TNF-α induces the generation of Langerin/(CD207)+ immature Langerhans-type dendritic cells from both CD14-CD1a- and CD14+CD1a- precursors derived from CD34+ cord blood cells

CD34(+) cell-derived hematopoietic precursors amplified with FLT3-ligand, thrombopoietin and stem cell factor became, after a 6-day induction with GM-CSF, IL-4 and TGF-beta1, HLA-DR+, CD1a(+), CD83(-), CD86(-), CD80(-) cells. A fraction of them expressed Langerin, Lag, and E-cadherin, resembling epidermal Langerhans cells (LC). TNF-alpha added for the last 3 days only marginally induced CD83 expression, but strikingly increased the proportion of immature Langerin(+)CD83(-) LC. Langerin(+)CD83(+) and Langerin(+)CD83(-) cells were functionally distinct, the former internalizing less efficiently Langerin than the latter. Both CD1a(-)CD14(-) and CD1a(-)CD14(+) cells sorted from FLT3-ligand, thrombopoietin and stem cell factor cultures responded to TNF-alpha by an increase of Langerin(+) cells. Thus, TNF-alpha rescued LC precursors irrespective of their commitment to the monocytic lineage. When added to GM-CSF, IL-4 and TGFbeta1 containing-cultures, LPS or IL-1beta also induced significant numbers of Langerin(+)CD83(-) immature cells displaying a low allostimulatory activity, while CD40-ligand largely promoted highly allostimulatory Langerin(-)CD83(+) cells. Altogether, these data show that in contrast to CD40-ligand, which induced LC maturation even in presence of TGF-beta1, nonspecific proinflammatory factors such as TNF-alpha, IL-1beta or LPS, essentially induced immature LC generation, and little cell activation in the presence of TGF-beta1.