International Reviews of Immunology, Early Online:1–17, 2013 C Informa Healthcare USA, Inc. Copyright ISSN: 0883-0185 print / 1563-5244 online DOI: 10.3109/08830185.2013.845181
REVIEW
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Interferon-Gamma Producing Regulatory T Cells as a Diagnostic and Therapeutic Tool in Organ Transplantation Volker Daniel,1 Haihao Wang,1,2 Mahmoud Sadeghi,1 and Gerhard Opelz1 1
Department of Transplantation-Immunology, Institute of Immunology, University of Heidelberg, Heidelberg, Germany; 2 Institute of Organ Transplantation, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology and Key Laboratory of Organ Transplantation, Ministry of Education, Key Laboratory of Organ Transplantation, Ministry of Health, Wuhan, China
There is increasing evidence that IFNg plays a major role in both induction of Tregs as well as immunosuppression mediated by IFNg-producing Tregs. The present review focuses on a small subset of iTregs that produces IFNg, comprises only 0.04% of all CD4+ T lymphocytes in the blood of healthy individuals, and increases strongly during an immune response. IFNg+ Tregs are induced by IFNg and IL12, making them sensors for inflammatory cytokines. They develop rapidly during inflammation and represent the first line of Tregs that suppress initial immune responses. The pool of IFNg+ Tregs consists of activated stable immunosuppressive thymus-derived nTregs as well as peripherally proliferating iTregs with in part only transient immunosuppressive function, which limits their diagnostic and therapeutic usefulness in organ transplantation. Apparently, a part of IFNg+ Tregs dies during the immune response, whereas others, after efficient immunosuppression with resolution of the immune response, differentiate toward Th1 lymphocytes. Goals of further research are the development of appropriate diagnostic tests for rapid and exact determinination of immunosuppressive IFNg+ iTregs, as well as the induction and propagation of stable immunosuppressive IFNg+ Tregs that establish and maintain good long-term graft function in transplant recipients. Keywords Diagnostic and therapeutic tool, IFNg, IFNg+ Tregs, immunosuppression, Helios, MLC, T-bet, transplantation, TSDR
OVERVIEW Tregs constitute an attractive diagnostic and therapeutic target given their essential role in controlling autoimmunity as well as immune responses against alloantigens. Before this tool can be fully employed, however, it must be considered that, at the current stage of knowledge, studies in animals, healthy individuals, and patients provide evidence for heterogeneity and plasticity within the Treg compartment [1].
Received 18 March 2013; accepted 9 September 2013. Address correspondence to Volker Daniel, MD, Department of Transplantation-Immunology, Institute of Immunology, University of Heidelberg, Im Neuenheimer Feld 305, 69120 Heidelberg, Germany. E-Mail: [email protected]
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V. Daniel et al.
Activated na¨ıve CD4+ T cells can differentiate into Th effector cell subsets (T helper lymphocyte 1 (Th1), Th2, Th17, and follicular helper) or into regulatory T cells (Tregs), depending on the type of antigen-presenting cell (APC), the APC maturation state, and the cytokine milieu encountered during differentiation [2, 3]. Tregs express the transcription factor foxhead box p3 (Foxp3) and the interleukin 2 receptor (IL2R, CD25) [4–7]. Expression of CD127 on the surface of human T cells decreases after cell activation and is inversely related with intracellular Foxp3 expression [8]. Additional markers are associated with activation and memory, homing and origin, suppressive and effector function as well as apoptosis and survival, forming a heterogenous and plastic Treg pool as highlighted by Sakaguchi et al. [1, 9]. Treg suppression is mediated by modulation of the cytokine microenvironment, secretion of immunosuppressive cytokines [IL10, transforming growth factor-beta (TGFβ)], conversion of molecules to immunosuppressants [CD39, cytotoxic T lymphocyte antigen4 (CTLA4, CD152)], consumption of vital cytokines [IL1, IL2, tumor-necrosis-factoralpha (TNFα)], metabolic disruption of the target cell, and alteration of DC activating capacity and cytolysis (delivery of granzymes and perforin) [10–18]. Furthermore, the site of immune reaction, type and activation state of the suppressed target cell, as well as the state of Treg activation may play a