Antigenic analysis of human haemopoietic progenitor cells expressing the growth factor receptor c-kit

Summary. The cell surface molecule encoded by the proto-oncogene c-kit has recently been identified as the receptor for a growth factor variously termed stem cell factor (SCF), mast cell growth factor or steel factor. Using the c-kit antibody 17F11 we analysed, in triple staining experiments, the surface molecule profile and scatter characteristics of c-kit⁺CD34⁺ human haemopoietic progenitor cells. In 10 normal bone marrow samples we found 19–51% of CD34⁺ bone marrow progenitor cells to coexpress c-kit. These c-kit⁺CD34⁺ bone marrow cells turned out to represent a phenotypically heterogeneous population. A considerable proportion coexpressed CD33 (52±23%), and/or CD71 (62 ±26) antigens, marker molecules previously shown to be expressed by committed in vitro colony forming cells but not by their precursors. In line with a relatively differentiated phenotype c-kit⁺CD34⁺ cells also gave rise to on average higher forward and right-angle light scattering signals. The proportions of CD38 and/or HLA-D expressing cells were similar in the c-kit⁺ and in the c-kit⁻ subsets of CD34⁺ progenitor cells. Coexpression of CD19 was found to be less frequent in the c-kit⁺ (4 ± 5%) as compared to the c-kit⁻ (17 ± 14%) fraction of CD34⁺ cells. CD7⁺CD34⁺ bone marrow cells were hardly detectable and their numbers too low to allow further subdivision in c-kit⁺ and c-kit⁻ subsets.