Cytokine production by non-adherent mouse splenocyte cultures to Echinacea extracts

Abstract

Background: Echinacea is commonly used in oral dosage as an immune stimulant to increase resistance to viral, bacterial and fungal infections of the upper respiratory tract. It has been suggested that Echinacea is able to stimulate innate immune responses, including those regulated by macrophages and natural killer cells. Indeed, macrophages respond to purified polysaccharide and alkylamide preparations. However, the mechanisms for stimulation of cells responsible for adaptive immunity have not been fully elucidated for other molecules present in Echinacea purpurea preparations. Methods: Adherent and non-adherent mouse splenocyte populations were incubated in vitro with Echinacea, or with water or alcohol soluble Echinacea extract preparations. Supernatants were collected at 48-h post-incubation, and tested by standard ELISA for presence of secreted cytokines and proinflammatory mediators. Results: Whole splenocyte populations were capable of producing significant amounts IL-6 (1014 pg/ml) in response to Echinacea preparations. The response was primarily contained towards products isolated to the water extract preparation; no IL-6 was produced upon challenge with the alcohol extract. The IL-6 response was produced by the non-adherent cellular population, which made 4912 pg/ml IL-6 when treated with water soluble extract at 1 mg/ml. Likewise, the water soluble extract of Echinacea was able to stimulate non-adherent splenocyte populations to produce TNF-α (2082 pg/ml), IL-10 (892 pg/ml) and MIP-1α (6486 pg/ml) from non-adherent splenocytes, but only significant concentrations of TNF-α and MIP-1α mediators were produced from adherent populations at similar dose concentrations. Neither population of splenocytes was capable of stimulating significant production of IFN-γ, IL-2 or IL-12 to any preparation of Echinacea examined. Conclusions: The immune stimulatory ability of components contained within E. purpurea extracts offer insight into possible therapeutic potential of this product to regulate non-adherent lymphocytes in immune responses and activation events.