role, as reviewed by Schmidt et al. [19]. Naturally occurring Tregs (nTregs) develop in the thymus and prevent autoimmunity. Specificity for self-peptides directs the selection of CD4+ CD25+ regulatory thymocytes by a process that is distinct from positive selection and deletion [20]. In contrast, induced Tregs (iTregs) form in the periphery after contact with alloantigen, are thymus-independent, and control alloresponses. CD4+ CD25+ Tregs can be generated in the periphery from CD4+ CD25− precursors in a pathway distinct from the pathway by which naturally occurring autoreactive CD4+ CD25+ Tregs develop [21]. Induced Foxp3+ Tregs are considered a potential new weapon for the treatment of autoimmune and inflammatory disease, extending to the treatment of transplant rejection [22–24]. Recently, Brunstein et al. reported results of the first-in-human clinical trial of ex vivo expanded umbilical cord blood (UCB)-derived CD4+ CD25+ Tregs in the setting of UCB transplantation [25]. The heterogeneity of the Treg pool limits the diagnostic and therapeutic application of Tregs. Klein and coworkers described that CD127low/− and Foxp3+ expression levels, both markers of Tregs, characterize different Treg cell populations in human peripheral blood [26]. Figure 1 shows the differential induction of CD4+ CD25+ Foxp3+ and CD4+ CD25+ CD127− iTregs during 9-day mixed lymphocyte culture (MLC) (Figure 1). Currently, the marker combination CD4+ CD25+ Foxp3+ CD127low/− is the most accepted phenotype for the identification of Tregs within the pool of CD4+ T lymphocytes (Figure 2). However, further Treg subsets lacking CD4, CD8, and markers of natural killer cell differentiation, but bearing the alpha/beta T-cell receptor (TCR), have been described in both humans and rodent models [27]. These double-negative Tregs are also able to prevent allograft rejection, graft versus host disease (GVHD), and autoimmune diabetes as reviewed by Juvet et al. [27]. The proliferative capacity of Tregs represents a further problem with respect to their therapeutic application. Mouse Tregs do not proliferate in vitro because they are consistently hyporesponsive in vitro [28]. This is true also for human effector CD45RA− Foxp3high Tregs. However, human na¨ıve CD45RA+ Tregs actively proliferate in vitro and differentiate to CD45RA− effector Tregs while suppressing effector cell proliferation [1]. Miyara et al. described three phenotypically and functionally distinct subpopulations of Tregs in human blood samples: CD45RA+ Foxp3low resting Tregs and CD45RA− Foxp3high activated Tregs, both of which are suppressive in vitro, and cytokine-secreting CD45RA− Foxp3low nonsuppressive T cells producing interferongamma (IFNg), IL2, and IL17 and representing activated CD4+ effector T cells [9]. The International Reviews of Immunology
IFNg+ Tregs in Transplantation +
% CD4 PBL co-expressing iTreg phenotypes 100,00% CD4+CD25+ CD4+CD25+FoxP3+ CD4+CD25+CD127CD4+CD25+FoxP3+CD127-
90,00% 80,00% 70,00% 60,00% 50,00% 40,00%
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30,00% 20,00% 10,00% 0,00% Unstimulated
Stimulated
MLC 3d
Unstimulated MLC 6d
Stimulated
Unstimulated
Stimulated
MLC 9d
FIGURE 1. Kinetics analysis of classical Treg phenotypes during 9-day MLC assays. Peripheral blood mononuclear cells (PBMC) of five healthy control individuals were stimulated with PBMCs that were HLA class I and II incompatible. Stimulator cells were irradiated. Responder cells were incubated with culture medium (unstimulated group) or stimulator cells (stimulated group) for 9 days. Compared with the unstimulated group, proportions of CD4+ CD25+ , CD4+ CD25+ Foxp3+ , CD4+ CD25+ CD127− , and CD4+ CD25+ Foxp3+ CD127− PBL remained stable after 3-day MLC (vs. unstimulated: p = n.s.) but increased after 6-day and 9-day MLC (vs. unstimulated: all p < 0.05), suggesting that different subpopulations of iTregs were induced after alloantigen stimulation. Expression of CD4+ CD25+ and CD4+ CD25+ CD127− PBL increased with time of stimulation (6day vs. 3-day and 9-day vs. 6-day: all p < 0.05), whereas expression of CD4+ CD25+ Foxp3+ and CD4+ CD25+ Foxp3+ CD127− PBL increased from 3 days to 6 days (6-day vs. 3-day: all p < 0.05) but remained stable from 6 days to 9 days (9-day vs. 6-day: all p = n.s.). After 9 days of alloantigen stimulation, 55% of CD4+ PBL expressed CD4+ CD25+ , 4.4% were CD4+ CD25+ Foxp3+ , 24% were CD4+ CD25+ CD127− , and 2.6% were CD4+ CD25+ Foxp3+ CD127− .
