Objective: To explore the effects and mechanism of Huanglian Wendan decoction on experimental autoimmune neuritis (EAN). Method: EAN model was established by immunizing Lewis rats with peripheral nerve myelin sheath antigen (P257-81)peptide and complete Freund's adjuvant (CFA). Lewis rats were randomly divided into Huanglian Wendan decoction high-dose group and low-dose group

the EAN model group and normal group. Huanglian Wendan decoction high-dose group and low-dose group were lavaged with 26.89 g·kg-1·d-1 or 6.79 g·kg-1·d-1 once daily from day 0 to day 15 post-immunization. The effects were assessed in terms of appearance of clinical signs

histopathology and T cells

macrophages infiltrating in sciatic nerve sections

T help 17 (Th17) cells and Foxp3+ regulatory T (Foxp3+Treg) cells in peripheral blood

mRNA levels of inflammatory cytokines: tumor necrosis factor-α (TNF-α)

interferon-γ (IFN-γ)

interleukin-6 (IL-6) and interleukin-17(IL-17) in the lymph nodes. Result: Huanglian Wendan decoction high-dose group primaryneurological signs were found at day 11.92±1.38

it was later than that in EAN group. The maximal neurological score (2.41±1.09) and the mean histological scores (0.58±0.51) of high-dose group were lower than that in EAN group. Huanglian Wendan decoction high-dose group and low-dose group reduced accumulation of macrophages and T cells in sciatic nerves. In peripheral blood

Foxp3+Treg cells in high-dose group and low-dose group (15.06±1.35

9.18±1.00)% were increased

but Th17 cells (1.88±0.47

2.71±0.39)%were decreased. Furthermore

TNF-α

IFN-γ

IL-6

IL-17mRNA levels in the lymph nodes of high-dose group (0.38±0.02)%

(0.45±0.08)%

(0.34±0.13)%

(0.63±0.17)%and low-dose group (0.45±0.03)%

(0.60±0.05)%

(0.74±0.12)%

(1.04±0.17)% significantly suppressed. Conclusion: Huanglian Wendan decoction could effectively suppress autoimmune response in EAN

it can treat EAN effectively.