The mechanism of action of interferon-alpha (IFN-alpha) in hairy-cell leukaemia; Hu-IFN-alpha 2 receptor expression by hairy cells and other normal and leukaemic cell types.

To investigate the possible direct effects of interferon-alpha (IFN-alpha) in hairy-cell leukaemia, IFN-alpha receptor expression by hairy cells (HCs) (11 cases) was measured by a radiolabelling technique and compared with that of MOLT-4, chronic lymphocytic leukaemia (CLL; 14 cases) and various other leukaemic and normal cell types. Purified peripheral blood (PB) and splenic HCs showed higher levels of receptor expression (approx. 1000 +/- 200 binding sites/cell; 11 cases tested) than other normal and leukaemic cells types. Purified normal PB and tonsil B cells showed low levels of receptors (approx. 120 +/- 100 binding sites/cell), while a range of B-cell leukaemias displayed intermediate levels of expression (approx. 100-500 sites/cell). In the 15 cases of CLL tested, 530 +/- 330 binding sites/cell were demonstrated, the high standard deviation reflecting the fact that approximately one third of cases had receptor levels comparable with those in HCL. Normal and HCL T cells, red cells and platelets had no demonstrable IFN receptors. It is suggested that these findings may be relevant to the efficacy of IFN in hairy-cell leukaemia.