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Regulatory T-cells in systemic lupus erythematosus and rheumatoid arthritis

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Regulatory T-cells in systemic lupus erythematosus and rheumatoid arthritis

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Regulatory T-cells (Tregs) are the guardians of peripheral tolerance acting to prevent autoimmune diseases such as systemic lupus erythomatosus (SLE) and rheumatoid arthritis (RA). Defects in Tregs have been reported in these two diseases despite significant differences in their clinical phenotype and pathogenesis. In both diseases the potency of Treg fails to keep pace with the activation of effector cells and are unable to resist the ensuing inflammation. This review will discuss the phenotypic, numeric, and functional abnormalities in Tregs and their role in patients and murine models of SLE and RA.
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Review
Regulatory T-cells in systemic lupus erythematosus and rheumatoid arthritis
Konstantia-Maria Chavele, Michael R. Ehrenstein
Centre of Rheumatology, The Rayne Building, University College London, 5 University Street, London WC1E 6JF, UK
article info
Article history:
Received 24 June 2011
Accepted 28 July 2011
Available online 4 August 2011
Edited by Richard Williams, Alexander
Flügel, and Wilhelm Just
Keywords:
Regulatory T-cells (Tregs)
Autoimmunity
SLE
RA
abstract
Regulatory T-cells (Tregs) are the guardians of peripheral tolerance acting to prevent autoimmune
diseases such as systemic lupus erythomatosus (SLE) and rheumatoid arthritis (RA). Defects in Tregs
have been reported in these two diseases despite significant differences in their clinical phenotype
and pathogenesis. In both diseases the potency of Treg fails to keep pace with the activation of effec-
tor cells and are unable to resist the ensuing inflammation. This review will discuss the phenotypic,
numeric, and functional abnormalities in Tregs and their role in patients and murine models of SLE
and RA.
Ó
2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
1. Introduction
Autoimmune diseases such as systemic lupus erythomatosus
(SLE) and rheumatoid arthritis (RA) arise due to a failure of immu-
nological self-tolerance. Despite central mechanisms of tolerance,
some T-cells recognizing self-antigens are released into the periph-
ery. One of the mechanisms employed to eliminate or control these
potentially damaging cells is regulatory T-cells (Tregs). The impor-
tance of Tregs is underscored by the overwhelming inflammation
and autoimmunity that results in their absence. This review will
highlight the role of Tregs in two autoimmune rheumatic diseases,
SLE and RA.
A number of immune regulatory cells have been described but
this review will focus on CD4
+
Tregs, which can be divided into nat-
urally occurring and adaptive [1]. In mouse, CD4 Tregs constitute
around 5% of the peripheral CD4
+
lymphocyte population [2]
whereas in humans only 1–2% [3]. Human Tregs were originally
characterized by Sakaguchi et al. as CD4
+
T-cells that constitutively
express the receptor of a chain of IL-2 (CD25) [4]. Unlike the
mouse, several human studies have suggested that only those
CD4
+
T-cells expressing the highest levels of CD25 (CD25
high
) have
in vitro suppressing activity. Although CD25 was the first Treg
marker to be identified, it is also expressed on activated CD4
+
T-
cells. CD127 (the
a
chain of the IL-7 receptor) has more recently
been used to distinguish human Tregs from activated CD25
+
T-
cells. Tregs are considered as CD127
low
whereas activated CD25
+
T-cells are CD127
high
[5,6]. Foxp3 is a critical transcription factor
for the development and function of Tregs and is vital to their phe-
notypic identification [7–9]. In mice, mutation [10] or depletion
[11] of the Foxp3 gene resulted in fatal autoimmune lymphoprolif-
erative disease whereas in human, several mutations of Foxp3 gene
have been linked to a disease called immune dysregulation, poly-
endocrinopathy, enteropathy X-linked syndrome (IPEX) [12,13].
Although Foxp3 is essential for Treg function, as with CD25, CD4
+
T-cells can upregulate the expression of Foxp3 upon activation
[14,15]. These activated Foxp3
+
T-cells are capable of producing
IL-2 in vitro indicating a lack of Treg function. This finding could
be relevant to diseases such as RA and SLE, which are characterized
by marked T cell activation.
Apart from the naturally occurring thymicaly derived Tregs,
stimulation of peripheral CD4
+
T-cells with anti-CD3 and anti-
CD28 in the presence of IL-2 and TGF-b can induce Foxp3 expression
[15,16]. These induced or adaptive Tregs are CD4
+
CD25
+
Foxp3
+
.
Thus the peripheral CD4
+
CD25
+
Foxp3
+
Treg population is a mixture
of both natural and induced Tregs. Recently, Helios has been
identified as a transcription factor that is expressed by natural, but
not induced, Tregs. Thornton et al. showed that all CD4
+
Foxp3
+
thy-
mocytes were Helios
+
whereas Helios expression in peripheral Tregs
was restricted to approximately 70% of CD4
+
Foxp3
+
in both human
and mice. Induced Tregs, either in vitro with anti-CD3 and anti-
CD28 antibody in the presence of IL-2 and TGF-b, or in vivo by expo-
sure to antigen orally, do not express Helios suggesting that Helios is
a thymic-derived Treg maker [17]. Apart from distinguishing differ-
ent populations of Tregs, Helios is also important in their function.
Helios binds the Foxp3 promoter and partially regulates its expres-
sion. Indeed in vitro inhibition of Helios by siRNA oligonucleotides
results in down-regulation of Foxp3 [16]. Additionally, natural Tregs
0014-5793/$36.00 Ó 2011 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.
doi:10.1016/j.febslet.2011.07.043
Corresponding author.
E-mail address: m.ehrenstein@ucl.ac.uk (M.R. Ehrenstein).
FEBS Letters 585 (2011) 3603–3610
journal homepage: www.FEBSLetters.org
have a stable Foxp3 gene expression, which is controlled by epige-
netic mechanisms. Human CD4
+
CD25
high
Tregs display a demethy-
lated FOXP3 promoter in contrast to CD4
+
CD25
low
T cells, where
FOXP3 is partially methylated. Furthermore, stimulated CD4
+
CD25
low
T cells transiently express FOXP3 but remained partially methyl-
ated, suggesting promoter methylation as a mechanism for regula-
tion of stable FOXP3 expression and Treg commitment [18]. Based
on Foxp3 expression, Tregs can also be divided in different popula-
tions. Miyara et al. defined these populations as naïve or resting
Tregs (CD25
high
CD45RA
+
Foxp3
high
) and activated Tregs (CD25
high
C-
D45RA
Foxp3
high
) both of which are suppressive in vitro. There is
also a non-regulatory population that is CD25
high
CD45RA
Foxp3
low
[19]. Several additional markers of Tregs have been identified
including cytotoxic T lymphocyte-associated protein 4 (CTLA-4),
glucocorticoid-induced TNF-receptor (GITR), lymphocyte activated
gene-3 (LAG-3), neutropilin-1 (Nrp1), CD62L
high
,CD39 and CD72
but once again they are not exclusive to Tregs and integrating these
molecules into a clear picture of Treg function remains elusive.
