RESUMEN
<p><b>OBJECTIVE</b>To explore the hematopoietic and immunologic reconstitution and transplantation-related complications of HLA one locus mismatched unrelated umbilical cord blood transplantation for the treatment of hematological malignancies.</p><p><b>METHODS</b>Two children with acute lymphoblastic leukemia received HLA-mismatched unrelated umbilical cord blood transplantation. The conditioning regimens were BU-CTX (case 1) and BU-CTX plus BCNU (case 2). GVHD prophylaxis regimen consisted of cyclosporine (CsA) and mycophenolate mofetil (MMF). The patients received 14.6 x 10(7) nucleated cells/kg with 7.24 x 10(5) CD(34)(+) cells/kg and 16.24 x 10(7) nucleated cells/kg with 21.11 x 10(5) CD(34)(+) cells/kg, respectively.</p><p><b>RESULTS</b>The two recipients, ANC > 0.5 x 10(9)/L occurred at day 27 and day 17, BPC > 50 x 10(9)/L at day 53 and day 46, the peripheral blood counts normalization at day 60 and day 52, the immune function normalization at day 134 and day 122 and the DNA fingerprinting showing engraftment at day 19 and day 17, respectively. The donor-recipient pair of case 1 was male to female, and the chromosome karyotype of recipients bone marrow and peripheral blood cells showed 100%, 46, XY cells at day 49. Grade II acute graft versus host disease (aGVHD) occurred at day 26 (case 1) and day 21 (case 2). The two recipients have survived for 353 days and 256 days.</p><p><b>CONCLUSION</b>The hematopoietic and immunologic reconstitution in umbilical cord blood transplantation were earlier and more durable. The transplantation-related complications were less and aGVHD were milder.</p>