Identification and functional characterization of human CD4(+)CD25(+) T cells with regulatory properties isolated from peripheral blood

CTLA-4 is expressed by human monocyte-derived dendritic cells and regulates their functions

Cytotoxic T lymphocyte antigen-4 (CTLA-4) is the major negative regulator of T-cell responses, although growing evidence supports its wider role as an immune attenuator that may also act in other cell lineages. Here, we have analyzed the expression of CTLA-4 in human monocytes and monocyte-derived dendritic cells (DCs), and the effect of its engagement on cytokine production and T-cell stimulatory activity by mature DCs. CTLA-4 was highly expressed on freshly isolated monocytes, then down-modulated upon differentiation toward immature DCs (iDCs) and it was markedly upregulated on mature DCs obtained with different stimulations (lipopolysaccharides [LPS], Poly:IC, cytokines). In line with the functional role of CTLA-4 in T cells, treatment of mDCs with an agonistic anti-CTLA-4 mAb significantly enhanced secretion of regulatory interleukin (IL)-10 but reduced secretion of IL-8/IL-12 pro-inflammatory cytokines, as well as autologous CD4+ T-cell proliferation in response to stimulation with recall antigen purified protein derivative (PPD) loaded-DCs. Neutralization of IL-10 with an anti-IL-10 antibody during the mDCs-CD4+ T-cell co-culture partially restored the ability of anti-CTLA-4-treated mDCs to stimulate T-cell proliferation in response to PPD. Taken together, our data provide the first evidence that CTLA-4 receptor is expressed by human monocyte-derived mDCs upon their full activation and that it exerts immune modulatory effects.

Adoptive regulatory T cell therapy: challenges in clinical transplantation

PURPOSE OF REVIEW

The identification and characterisation of regulatory T cells (Tregs) has recently opened up exciting opportunities for Treg cell therapy in transplantation. In this review, we outline the basic biology of Tregs and discuss recent advances and challenges for the identification, isolation and expansion of these cells for cell therapy.

RECENT FINDINGS

Tregs of thymic origin have been shown to be key regulators of immune responses in mice and humans, preventing autoimmunity, graft-versus-host disease and organ graft rejection in the transplantation setting. To date, a variety of different methods to isolate and expand Tregs ex vivo have been advocated. Although promising, relatively few clinical trials of human Treg cell infusion have been initiated.

SUMMARY

Many key questions about Treg cell therapy still remain and here we provide an in-depth analysis and highlight the challenges and opportunities for immune intervention with Treg-based therapeutics in clinical transplantation.

Peripheral blood T regulatory cell counts may not predict transplant rejection

Background

Recent evidence shows that allograft survival rates show a positive correlation with the number of circulating T regulatory cells (Tregs). This study investigated both the number and the cytokine profiles exhibited by Foxp3⁺ Tregs in blood, spleen and lymph nodes of Lewis rat recipients of BN rat cardiac allografts after a single-dose of Rapamycin (RAPA).

Results

Rats were divided into three groups: control group (containing healthy control and acute rejection group), and recipients treated with a single dose of RAPA on either Day 1 (1D group)or Day 3 (3D group) post-transplant. We analyzed the number of Foxp3+Tregs and the expression of Foxp3 and cytokines in the peripheral blood and the peripheral lymphoid tissues. No difference was found in the numbers of circulating Foxp3+ Tregs between these three groups. RAPA administration significantly increased Foxp3 expression in peripheral lymphoid tissues after a single dose of RAPA on Day 3 post-transplant. Foxp3+Tregs inhibited the activity of effector T cells (T_eff) via the secretion of TGF-β1.

Conclusion

The number of Tregs in the recipient's blood may not be a good predictor of transplant rejection. Foxp3+Tregs inhibit the activity of T_eff cells mainly in the peripheral lymphoid tissues.

NKT cells, Treg, and their interactions in bone marrow transplantation

Bone marrow transplantation (BMT) is a potentially curative treatment for patients with leukemia and lymphoma. Tumor eradication is promoted by the anti-tumor activity of donor T cells contained in the transplant; however, donor T cells also mediate the serious side effect of graft-versus-host disease (GVHD). Separation of GVHD from graft anti-tumor activity is an important goal of research in improving transplant outcome. One approach is to take advantage of the immunomodulatory activity of regulatory NKT cells and CD4(+)CD25(+) Treg of host and/or donor origin. Both host and donor NKT cells and donor Treg are able to prevent GVHD in murine models. In this review, we summarize the mechanisms of NKT cell- and Treg-mediated protection against GVHD in mice while maintaining graft anti-tumor activity. In addition, we also examine the interactions between NKT cells and Treg in the context of BMT, and integrate the data from murine experimental models with the observations made in humans.

