Clonal T-lymphocytes from untreated hairy-cell leukaemia patients enhance the growth of BFU-E.

The anaemia in hairy cell leukaemia (HCL) has been suggested to be mediated in part by T lymphocytes. Consequently, we have investigated the role of T lymphocytes in this disease by cloning pre-treatment HCL T lymphocytes and testing their influence on the in vitro growth of BFU-E from autologous post-treatment and normal donors T-lymphocyte depleted peripheral blood mononuclear cells (PBMNC-T). Altogether, 24 CD4+/CD8- and 17 CD4-/CD8+ T-lymphocyte clones from 3 different HCL patients were tested. All were found to enhance the growth of BFU-E, the degree of enhancement being independent of the length of IFN treatment at the time of the post-treatment sampling. Likewise, no difference in the extent of enhancement was seen between CD4+/CD8- and CD4-/CD8+ clones, or whether the clones were tested for modulation of BFU-E from PBMNC-T of autologous or allogeneic origin. Finally, no differences could be observed between different patients in the extent of clonal enhancement. These findings, which are in line with our previous ones in normal donors, indicate that the T-lymphocyte function with regard to regulation of the erythropoiesis is normal in HCL, arguing against a T-lymphocyte mediated suppression of the erythropoiesis in HCL.