Interferon-alpha treatment of a patient with acute lymphoblastic leukaemia and Down's syndrome. Effects on natural killer cell activity and mitogen responsiveness.

A 32-year-old female with Down's syndrome and common ALL was treated with human leucocyte interferon-alpha (IFN-alpha) at a dose of 3 X 10(6) units i.m. daily. Side-effects consisted of slight tenderness and localized haematomas at the sites of injection. During treatment the number of leukaemic cells decreased in the peripheral blood. The proportion of blast cells in the bone marrow decreased only slightly, but a large fraction of them became vacuolized. After the initial response the disease progressed and IFN was withdrawn after treatment for 67 d. Prior to initiation of IFN treatment the natural killer activity of the patient's lymphocytes, as well as the response of these cells to mitogenic stimuli, was low. During IFN therapy these functions increased. Following the withdrawal of IFN therapy the patient received vincristine/prednisone treatment and a complete remission was achieved after 5 weeks. She is still in remission and on maintenance therapy 24 months after initiation of treatment.