proportions of these three subpopulations differed between cord blood, aged individuals, and patients with immunological diseases such as active sarcoidosis or active SLE patients. Terminally, differentiated activated Tregs rapidly die, whereas resting Tregs proliferate and convert to activated Tregs in vitro and in vivo [9]. In na¨ıve T cells, TGFβ induces Foxp3, inhibits Th1 and Th2 differentiation, and suppresses T-cell activation and proliferation [29–32]. IL4 dampens Foxp3 induction, whereas IL21 and IFNg clearly enhance this ability [33]. There is increasing evidence that IFNg plays a major role in both induction of Tregs as well as immunosuppression mediated by IFN-producing Tregs [34, 35]. The present review focuses on a small subset of iTregs that produces IFNg and comprises only 0.04% of all CD4+ T lymphocytes in the blood of healthy individuals and increases strongly during an immune response (Table 1, Figures 3 and 4). IFNg+ Tregs are increasingly moving into the focus of research. Alloreactive IFNg+ iTregs in Mice IFNg+ Tregs, also termed Th1-like Tregs, represent a subset of induced Tregs generated after contact with alloantigen. In mouse experiments, Sawitzki et al. reported on IFNg production by alloantigen-reactive Tregs that was important for their regulatory function in vivo [36]. Mice were pretreated with alloantigen and anti-CD4 monoclonal antibody and subsequently received allogeneic skin grafts. Naive CD4+ CD45RBhigh C Informa Healthcare USA, Inc. Copyright
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V. Daniel et al.
FIGURE 2. Gating strategy and proportions of four classical Treg phenotypes in freshly isolated PBMC. After separation from peripheral blood, PBMCs of five healthy controls were investigated using eight-color fluorescence flow cytometry. First, PBLs were gated in a FSC/SSC dot plot. Then, CD4+ CD25+ PBL were determined and further analyzed for co-expression of Foxp3+ and/or CD127− as Treg phenotype. Twenty-nine percent of all CD4+ T cells in the blood expressed CD4+ CD25+ , whereas 2.0% of all CD4+ T cells were CD4+ CD25+ Foxp3+ and 11% expressed CD4+ CD25+ CD127− . The proportion of CD4+ T cells that expressed CD4+ CD25+ Foxp3+ CD127− was 1.5%.
T cells developed in recipient animals and were shown to prevent rejection of donorspecific skin grafts. When rechallenged with donor antigen in vivo, CD4+ CD25+ but not CD4+ CD25− T lymphocytes showed a five-fold increase in IFNg mRNA expression within 24 h of re-encountering alloantigen. This expression was highly antigen-specific and functionally relevant. Neutralization of IFNg at the time of co-transfer of alloantigen-reactive Tregs, together with injection of CD4+ CD45RBhigh effector T cells into skin graft recipients with recombination-activating gene defects (RAG−/− ), resulted in skin graft necrosis in all recipients. The generation and function of alloantigen-reactive Tregs was strikingly impaired in IFNg-deficient mice [36]. Based on these experiments, Wood et al. suggested that the early production of IFNg by induced Tregs during an immune response can directly inhibit the activation and proliferation of IFNg receptor 1 (R1)- and IFNgR2-bearing T cells by creating a microenvironment that influences the function of APCs as a result of IFNg-induced nitric oxide synthase (NOS), indoleamine-2,3-dioxygenase (IDO), and heme oxygenase-1 expression (HO1) [37]. Alloreactive IFNg+ iTregs in Humans CD4+ CD25+ Foxp3+ IFNg+ T cells are also detectable in humans and might have an immunoregulatory role in organ transplantation [38]. Renal transplant International Reviews of Immunology
IFNg+ Tregs in Transplantation TABLE 1 Percentages of different Treg subsets in fresh cells or alloantigen stimulated PBL. Fresh cells (0 day)
Stimulated cells (9 days)
p value
29% ± 11% 2.0% ± 0.91% 11% ± 4.1% 1.5% ± 0.70%
55% ± 2.8% 4.4% ± 2.3% 24% ± 4.0% 2.6% ± 1.2%
REVIEW
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Interferon-Gamma Producing Regulatory T Cells as a Diagnostic and Therapeutic Tool in Organ Transplantation Volker Daniel,1 Haihao Wang,1,2 Mahmoud Sadeghi,1 and Gerhard Opelz1 1