2. Properties and function of Tregs
Regardless of the origin of Tregs (natural or adaptive Tregs),
these cells are considered suppressor cells and able to play a piv-
otal role in the maintenance of immune tolerance. Their impor-
tance in the development of autoimmune diseases was
recognised by Sakaguchi and colleagues who were the first to show
that transfer of CD4
+
T-cells depleted of CD25
+
T-cells, by specific
monoclonal antibodies against CD25, into BALB/c athymic nude
mice caused spontaneous development of T-cell dependent
autoimmune diseases (such as thyroiditis, gastritis, insulitis, sialo-
adenitis, adrenalitis, oophoritis, glomerulonephritis (GN), and pol-
yarthritis). When these mice were reconstituted by CD4
+
CD25
+
T-
cells within a limited period after CD4
+
CD25
T-cell transfer, the
autoimmune disease development was successfully prevented [4].
Most of our knowledge of the function of human Tregs comes
from in vitro experiments. In vitro, Tregs upon antigen stimulation
are anergic and characterized by low proliferation rate and low
secretion of IL-2. Tregs can be expanded in vitro in the presence
of anti-CD3 and IL-2 or when simulated with anti-CD3/CD28. In
vivo, these cells have a high proliferation rate [20]. Tregs after
in vitro activation can suppress proliferation and cytokine produc-
tion of CD4
+
CD25
T-cells [3,21,22]. Tregs can also suppress mono-
cytes, macrophages [23] B-cells [24] and dendritic cells [25]. Tregs
exert their suppressive function through different mechanisms,
which includes secretion of inhibitory cytokines and cytotoxic fac-
tors or by metabolic disruption, or by modulating antigen present-
ing cell (APC) maturation and function.
One mechanism by which Tregs exert suppressive function is
via the secretion of inhibitory cytokines such as IL-10, TGF-b [26]
and IL-35 [27] as well as cytotoxic factors including perforin and
granzymes. Deletion of IL-10 specifically in Treg leads to inflamma-
tion at mucosal surfaces but does not trigger systemic autoimmu-
nity [28]. IL-10 affects the differentiation of dendritic cells and
inhibits the production of IL-12 thus impairing the ability of den-
dritic cells to promote T-cell activation and Th1 differentiation
[29]. Tregs express TGF-b on their surface which is increased upon
in vitro stimulation with anti-CD3, in the presence of monocytes its
membrane expression is increased. Blockade of Treg TGF-b expres-
sion with neutralizing antibodies [26], results in disruption of Treg
suppression suggesting that TGF-b is an important mediator of
Treg suppression activity. IL-35 is another inhibitory cytokine se-
creted by Tregs and required for their suppressive activity. It is a
heterodimer of Epstein-Barr virus-induced gene 3 (Ebi3) and p35
(or Il12
a
). Both genes are highly expressed on mouse Foxp3
+
Tregs
[27,30] but not by resting and activated T-effector cells. In contrast
the heterodimer cytokine IL-35 is constitutively expressed by Treg
but not T-effector cells. Mouse Tregs deficient in Ebi3 and p35 had
significant reduced suppression activity in vitro, and fail to control
homeostatic proliferation and to cure inflammatory bowel disease
in vivo. In addition, ectopic expression of IL-35 confers regulatory
activity on naive T cells, whereas recombinant IL-35 suppresses
T-cell proliferation [27].
Cytolysis through secretion of cytotoxic factors like perforin
and granzyme B is another mechanism used by Tregs to mediate
their suppressive activity. Perforin is a cytotoxic protein that
polymerizes in target-cell membranes to form transmembrane
pores. Granzymes (A and B) is a serine protease, which activates
apoptosis once in the cytoplasm of the target cell. Human adap-
tive Treg cells preferentially express granzyme B whereas acti-
vated human CD4
+
CD25
+
natural Treg cells express granzyme A
but very little granzyme B. Furthermore, both Treg subtypes dis-
play perforin-dependent cytotoxicity against autologous target
cells suggesting that the perforin/granzyme pathway is one of
the mechanisms that Treg cells harness to control immune re-
sponses [31].
Recently, ‘metabolic disruption’ has been described as a further
mechanism of T-effector cells suppression by Tregs and is thought
to involve cytokine deprivation leading to T-effector cell apoptosis.
There is a debate as to whether the high levels of CD25 expression
in Tregs results in local consumption of IL-2 causing IL-2 depriva-
tion of T-effector cells and their apoptosis. Pandiyan et al. showed
in a mouse model of inflammatory disease that cytokine depriva-
tion-induced apoptosis is a prominent mechanism by which Tregs
inhibit T-effector cell responses [32] whereas in humans IL-2
depletion alone was not required by Tregs to suppress T-effector
cells [33]. Tregs can also directly suppress T-effectors by transfer-
ring the inhibitory second messenger cyclin adenosine monophos-
phate (cAMP) through gap junctions to T-effector cells [34]. Finally,
Tregs express ectoenzymes like CD39 and CD73 that generate per-
icellular adenosine, which suppressed T-effector cell function
through activation of adenoisine receptor 2A (A2aR) [35–37].
Adenosine binds to A2aR leading to the induction of Treg cells
through inhibition of IL-6 expression while promoting TGF-b secre-
tion [38].
Tregs can also exert their suppressive function by directly
affecting dendritic cells (DC). One of the molecules involved in
this mechanism is CTLA-4 which is constantly expressed by
Tregs but also by CD4
+
T-cells upon activation. CTLA-4, like
CD28, binds to CD80/CD86 co-stimulatory molecules expressed
by antigen presenting cells and sends a negative signal that
causes inhibition of T-cell activation. Blockade of Treg CTLA-4 re-
sults in reduced T-effector cell suppression mediated by DC [39].
