Correlation between IL-3 receptor expression and growth potential of human CD34+ hematopoietic cells from different tissues

Abstract

CD123 (α-subunit of IL-3 receptor) expression on primitive and committed human hematopoietic cells was studied by multicolor sorting and single-cell culture. The sources of cells included fetal liver (FLV), fetal bone marrow, umbilical cord blood, adult bone marrow and mobilized peripheral blood. Three subsets of CD34+ cells were defined by the levels of surface CD123: CD123(negative), CD123(low), and CD123(bright). Coexpression of lineage markers showed that a majority of CD34+CD123(bright) cells were myeloid and B-lymphoid progenitors, while erythroid progenitors were mainly in the CD34+CD123(negative) subset. The CD34+CD123(low) subset contained a heterogeneous distribution of early and committed progenitor cells. Single CD34+ cells from the CD123 subsets were cultured in a cytokine cocktail of stem cell factor, interleukin 3 (IL-3), IL-6, GM-CSF, erythropoietin, insulin-like growth factor-1, and basic fibroblast growth factor. After 14 days of incubation, a higher cloning efficiency (CE) was observed in the CD34+CD123(negative) and CD34+CD123(low) fractions (37 ± 23% and 44 ± 23%, respectively) than in the CD34+CD123(bright) fraction (15 ± 21%). Using previously published criteria that colonies containing dispersed, translucent cells (dispersed growth pattern, DGP) were derived from primitive cells and that colonies composed solely of clusters were from committed cells, early precursors were distributed evenly in the CD34+CD123(negative) and CD34+CD123(low) subsets. When CD38 and CD90 (Thy-1) were used for further characterization of CD34+ cells from FLV, CE increased from 37 ± 23% in CD123(negative) to 70 ± 19% in CD123(negative)CD38- and from 44 ± 23% in CD123(low) to 66 ± 19% in CD123(low)CD38-. No significant increase in CE or DGP progenitors was observed when CD34+ cells were sorted by CD90 and CD123. We concluded that: A) high levels of CD123 were expressed on B-lymphoid and myeloid progenitors; B) early erythroid progenitors had little or no surface CD123, and C) primitive hematopoietic cells are characterized by CD123(negative/low) expression.