To investigate the effect of immature dendritic cells (iDCs) on experimental autoimmune myasthenia gravis (MG), iDCs were generated in low dose of GM-CSF, and then they were pulsed with acetylcholine receptor (AchR) and transferred to allogeneic rats. After 3 weeks, all rats were immunized with AchR and complete Freund's adjuvant (CFA) and observed for the corresponding indices of MG for 7 weeks. Our results showed that compared with mature DCs (mDCs) generated at high dose of GM-CSF plus additional stimulation by lipopolysaccharide, iDCs expressed significantly lower levels of MHC-Ⅱ , CD80 and CD86, and their ability to uptake FITC-Dextran was stronger but the ability of stimulating proliferation of allogeneic T cells were weaker. Like controls,after immunization, all rats transferred with iDCs, mDCs and AchR-pulsed mDCs showed typical symptoms in 4 to 7 weeks. The amplitude of electromyogram wave dropped obviously, the level of serum AchRab increased and neuromuscular junction showed typical damage of MG. In contrast, no conspicuous changes were noted in rats transferred with AchR-pulsed iDCs. The results suggest that iDCs could be generated by inducing bone marrow precursors in low dose of GM-CSF, AchRpulsed iDCs could induce tolerance of EAMG. The dysfunction of DCs may play an important role in the initiation and maintenance of normal immune response in MG.