BACKGROUND: Regulatory T cells (Tregs) have been investigated intensively for some decades. These cells regulate the immune system, prevent overactivated immune responses and can be used therapeutically. For rheumatoid arthritis (RA), understanding the functions and status of Tregs is an important step for understanding immune regulation in this autoimmune disease.0aMETHODS: We investigated the percentages, phenotypes and suppressive functions of CD4RESULTS: The percentages were higher in the patients (n25oing inflammation ineffectively. It might be possible to apply IL-10 to induce the proliferation of IL-10-producing Tregs as therapy for RA