Anti‐tumour response despite loss of donor chimaerism in patients treated with non‐myeloablative conditioning and allogeneic stem cell transplantation

Summary Based on a murine model, we conducted a series of trials of m‐myeloablative human leucocyte antigen (HLA)‐matched or mismatched related donor stem cell transplantation (SCT) with the intention of inducing mixed chimaerism (MC), then administering prophylactic donor lymphocyte infusions (DLIs), for the treatment of advanced haematologic malignancies. Preparative therapy consisted of cyclophosphamide, equine anti‐thymocyte globulin (ATG) or MEDI‐507 (an anti‐CD2 monoclonal antibody) for in‐vivo T‐cell depletion, thymic irradiation on day −1 and cyclosporine alone for graft‐versus‐host disease (GVHD) prophylaxis. DLIs were given as early as 5 weeks post‐SCT in patients with MC without evidence of GVHD. Twenty‐two patients ultimately lost their graft (