OBJECTIVE: The immunosuppressive mechanism of sinomenine in organ allotransplantation was investigated, especially its effect of blocking dendritic cell (DC) maturation, which might influence the frequency of regulatory T cells (Tregs). METHODS: Bone marrow cells from male donor Wistar rats were induced to differentiate into DCs in vitro in the presence or absence of sinomenine, and characterized by flow cytometry. These two groups of DCs were respectively injected into male recipient Sprague-Dawley rats via the tail vein, at both high and low doses. Sprague-Dawley rats receiving saline inject...