immunology allergic disorders
Hematopoietic Stem Cell Transplantation
Procedure
Forbone marrow stem cell harvest,700 to 1500 mL (maximum 15 mL/kg) of marrow is aspirated from the donor’s posterior iliac crests; a local or general anesthetic is used. Forperipheral blood harvest,the donor is treated with recombinant growth factors (granulocyte colony-stimulating factor or granulocyte-macrophage colony-stimulating factor) to stimulate proliferation and mobilization of stem cells; standard apheresis is done 4 to 6 days afterward. Forumbilical cord blood harvest,the cord is clamped after delivery of the baby, and blood is drawn from the cord with a needle and collected in a sterile bag. Fluorescence-activated cell sorting is used to identify and separate stem cells from other cells. Stem cells are then infused over 1 to 2 hours through a large-bore central venous catheter. Before allogeneic hematopoietic stem cell transplantation for cancer, the recipient first is given a conditioning regimen (eg, a myeloablative regimen such ascyclophosphamide60 mg/kg IV once a day for 2 days with full-dose total body irradiation orbusulfan1 mg/kg orally 4 times a day for 4 days pluscyclophosphamidewithout total body irradiation) to induce remission and suppress the immune system so that the graft can be accepted. Similar conditioning regimens are used before allogeneic hematopoietic stem cell transplantation, even when cancer is not the indication, to reduce incidence of rejection and relapse. Such conditioning regimens are not used before autologous hematopoietic stem cell transplantation for cancer; cancer-specific drugs are used instead. Nonmyeloablative conditioning regimens (eg, withcyclophosphamide, thymic irradiation,antithymocyte globulin[ATG], and/orcyclosporine) may reduce morbidity and mortality risks and may be useful for older patients, patients with comorbidities, and patients susceptible to a graft-vs-tumor effect (eg, those with multiple myeloma). Reduced intensity regimens (eg,fludarabinewithmelphalan, oralbusulfan, orcyclophosphamide) have intensity and toxicity between myeloablative and nonmyeloablative regimens. Resulting cytopenias may be prolonged and result in significant morbidity and mortality, and require stem cell support. After hematopoietic stem cell transplantation, recipients are given colony-stimulating factors to shorten duration of posttransplantation leukopenia, Infection , and, after allogeneic hematopoietic stem cell transplantation, up to 6 months of prophylactic immunosuppressants (typically Engraftment typically occurs 10 to 20 days after hematopoietic stem cell transplantation (earlier with peripheral blood stem cells) and is defined by an absolute neutrophil count>500/mcL (>0.5×109/L). 