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Objective This pilot clinical study was undertaken to investigate the role of T cell vaccination in the induction of regulatory immune responses in patients with rheumatoid arthritis (RA). Methods Autologous synovial T cells were selected for pathologic relevance, rendered inactive by irradiation, and used for vaccination. Fifteen patients received T cell vaccination via 6 subcutaneous inoculations over a period of 12 months. Results T cell vaccination led to induction of CD4+ Tregs and CD8+ cytotoxic T cells specific for T cell vaccine. There was selective expansion of CD4+,Vβ2+ Tregs that produced interleukin-10 (IL-10) and expressed a high level of transcription factor Foxp3, which coincided with depletion of overexpressed BV14+ T cells in treated patients. CD4+ IL-10–secreting Tregs induced by T cell vaccination were found to react specifically with peptides derived from IL-2 receptor α-chain. The expression level of Foxp3 in CD4+ T cells and increased inhibitory activity of CD4+,CD25+ Tregs were significantly elevated following T cell vaccination. The observed regulatory immune responses collectively correlated with clinical improvement in treated patients. In an intent-to-treat analysis, a substantial response, defined as meeting the American College of Rheumatology 50% improvement criteria, was shown in 10 of the 15 patients (66.7%) and was accompanied by a marked improvement in RA-related laboratory parameters. Conclusion These findings suggest that T cell vaccination induces regulatory immune responses that are associated with improved clinical and laboratory variables in RA patients.