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1/6. Posttransplant immune-mediated hemolysis.

    BACKGROUND: Immune-mediated hemolysis is a well-recognized complication of transplantation, but few reports have drawn together the different mechanisms that could be involved. STUDY DESIGN AND methods: The clinical and laboratory records of three patients are used to illustrate different types and complexities of posttransplant immune-mediated RBC destruction. RESULTS: Patient 1 received bone marrow from an HLA-matched, unrelated donor. At 7 months after transplant, his Hb level fell to 50 g per L. The serum contained warm autoantibodies, and the DAT was strongly positive for IgG, IgM, and C3d; an eluate yielded IgG and IgM autoantibodies. Autoimmune hemolytic anemia was diagnosed. Patient 2, blood group A, experienced severe hemolysis 14 days after receiving a lung from a group O donor. The DAT was positive for IgG. serum and RBC eluate contained anti-A produced by immunocompetent B cells in the transplanted lung-this was the passenger lymphocyte syndrome. Patient 3 experienced posttransplant hemolysis caused by two different immune mechanisms. Originally group A, D- with anti-C, -D, -E, she received a peripheral blood progenitor cell (PBPC) transplant from her HLA-identical group A, D son. Six months later, chimerism was evident; the remaining recipient marrow was still producing antibodies that destroyed D RBCs made by the transplant. Later, autoimmune hemolytic anemia also developed; the DAT became positive for IgG, and warm autoantibodies were eluted from D- RBCs. CONCLUSION: An understanding of the causes and circumstances under which posttransplant immune hemolysis arises is required for proper management. As more patients become long-term survivors of unrelated bone marrow and/or PBPC transplants, chimerism and complex serologic problems will become more common.
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2/6. Fludarabine- and cyclophosphamide-based nonmyeloablative conditioning regimen for transplantation of chronic granulomatous disease: possible correlation with prolonged pure red cell aplasia.

    An 18-year-old patient with chronic granulomatous disease who had had at least 2 episodes of life-threatening aspergillus pneumonia was treated with nonmyeloablative allogeneic stem cell transplantation (NSCT) from an HLA-identical and major ABO-incompatible sibling. The conditioning regimen consisted of cyclophosphamide at a dose of 60 mg/kg (days -5, -4) and fludarabine at a dose of 30 mg/m2 (days -5, -4, -3, -2, -1). Full donor T-cell engraftment was attained on day 28, and full myeloid engraftment was established by day 150 after tacrolimus withdrawal. The bacteriocidal activity of neutrophils, as indicated by flow cytometry with the use of a dichlorofluorescein diacetate oxidation assay, remained low until 150 days after transplantation, but no infection was detected, a finding that suggests mixed chimerism of granulocytes controlled infection. Graft-versus-host disease and severe regimen-related toxicity (grade 3 or greater) were not observed. This patient developed prolonged pure red cell aplasia, possibly caused by persistent antidonor isohemagglutinin produced by the residual host B-cells. The aplasia resolved with the combination of erythropoietin, double filtration plasmapheresis, and rituximab. In the setting of major ABO-incompatible NSCT, a fludarabine- and cyclophosphamide-based conditioning regimen may lead to prolonged PRCA.
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3/6. Successful treatment of pure red cell aplasia with repeated, low doses of rituximab in two patients after ABO-incompatible allogeneic haematopoietic stem cell transplantation for acute myeloid leukaemia.

