Interleukin-17 (IL-17)-producing CD4(+) T cells (Th17 cells) have been proven to play a critical role in the pathogenesis of systemic lupus erythematosus (SLE). To shed light on the mechanism of immunoregulation of adipose-derived stem cells (ADSCs), we investigated the effects of allogeneic ADSCs on the Th17 lymphocytes of patients with active SLE by co-culturing ADSCs and peripheral blood mononuclear cells of these patients in vitro. The results indicated that ADSCs from passage 3 (P3) down-regulated the proportion of Th17 cells and their abilities to produce IL-17, whereas ADSCs from passage 8 (P8) had contrasting effect. The results also showed cell-cell contact played a role in P3 down-regulation. Blocking the functional pathway of IL-23 (both its ligand and its receptor) also contributed to this suppression. These results suggested that immunomodulation of ADSCs may be achieved by partially suppressing the number and capability of Th17 lymphocytes, indicating that ADSCs could be employed as therapeutic tools for the autoimmune diseases.