Characterization of lympho-myeloid-erythroid-megakaryocytic stem cells in peripheral blood of hairy cell leukemia patients.

Circulating stem cells with lympho-myeloid-erythroid differentiative capacity have been described in the peripheral blood of hairy cell leukemia (HCL) patients (Michalevicz R. & Revel M. (1987) Interferons regulate the in vitro differentiation of multilineage lympho-myeloid stem cells in Hairy Cell Leukemia. Proc. natn. Acad. Sci. U.S.A. 84, 2307.) The aim of the present work was to enrich the progenitors and characterize their antigenic and growth properties. Peripheral blood (PB) from HCL patients was stained with antibodies (BI3C5 (CD34) and/or My10 as well as RFB7 (CD20) and RFT12 (CD7) and sorted using flow cytometry (FCM) into positive and negative fractions. Peripheral blood cells from several patients showed 4-16% cells positive for the BI3C5/My10. The positive fraction contained all the colony-forming cells and LGEM/LG/LGM colonies were enriched approximately ten-fold as compared to the unsorted population. No colony was found in the negative fraction. All colony forming cells were in the RFB7 and RFT12-negative fractions. Thus, circulating stem cells with lymphoid/myeloid potential can be isolated from PB of HCL patients.