Enhancement of innate and adaptive immune functions by multiple Echinacea species

Abstract

Echinacea preparations are commonly used as nonspecific immunomodulatory agents. Alcohol extracts from three widely used Echinacea species, Echinacea angustifolia, Echinacea pallida, and Echinacea purpurea, were investigated for immunomodulating properties. The three Echinacea species demonstrated a broad difference in concentrations of individual lipophilic amides and hydrophilic caffeic acid derivatives. Mice were gavaged once a day (for 7 days) with one of the Echinacea extracts (130 mg/kg) or vehicle and immunized with sheep red blood cells (sRBC) 4 days prior to collection of immune cells for multiple immunological assays. The three herb extracts induced similar, but differential, changes in the percentage of immune cell populations and their biological functions, including increased percentages of CD49+ and CD19+ lymphocytes in spleen and natural killer cell cytotoxicity. Antibody response to sRBC was significantly increased equally by extracts of all three Echinacea species. Concanavalin A-stimulated splenocytes from E. angustifolia- and E. pallida-treated mice demonstrated significantly higher T cell proliferation. In addition, the Echinacea treatment significantly altered the cytokine production by mitogen-stimulated splenic cells. The three herbal extracts significantly increased interferon-alpha production, but inhibited the release of tumor necrosis factor-gamma and interleukin (IL)-1beta. Only E. angustifolia- and E. pallida-treated mice demonstrated significantly higher production of IL-4 and increased IL-10 production. Taken together, these findings demonstrated that Echinacea is a wide-spectrum immunomodulator that modulates both innate and adaptive immune responses. In particular, E. angustifolia or E. pallida may have more anti-inflammatory potential.

FIG. 1

Effect of Echinacea preparations on the percentages of (A) splenic CD49+ and (B) CD19+ subsets. Male BALB/c mice were orally administered one of three Echinacea preparations, 130 mg/kg daily for 7 consecutive days. The vehicle control mice received an equal volume of 5% ethanol vehicle. Spleen cells were isolated to analyze the expression of the CD49 (NK cell subset) and CD19 (B-cell subset) markers by flow cytometry as described in Materials and Methods. Results are presented as mean ± SE values of two independent experiments (n = 6). *Significant group difference from vehicle control at P < .05.

FIG. 2

Effect of Echinacea preparations on NK cytotoxity after covarying for the percentage of CD49+ splenocytes in each animal. NK cell cytotoxicity was measured as described in Materials and Methods and expressed as percentage cytolysis of target cells. Results are presented as mean ± SE values of two independent experiments (n = 6). E:T, effector:target cell ratio; trt, treatment.

FIG. 3

Effect of Echinacea preparations on splenic PFC response after covariance for the percentage of CD19+ splenocytes in each animal. PFC response was assayed as described in Materials and Methods and expressed as PFCs per 10⁶ splenocytes. Results are presented as mean ± SE values of two independent experiments (n = 6).

FIG. 4

Effect of Echinacea preparations on (A) splenic and (B) blood lymphocyte proliferation. The lymphocyte proliferation assay was conducted as described in Materials and Methods. Results were expressed as cpm (³H incorporation) × 10³ and are presented as mean ± SE values of two independent experiments (n = 6). Numbers in parentheses are the concentration of each mitogen (in μg/mL). *Significant difference from vehicle control at P < .05.

FIG. 5

Effect of Echinacea preparations on T_H2 cytokine production by mouse splenocytes stimulated in vitro without or with mitogen. Spleen cells were incubated without or with Con A at 10 μg/mL for 72 hours. Cytokine levels were determined as described in Materials and Methods. Results are presented as mean ± SE values of two independent experiments (n = 6). *Significant difference from vehicle control at P < .05. ^#Significant difference for the combination of corresponding Echinacea treatment groups from vehicle control.

FIG. 6

Effect of Echinacea preparations on T_H1cytokine production by mouse splenocytes stimulated in vitro without or with mitogen. Spleen cells were incubated without or with Con A at 10 μg/mL for 48 hours. Cytokine levels were determined as described in Materials and Methods. Results are presented as mean ± SE values of two independent experiments (n = 6). *Significant difference from vehicle control at P <.05. ^#Significant difference for the combination of corresponding Echinacea treatment groups from vehicle control.

FIG. 7

Effect of Echinacea preparations on macrophage cytokine production in vitro without or with mitogen. Spleen cells were incubated without or with LPS at 10 μg/mL for 24 hours at 37°C in a 7% CO₂ incubator. Cytokine levels were determined as described in Materials and Methods. Results are presented as mean ± SE values of two independent experiments (n = 6). *Significant difference from vehicle control at P <.05. ^#Significant difference for the combination of corresponding Echinacea treatment groups from vehicle control.