Immune and hematopoietic reconstitution after transplantation of cord blood progenitor cells: Case report and review of the literature

Transplantation using umbilical cord progenitor cells as the source of the stem cells is increasingly recognized as another form of allogeneic transplantation with curative intent. However, the different patterns of hematopoietic and immunological reconstruction have been described in very few patients. A 20-month-old boy presented with acute leukemia. He received standard AML induction and consolidation therapy, after which he underwent allogeneic transplantation using HLA-matched sibling stem cells obtained from the umbilical cord. The preparative regimen consisted of busulfan and cyclophosphamide. White cell recovery, despite concomitant use of G-CSF, was slow, reminiscent of the engraftment pattern without the use of growth factor. Erythroid recovery was best recorded using fetal cell HbF level. Platelet transfusion independence occurred on day +31. Immunologic reconstitution revealed an early NK cell recovery by 6 weeks and progressive T cell recovery until 3 months, with continued increase in counts thereafter. However, the CD4/CD8 ratio remained low even at 14 months post-transplantation. Recovery of B cells was slower until day +120. Proliferative response was within normal range on day +120. This report describes the unique engraftment pattern following umbilical cord blood transplant and emphasizes the pattern of immunological and hematological reconstitution.