Target cells for granulocyte colony-stimulating factor, interleukin-3, and interleukin-5 in differentiation pathways of neutrophils and eosinophils

To study the relationship between hematopoietic factors and their responsive hematopoietic progenitors in the differentiation process, both purified factors and enriched progenitors are required. We isolated total CD34⁺ cells, CD34⁺,CD33⁺ cells, and CD34⁺,CD33^- cells individually from normal human bone marrow cells by fluorescence-activated cell sorter (FACS), and examined the effects of granulocyte colony-stimulating factor (G-CSF), interleukin-3 (IL-3), and IL-5 on in vitro colony formation of these cells. CD34⁺,CD33⁺ cells formed granulocyte colonies in the presence of G-CSF. Both CD34⁺,CD33⁺ cells and CD34⁺,CD33^- cells formed granulocyte/macrophage colonies in the presence of IL-3. Eosinophil (Eo) colonies were only formed by CD34⁺,CD33^- cells in response to IL-3, but scarcely formed by CD34⁺ cells in the presence of IL-5. We performed the two-step cultures consisting of the primary liquid culture for 6 days and the secondary methylcellulose culture, and serially examined changes in phenotypes of the cells cultured in the primary culture. CD34^-,CD33⁺ cells derived from CD34⁺,CD33⁺ cells by preincubation with G-CSF or IL-3 formed Eo colonies in the presence of IL-5 but not IL-3. CD34^-,CD33⁺ cells derived from CD34⁺,CD33^- cells by preincubation with IL-3 also formed Eo colonies by support of IL-5 as well as IL-3. Both CD34⁺ cells gradually lost the CD34 antigen by day 6 of incubation with G-CSF or IL-3. Loss of this antigen was well-correlated with acquisition of susceptibility to IL-5. It was concluded that G-CSF supported the neutrophil differentiation of committed colony-forming cells, IL-3 supported that of both committed and multipotent colony-forming cells. G-CSF and IL-3 also supported the early stage of E. differentiation; IL-5 supported the late stage of that.