T cell and NK cell mediated graft-versus-leukaemia reactivity following donor buffy coat transfusion to treat relapse after marrow transplantation for chronic myeloid leukaemia.

Two patients with chronic myeloid leukaemia in cytogenetic relapse following T lymphocyte-depleted BMT were treated with transfusions of donor buffy coat leucocytes. In both patients the marrow reverted to a completely normal karyotype and was negative for the BCR-ABL fusion gene transcript by polymerase chain reaction analysis. Before buffy coat transfusion the cytotoxic T lymphocyte precursor frequency against pre-BMT patient leukaemia cells (Lk-CTLP) was lower than that against pre-BMT patient PHA-transformed lymphocytes (Ly-CTLP) in both cases. At 2 weeks (case 1) and 8 weeks (case 2) after transfusion this ratio inverted so that Lk-CTLP predominated. Natural killer (NK) function fell initially and then recovered to exceed pre-transfusion values prior to normalization of the bone marrow karyotype. These changes in cytotoxic T lymphocytes and NK cells following donor buffy coat transfusions for patients with relapsed chronic myeloid leukaemia after marrow transplantation support the concept of a graft-versus-leukaemia effect mediated by both MHC restricted and non-restricted pathways.