COEXPRESSION OF KIT AND THE RECEPTORS FOR ERYTHROPOIETIN, INTERLEUKIN-6 AND GM-CSF ON HEMATOPOIETIC-CELLS

The detection of functional growth factor (GF) receptors on subpopulat ions of hemopoietic cells may provide a further dissection of immature cell subsets, Since little information is available about coexpressio n of different GF receptors at the level of single hemopoietic cells, we studied the feasibility of simultaneous cell staining with a combin ation of biotin- and digoxigenin-labeled GFs for flow cytometric detec tion of functional receptors, Using this methodology, coexpression of Kit and receptors for erythropoietin (EPO), interleukin 6 (IL-6), and GM-CSF on hemopoietic cells was studied by triple-staining of rhesus m onkey bone marrow (BM) cells with labeled GFs and antibodies against o ther cell surface markers, Most of the immature, CD34(++) cells were K it(+) but did not display detectable levels of EPO-receptors (EPO-Rs) or GM-CSF-R, Approximately 60% of these CD34(++)/Kit(+) cells coexpres sed the IL-6-R, demonstrating that immature cells are heterogeneous wi th respect to IL-6-R expression, Maturation of mono-myeloid progenitor s, as demonstrated hy decreasing CD34 and increasing CD11b expression, is accompanied hy a decline of Kit and an increase in GM-CSF-R expres sion in such a way that Kit(+)/GM-CSF-R+ cells are hardly detectable, IL-6-R expression is maintained or even increased during monomyeloid d ifferentiation. IL-6-R and CM-CSF-R were not identified on most CD71(+) cells, which indicated that these receptors are probably not expres sed during erythroid differentiation. Together with previous results, our data show that both Kit and CD71 are upregulated, with ergthroid c ommit ment of immature progenitors, Upon further differentiation, Kit( +)/EPO-R- cells lose CD34 and acquire EPO-R. Maturing erythroid cells eventually lose CD71 and Kit expression but retain the EPO-R, In concl usion, this approach enables further characterization of the specifici ty of GFs for different bone marrow subpopulations. Apart from insight into the differentiation stages on which individual GFs mag act, info rmation shout receptor coexpression may be used to identify individual cells that can respond to multiple GFs, and allows for further charac terization of the regulation of lineage-specific differentiation.