Recently, Qureshi et al. revealed the mechanism of CTLA-4 ac-
tion. CTLA-4 can capture CD80 and CD86 from opposing cells
by a process of trans-endocytosis. After removal, these costimu-
latory ligands are degraded inside CTLA-4 expressing cells,
resulting in impaired costimulation via CD28 [40]. Another way
that Tregs control APCs is by upregulating expression of indole-
amine 2,3-dioxygenase (IDO) which catalyzes tryptophan degra-
dation and kynurenine generation which is associated with T-cell
hyporesponsiveness and apoptosis. IDO is up-regulated by proin-
flammatory cytokines in an attempt to modulate immune
responsiveness and therefore represents a negative regulatory
pathway. Additionally, CTLA-4 signaling through CD80/CD86 in
APC may also up-regulate IDO [41]. IDO expression by DC results
in inhibition of T-effector cell function, including proliferation
and clonal expansion, and reduced survival. Moreover, IDO-
expressing DC may favor the emergence of CD4
+
CD25
+
Foxp3
+
Tregs by the expansion/conversion from naive CD4
+
CD25
Foxp3
T cells [42,43].
3604 K.-M. Chavele, M.R. Ehrenstein / FEBS Letters 585 (2011) 3603–3610
It appears that Treg have multiple mechanisms at their disposal
to suppress immune responses which vary according to the envi-
ronmental and inflammatory context.
3. Tregs in systemic lupus erythromatosus
SLE is a systemic autoimmune disease targeting multiple or-
gans including the skin, joints, kidneys, and central nervous
system. SLE is characterized by abnormalities in both the B-
and T-cell compartments associated with loss of tolerance fol-
lowed by activation and expansion of autoreactive lymphocytes,
the production of inflammatory cytokines and abundant produc-
tion of a wide array of potentially pathogenic autoantibodies. In
SLE, autoantibodies are directed against intranuclear nucleic
acids, proteins and nucleoprotein complexes. Thus autoantibod-
ies in conjunction with loss of tolerance play an important role
in the pathogenesis and clinical manifestation of disease. In both
murine and human SLE, the mechanisms of central tolerance ap-
pears to be unaffected implying that there might be a break-
down in the peripheral tolerance. Given that Tregs are involved
in controlling peripheral tolerance even subtle defects could con-
tribute to the development of disease. The uncontrolled activa-
tion of B- and T-cells and pathogenesis of SLE may be partly
attributed to defects in Tregs.
3.1. Tregs in murine models of SLE
The role of Tregs in lupus-prone mice has been extensively
studied. The first evidence that Tregs have protective effects came
form Treg depletion studies. Hayashi et al. showed that the admin-
istration of anti-mouse CD25
+
T-cell monoclonal antibody (PC61.5)
in autoimmune-prone female NZB NZW F1 (B/WF1) mice, 3 days
after birth, induced the development of nephritis with an increase
in IgG2a antinuclear antibody, elevated IL-6 and IFN-
c
but de-
creased TGF-b production, [44]. New Zealand Mixed 2328
(NZM2328) mice spontaneously develop lupus-like disease with
high circulating levels of autoantibodies to double stranded DNA
and fatal glomerulenephritis. Three-day thymectomy, resulted in
an accelerated double stranded DNA autoantibody response and
early onset of severe proliferative glomerulenephritis with exten-
sive mesangial immune complexes. Transfer of CD25
+
T-cells from
6-week old asymptomatic donors effectively suppressed autoanti-
body production and the development of autoimmune diseases,
with the exception of proliferative lupus nephritis and sialoadeni-
tis [45]. Scalapino et al. nephritis showed that in (New Zealand
Black New Zealand White) F (1) (B/W) lupus-prone mice, adop-
tive transfer of purified and ex vivo expanded (with IL-2 and TGF-
b) CD4
+
CD25
+
CD62L
high
thymic-derived Tregs reduced the inci-
dence of renal disease, or slowed the progression of renal disease
when administered after development of proteinuria [46].
In many of these murine lupus-prone mice strains, such as
(New Zealand Black New Zealand White) F1 (BWF1) and (SWR
Xx New Zealand Black) F1 (SNF1) that spontaneously develop
lupus-like disease the number CD4
+
CD25
+
Tregs is significantly
lower compared to other non-autoimmune mouse strains [46–
48]. In addition, NZM2410 mice that are congenic for the Sle1 locus
have reduced numbers of Foxp3
+
Tregs which correlates with auto-
antibody production and lupus like features [49]. Some of the data
on Treg function in lupus murine models are conflicting. Lupus
prone mouse strains have hyperactive B- [50] and T-cells [51] with
a lower threshold of activation. Several groups have found that
Tregs isolated from lupus-prone mice and cultured in vitro re-
tained their suppressive activities [46,48] whereas other groups
have reported the opposite [52,53]. In addition, T cells from
MLR/lpr mice appear resistant to Treg suppression [52]. Tregs are
therefore not able to control T-cell activation and proinflammatory
cytokine production leading to chronic inflammation. MLR/lpr
mice also have an altered Treg phenotype (CD62L
CD69
+
)
with a profound reduction in Dicer expression and an altered
microRNA profile compared to non-autoimmune strains of mice
[53]. Overall, these observations suggest that both the quantity
and quality of Tregs are important in the development of lupus-like
disease.
These findings also illustrate the important concept that in
diseases such as SLE, Treg function needs to keep pace with
autoreactive T cells causing inflammation and autoimmunity.
Thus if therapies are directed at Treg, restoration of Treg func-
tion to healthy levels may not be sufficient. In order to regain
control of ongoing inflammation, Treg with increased potency
are required. The murine model of chronic graft versus host
(cGVHD) disease is characterized by persistent lymphoid hyper-
plasia and SLE-like disease with splenomegaly, B-cell expansion,
autoantibodies and severe immune complex glemerulonephritis.
Zhang et al. showed that administration of short-term low-dose
anti-CD3 antibody treatment induced significant remission of
proteinuria, production of autoantibodies and renal immune
complex deposition in lupus nephritic mice. These improvements
are associated with up-regulation of renal Foxp3 and IL-10
mRNA expression compared to those treated with control IgG
suggesting that anti-CD3 therapy may induce IL-10 secreting
Foxp3
+
Tregs that eventually suppress T-effector function and
ameliorate lupus nephritis [54].
