Rheumatoid Tregs (6). Today, it is an

Rheumatoid arthritis (RA) is a chronic inflammatory condition which
has approximately 1% prevalence in the world (1). RA is an autoimmune disorder which is mainly characterized by
synovial inflammation, progressive articular cartilage destruction and finally
bone resorption (2). Inflammatory process in RA is chronic which reflects disruption
of immune regulation. This may be triggered by defect in the mechanisms that
control the immune responses. Lack of these mechanisms lead to an extreme
inflammatory condition which is hallmark of RA (3). Tregs are among critical factors that limits exagerated immune
responses. Tregs as master regulator, play an important role in protecting the
host from autoimmune disorder by suppressing surplus response especially
self-reactive one (4). Tregs are a subset of CD4+ T cells that express
transcription factor forkhead box P3 (Foxp3) which is critical for their
generation and maintenance (1). Stable expression of Foxp3 is regulated by various factors: Demethylation
of the Foxp3 gene locus serves to maintain a stable regulatory T cell
phenotype (5). Treg-specific demethylated region (TSDR) is a CpG rich and highly
conserved region in the first intron of the Foxp3 gene. It seems that
Demethylation in TSDR region is relevant to stability of Foxp3 expression and
the maintenance of the suppressive phenotype for Tregs (6). Today, it is an agreement that epigenetic changes like DNA
methylation are involved in regulating the gene expression (7).  DNA methylation occurs at
the 5 position of cytosine of a CpG dinucleotide and forms 5-methylcytosine (8). These epigenetic changes are now used to identify Tregs in basic
and clinical research (5). Another factor is Helios, a member of the Ikaros transcription
factor family, up-regulates Foxp3 gene expression by binding to the foxp3
promoter and siRNA-mediated Helios knockdown Tregs reveal decreased Foxp3
levels (9). Close to 60–70% of Foxp3+ Tregs  express the transcription factor Helios, but
its exact role in Tregs function remains unknown (10). It has been reported that Helios regulates interleukin-2 (IL-2)
production in Tregs via silencing IL-2 gene transcription and keeps suppressive
function of Tregs (11). Moreover, association of this transcription factor with several
autoimmune disease such as type 1 diabetes mellitus (12), myasthenia gravis (13) and systemic lupus erythematosus (14, 15) have been shown. It can be said that Helios expression controls
certain features of Tregs including suppressive function, differentiation,
survival, and Foxp3 expression (10). As mention above, the function of Tregs in immune hemostasis and
preventing autoimmune reactivity will not be possible without constant Foxp3
expression. In this study, we assumed that Tregs function in RA patients has
been attenuated through altered TSDR methylation and Helios gene expression. Thus,
Foxp3 gene expression along with TSDR methylation was analyzed to compare Tregs
population in RA patients with healthy subjects. In the following, Helios
expression was measured to determine correlation of this factor with Foxp3
expression.