CCL17 and CCL22 chemokines within tumor microenvironment are related to infiltration of regulatory T cells in esophageal squamous cell carcinoma

It has been reported that an increased population of regulatory T cells (T-regs) is one of the reasons for impaired anti-tumor immunity. We investigated the frequency of Foxp3(+) T-regs in tumor-infiltrating lymphocytes (TILs) and peripheral blood lymphocytes (PBLs) of patients with esophageal squamous cell carcinoma (ESCC). Furthermore, in order to elucidate the mechanisms behind T-regs accumulation within tumors, we evaluated the relationship between CCL17 or CCL22 expression and the frequency of Foxp3(+) T-regs. CD4(+)CD25(+)Foxp3(+) T-regs as a percentage of CD4(+) cells were counted by flow cytometry. The frequency of CCL17(+) or CCL22(+) cells among CD14(+) cells in tumors was also evaluated by flow cytometry. Moreover, an in vitro migration assay using T-regs derived from ESCC was performed in the presence of CCL17 or CCL22. The frequency of Foxp3(+) T-regs in TILs was significantly higher than that in the normal esophageal mucosa (24.6 +/- 10.0 vs 7.1 +/- 5.9%, P < 0.01). The frequency of Foxp3(+) T-regs in PBLs of ESCC patients was significantly higher than that in normal healthy donors (7.0 +/- 4.2 vs 2.5 +/- 1.0%, P < 0.01). Furthermore, the frequency of CCL17(+) or CCL22(+) cells among CD14(+) cells within tumors was significantly higher than that of normal esophageal mucosa, and there was a significant correlation between the frequency of CCL17(+) or CCL22(+) cells and Foxp3(+) T-regs in TILs. In addition, the in vitro migration assay indicated that T-regs were significantly induced to migrate by CCL17 or CCL22. In conclusion, CCL17 and CCL22 within the tumor are related to the increased population of Foxp3(+) T-regs in ESCC.

Lifelong dynamics of human CD4+CD25+ regulatory T cells: insights from in vivo data and mathematical modeling

Despite their limited proliferation capacity, regulatory T cells (T(regs)) constitute a population maintained over the entire lifetime of a human organism. The means by which T(regs) sustain a stable pool in vivo are controversial. Using a mathematical model, we address this issue by evaluating several biological scenarios of the origins and the proliferation capacity of two subsets of T(regs): precursor CD4(+)CD25(+)CD45RO(-) and mature CD4(+)CD25(+)CD45RO(+) cells. The lifelong dynamics of T(regs) are described by a set of ordinary differential equations, driven by a stochastic process representing the major immune reactions involving these cells. The model dynamics are validated using data from human donors of different ages. Analysis of the data led to the identification of two properties of the dynamics: (1) the equilibrium in the CD4(+)CD25(+)FoxP3(+)T(regs) population is maintained over both precursor and mature T(regs) pools together, and (2) the ratio between precursor and mature T(regs) is inverted in the early years of adulthood. Then, using the model, we identified three biologically relevant scenarios that have the above properties: (1) the unique source of mature T(regs) is the antigen-driven differentiation of precursors that acquire the mature profile in the periphery and the proliferation of T(regs) is essential for the development and the maintenance of the pool; there exist other sources of mature T(regs), such as (2) a homeostatic density-dependent regulation or (3) thymus- or effector-derived T(regs), and in both cases, antigen-induced proliferation is not necessary for the development of a stable pool of T(regs). This is the first time that a mathematical model built to describe the in vivo dynamics of regulatory T cells is validated using human data. The application of this model provides an invaluable tool in estimating the amount of regulatory T cells as a function of time in the blood of patients that received a solid organ transplant or are suffering from an autoimmune disease.