3.2. Tregs in human SLE
Considerable efforts have been made to delineate the role of
Tregs in the development of SLE in patients. Most of the initial
studies have focused on phenotypic characterization of circulating
Tregs in SLE patients and comparing them with healthy individuals
as well as other patients with autoimmune diseases. Unfortu-
nately, due to limitation in Treg specific markers, this type of inves-
tigation has been challenging to interpret and the results obtained
by different investigators are contradictory. Early reports revealed
that in patients with SLE the number of circulating CD4
+
CD25
+
Tregs were decreased [55–58]. These studies were open to doubt
since identification of Tregs relied on CD25 which can be expressed
by activated CD4
+
T-cells. In more recent studies, investigators
analyzed Tregs as CD4
+
CD25
high
and still found a decrease percent-
age in SLE patients [59–62]. A number of groups have described
that CD4
+
CD25
+
inversely correlate with disease activity. Active
SLE patients also appear to have decreased levels of CD4
+
CD25
high
Tregs compared to inactive SLE patients and healthy individuals
[60]. In addition, different types of treatments used on SLE patients
such as corticosteroid therapy [63], therapeutic plasmapheresis
[64] and B-cell depletion with Rituximab [65,66] increase the cir-
culating percentage of CD4
+
CD25
high
Tregs. In contrast to most
studies, three different groups reported similar levels of circulating
CD4
+
CD25
high
Tregs in SLE patients and healthy individuals
[67–69].
The phenotypic characterization of circulating Tregs in SLE
patients has also been analyzed based on expression of intracel-
lular Foxp3 transcription factor. The results from these studies
did little to resolve the contradictory results from studies based
on CD25 expression. Three reports have shown a decrease of
CD4
+
Foxp3
+
Tregs in SLE patients compared to healthy individu-
als [61,70,71] and another three revealed normal levels of
CD4
+
CD25
+
Foxp3
+
Tregs [67,68,72]. Studies that showed a de-
crease in CD4
+
Foxp3
+
Tregs in SLE patients found an inverse cor-
relation with disease activity [61,70] or showed no correlation
[71]. There are also reports showing an increase of circulating
CD4
+
CD25
+
Foxp3
+
Tregs that correlates with disease activity
K.-M. Chavele, M.R. Ehrenstein / FEBS Letters 585 (2011) 3603–3610
3605
[59,73–76]. Recently, Bonelli et al. showed that SLE patients have
increased numbers of CD4
+
CD25
Foxp3
+
that phenotypically
resemble CD4
+
CD25
+
Foxp3
+
Tregs rather than activated T-cells.
In vitro functional analysis on these cells revealed that they
are able to suppress T-cell proliferation but not IFN-
c
production
[77]. Zhao et al. reported that the proportion of blood
CD4
+
CD25
+
CD127
dim
T-cells of the SLE patients was not signifi-
cantly different from that of the healthy individuals. However,
the proportions of CD4
+
CD25
+
FOXP3
+
T-cells and CD4
+
CD25
high
T-cells of SLE patients were significantly lower than those of
the healthy individuals [72].
Trying to quantify circulating Tregs in patients with SLE may
be influenced by the deposition of these cells in lymph nodes
and inflamed tissues. Unfortunately, there is limited information
about Tregs infiltration and deposition in lymph nodes and in-
flamed organs such as the skin and kidney in SLE patients. Miy-
ara et al. reported a decreased number of Foxp
+
Tregs in lymph
nodes from patients with SLE and reduced levels of Foxp3 mRNA
isolated from SLE patients with active nephritis [60]. Another
study done in patients with cutaneous SLE, also found a de-
creased number of Foxp3
+
Tregs in skin specimens obtained de-
spite the fact that these patients had a normal number of
circulating Foxp3
+
Tregs [69].
Apart from the quantitative analysis of Tregs in SLE patients,
several studies were also focused on the qualitative and functional
analysis of Tregs in SLE patients. These studies also show diverse
results. Several groups have reported abnormalities in the suppres-
sive function of CD4
+
CD25
high
Tregs [59,61,62,67,70,71,74,78]
whereas other groups did not confirm such alteration [57,75,79–
81]. In most studies, the suppressive defects of SLE patients were
attributed to Tregs, whereas others have indicated an increased
resistance to suppression by T-responder cells. Venigalla et al.
showed that CD4
+
CD25
T-responder cells isolated from patients
with active SLE were significantly less sensitive than those from
patients with inactive SLE to the suppressive function of autolo-
gous or normal donor CD4
+
CD25
+
CD127
dim
T-cells. Furthermore,
a significant inverse correlation was observed between regulatory
T cell suppressor function and the level of lupus disease activity
[67]. Consistent with this finding, other groups have reported im-
paired Treg function when cultured with autologous T-effector
cells but not when T-effector cells come from healthy individuals
suggesting a possible resistance of lupus T effector cells to Treg
suppression [62,67,78].
Despite the plethora of studies focused on Tregs and SLE, their
role in disease initiation and development remains elusive. A num-
ber of reasons are likely to account for this lack of clarity. The
markers that define Treg such as CD25 and Foxp3 can also be in-
duced at least transiently upon T-cell activation [1,14,82,83]. One
of the basic features of SLE is persistent T cell activation. For this
reason, studies based on phenotypic characterization of circulating
Tregs must be regarded with caution. In addition, SLE is a disease
with a very heterogeneous patient population and their pathogen-
esis is unlikely to be uniform. Disease activity and different thera-
pies could also alter Treg numbers or function. For example active
disease was positively correlated with decreased numbers and
suppressive function of Tregs whereas patients with inactive dis-
ease showed no difference to healthy individuals [60]. Addition-
ally, patients treated with corticosteroid therapy [63],
therapeutic plasmapheresis [64] and B-cell depletion with Ritux-
imab [65,66] have increased numbers of Tregs in their circulation.
Discrepancies in findings related to Treg function could be due to
different methods used to isolate Tregs from blood (e.g. Treg isola-
tion with magnetic beads versus FACS sorting), the different cell
markers used to isolate Tregs, the different in vitro stimuli used
to activate T-effector cells as well as the presence or absence of
accessory cells (e.g. monocytes) in the in vitro assays.
4. Tregs in rheumatoid arthritis
Rheumatoid arthritis (RA) is characterized by swelling of the
synovium and damage of the cartilage around the joints leading
finally to the joint destruction. Several factors play a role in dis-
ease development. The role of TNF-
a
and IL-6 as key mediators
of RA has been proven and blokade of these cytokines has been
successfully introduced as therapies in RA patients. The role of
Tregs has been demonstrated in both murine models of autoim-
mune arthritis and patients with RA. On the whole, Treg func-
tion has been reported to be impaired whereas the number of
circulating Tregs varies depending on the study. Recently inves-
tigations into Tregs focus on the balance between Tregs and
other proinflammatory T-cell populations such as Th17 cells
[85].