Department of Transplantation-Immunology, Institute of Immunology, University of Heidelberg, Heidelberg, Germany; 2 Institute of Organ Transplantation, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology and Key Laboratory of Organ Transplantation, Ministry of Education, Key Laboratory of Organ Transplantation, Ministry of Health, Wuhan, China
There is increasing evidence that IFNg plays a major role in both induction of Tregs as well as immunosuppression mediated by IFNg-producing Tregs. The present review focuses on a small subset of iTregs that produces IFNg, comprises only 0.04% of all CD4+ T lymphocytes in the blood of healthy individuals, and increases strongly during an immune response. IFNg+ Tregs are induced by IFNg and IL12, making them sensors for inflammatory cytokines. They develop rapidly during inflammation and represent the first line of Tregs that suppress initial immune responses. The pool of IFNg+ Tregs consists of activated stable immunosuppressive thymus-derived nTregs as well as peripherally proliferating iTregs with in part only transient immunosuppressive function, which limits their diagnostic and therapeutic usefulness in organ transplantation. Apparently, a part of IFNg+ Tregs dies during the immune response, whereas others, after efficient immunosuppression with resolution of the immune response, differentiate toward Th1 lymphocytes. Goals of further research are the development of appropriate diagnostic tests for rapid and exact determinination of immunosuppressive IFNg+ iTregs, as well as the induction and propagation of stable immunosuppressive IFNg+ Tregs that establish and maintain good long-term graft function in transplant recipients. Keywords Diagnostic and therapeutic tool, IFNg, IFNg+ Tregs, immunosuppression, Helios, MLC, T-bet, transplantation, TSDR
OVERVIEW Tregs constitute an attractive diagnostic and therapeutic target given their essential role in controlling autoimmunity as well as immune responses against alloantigens. Before this tool can be fully employed, however, it must be considered that, at the current stage of knowledge, studies in animals, healthy individuals, and patients provide evidence for heterogeneity and plasticity within the Treg compartment [1].
Received 18 March 2013; accepted 9 September 2013. Address correspondence to Volker Daniel, MD, Department of Transplantation-Immunology, Institute of Immunology, University of Heidelberg, Im Neuenheimer Feld 305, 69120 Heidelberg, Germany. E-Mail: [email protected]
Int Rev Immunol Downloaded from informahealthcare.com by Nyu Medical Center on 11/26/13 For personal use only.
V. Daniel et al.
Activated na¨ıve CD4+ T cells can differentiate into Th effector cell subsets (T helper lymphocyte 1 (Th1), Th2, Th17, and follicular helper) or into regulatory T cells (Tregs), depending on the type of antigen-presenting cell (APC), the APC maturation state, and the cytokine milieu encountered during differentiation [2, 3]. Tregs express the transcription factor foxhead box p3 (Foxp3) and the interleukin 2 receptor (IL2R, CD25) [4–7]. Expression of CD127 on the surface of human T cells decreases after cell activation and is inversely related with intracellular Foxp3 expression [8]. Additional markers are associated with activation and memory, homing and origin, suppressive and effector function as well as apoptosis and survival, forming a heterogenous and plastic Treg pool as highlighted by Sakaguchi et al. [1, 9]. Treg suppression is mediated by modulation of the cytokine microenvironment, secretion of immunosuppressive cytokines [IL10, transforming growth factor-beta (TGFβ)], conversion of molecules to immunosuppressants [CD39, cytotoxic T lymphocyte antigen4 (CTLA4, CD152)], consumption of vital cytokines [IL1, IL2, tumor-necrosis-factoralpha (TNFα)], metabolic disruption of the target cell, and alteration of DC activating capacity and cytolysis (delivery of granzymes and perforin) [10–18]. Furthermore, the site of immune reaction, type and activation state of the suppressed target cell, as well as the state of Treg activation may play a role, as reviewed by Schmidt et al. [19]. Naturally occurring Tregs (nTregs) develop in the thymus and prevent autoimmunity. Specificity for self-peptides directs the selection of CD4+ CD25+ regulatory thymocytes by a process that