OBJECTIVE: Rheumatoid arthritis (RA) is an autoimmune disease caused by loss of immunologic self tolerance and characterized by chronic joint inflammation. Cells isolated from human amniotic membrane (HAMCs) were recently found to display immunosuppressive properties. The aim of this study was to characterize the effect of HAMCs on antigen-specific T cell responses in RA patients and to evaluate their therapeutic potential in a preclinical experimental model of RA. METHODS: We investigated the effects of HAMCs on collagen-reactive T cell proliferation and cytokine production, on the production of mediators of inflammation by synoviocytes, and on the generation of Treg cells in peripheral blood mononuclear cells and synovial membrane cells isolated from RA patients. Mice with collagen-induced arthritis (CIA) were treated with HAMCs after disease onset, and clinical scores and joint levels of mediators of inflammation were evaluated. We determined Th1/Th17-mediated autoreactive responses in the mice by measuring the proliferation and the cytokine profile of lymph node cells restimulated with collagen. RESULTS: Treatment with HAMCs suppressed synovial inflammatory responses and antigen-specific Th1/Th17 activation in cells isolated from RA patients. Moreover, HAMCs stimulated the generation of human CD4+CD25+FoxP3+ Treg cells with a capacity to suppress collagen-specific T cell responses. Systemic infusion of HAMCs significantly reduced the incidence and severity of CIA by down-regulating the 2 deleterious components of disease: Th1-driven autoimmunity and inflammation. In mice with CIA, HAMC treatment decreased the production of various inflammatory cytokines and chemokines in the joints, impaired antigen-specific Th1/Th17 cell expansion in the lymph nodes, and generated peripheral antigen-specific Treg cells. HAMCs also protected the mice from experimental sepsis, inflammatory bowel disease, and autoimmune encephalomyelitis. CONCLUSION: HAMCs have emerged as attractive candidates for a cell-based therapy for RA.