Echinacea Purpurea L. modulates human t-cell cytokine response
The study evaluates the chemical composition of an Echinacea purpurea (EchNWA) extract previously shown to modifiy the course of influenza infection in a mouse model and assessed immunomodulatory effects on human T-cells. EchNWA extract was obtained from fresh aerial parts extracted with water, followed by ethanolic precipitation, and size-exclusion chromatography. The chemical profile was characterized by chromatographic techniques, including size-exclusion, HPLC, GC-MS and HPLC-PDA. Jurkat T-cells were pretreated with doses of EchNWA followed by activation with phorbol 12-myristate 13-acetate plus ionomycin (PMA+I). Interleukin-2 (IL-2) and interferon gamma (IFNγ) cytokine secretion as well as CD25 expression were measured. EchNWA contains 80% poly-saccharides and phenolic compounds, but alklyamides were not detected. The extract, but not phenolic compounds, mediated dose-dependent enhancment of high-density T-cell production of IL-2 and IFNγ response to PMA+I. EchNWA also enhanced mean fluorescence intensity of IL-2 in Jurkat T-cells activated by PMA+I or ionomycin alone. The extract alone did not stimulate T-cells. Conversely the extract supressed low-density T-cell production of IFNγ and percentage of CD25+ T-cells. Conclusions are that E. purpurea polysaccharides have dose-related adjuvant effects on human T- cell cytokine responses that are characterized by enhancing and suppressive effects and regulated by T- cell density.