is distinct from positive selection and deletion [20]. In contrast, induced Tregs (iTregs) form in the periphery after contact with alloantigen, are thymus-independent, and control alloresponses. CD4+ CD25+ Tregs can be generated in the periphery from CD4+ CD25− precursors in a pathway distinct from the pathway by which naturally occurring autoreactive CD4+ CD25+ Tregs develop [21]. Induced Foxp3+ Tregs are considered a potential new weapon for the treatment of autoimmune and inflammatory disease, extending to the treatment of transplant rejection [22–24]. Recently, Brunstein et al. reported results of the first-in-human clinical trial of ex vivo expanded umbilical cord blood (UCB)-derived CD4+ CD25+ Tregs in the setting of UCB transplantation [25]. The heterogeneity of the Treg pool limits the diagnostic and therapeutic application of Tregs. Klein and coworkers described that CD127low/− and Foxp3+ expression levels, both markers of Tregs, characterize different Treg cell populations in human peripheral blood [26]. Figure 1 shows the differential induction of CD4+ CD25+ Foxp3+ and CD4+ CD25+ CD127− iTregs during 9-day mixed lymphocyte culture (MLC) (Figure 1). Currently, the marker combination CD4+ CD25+ Foxp3+ CD127low/− is the most accepted phenotype for the identification of Tregs within the pool of CD4+ T lymphocytes (Figure 2). However, further Treg subsets lacking CD4, CD8, and markers of natural killer cell differentiation, but bearing the alpha/beta T-cell receptor (TCR), have been described in both humans and rodent models [27]. These double-negative Tregs are also able to prevent allograft rejection, graft versus host disease (GVHD), and autoimmune diabetes as reviewed by Juvet et al. [27]. The proliferative capacity of Tregs represents a further problem with respect to their therapeutic application. Mouse Tregs do not proliferate in vitro because they are consistently hyporesponsive in vitro [28]. This is true also for human effector CD45RA− Foxp3high Tregs. However, human na¨ıve CD45RA+ Tregs actively proliferate in vitro and differentiate to CD45RA− effector Tregs while suppressing effector cell proliferation [1]. Miyara et al. described three phenotypically and functionally distinct subpopulations of Tregs in human blood samples: CD45RA+ Foxp3low resting Tregs and CD45RA− Foxp3high activated Tregs, both of which are suppressive in vitro, and cytokine-secreting CD45RA− Foxp3low nonsuppressive T cells producing interferongamma (IFNg), IL2, and IL17 and representing activated CD4+ effector T cells [9]. The International Reviews of Immunology
IFNg+ Tregs in Transplantation +
% CD4 PBL co-expressing iTreg phenotypes 100,00% CD4+CD25+ CD4+CD25+FoxP3+ CD4+CD25+CD127CD4+CD25+FoxP3+CD127-
90,00% 80,00% 70,00% 60,00% 50,00% 40,00%
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30,00% 20,00% 10,00% 0,00% Unstimulated
Stimulated
MLC 3d
Unstimulated MLC 6d
Stimulated
Unstimulated
Stimulated
MLC 9d
FIGURE 1. Kinetics analysis of classical Treg phenotypes during 9-day MLC assays. Peripheral blood mononuclear cells (PBMC) of five healthy control individuals were stimulated with PBMCs that were HLA class I and II incompatible. Stimulator cells were irradiated. Responder cells were incubated with culture medium (unstimulated group) or stimulator cells (stimulated group) for 9 days. Compared with the unstimulated group, proportions of CD4+ CD25+ , CD4+ CD25+ Foxp3+ , CD4+ CD25+ CD127− , and CD4+ CD25+ Foxp3+ CD127− PBL remained stable after 3-day MLC (vs. unstimulated: p = n.s.) but increased after 6-day and 9-day MLC (vs. unstimulated: all p < 0.05), suggesting that different subpopulations of iTregs were induced after alloantigen stimulation. Expression of CD4+ CD25+ and CD4+ CD25+ CD127− PBL increased with time of stimulation (6day vs. 3-day and 9-day vs. 6-day: all p < 0.05), whereas expression of CD4+ CD25+ Foxp3+ and CD4+ CD25+ Foxp3+ CD127− PBL increased from 3 days to 6 days (6-day vs. 3-day: all p < 0.05) but remained stable from 6 days to 9 days (9-day vs. 6-day: all p = n.s.). After 9 days of alloantigen stimulation, 55% of CD4+ PBL expressed CD4+ CD25+ , 4.4% were CD4+ CD25+ Foxp3+ , 24% were CD4+ CD25+ CD127− , and 2.6% were CD4+ CD25+ Foxp3+ CD127− .