FOXP3+ regulatory T cells in the human immune system

Forkhead box P3 (FOXP3)(+) regulatory T (T(Reg)) cells are potent mediators of dominant self tolerance in the periphery. But confusion as to the identity, stability and suppressive function of human T(Reg) cells has, to date, impeded the general therapeutic use of these cells. Recent studies have suggested that human T(Reg) cells are functionally and phenotypically diverse. Here we discuss recent findings regarding human T(Reg) cells, including the ontogeny and development of T(Reg) cell subsets that have naive or memory phenotypes, the unique mechanisms of suppression mediated by T(Reg) cell subsets and factors that regulate T(Reg) cell lineage commitment. We discuss future studies that are needed for the successful therapeutic use of human T(Reg) cells.

Adenosine and prostaglandin E2 cooperate in the suppression of immune responses mediated by adaptive regulatory T cells

Adaptive regulatory T cells (Tr1) are induced in the periphery upon encountering cognate antigens. In cancer, their frequency is increased; however, Tr1-mediated suppression mechanisms are not yet defined. Here, we evaluate the simultaneous involvement of ectonucleotidases (CD39/CD73) and cyclooxygenase 2 (COX-2) in Tr1-mediated suppression. Human Tr1 cells were generated from peripheral blood mononuclear cell-derived, sorted CD4(+)CD25(-) T cells and incubated with autologous immature dendritic cells, irradiated COX-2(+) or COX-2(-) tumor cells, and IL-2, IL-10, and IL-15 (each at 10-15 IU/ml) for 10 days as described (Bergmann, C., Strauss, L., Zeidler, R., Lang, S., and Whiteside, T. L. (2007) Cancer Immunol. Immunother. 56, 1429-1442). Tr1 were phenotyped by multicolor flow cytometry, and suppression of proliferating responder cells was assessed in carboxyfluorescein diacetate succinimidyl ester-based assays. ATP hydrolysis was measured using a luciferase detection assay, and levels of adenosine or prostaglandin E(2) (PGE(2)) in cell supernatants were analyzed by mass spectrometry or ELISA, respectively. Intracellular cAMP levels were measured by enzyme immunoassay. The COX-2(+) tumor induced a greater number of Tr1 than COX-2(-) tumor (p < 0.05). Tr1 induced by COX-2(+) tumor were more suppressive, hydrolyzed more exogenous ATP (p < 0.05), and produced higher levels of adenosine and PGE(2) (p < 0.05) than Tr1 induced by COX-2(-) tumor. Inhibitors of ectonucleotidase activity, A(2A) and EP(2) receptor antagonists, or an inhibitor of the PKA type I decreased Tr1-mediated suppression (p < 0.05), whereas rolipram, a PDE(4) inhibitor, increased the intracellular cAMP level in responder cells and their susceptibility to Tr1-mediated suppression. Tr1 present in tumors or the peripheral blood of head and neck squamous cell carcinoma patients co-expressed COX-2, CD39, and CD73. A concomitant inhibition of PGE(2) and adenosine via the common intracellular cAMP pathway might be a novel approach for improving results of immune therapies for cancer.

Regulatory CD4+ T cells in allergic asthma

Active suppression by regulatory T cells (T(regs)) appears to play a key role in the downregulation of T-cell responses to foreign antigens. Several subtypes of T(regs) have been described but their mechanisms of action remain unclear. Recent data demonstrate that the suppressive capacity of natural T(regs) could be associated with cytotoxicity due to the release of granzymes, which are capable of apoptosis induction in target effector T lymphocytes and in antigen-presenting cells, such as dendritic cells. The mechanism of such nonspecific T(regs) is discussed. Peptide immunotherapy is thought to induce regulatory cells capable of suppressing autoimmune and allergic diseases. We have recently optimized a vaccination strategy by which cytotoxic antigen-specific adaptive T(regs) can be elicited towards allergens involved in allergic asthma. Such a strategy could be of value in the treatment of allergic asthma.

