Alpha-interferon in myelodysplasia; clinical observations and effects on NK cells.

A total of 15 patients with myelodysplastic states (MDS) were studied. Of the eight patients treated with alpha-interferon (alpha IFN) (3 megaunits/day for up to 6 months), one patient with refractory anaemia with excess blasts (RAEB) underwent an almost complete response while one case of chronic myelomonocytic leukaemia (CMML) showed a reduction in monocyte count; no improvement was observed in refractory anaemia (RA) or refractory anaemia with excess blasts in transformation (trRAEB). In all patients Leu7+ and Leu11a+ phenotypic natural killer (NK) cells were consistently normal in percentage numbers but functional NK activity was consistently reduced in all MDS subgroups. NK activity was enhanced by exposure to alpha IFN in vitro, but was very variable in patients being treated with the agent. There was no correlation between clinical response and changed NK activity in patients receiving alpha IFN. It is concluded that NK cells are unlikely to play a central role in the biology of myelodysplasia.