proportions of these three subpopulations differed between cord blood, aged individuals, and patients with immunological diseases such as active sarcoidosis or active SLE patients. Terminally, differentiated activated Tregs rapidly die, whereas resting Tregs proliferate and convert to activated Tregs in vitro and in vivo [9]. In na¨ıve T cells, TGFβ induces Foxp3, inhibits Th1 and Th2 differentiation, and suppresses T-cell activation and proliferation [29–32]. IL4 dampens Foxp3 induction, whereas IL21 and IFNg clearly enhance this ability [33]. There is increasing evidence that IFNg plays a major role in both induction of Tregs as well as immunosuppression mediated by IFN-producing Tregs [34, 35]. The present review focuses on a small subset of iTregs that produces IFNg and comprises only 0.04% of all CD4+ T lymphocytes in the blood of healthy individuals and increases strongly during an immune response (Table 1, Figures 3 and 4). IFNg+ Tregs are increasingly moving into the focus of research. Alloreactive IFNg+ iTregs in Mice IFNg+ Tregs, also termed Th1-like Tregs, represent a subset of induced Tregs generated after contact with alloantigen. In mouse experiments, Sawitzki et al. reported on IFNg production by alloantigen-reactive Tregs that was important for their regulatory function in vivo [36]. Mice were pretreated with alloantigen and anti-CD4 monoclonal antibody and subsequently received allogeneic skin grafts. Naive CD4+ CD45RBhigh C Informa Healthcare USA, Inc. Copyright
Int Rev Immunol Downloaded from informahealthcare.com by Nyu Medical Center on 11/26/13 For personal use only.
V. Daniel et al.
FIGURE 2. Gating strategy and proportions of four classical Treg phenotypes in freshly isolated PBMC. After separation from peripheral blood, PBMCs of five healthy controls were investigated using eight-color fluorescence flow cytometry. First, PBLs were gated in a FSC/SSC dot plot. Then, CD4+ CD25+ PBL were determined and further analyzed for co-expression of Foxp3+ and/or CD127− as Treg phenotype. Twenty-nine percent of all CD4+ T cells in the blood expressed CD4+ CD25+ , whereas 2.0% of all CD4+ T cells were CD4+ CD25+ Foxp3+ and 11% expressed CD4+ CD25+ CD127− . The proportion of CD4+ T cells that expressed CD4+ CD25+ Foxp3+ CD127− was 1.5%.
T cells developed in recipient animals and were shown to prevent rejection of donorspecific skin grafts. When rechallenged with donor antigen in vivo, CD4+ CD25+ but not CD4+ CD25− T lymphocytes showed a five-fold increase in IFNg mRNA expression within 24 h of re-encountering alloantigen. This expression was highly antigen-specific and functionally relevant. Neutralization of IFNg at the time of co-transfer of alloantigen-reactive Tregs, together with injection of CD4+ CD45RBhigh effector T cells into skin graft recipients with recombination-activating gene defects (RAG−/− ), resulted in skin graft necrosis in all recipients. The generation and function of alloantigen-reactive Tregs was strikingly impaired in IFNg-deficient mice [36]. Based on these experiments, Wood et al. suggested that the early production of IFNg by induced Tregs during an immune response can directly inhibit the activation and proliferation of IFNg receptor 1 (R1)- and IFNgR2-bearing T cells by creating a microenvironment that influences the function of APCs as a result of IFNg-induced nitric oxide synthase (NOS), indoleamine-2,3-dioxygenase (IDO), and heme oxygenase-1 expression (HO1) [37]. Alloreactive IFNg+ iTregs in Humans CD4+ CD25+ Foxp3+ IFNg+ T cells are also detectable in humans and might have an immunoregulatory role in organ transplantation [38]. Renal transplant International Reviews of Immunology
IFNg+ Tregs in Transplantation TABLE 1 Percentages of different Treg subsets in fresh cells or alloantigen stimulated PBL. Fresh cells (0 day)
Stimulated cells (9 days)
p value
29% ± 11% 2.0% ± 0.91% 11% ± 4.1% 1.5% ± 0.70%
55% ± 2.8% 4.4% ± 2.3% 24% ± 4.0% 2.6% ± 1.2%
