• AC133 antigen;
  • CD34+ cells;
  • Peripheral blood;
  • Proliferation;
  • CFC;
  • LTC-IC;
  • Apoptosis


AC133 antigen is a novel marker for human hematopoietic stem/progenitor cells. In this study, we examined the expression and proliferation potential of AC133+ cells obtained from steady-state peripheral blood (PB). The proportion of AC133+ cells in the CD34+ subpopulation of steady-state PB was significantly lower than that of cord blood (CB), although that of cytokine-mobilized PB was higher than that of CB. The proliferation potential of AC133+CD34+ and AC133CD34+ cells was examined by colony-forming analysis and analysis of long-term culture-initiating cells (LTC-IC). Although the total number of colony-forming cells was essentially the same in the AC133+CD34+ fraction as in the AC133CD34+ fraction, the proportion of LTC-IC was much higher in the AC133+CD34+ fraction. Virtually no LTC-IC were detected in the AC133CD34+ fraction. In addition, the features of the colonies grown from these two fractions were quite different. Approximately 70% of the colonies derived from the AC133+CD34+ fraction were granulocyte-macrophage colonies, whereas more than 90% of the colonies derived from the AC133CD34+ fraction were erythroid colonies. Furthermore, an ex vivo expansion study observed expansion of colony-forming cells only in the AC133+CD34+ population, and not in the AC133CD34+ population. These findings suggest that to isolate primitive hematopoietic cells from steady-state PB, selection by AC133 expression is better than selection by CD34 expression.