Surface antigens of hESC-derived cells. (A) Surface antigen expression at each level of differentiation of hESC-derived cells was analyzed by flow cytometry. CD45 was expressed in almost all the cells. CD34, CD117, and CD133, immature markers of hematopoiesis, were detected in a small population of the cells on day 7, and had almost disappeared by day 10. Common myeloid antigens CD33 and CD15 were highly expressed, and the expression of CD11b increased during maturation. CD13 was expressed in less than 20% of the cells throughout the culture period. The expression of CD16, a mature neutrophil marker, increased following maturation, but was observed in only approximately 45% of the cells, even on day 13. CD14 and CD64 expression was aberrantly observed in some cells. Bars represent SDs (n = 3). (B) In the steady state, mature neutrophils in peripheral blood were CD15⁺, CD11b⁺, and CD16⁺. (i) In hESC-derived cells on day 13, 63.3% plus or minus 2.6% of the CD15⁺ and CD11b⁺ cells were CD16⁺, and (ii) almost all of the CD15⁺ and CD16⁺ cells were CD11b⁺. (iii-iv) On the other hand, CD64 and CD14 were rarely expressed on mature neutrophils in the peripheral blood. CD15⁺ and CD16⁺ cells from hESCs, consistent with the phenotype of mature neutrophils, showed aberrant expression of CD64 (iii) and CD14 (iv), in 94.1% plus or minus 3.8% and 45.1% plus or minus 9.6% of the cells, respectively. Data are presented as mean plus or minus SD (n = 3).