimerism (initial detection of donor RBCs in peripheral blood) was markedly delayed following NST versus myeloablative SCT (median, 114 versus 40 days; P < .0001) and strongly correlated with decreasing host antidonor isohemagglutinin levels. Antidonor isohemagglutinins declined to clinically insignificant levels more slowly following NST than myeloablative SCT (median, 83 versus 44 days; P ‫؍‬ .03). Donor RBC chimerism was delayed more than 100 days in 9 of 14 (64%) and PRCA occurred in 4 of 14 (29%) patients following NST, while neither event occurred in 12 patients following myeloablative SCT. Conversion to full donor myeloid chimerism following NST occurred significantly sooner in cases with, compared with cases without, PRCA (30 versus 98 days; P ‫؍‬ .008). Cyclosporine withdrawal appeared to induce graftmediated immune effects against recipient isohemagglutinin-producing cells, resulting in decreased antidonor isohemagglutinin levels and resolution of PRCA following NST. These data indicate that significantly delayed donor erythropoiesis is (1) common following major ABO-incompatible NST and (2) IntroductionThe ABO blood group system is of critical importance in transfusion medicine, but has had less dramatic impact in hematopoietic transplantation. 1-4 ABO antigens are potently immunogenic and are expressed on multiple tissues in addition to red blood cells (RBCs). 5 Human beings begin to produce isohemagglutinins against non-self-ABO antigens shortly after birth and continue to do so throughout adult life. 1 Since ABO and human leukocyte antigens (HLAs) are inherited independently, ABO incompatibility may occur in up to 20% to 40% of HLA-matched allogeneic hematopoietic stem cell transplants (SCTs). 4 Graft failure does not occur with increased frequency, and most studies indicate that the incidence of graft-versus-host disease (GVHD) is also not increased following ABO-incompatible versus ABO-identical SCT. 2,4,6 Although increased transfusion requirements and immunohematologic events occur, the overall impact of ABO incompatibility in SCT is generally considered low, provided that appropriate transfusion practices are followed. 2,4,[7][8][9][10] Major ABO incompatibility in SCTs, defined as incompatibility of donor ABO antigens with the recipient's immune system, has been associated with pure red cell aplasia (PRCA) following conventional myeloablative conditioning. [11][12][13][14][15][16][17] Proposed risks for PRCA in this setting include the use of cyclosporine ...

The National Marrow Donor Program (NMDP) has been facilitating hematopoietic cell transplants since 1987. Volunteer donors listed on the NMDP Registry may be asked to donate either bone marrow (BM) or peripheral blood stem cells (PBSC); however, since 2003, the majority of donors (72% in 2007) have been asked to donate PBSC. From the donor's perspective these stem cell sources carry different recovery and safety profiles. The majority of BM and PBSC donors experienced symptoms during the course of their donation experience. Pain is the number 1 symptom for both groups of donors. BM donors most often reported pain at the collection site (82% back or hip pain) and anesthesia-related pain sites (33% throat pain; 17% post-anesthesia headache), whereas PBSC donors most often reported bone pain (97%) at various sites during filgrastim administration. Fatigue was the second most reported symptom by both BM and PBSC donors (59% and 70%, respectively). PBSC donors reported a median time to recovery of 1 week compared to a median time to recovery of 3 weeks for BM donors. Both BM and PBSC donors experienced transient changes in their WBC, platelet, and hemoglobin counts during the donation process, with most counts returning to baseline values by 1 month post-donation and beyond. Serious adverse events are uncommon, but these events occurred more often in BM donors than PBSC donors (1.34% in BM donors, 0.6% in PBSC donors) and a few BM donors may have long-term complications. NMDP donors are currently participating in a randomized clinical trial that will formally compare the clinical and quality-of-life outcomes of BM and PBSC donors and their graft recipients.

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Marked, progressive increases in serum citrate levels occur during plateletpheresis, accompanied by symptomatic decreases in iCa and iMg, with significantly increased renal excretion of calcium, magnesium, and citrate.

Prophylactic Ca infusions safely attenuate the marked metabolic effects of citrate administration and promote faster, more comfortable, leukapheresis procedures.

The independent genomic inheritance of the human leukocyte antigen (HLA) and the ABO-blood group system allows for HLA-matched hematopoietic progenitor cell transplantation (HCT) to occur in donors who are not matched for ABO blood groups. In fact, nearly one-half of all HCT will involve recipient-donor ABO incompatibility. This places the recipient at increased risk for acute and delayed hemolytic reactions, delayed RBC engraftment, and pure red blood cell aplasia. Additionally, clinical and laboratory evaluation for potential non-ABO, minor RBC antigen-antibody discrepancies may be beneficial to facilitate safe transfusions before, during, and after transplantation. In addition to posing potential clinical risks, analyses of outcomes in ABO-incompatible HCT have yielded inconsistent results with respect to overall survival, relapse risk, incidence of acute or chronic graft-versus-host disease, and engraftment of platelets and granulocytes. As such, pretransplantation donor-recipient evaluation and management for ABO-incompatible HCT requires adopting unique strategies when major, minor, and bidirectional differences exist. These strategies have the potential to improve patient outcomes and allow for effective management of the blood bank inventory. The purpose of this article is to describe practical approaches to screening for and managing ABO-incompatible HCT, with the goal of reducing preventable morbidity and mortality after transplantation.

Summary. Immune haemolysis as a result of minor ABO incompatibility is an underappreciated complication of haematopoietic transplantation. The increased lymphoid content of peripheral blood stem cell (PBSC) transplants may increase the incidence and severity of this event. We observed massive immune haemolysis in 3 out of 10 consecutive patients undergoing HLA-identical, relateddonor PBSC transplants with minor ABO incompatibility. Non-ablative conditioning had been given in 9 of these 10 cases, including two with haemolysis. Cyclosporin alone was used as prophylaxis against graft-vs.-host disease (GVHD). Catastrophic haemolysis of 78% of the circulating red cell mass led to anoxic death in the first case seen, but severe consequences were avoided by early, vigorous donorcompatible red cell transfusions in the subsequent two cases. Haemolysis began 7±11 d after PBSC infusion and all patients with haemolysis had a positive direct antiglobulin test (DAT), with eluate reactivity against the relevant recipient antigen. However, neither the intensity of the DAT, the donor isohaemagglutinin titre, nor other factors could reliably be used to predict the occurrence of haemolysis. Our data indicate that haemolysis may be frequent and severe after transplantation of minor ABOincompatible PBSCs when utilizing cyclosporin alone to prevent GVHD. Meticulous clinical monitoring and early, vigorous donor-compatible red cell transfusions should be practiced in all instances.