Mononuclear cells from peripheral blood of untreated hairy-cell leukaemia patients enhance the growth of BFU-e.

To further characterise the regulation of haematopoiesis in hairy-cell leukaemia (HCL), we investigated the effect of mononuclear cells from peripheral blood (PBMNC) of untreated HCL patients on the in vitro growth of BFU-e. The effect was tested in an autologous system employing post-treatment HCL PBMNC, and in an allogeneic system. A significant enhancing effect of the pre-treatment HCL PBMNC was seen. In contrast to studies by others, IFN-alpha consistently inhibited the growth of BFU-e from normal donors, from pre- and post-treatment HCL PBMNC, and mixtures thereof. Since PBMNC from patients with very high percentages of circulating hairy cells (HC) also had an enhancing effect, HC was a likely source of one or more enhancing factors. Thus, even though we cannot exclude a minor inhibitory activity of the HC by our assay, their net effect seems to be enhancing, and therefore it seems unlikely that the HC is directly responsible for the anaemia in HCL.