Objective: To explore the significance of AC(133) antigen expression on cord blood (CB) hematopoietic cells.
Methods: The immunophenotype of CB hematopoietic cells was analyzed by flow cytometric two-color direct immunofluorescence method. Hematopoietic activity of AC(133)(+), CD(34)(+) and AC(133)(-) CD(34)(+) cells in CB was examined by analyzing clonogenic capacity, number of LTC-IC and ex vivo expansion ability.
Results: AC(133)(+) cells consisted of 0.67% of the total CB MNCs. Of the AC(133)(+) cells, 93.4% expressed CD(34) antigen and 94.2% was PKH(26)(+). Although the total number of CFC was the same in the AC(133)(-) CD(34)(+) fraction as in the CD(34)(+) and AC(133)(-) fractions, the number of LTC-IC was much higher in the AC(133)(+) fraction. In addition, the features of the colonies grown from these three fractions were quite different. Approximately 50% of the colonies derived from the AC(133)(+) fraction were CFU-GM, whereas more than 60% of the colonies derived from the CD(34)(+) fraction and 80% of the colonies derived from the AC(133)(-) CD(34)(+) fraction were BFU-E. After 7 d ex vivo expansion, the total number of cells and CFC increased 28.2-fold and 7.1-fold respectively in AC(133)(+) cell populations, 6.8% of the cells was PKH(26)(+).
Conclusions: These findings suggest that the early stem/progenitor cells of CB are enriched in AC(133)(+) fraction, AC(133)(+) cells contain higher proliferative efficiency during ex vivo culture. It can generate either committed progenitors or early stem/progenitors. AC(133) antigen would be a useful marker for clinical selection of hematopoietic stem/progenitors.