Umbilical cord blood transplantation from unrelated donors in an adult weighing 90 kilograms. Role of immunosuppression in engraftment.

A 40-year-old male weighing 90 kilograms was diagnosed with acute myeloblastic leukaemia M5a which was resistant to chemotherapy. Neither a related nor an unrelated HLA-compatible bone marrow donor could be found. A unit of cord blood was found with an HLA compatibility of four out of six loci, and was infused after conditioning with cyclophosphamide, total body irradiation and antilymphocyte globulin. The infused cord blood had 0.98 x 10(7) nucleated cells per kilogram. On day 35 after infusion the patient was considered to have graft failure. A second unit of cord blood was found, and after 3 days of antilymphocyte globulin, it was infused (day 41). The course was complicated by severe hypoxia and bilateral interstitial pulmonary infiltrates, and the patient was treated with high doses of methylprednisolone. On day 58 the leukocyte count increased to 3 x 10(9)/l, and there was total chimerism of the first cord blood unit infused. Two weeks later leukocyte counts decreased progressively and the patient died of a disseminated fungal infection. We discuss the importance of the number of nucleated cells per kilogram of body weight infused, and the role of intensive immunosuppression in engraftment of cord blood transplantations in adults.