TNF-alpha enhances phenotypic and functional maturation of human epidermal Langerhans cells and induces IL-12 p40 and IP-10/CXCL-10 production.

Dendritic cells (DC) play a central role in immunity/tolerance decision, depending on their activation/maturation state. TNF-alpha is largely produced in the skin under inflammatory conditions. However, it still remains to be defined how TNF-alpha modulates the activation status of human LC, the most specialized DC controlling skin immunity. Here, we reported that fresh immature LC, highly purified from healthy human skin and exposed for two days to TNF-alpha under serum-free conditions, expressed up-regulated level of co-stimulatory molecules (CD40, CD54, CD86), maturation markers (CD83, DC-LAMP), CCR7 lymph node homing receptor, and down-regulated Langerin level, in a dose-dependent manner. This mature phenotype is closely associated with enhanced LC allostimulatory capacity. Furthermore, TNF-alpha significantly increased the number of viable LC and decreased their spontaneous apoptosis. More importantly, TNF-alpha induced LC to produce both IFN-gamma-inducible-protein IP-10/CXCL10, a Th1-attracting chemokine and IL-12 p40. Bioactive IL-12 p70 was never detected, even after additional CD40 stimulus. The results implicate LC as an effective target through which TNF-alpha may up- or down-regulate the inflammatory skin reactions.