Quantification and phenotype of regulatory T cells in rheumatoid arthritis according to disease activity score-28

Here we studied and characterized different peripheral blood (PB) regulatory T cell (Treg) subsets in rheumatoid arthritis (RA) patients and tested the hypothesis that changes in these cells can be linked to the degree of inflammation and relapsing/remission periods. PB cells were examined from RA subjects (n = 60) with different disease activity score-28 (DAS28) and from healthy controls (n = 40). Frequencies of Treg subsets expressing characteristic membrane antigens, FoxP3 or intracellular cytokines were quantified by flow cytometry. We observed a decrease in the percentages of CD4(+)CD25(high), CD4(+)CD25(int), CD4(+)CD25(int/high)FoxP3(+), CD4(+)CD38(+), CD4(+)CD62L(+), CD8(+)CD25(high)CD45RA(+) and CD8(+)CD25(int)CD45RA(+) T cells in PB of RA patients compared to healthy controls. In addition, we found increased percentages of cells expressing membrane/intracellular regulatory antigens such as OX40 (CD134), CD45RB(low) or CTLA-4 (CD152), and a higher proportion of other T cell subsets including CD4(+)CTLA-4(+), CD4(+)IL10(+), CD4(+)CD25(int)IL10(+), CD4(+)CD25(int) TGFbeta(+), CD4(+)CD25(low) TGFbeta(+) and CD8(+)CD28(- ). We show that most of these changes parallel the intensity of inflammation, with lowest or highest values in patients with moderately/very active disease compared to healthy controls and at times to patients with inactive RA. The balance between these cell subsets and their antigen expression would determine the inflammation levels and could thus be linked to the relapsing/remission periods of the disease.

Foxp3 expressing regulatory T-cells in allergic disease

Allergic diseases such as asthma, rhinitis and eczema are increasing in prevalence worldwide, in particular in industrialised countries affecting up to 20% of the population. Regulatory T-cells (Tregs) have been shown to be critical in T-cell homeostasis and in the maintenance of immune responses, such as prevention of autoimmunity and hampering allergic diseases. The so-called 'natural' CD4+CD25+ Tregs and/or IL-10-producing Tr1 cells have been shown to be responsible for the protection of immune tolerance and intact immune reactions following exposure to allergens such as aeroallergens or food allergens. In this regard, both cell-cell contact (through membrane bound TGF-beta or via suppressive molecules such as CLTA-4) and soluble cytokine-(TGF-beta and IL-10) dependent mechanisms have been shown to contribute to the ability of Tregs to operate effectively. The transcription factor Foxp3, a member of the forkhead-winged helix family, appears to be critical in the suppressive abilities of regulatory T-cells. Adoptive transfer of CD4+CD25+ Tregs from healthy to diseased animals corroborated and provided further evidence of the vital role of these populations in the prevention or cure of certain autoimmune conditions. Clinical improvement seen after allergen immunotherapy for allergic diseases such as rhinitis and asthma has also been associated with the induction of IL-10 and TGF-beta producing Trl cells as well as Foxp3 expressing CD4+CD25+ T-cells, resulting in the suppression ofTh2 cytokine milieu. Activation and expansion ofantigen-specific CD4+CD25+ Tregs in vivo using adjuvants such as IL-10 or pharmacological agents such as low dose steroids or vitamin D3 could represent novel approaches to induce antigen-specific tolerance in immune-mediated conditions such as allergic asthma, autoimmune disease and the rejection of transplanted organs in man.

Effect of regulatory T cells and adherent cells on the expansion of HBcAg-specific CD8+ T cells in patients with chronic hepatitis B virus infection

Patients with chronic HBV infection show poor immune response to HBV-specific CD8+ T cells. Several studies demonstrate that regulatory T cells (Treg) and dendritic cells (DC) are important to maintain peripheral immune tolerance. In this study, we investigated the effects of CD4+CD25+Treg and/or the adherent cells (AC) on the proliferation of HBc18-27-specific CD8+ T cells (c18-27-CD8Ts) in response to in vitro stimulation. The frequency of c18-27-CD8Ts in four different mixed leukocyte reactions (MLRs) were analyzed using an HLA-A2-HBc18-27 tetramer. The data indicated that the median percentage of c18-27-CD8Ts in four different MLRs were significant difference in patients with chronic HBV infection. Our results showed that Treg and/or AC might suppress the frequency of HBc18-27-specific CD8+ T cell proliferation in response to in vitro stimulation in chronic HBV patients, and AC might be more effective than Treg.

