immediate exposure to tnf-α activates dendritic cells derived from non-purified cord blood mononuclear cells

background: tumor necrosis factor alpha (tnf-α) is a primary mediator of immune regulation and might be required in the early stages of dc development from cd34+ cells. however, details of optimal timing of exposure to tnf-α in dc development process in monocytes or non-purified hematopoitic cells are still lacking and clear benefits of this approach to the development of dcs remain to be validated. objective: to evaluate the effect of early and late exposure to tnf-α on dc devel-opment from non-purified cord blood mononuclear cells. methods: to define the ef-fects of early exposure to tnf-α on cord blood mononuclear cells, we cultured ucb-mnc in the presence of scf, flt3l, gm-csf and il-4 for 14 days and matured them for an extra 4 days. tnf-α was added on day 0, 7 and 14 in tnf-α + group, and only on day 14 in tnf-α - group where it was used only as a maturation factor. results: immediate exposure to tnf-α was shown to: (1) enhance the survival of cells in the first week of culture; (2) produce mature dcs with higher maturation markers (cd80, cd83, cd86 and hla-dr); and (3) increase secretion of il-12 by mature dcs. in contrast, delayed exposure to tnf-α stimulate mature dcs with less purity producing a high level of il-10 and a low level of il-12. conclusion: we developed a simple, easy and cost effective method to generate dcs from non-fractionating mononuclear cells in this study. also we confirm the presence of a large number of functional dcs under inflammatory conditions, where local concentrations of tnf-α were high.