4.1. Tregs in murine models of rheumatoid arthritis
Collagen-induced arthritis (CIA) is the most common murine
model used to investigate the role of Tregs in disease and is in-
duced after immunization of mice with bovine type II collagen
emulsified in complete Freund’s adjuvant [86,87]. Morgan et al.
targeted CD4
+
CD25
+
Tregs in these arthritic mice by administra-
tion of a monoclonal antibody specific for CD25. As a result,
these anti-CD25 treated mice had worse disease than controls.
Disease exacerbation was accompanied by higher antibody titers
against collagen, and in vitro tests showed increased prolifera-
tion of collagen-specific T cells. When CD4
+
CD25
+
Tregs were
administered back into CD25
+
depleted mice, at the time point
of immunization, disease severity was reduced [88]. Tregs slo-
wed disease progression although there was no difference in T-
and B-cell responses. Adoptively transferred CD4
+
CD25
+
Tregs
were located in the synovial tissue of affected joints soon after
transfer indicating that regulation may occur locally in the joint
[89]. Transfer of Foxp3-transduced CD4
+
T-cells also ameliorated
CIA although the time point of transfer is critical for modulating
disease severity. CD4
+
Foxp3
+
Tregs were able to reduce the
severity of CIA when transferred prior to collagen immunization.
When transferred 20 days after collagen immunization, a higher
number of CD4
+
Foxp3
+
Tregs was needed suggesting increased
resistance to suppression whereas if transferred even later after
the booster immunization they had no effect on disease modula-
tion. Apart from the time point of Treg transfer, the route of
administration is also important. Tregs administered systemically
rather than directly into the inflamed joint were more effective
in modifying disease [90].
Antigen-induced arthritis (AIA) is another model of murine
rheumatoid arthritis and is induced by pre-immunization of
mice with methylated bovine serum albumin in complete Fre-
und’s adjuvant followed 21 days later by an intra-articular injec-
tion of the knee joint with methylated bovine serum albumin
diluted in saline [91]. In AIA, depletion of CD25
+
expressing cells
in immunized animals before arthritis induction led to an exac-
erbation of arthritis as indicated by knee swelling and histolog-
ical scores and increased cellular and humoral immune
responses to the inducing antigen. Transfer of CD4
+
CD25
+
cells
into immunized mice at the time of induction of antigen-in-
duced arthritis decreased the severity of disease but was not
able to cure established arthritis. As in the CIA models, trans-
ferred CD4
+
CD25
+
cells accumulated in the inflamed joint [92].
Regardless of the murine model of disease, Treg depletion and
adoptive transfer experiments have shown that Tregs are able
to modify disease severity and immune responses. However,
the exact mechanism by which Treg modulate disease remain
unclear.
3606 K.-M. Chavele, M.R. Ehrenstein / FEBS Letters 585 (2011) 3603–3610
Manipulation of Tregs either directly or indirectly has also been
proven successful in treating arthritis in murine models of disease.
Wright et al. showed that adoptive transfer of antigen specific
Tregs (generated by retroviral T-cell receptor gene transfer into
purified CD4
+
CD25
+
Tregs) in mice with AIA resulted in reduction
of Th17 cells and a significant decrease in arthritic bone destruc-
tion [93]. Recently, an indirect way of targeting Tregs in the AIA
model of arthritis by using tolerogenic DC loaded with antigen
has been described. Administration of DC transfected with an
ERK activator and OVA in mice with AIA, maintains DC in an imma-
ture state. As a result, DC present antigen at suboptimal levels,
leading to inhibition of CD8 T-cell expansion and secretion of
TGF-b that directs antigen specific Treg differentiation and prolifer-
ation rather than expansion of CD4
+
T-effector cells. As a result
arthritis is significantly inhibited through antigen specific Tregs
[94]. Finally, administration of anti-CD3 monoclonal antibody in
the CIA murine model of arthritis has proven to be effective in
treating disease severity through expansion of naturally occurring
CD4
+
CD25
+
Foxp3
+
Tregs and the generation of CD8
+
CD25
+
Foxp3
+
Tregs [95].
4.2. Tregs in human rheumatoid arthritis
As with SLE, many human RA studies focused on quantifying
Treg numbers in the peripheral blood, but also at the site of inflam-
mation. In RA patients the number of Tregs present in synovial
fluid is higher than that in the peripheral blood. Tregs accumulated
in inflamed joints express high levels of surface and intracellular
CTLA-4, GITR, OX-40, and Foxp3 [96]. Data regarding the number
of Tregs in the circulation of RA patients compared to healthy indi-
viduals are inconclusive and contradictory. Some studies showed a
decrease of circulating Treg in RA patients [97–99] whereas others
showed no difference in circulating Treg numbers compared to
healthy individuals [96,100–102] and some indicated an increase
in circulating Treg numbers [103,104].
Studying Treg function in patients with RA has been informa-
tive. Although Tregs present in the synovial fluid of patients with
RA have an enhanced capacity to suppress both T-cell proliferation
and cytokine production (TNF-
a
and IFN-
c
) disease is still able to
progress. T-responder cells present in the synovial fluid were less
susceptible to suppression compared with circulating T-responder
cells [103]. This data is consistent with the observation that
strongly activated CD4
+
T-cells are resistant to Treg suppression
[105]. Our group has reported that CD4
+
CD25
+
circulating Tregs
are able to suppress proliferation of T-effectors but were unable
to suppress proinflammatory cytokine secretion from activated
T-cells and monocytes [102]. This deficiency of RA Tregs is associ-
ated with defective expression and function of CTLA-4, a key mol-
ecule linked to their suppressive function. Expression of CTLA-4 is
reduced in RA Tregs compared to healthy Tregs which correlates
with reduced function. Artificial induction of CTLA-4 expression
on RA Treg in vitro restored their suppressive capacity. Further-
more, CTLA-4 blockade impaired healthy Treg suppression of T-cell
IFN-
c
production, but not T-cell proliferation. These data suggest
that Tregs control T-cell proliferation and cytokine production
through different mechanisms [106]. Furthermore, CTLA-4 gene
polymorphisms have also been correlated with autoimmune dis-
eases like RA [107] and SLE [108].
