Functional maturation of myeloid cells during in vitro differentiation from human cord blood CD34+ cells

CD34+ cells purified from human cord blood were expanded in the presence of several cytokines. The cultured cells were assayed for myeloid effector functions, including phagocytic activity, respiratory burst and microbicidal activity. The results showed that phagocytic activity was observed as early as day 6, irrespective of the type of cytokines used. By contrast, respiratory burst and microbicidal activity peaked on day 15 and were dependent on the type of cytokines used. In particular, granulocyte-colony stimulating factor and interleukin-6 markedly enhanced respiratory burst and microbicidal activity.