Background: Tumor necrosis factor alpha (TNF-alpha) 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-alpha 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-alpha on DC development from non-purified cord blood mononuclear cells.
Methods: To define the effects of early exposure to TNF-alpha 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-alpha was added on day 0, 7 and 14 in TNF-alpha + group, and only on day 14 in TNF-alpha - group where it was used only as a maturation factor.
Results: Immediate exposure to TNF-alpha 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-alpha 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-alpha were high.