In RA, Tregs especially those present in the synovial fluid are
also influenced by the cytokine profile. TNF-
a
, IL-6, IL-15, and IL-
1 present in the inflamed joint act to increase the number of
infiltrating Tregs in the inflamed joint but at the same time im-
pair their function. For example IL-6 secreted by DC after TLR
stimulation induces T-responder cell resistance to Treg mediated
suppression [109]. TNF-
a
and IL-7 secreted by activated mono-
cytes in the inflamed joint have a direct effect on CD4
+
CD25
+
Tregs by abrogating their suppressive activity [110]. In vitro
addition of TNF-
a
at high concentrations in Treg suppression as-
says inhibit the suppressor function of Tregs by down regulating
Foxp3 expression [111].
Different types of RA treatment can also affect the function of
Tregs. Our group has demonstrated that after the resolution of
inflammation by administration of anti-TNF therapy (anti-TNF
a
antibody infliximab) the Treg function that was originally im-
paired appeared to be restored [102]. Patients treated with inf-
liximab had two different populations of Tregs. Natural Tregs
characterized by CD62 Ligand expression (CD62L
+
) and induced
Tregs that were CD62L
. In patients who responded to anti-
TNF therapy, the CD62L
+
Tregs were still unable to suppress
TNF-
a
and IFN-
c
production by T-responder cells whereas in-
duced CD62L
Tregs from the same patients suppressed TNF-
a
and IFN-
c
production by T-responder cells through the produc-
tion of IL-10 and TGF-b rather than CTLA-4 [112]. Although
anti-TNF treatment works for most patients, after withdrawal
of treatment relapse usually ensues raising the possibility that
to induce long lasting remission natural Tregs need to be func-
tionally restored. Some of these findings have recently been con-
firmed using a mouse model of arthritis. Regulatory T cells with
a reduced expression of CD62L are increased in a TNF driven ar-
thritic mouse model treated with anti-TNF [113].
Treg stability in inflammatory conditions like RA and their rela-
tionship with inflammatory Th17 cells has been studied in the last
few years. In an inflammatory condition like RA, it is quite possible
that Tregs in the presence of the different proinflammatory cyto-
kines will become unstable and convert to pathogenic T-cells. Treg
secreting Th17 have been described though their function is not
necessarily impaired. Ayyoub et al. showed that circulating mem-
ory Tregs secrete IL-17 ex vivo [114]. In addition, memory Tregs
when cultured in vitro with IL-1b and IL-6 secrete IL-17 whereas
IL-17 secretion was prevented in the presence of TGF-b suggesting
that inflammatory conditions impair Tregs cell function and pro-
mote IL-17 production [115]. The mechanisms affecting Treg sta-
bility under inflammatory conditions are linked to regulation and
epigenetic modification of the Foxp3 gene. Complete demethyla-
tion of CpG residues in the proximal promoter of Foxp3 gene is re-
quired for stable Foxp3 expression. IL-6 and possibly other
proinflammatory cytokines like TNF-
a
and IL-1b promote reme-
thylation of CpG residues in the proximal promoter of Foxp3 gene
resulting in downregulation of Foxp3 expression by Tregs
[116,117].
5. Conclusion
Tregs play a pivotal role in controlling autoimmune responses
and inflammation. Subtle changes in Treg number, function or
phenotype could lead to the development of autoimmune dis-
eases such as SLE and RA, but also may be a consequence of
the inflammatory environment (Fig. 1). In comparison to data
from murine models of disease, clear conclusions as to the nat-
ure of Treg defects in patients with SLE and RA have yet to be
realized due to the many contradictory reports. The discovery
of new specific Treg markers will help to resolve these issues
but disease heterogeneity and the number of therapies available
also contributes to some of the conflicting findings. Accurate pa-
tient classification and analysis of subgroups of patients will be
important in future studies. In addition, the importance of Treg
at different phases of disease may vary. Evidence from both dis-
eases suggest that the potency of T-effectors and the suppressive
effects of Treg need to be carefully balanced. Further research is
needed in human diseases to determine how to increase the
suppressive power of Tregs, perhaps only for a short period, in
order to restore immunological tolerance.
K.-M. Chavele, M.R. Ehrenstein / FEBS Letters 585 (2011) 3603–3610
3607
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3610 K.-M. Chavele, M.R. Ehrenstein / FEBS Letters 585 (2011) 3603–3610
... The binding of HLA-G to LILRB1 on NK cells, T cells, and macrophages can inhibit the cytotoxicity of NK cells and CD8+ T cells as well as increase the number Treg cells, contributing to development of immune tolerance 21 . We hypothesize that the loss-of-function variant in LILRB1 with a significantly lower LILRB1 on the surface of activated Treg cells might lead to defective suppressive function and immune regulation failure leading to autoimmune diseases 22 . ...
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... RA also suppresses Th17 cell development by increasing TGF-β signalling and reducing the level of expression of the IL-6 receptor (105,106). It is thought that when conditions favour immune tolerance, there is a balance between effector T cells and Treg cells, whereas imbalances occur in autoimmunity, which could be due to inadequate numbers of Treg cells, defects in Treg function or phenotype or reduced responsiveness of effector T cells to Treg-mediated suppression (107). Therefore relative increase in iTreg and the inhibition of Th17 development mediated by RA, can shift the balance of these cells toward more effective immune homeostasis (20). ...
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... Considering (a) the ability of GDF15 to stimulate immunoregulatory Treg maturation as well as their role in immune tolerance [21] and (b) the pleiotropic suppressive function of GDF15 on DC and macrophage activation and their role in systemic inflammation [22], we hypothesized that GDF15 suppresses progression of lupuslike autoimmunity in mice. In particular, we postulated an aggravated serologic and nephritic phenotype in lupus-prone C57BL/6 lpr/lpr mice in the absence of GDF15. ...
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Growth and differentiation factor 15 (GDF15), a divergent member of the transforming growth factor-β superfamily, has been associated with acute and chronic inflammatory conditions including autoimmune disease, i.e., type I diabetes and rheumatoid arthritis. Still, its role in systemic autoimmune disease remains elusive. Thus, we studied GDF15-deficient animals in Fas-receptor intact (C57BL/6) or deficient (C57BL/6lpr/lpr) backgrounds. Further, lupus nephritis (LN) microdissected kidney biopsy specimens were analyzed to assess the involvement of GDF15 in human disease. GDF15-deficiency in lupus-prone mice promoted lymphoproliferation, T-, B- and plasma cell-expansion, a type I interferon signature, and increased serum levels of anti-DNA autoantibodies. Accelerated systemic inflammation was found in association with a relatively mild renal phenotype. Splenocytes of phenotypically overall-normal Gdf15−/− C57BL/6 and lupus-prone C57BL/6lpr/lpr mice displayed increased in vitro lymphoproliferative responses or interferon-dependent transcription factor induction in response to the toll-like-receptor (TLR)-9 ligand CpG, or the TLR-7 ligand Imiquimod, respectively. In human LN, GDF15 expression was downregulated whereas type I interferon expression was upregulated in glomerular- and tubular-compartments versus living donor controls. These findings demonstrate that GDF15 regulates lupus-like autoimmunity by suppressing lymphocyte-proliferation and -activation. Further, the data indicate a negative regulatory role for GDF15 on TLR-7 and -9 driven type I interferon signaling in effector cells of the innate immune system.