    We describe two patients with acute myeloid leukemia successfully treated with anti-CD20 antibody for pure red cell aplasia (PRCA) following ABO-mismatched allogeneic hematopoietic stem cell transplantation (HSCT). PRCA following HSCT is associated with major ABO incompatibility between donor and recipient and is due to an inhibition of donor erythroid precursors by residual host isoagglutinins. The first patient developed PRCA resistant to several treatment options including donor-derived leukocyte infusions (DLI), high-dose erythropoietin (EPO), and rapid tapering of cyclosporin A (CsA). This patient also received anti-viral therapy as CMV and parvovirus B19 infections were regarded as additional causes of PRCA. Due to a loss of donor chimerism, he underwent second HSCT, but PRCA still persisted. He showed no evidence of graft-versus-host disease (GVHD). Finally he was administered anti-CD20 antibody (rituximab) at a dose of 150/m2 and PRCA resolved in a short period of time. The case was complicated by life-threatening pulmonary aspergillosis with septic shock, successfully treated with anti-fungal therapy. The second case concerns a patient, who revealed PRCA after major ABO-incompatible HSCT from his brother. Considering our experience with the previously described patient, he proceeded to rituximab at a dose of 150/m2 as first line treatment. We observed rapid recovery from PRCA without any side effects. We conclude that rituximab seems to be a promising therapeutic option in patients with PRCA after ABO-mismatched HSCT, in whom conventional treatment fails.
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4/6. Use of the gel test to follow up chimerism in ABO mismatched bone marrow transplantation patient: a case report.

    OBJECTIVE: The authors report here our experience using the gel test to follow up chimerism in a 5 year old girl with beta thalassemia/hemoglobin e disease (beta thal/HbE), post allogeneic bone marrow transplantation with Hb E trait HLA identical sibling donor. They were ABO blood group major mismatched donor-recipient pairs (donor and recipient blood group are B and O, respectively). MATERIAL AND METHOD: Pre and post transplanted EDTA blood samples from the girl with beta thalassemia/ hemoglobin e were tested for ABO, Rh and direct antiglobulin test (DAT) using the A-B-AB-D-ctl/ AHG card and the titer of anti-A and anti-B were tested by the conventional tube technique. The sex chromosome study and hemoglobin typing were also examined. RESULTS: In this technique, mixed field agglutination is clearly identified from positive and negative results. The authors detected peripheral recovery, mixed O/B population after transplantation on day 26 with positive DAT. The DAT was negative on day 67 after transplantation and the recipient blood group was completely changed to B on day 123. In addition, Hb typing was changed to Hb E trait with Hb F less than 5 % on day 37. The engraftment of neutrophils, more than 5x10(9)/L, was detected on day 14 and platelet count was more than 20x10(9)/L on day 28. On day 90, the patient was transfusion-independent with the mean Hb level at 11.4 g/dL (10.4-13.1). The sex chromosome and hemoglobin typing were changed to the donor on day 300. CONCLUSION: The gel test is an alternative method which is simple and helpful in detecting mixed red blood cell populations, particularly in the ABO or other blood group mismatched bone marrow transplantation.
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5/6. Rhesus incompatibility and aplastic anemia as the consequence of split chimerism after bone-marrow transplantation for severe combined immunodeficiency.

    A patient with severe combined immunodeficiency received three transplants of bone marrow from the HLA-B- and -D-identical mother. The first transplantation led to a severe graft-versus-host reaction followed by immunological reconstitution. A split chimerism was found with engraftment only of the maternal lymphocytes. Five months after the transplantation an autoimmune hemolytic anemia was observed which was due to rhesus incompatibility as well as polyspecific antibodies. At the same time agranulocytosis developed and 9 mth after the first transplantation the child suffered from aplastic anemia. Two further attempts failed to engraft the maternal hematopoiesis. The child died during the treatment with cyclophosphamide as conditioning for a third transplantation.
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keywords = chimerism
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6/6. Mixed erythrocyte chimerism: implications for tolerance of the donor immune system to recipient non-ABO system red cell antigens.

    We report a case of a minor degree of ABO incompatibility in a BMT recipient, demonstrating mixed RBC chimerism, who, late in the post-transplant period, developed a warm autoimmune hemolytic anemia and subsequently developed antibodies with donor-anti-recipient specificities for non-ABO system RBC antigens. While this implies a lack of tolerance of the donor immune system for recipient non-ABO system RBC antigens, other factors may be operating and should be evaluated before such a conclusion is reached. Underscored is the importance of obtaining pretransplant RBC antigen phenotypes on both the recipient and donor.
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