Donor leukocyte infusions

Donor leukocyte therapy has resulted in a remission rate in excess of 70% in patients with relapse of chronic myeloid leukaemia (CML) following allogeneic bone marrow transplantation (BMT). Induction of remission with donor leukocyte infusions has been primarily successful for CML patients who have cytogenetic relapse or those with chronic-phase haematological relapse. Response rates appear to be lower in patients who have advanced-phase CML. The majority of patients with CML who enter remission have no detectable minimal residual disease when analysed for BCR-ABL mRNA transcripts by reverse-transcription polymerase chain reaction. The efficacy of donor leukocyte infusions and the ease of therapy are balanced by the potential for significant toxicity. The reported treatment-related mortality rate is almost 20%. The major toxicities of this treatment are secondary to marrow aplasia and graft-versus-host disease (GVHD) which may occur in up to 50% and 90% of responders respectively. Donor leukocytes with a T-cell content of only 1 x 10(7)/kg, approximately a factor of 10 fewer T cells than used in most early studies, are capable of inducing remissions in some patients. The use of lower doses of T cells or CD8+ depleted T cells may be associated with less GVHD. The optimal treatment schedule using donor leukocytes has yet to be determined. Factors which might influence outcome include phase of disease, use of interferon alpha, use of unrelated donors and human leukocyte antigen disparity, T-cell dose, CD8+ depletion of leukocytes and time from BMT to leukocyte infusion.