Anti-human PDI antibodies are associated with the induction of a clinical response in a patient with acute myeloid leukemia. A longitudinal analysis of humoral reactivity to human PDI (•) and human PBEF (○) was performed with serial sera samples diluted 1:100 and a secondary anti–human pan-IgG secondary antibody. This leukemia patient first underwent a nonmyeloablative allogeneic bone marrow transplant (BMT) and then was vaccinated with irradiated, autogous GM-CSF–secreting leukemia cells as indicated. Reduction of the immunosuppression for prophylaxis of graft-versus-host disease preceded the complete hematologic response, which has been maintained with 17 months of follow-up.