Haploidentical cord blood transplant contaminated with maternal T cells in a patient with advanced leukaemia

Myeloablative treatment followed by lymphohaematopoietic reconstitution with stem cells from umbilical cord blood (UCB) can cure children with leukaemia. The clinical experience of UCB transplantation with HLA 2- and 3-antigen mismatched siblings is rather limited and there are no reports of such patient being given UCB significantly contaminated with maternal T lymphocytes. In this study, we report our experience in treating a child with chronic myeloid leukaemia in blast crisis who was transplanted using UCB cells from mismatched sibling donor containing a significant number of maternal T cells. The patient received 1.17 x 10(8) nucleated cells/kg after conditioning with Ara-C, busulphan, TBI and cyclophosphamide. GVHD prophylaxis was with cyclosporine and an anti-CD25 monoclonal antibody. Although engraftment was somewhat slow it was complete as documented by cytogenetic analysis and DNA studies. Results of minimal residual disease monitoring by RT-PCR for the hybrid BCR/ABL gene showed no evidence of leukaemic mRNA post-transplant. Acute GVHD, skin only, developed on day +14 but promptly responded to low-dose steroids. The technique used for UCB collection may have cell contamination found. In spite of these potential disadvantages: advanced disease, HLA antigen disparate donor and significant maternal T cell contamination, the transplant was successful and at a follow-up of 14 months the child is well with no evidence of chronic GVHD. Immune naivety of cord blood and lack of immunological reactivity of maternal T cells in this context may have played a significant role in the outcome of this case.