... Inhibition of glycolysis and fatty acid oxidation can promote the development and differentiation of Treg cells, and inhibit the differentiation of Th17 cells (315). Deficient or scarce Treg cells have been found both in murine models of SLE and in human SLE studies (316). Studies have shown that peripheral blood Treg cells decline in number and abnormal Treg cell phenotypes are present in SLE patients (317). ...
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... This finding may explain the impaired role of regulatory T cells during the autoimmune process. 44 We also evaluated the ratio of T helper subsets including Th1/Th2, Th1/Treg, Th2/Treg, and Th17/Treg using the specific transcription factors. Our results indicated that the ratio of T-bet/GATA3 and T-bet/foxp3 mRNA levels were increased in group A in comparison to other groups showing skewness of Th subsets towards Th1. ...
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Mechanisms underlying the systemic lupus erythematosus (SLE) have not yet been elucidated. In this study, we evaluated the balance of T cell subsets in BALB/c mice model of SLE induced; using Con A and polyamines as DNA immunogenicity modifiers. BALB/c mice were immunized subcutaneously with 50 µg extracted DNA from cells cultured in different conditions: splenocytes+ polyamines (group P), splenocytes+ Con A (group A), splenocytes+ polyamines+ Con A (group PA) and splenocytes only (control). Anti-double-stranded DNA –(ds-DNA) antibodies, proteinuria, and antinuclear autoantibodies were assessed by enzyme-linked immunosorbent assay, Bradford method, and immunofluorescence respectively. Transcription factors of different T helper subsets were examined by real-time polymerase chain reaction. The serum level of the anti-dsDNA antibody in group PA was higher than that in the other groups (p>0.05). Antinuclear antibody (ANA) titer increased in groups A and PA. Proteinuria level in group PA was significantly higher than that in the control group (p0.05). Our results revealed an increased ratio of Th1 to Th2 and decreased expression of Foxp3 in group A, but group PA manifested more obvious signs of the disease. These results suggest that other mechanisms rather than disturbance in T cells' balance may involve the development of disease symptoms.
... Other groups have observed no abnormalities (62,63). These discrepancies are due in part to the lack of a unique marker or combination of markers for identifying and isolating bona fide Tregs, the use of different in vitro stimuli, and the presence or absence of antigen-presenting cells (APCs) in ex vivo functional assays (64). An important challenge in the study of the pathogenesis of SLE is the difficulty of obtaining patient lymphoid tissues to assess TFRs directly; for this reason, most studies have focused on circulating Tregs in peripheral blood. ...
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Systemic lupus erythematosus (SLE) is a chronic multi-organ autoimmune disease involving the production of a wide range of autoantibodies and complement activation. The production of these high-affinity autoantibodies requires T cell/B cell collaboration as well as germinal center (GC) formation. T follicular regulatory cells (TFRs) are functional specialized T regulatory cells (Tregs) that safeguard against both self-reactive T and B cells. However, recent evidence suggests that TFRs are not always stable and can lose Foxp3 expression to become pathogenic “ex-TFRs” that gain potent effector functions. In this review, we summarize the literature on intrinsic and extrinsic mechanisms of regulation of TFR stability and discuss the potential role of TFR reprogramming in autoantibody production and SLE pathogenesis.
... Because depletion of naturally occurring Tregs leads to excessive proliferation of effector T cells, they plays a crucial role in immune tolerance and regulation of immune balance [12,13]. Our previous study [14] found that decreased and increased proportions of Tregs and Th17 cells, respectively, positively correlated with disease severity in LN. ...
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In this study, we first analyzed the expression level of fractalkine (FKN) in the serum of patients with lupus nephritis (LN) and the distribution of peripheral blood Treg cells, and explored FKN and Treg cells, systemic lupus erythematosus disease activity index 2000 (SLEDAI-2K) correlation. Subsequently, we explored the specific role of FKN in tubule interstitial lesions (TILs) and regulatory T (Treg) cells/T helper (Th) 17 cell balance in lupus model mice. Treated with an anti-FKN antibody (aFKN), recombinant FKN (rFKN), or an isotype antibody (IgG) in MRL/MpJ-Faslpr/J and C57BL/6 mice, and then detected TIL level and forkhead box p3 (Foxp3), IL-10, IL-17 and IL-6 expression levels in the kidney and spleen in the proportion of Treg and Th17 cells. Finally, then use aFKN, rFKN, or IgG to intervene in polarized Tregs with IL-6, TGF-β, IL-23, anti-interferon, and Th17 cells with anti-IL-4 after transforming to transform growth factor (TGF)-β and interleukin (IL)-2 in isolated mouse spleen lymphocytes. The results showed that the expression level of FKN was positively correlated with SLEDAI-2K and negatively correlated with the distribution of Treg cells. After treatment with aFKN in lupus model mice, kidney damage was delayed, TIL formation was reduced, Foxp3 and IL-10 levels were up-regulated, IL-17 and IL-6 levels were down-regulated in renal tissues, Th17 cell subsets and Treg cell subsets were reduced The increase is in the spleen, and rFKN treatment has the opposite effect in mouse. In addition, after interfering with polarized cells by aFKN, it was found that IL-17 and IL-6 expression levels were down-regulated in Th17 cells, Foxp3 and IL-10 levels in Tregs were up-regulated, and rFKN treatment had the opposite effect in vitro. These results indicate that FKN participates in and promotes SLE target organ damage including: secretion of inflammatory factors and renal TIL, and most importantly, these effects might have been due to modification of the Treg/Th17 cell balance.
... Previous study proposed that in an inflammatory disorder, it was relatively possible that T-regs in the presence of the different pro-inflammatory cytokines will become unbalanced and convert to pathogenic T-cells. Serum cytokine environment of active RA illness is not in favor of the development of Tregs cells (Chavele and Ehrenstein, 2011). T-regs which are specialized in the maintenance of immune tolerance and homeostasis and which secrete several immune-suppressive and antiinflammatory cytokines such as IL-10, IL-27, Transforming growth factor- (TGF-) and IL-3. ...
