[Graft-versus-leukemia effect by lymphocytes from the first donor after second cord blood transplantation in a patient with T-lymphoblastic lymphoma].

A 19-year-old girl with T-lymphoblastic lymphoma (T-LBL) was referred to our hospital because of refractory disease. After complete remission was achieved by the JALSG ALL-97 protocol, she received a bone marrow transplantation (BMT) from an unrelated, HLA-matched donor with myeloablative conditioning. Four months after BMT, T-LBL relapsed and donor lymphocyte infusion was ineffective. After partial remission was achieved with l-asparaginase therapy, she received 2 antigen-mismatched cord blood transplantation with non-myeloablative conditioning; however, sustained engraftment of cord blood stem cells has failed. This was associated with the reappearance of the blood cells from the first donor and the disappearance of leukemic cells from both the peripheral blood and bone marrow. Computed tomography showed no enlarged lymph nodes. The patient and the cord blood donor shared two minor histocompatibility antigens (mHAgs), while these mHAgs were not detected in the blood cells of the first donor. TCR analysis disclosed expanded oligoclonal Vbeta2T cells in the peripheral blood at relapse, and these cells secreted IFN-gamma in response to stimulation by the patient's leukemic cells. Moreover, these cells exhibited cytotoxicity against both leukemic cells and cord blood mononuclear cells. These results strongly suggest that Vbeta2T cells, derived from the first donor, may have been cytotoxic lymphocytes against both leukemic cells and cord blood stem cells.