Standardized extracts from Chinese herbs induce IL-10 production in human monocyte-derived dendritic cells and alter their differentiation in vitro

Background: The efficacy of traditional Chinese medicine (TCM) as a treatment for atopic dermatitis has been evaluated in clinical trials. Until now, the underlying mechanism of this treatment has remained completely elusive; this is particularly true of its putative effects on dendritic cells (DCs), which might play a pivotal role in the disease. Objective: We investigated the influence of a standardized extract from 10 Chinese herbs that was successfully used in clinical trials on the generation of monocyte-derived DCs from atopic donors. Methods: Detailed phenotypic and functional exploration of DCs generated in the presence of IL-4 and GM-CSF and treated with different concentrations of TCM or a placebo control was performed. Results: TCM profoundly affected the morphology and phenotype of the developing DCs. They lost their typical dendritic morphology and decreased their expression of CD1a as well as the low-affinity IgE receptor CD23. Most importantly, TCM-exposed DCs exhibited a diminished stimulatory activity toward autologous antigen-specific and allogeneic T cells while secreting high amounts of IL-10. Conclusion: TCM induces immunopharmacologic alterations on DCs from atopic donors in vitro. These alterations might account, at least in part, for the therapeutic effect of this treatment in AD in vivo.