Abstract: To explore the effects of dehydroepiandrosterone (DHEA) on the development of experimental autoimmune neuritis (EAN) and to explore its mechanism. Methods Thirty-six Lewis rats were randomly divided into the DHEA 0.5mg treatment group, the DHEA 2mg treatment group and the control group (n=12). The treatment groups were subcutaneously injected every day with DHEA and the control group was subcutaneously injected with the same volume of DHEA dissolvent from day 5 post-immunization (p.i.) to day 28 p.i. with bovine peripheral myelin（BPM）in Freund′s complete adjuvant (CFA). The effects were assessed in terms of appearance of clinical signs, clinical score, histopathology and IFN-γ and TNF-α positive cells in sciatic nerve sections, and T-cell proliferation and inflammatory cytokines (IFN-γ,TNF-α and IL-10) synthesis by draining lymph nodes and spleen cells. ResultsRats receiving DHEA in the two different therapeutic regimens displayed a significant delay in onset (P<0.05 and P<0.05), a decreased inflammatory cell infiltration into the PNS (P<0.05,P<0.05) and decreased numbers of IFN-γ and TNF-α expression cells in the PNS(P<0.05 and P<0.05 ), and reduced BPMstimulated T cell proliferation(P<0.05 and P<0.05) and IFN-γ and TNF-αsecretion in the draining lymph node and spleen (P<0.05, P<0.05) compared to the control group. Only the DHEA 2mg treatment group had the significant differences of supernatant IL-10 were found among the different treatment and control groups（P>0.05）.ConclusionAdministration of exogenous DHEA ameliorates the severity of EAN, presumably by suppressing the proliferation of auto-reactive T-cells and moderating the over-expression of pro-inflammatory cytokines. DHEA 2mg therapy is more effective than DHEA 0.5mg therapy.

Key words: Neuritis, experimental allergic, Dehydroepiandrosterone, Cytokines, Rats, inbred Lew