2004;172(9):5213C21. of PC61 (anti-CD25 antibody) i.p. was used to delete Tregs in arthritic mice. Results Infusion of GMSCs in DBA/1J mice with CIA LIN41 antibody significantly Etidronate (Didronel) decreased the severity of arthritis and pathology scores, and down-regulated inflammatory cytokine (IFN-, IL-17A) production. Infusion of GMSCs resulted in an increase in CD4+CD39+Foxp3+ cells in arthritic mice. These increases were noted early in spleen Etidronate (Didronel) and LN and later in synovial fluid. The increased frequency of Foxp3+ Treg cells consisted of cells that were mainly Helios unfavorable. Infusion of GMSCs partially interfered with the progress of CIA when Treg cells were depleted. Pre-treatment of GMSCs with CD39 or CD73 inhibitor significantly reversed the protective effect of GMSCs on CIA. Conclusion The role of GMSCs in controlling CIA pathology mostly depends upon CD39/CD73 signals and partially upon the induction of CD4+CD39+Foxp3+ Treg cells. GMSCs provide a promising approach for the treatment of autoimmune diseases. Rheumatoid arthritis Etidronate (Didronel) (RA) is usually a symmetric polyarticular arthritis that primarily affects the small diarthrodial joints of body (1). Clinical drug development for treatment of RA has progressed slowly. Currently, only about half of RA patients respond to most products such as TNF inhibitors, IL-1 antagonists, and anti-IL-6 receptor antibody. None of them are curative for RA (1). Novel approaches to cure this disease are sorely needed. Mesenchymal stem cells (MSCs) can exhibit immunomodulatory effects. They inhibit T-cell proliferation in mixed lymphocyte cultures, prolong skin allograft survival, and decrease graft-versus-host disease (GVHD) when co-transplanted with hematopoietic stem cells (2). These properties make them well-suited to serve as a candidate for a new approach in the prevention and treatment of allograft rejection, GVHD and other autoimmune diseases. Bone marrow-derived MSCs (BMSCs) have been considered as a potential strategy in clinical cell therapy, however, there are some drawbacks and limitations for their clinical feasibility such as the difficulty in obtaining sufficient numbers for therapeutic use. Recent study has confirmed that gingival tissue-derived MSCs (GMSCs), a populace of stem cells exists in the human gingiva (3), have been shown to have several advantages over BMSCs. GMSCs are easy to isolate, they are homogenous and proliferate more rapidly than BMSCs (4). Additionally, GMSCs display stable morphological and functional characteristics at higher passage numbers and are not tumorigenic (4). Although GMSCs demonstrate beneficial effects in preventing experimental colitis (3) and mitigating chemotherapy-induced oral mucositis (5), utilization of GMSC for the treatment of autoimmune arthritis and other immune diseases has not been explored. Recent studies have exhibited that adoptive transfer of MSCs can upregulate CD4+CD25+Foxp3+ regulatory T cells (Tregs) (6-7). Treg cells play an important role in the prevention and control of experimental autoimmune arthritis, an animal model that shares many features of rheumatoid arthritis (8-9). It is less clear what role is usually played by Tregs in the suppressive effect that MSCs exhibit on immune responses. Deaglio (10) have shown that this co-expression of CD39 (nucleoside triphosphate diphosphohydrolase-1, NTPDase 1) and CD73 (ecto-5′-nucleotidase) in Treg cells contribute to its inhibitory function. CD39 promotes the hydrolysis of adenosine triphosphate (ATP) and adenosine diphosphate (ADP) to generate adenosine monophosphate (AMP), which is usually then hydrolyzed by CD73 to adenosine. ATP is an important signaling molecule involved in many biological processes including immune responses. While MSCs are known to express CD73, it is unclear whether they also express CD39, and also whether either of these ectoenzymes participates in their immunoregulatory function. In the present study, we demonstrate that GMSCs significantly attenuate inflammatory arthritis in CIA. The therapeutic effects of GMSCs depend mainly upon CD39/CD73 signals. We also find that their effects are at least partially dependent upon the induction and growth of regulatory T (Treg) cells with PMA (50 ng/ml) and ionomycin (500 ng/ml) for 5h, with brefeldin A (10 g/ml; all from Calbiochem) for 4h, and intracellular IL-4, IL-17, IFN-, TNF-, IL-2 and IL-10 expression was analyzed by flow cytometry. Murine na?ve CD4+ T cell differentiation differentiation into T helper cells. GMSCs.