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The aim of the study to determination of the precise percentage of T-regs cells in rheumatoid arthritis (RA) patients to discover the manipulating role of menopause statues (pre and post) in the percentage of these cells in patients and may eventually influence the development of rheumatoid arthritis. Also to explore the possibility of using some cytokines as a marker for disease activity by evaluating the direct potential role of IL-35 and the indirect potential contribution of IL-33 and its soluble receptor sST2 on the percentage of effectors T-regs cells. This study was conducted on a total of 90 women: 60 of them were RA women patients (30 premenopausal and 30 postmenopausal women) and 30 healthy controls (15 premenopausal and 15 postmenopausal women). All RA patients and controls were diagnosed by measuring (ESR, CRP, Anti CCP and RF). IL 33, sST2 and IL-35 level was measured in the serum of both RA patient group and control group by ELISA, were the T-regs percentages evaluated in whole blood by flowcytometery. The results showed that the total mean concentration of IL-33/sST2 in women infected with RA was significantly (p<0.01) increased in comparison to total control group. However, postmenopausal women scored highly significant (p<0.01) increase of IL-33/sST2 in comparison to premenopausal women both stages declared a significant (p<0.01) increase in comparison to control group. The total mean concentration of IL-35 and T-regs percentages in women infected with RA was significantly (p<0.01) decreased in comparison to total control group. However, postmenopausal women scored highly significant (p<0.01) decreased of IL-35 and T-regs percentages in comparison to premenopausal women. Serum IL 33/sST2 showed significantly positive correlations with DAS 28, while IL-35 and T-regs showed significantly negative correlations with DAS 28. It can be conclude that IL 33/sST2 has an important pro-inflammatory role in the pathogenesis of RA, while IL-35 and T-regs has an important anti-inflammatory role correlation with disease activity. Highly positive significant linear correlation was seen between T-regs and IL-35 they may become potential therapeutic targets for RA.
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A model of arthritis was established by the injection of type II collagen into mice. Only mice bearing the H-2q haplotype were susceptible to the disease. Susceptibility was further mapped by the use of recombinant strains on the Iq locus. Type II collagen arthritis was observed in the (resistant X susceptible) F1 cross. Mice strains were designated high, intermediate, or low responders with respect to the anti-type II antibody levels measured by radioimmunoassay. Arthritis-susceptible strains were all classified as high antibody responders. The clinical and histological appearance of type II collagen arthritis in the mouse indicates that it may be a good animal model for the investigation of various immunogenetic traits in rheumatoid arthritis.
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Antigen-induced arthritis was established in the mouse by immunization with methylated bovine serum albumin (mBSA) in complete Freund's adjuvant with B pertussis vaccine. The knee joint was injected after 21 days with mBSA in saline. The arthritis was chronic, antigen-specific, and T-cell dependent in hypothymic nu/nu mice. C57BL and BALB/c mice were susceptible, whereas CBA mice were relatively resistant. Susceptibility was dominant; one gene was loosely linked to the “b” allele of the H-2 complex of C57BL mice.
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Accumulating evidences support that CD4(+)CD25(high) T regulatory (Treg) cells play an essential role in controlling and preventing autoimmunity. Paradoxically, RA patients have elevated numbers of circulating CD4(+)CD25(high) T cells, however, the inflammation is still ongoing. Further identification of these CD4(+)CD25(high) T cells may contribute to a better understanding of underlying mechanisms. We show here that these CD4(+)CD25(high) T cells were composed of CD4(+)CD25(high)FoxP3(+) Treg cells and activated CD4(+)CD25(high)FoxP3(-) effector cells. Moreover, there were significantly more Treg cells and effector T cells expressing GITR, and more monocytes expressing GITR-L. Thus, although RA patients have elevated numbers of CD4(+)CD25(high) T cells, the suppressive function is not increased, because of the increased number of activated effector T cells. In addition, the GITR-GITR-L system was activated in RA patients, which might lead to diminish suppressive activity of Treg cells and/or lead to resistance of activated effector T cells to suppression by Treg cells, thus, contributing to the ongoing inflammation in RA patients.
To detect the new and old surface markers of regulatory T cells (Treg cells) in the CD4+ T cells of the patients with systemic lupus erythematosus (SLE) in order to reveal the role of Treg cells in the pathogenesis of SLE. Peripheral blood samples were collected from 29 newly diagnosed and treatment-naïve SLE patients, 3 males and 26 females, aged (34 +/- 13), and 24 sex and aged-matched healthy controls. Three-color flow cytometry was used to detect the CD4+CD25+ CD127(low/-) T cells, CD4+CD25high T cells, and CD4+CD25+FOXP3+ T cells. The serum anti-nuclear antibody (ANA), anti-ds-DNA antibody, anti-smooth muscle antibody, anti-nucleosome antibody, anti-C1q, C3, and C4 were detected. Blood and urine routine examinations were conducted. The proportion of blood CD4+ CD25+CD127(low/-) T cells of the SLE patients was not significantly different from that of the controls (P > 0.05), however, the proportions of CD4+CD25+FOXP3+ T cells and CD4+CD25high T cells of the SLE patients were 2.1 +/- 1.2 and 0.8 +/- 0.4 respectively, both significantly lower than those of the controls (4.0 +/- 1.4 and 1.8 +/- 0.8 respectively, both P <0.01). The ratios of the CD4+CD25+CD127(low/-) T cells, CD4+CD25high T cells, and CD4+CD25+FOXP3+ T cells to the CD4+CD25+ T cells of the SLE patients were 0.5 +/- 0.1, 0.1 +/- 0, and 0.3 +/- 0.1 respectively, all significantly lower than those of the controls (0.6 +/- 0.1, 0.2 +/- 0.1, and 0.5 +/- 0. respectively, all P <0.01). The level of CD4+CD25+CD127(low/-) T cell was positively correlated with the levels of CD4+CD25+FOXP3+ T cells and CD4+CD25high T cell (both P < 0.01). The levels of these 3 kinds of cells and their ratios to CD4+CD25+ T cells had no correlation with age, sex, course, IgG, IgA, IgM, urine protein, TIPU, anti-dsDNA, anti-C1q, anti-nuclear body antibody (all P > 0.05), however, were significantly associated negatively with SLE disease activity index, P < 0.05). Only the CD4+CD25+CD127(low/-) T cells/ CD4+CD25+ T cells was negatively correlated with C4 (P <0.01). The relative ratio of Treg cells to the activated CD4+ T cells may play an important role in the pathogenesis of SLE.