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Dendritic cells (DCs) are the most efficient and professional antigen-presenting cells of the immune system required for induction and dispersion of immune responses. DCs also have an important role in the induction and maintenance of tolerance. In response to infections, DCs drive the production of effector CD4+ T helper 1 (Th1) and CD8+ T cell-dominated immune responses. DCs can be designated to become tolerogenic and enhance regulatory T cells (Tregs) that regulate effector T cell responses, a process that is essential for the maintenance of immune homeostasis and control of autoimmune diseases and hypersensitivities. DCs can exist in three states: immature, semi-mature, and mature DCs. The difference between immature and mature DCs is distinctly based on variations occurring on a phenotypic level and functional level. Immature dendritic cells manifested characteristics of primitive cells, defined by expression of classical dendritic cell surface markers CD11c, CD11b and major histocompatibility complex class II (MHC-II). Phenotypic maturation is accomplished when DCs upregulate surface maturation markers such as CD80, CD83, and CD86.

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Background: Extracts of Echinacea have been used traditionally for the treatment of diverse types of infections and wounds. They have become very familiar immunostimulant herbal medicine. However, the specific immunomodulatory effect of Echinacea remains to be elucidated.Aim: In our study, the effect of Echinacea purpurea extract on the generation of immature DCs from monocytes was described, as well as its effect on DC differentiation. In addition, an in vivo experiment was conducted to investigate whether treatment of mice with extracts derived from E. purpurea has immunomodulatory effect on murine splenic DCs.Methods: Immature DCs were generated by incubating peripheral blood monocytes with cytokine cocktail (GM-CSF + IL-4) and matured by tumor necrosis factor-a (TNF-a). The cells were randomized to 5 groups to investigate E. purpurea effect in different stages. Phenotypic analysis of cell marker CD83-expressed on DCs was performed by flow cytometry. Mice were randomly divided into 3 groups; control, E. purpurea treated and E. purpurea-TNF-a treated group. The murine splenic DCs were isolated and phenotyped for CD83 and CD11c by flow cytometry.Results: Treatment of monocytes with E. purpurea prior to addition of the maturation factor TNF-a resulted in a significant decrease in the yield of DC expressing CD83. On the other hand, immature DCs generated in the culture in the presence of GM-CSF and IL-4, when treated simultaneously with E. purpurea and TNF-a, exhibited an insignificant change in the yield of CD83-expressing DCs compared with untreated control. The in vivo experiments showed that splenic DCs obtained from mice treated with E. purpurea with or without TNF-a did not exhibit significant changes in CD83 or CD11c compared with those obtained from control mice.Conclusion: Our findings suggest that the immunomodulatory mechanisms of E. purpurea impact generation fate of DCs rather than differentiation stages. The results obtained in the in vivo study utilizing murine splenic DCs supported those observed in vitro.ª 2015 Production and hosting by Elsevier B.V. on behalf