Alpha interferon production in patients with hairy cell leukemia: correlations with disease activity and remission status.

Nineteen patients with hairy cell leukemia (HCL) were studied for in vitro production of alpha interferon (IFN alpha). The patients were divided into three groups. The first group consisted of 8 patients with active disease, all of whom showed a severe deficiency in IFN alpha production (no detectable titers in 6 and less than 40 units/ml in the other 2) compared to normal controls (range: 320-10,500 units/ml; median: 2,560 units/ml). The second group consisted of 6 patients who achieved a partial remission (PR) after IFN alpha treatment. These 6 patients had normal numbers of mononuclear cells in the peripheral blood, but still had deficient IFN alpha production (titers of IFN alpha were below 10 units/ml in 5 of the 6 patients). The third group consisted of 5 patients in complete remission (3 after IFN alpha treatment and 1 each after splenectomy and infection). This group had IFN alpha production that was not significantly different from that of controls 35 years or older (median: 640 units/ml; range 60-2,560 units/ml for patients vs. 1,513 units/ml; range 320-5,120 units/ml for controls; p greater than 0.05). These data show a direct relationship between the activity of HCL and the capacity to produce IFN alpha in vitro. The data also suggest that deficiency of endogenous production of IFN alpha may be relevant to the induction and sustenance of remissions in this disease and that relapses may be partly associated with failure to fully restore endogenous IFN alpha production.