Regulatory T cells are necessary for implantation and maintenance of early pregnancy but not late pregnancy in allogeneic mice

Maternal T cells acquire a transient state of tolerance specific for paternal alloantigens during pregnancy. CD4(+)CD25(+) regulatory T (Treg) cells play a central role in induction and maintenance of tolerance. We have studied the role of Treg cells for the maintenance of allogeneic pregnancy during the implantation period, early pregnancy period and late pregnancy period. We performed depletion of Treg cells using treatment with anti-CD25 monoclonal antibody (mAb) in allogeneic or syngeneic pregnant mice. BALB/c or C57BL/6 female mice were mated with BALB/c or C57BL/6 male mice, and anti-CD25 mAb was injected intraperitoneally on day 2.5 post-coitum (pc), or days 4.5 and 7.5 pc, or days 10.5 and 13.5 pc. Administration of 0.5mg of anti-CD25 mAb induced depletion of CD4(+)CD25(+)Foxp3(+) Treg cells in both allogeneic and syngeneic pregnancy. The extent of depletion of CD4(+)CD25(+) Treg cells in spleen cells was 82.7%. This mAb treatment on day 2.5 pc of pregnancy induced implantation failure in allogeneic pregnant mice, but not in syngeneic pregnant mice. In addition, anti-CD25 mAb treatment on days 4.5 and 7.5 pc significantly increased resorption rates in allogeneic pregnant mice, but not in syngeneic pregnant mice. Interestingly, anti-CD25mAb treatment on days 10.5 and 13.5 pc reduced Treg cell numbers, but this treatment did not induce any abnormal pregnancy parameters such as intrauterine growth restriction, hypertension, or proteinuria. These findings suggest that CD4(+)CD25(+)Foxp3(+) Treg cells are important to mediate maternal tolerance to the allogeneic fetus in the implantation phase and early stage of pregnancy, but Treg cells might not be necessary for maintenance of the late stage of allogeneic pregnancy.

Refractory colitis following anti-CTLA4 antibody therapy: analysis of mucosal FOXP3+ T cells

Ipilimumab is a humanized antibody to CTLA4 and is used to treat cancers refractory to conventional treatment. We treated 21 patients with refractory melanoma or prostate cancer with anti-CTLA4 antibody (ipilimumab), with subsequent development of significant colitis in nine cases. Two of these nine did not respond rapidly to high-dose (2 mg kg(-1) day(-1)) glucocorticoids or infliximab. They required additional immunosuppression, and one ultimately died of opportunistic infection, representing a more refractory course than has previously been described complicating ipilimumab therapy. Both patients had received radiation to the pelvis for prostate cancer less than 1 year prior to receiving ipilimumab. We performed immunohistochemical analysis of colon biopsies from ipilimumab recipients to determine if colitis correlates with depletion of intramucosal FOXP3(+) regulatory T cells (Tregs), which normally express CTLA4. However, we found no evidence of FOXP3(+) T cell depletion in any of the nine patients who developed colitis.

Dendritic cell vaccination as a treatment modality for melanoma

As melanoma is an immunogenic tumor, immunotherapy has been investigated as a possible treatment modality for melanoma patients at high risk of relapse and those with metastatic disease. In the past decade progress has been made, ranging from rather nonspecific stimulations of the immune system with IL-2 and IFN-alpha to more specific approaches based on vaccination with tumor antigens. Owing to their unique features, dendritic cells (DCs) represent an important tool for tumor antigen-specific immunotherapy. However, clinical vaccination trials with DCs showed sobering results with respect to objective responses and improvement of overall survival. In this review, principles and methods of DC-based vaccination are presented. Mechanisms impairing clinically successful vaccination strategies are described. Finally, we will discuss perspectives for future developments of DC-based vaccines that might lead melanoma treatment to a new era.

Proliferation of CD4CD25Foxp3 regulatory T lymphocytes in ex vivo expanded ascitic fluid from primary and recurrent ovarian carcinoma

OBJECTIVE

Regulatory T lymphocytes evoke the immune tolerance by suppressing and inactivating cytotoxic T lymphocytes. The objective of this study was to compare the proportion of regulatory T lymphocytes, precisely defined as CD4(+)CD25(high+)Foxp3(+) T lymphocytes, in primary and recurrent ovarian carcinoma before and after ex vivo expansion of ascites with interleukin-2 (IL-2).

METHODS

Ascitic fluid samples were obtained from 26 patients with ovarian carcinoma. Lymphocytes were isolated from ascites and cell markers were analyzed by flow cytometry using anti-CD3/CD4/CD8/CD16/CD56/CD25 and anti-Foxp3 antibodies. Lymphocytes were incubated for 2 to 3 weeks and expanded ex vivo by IL-2 stimulation and their phenotypes were analyzed by flow cytometry.

RESULTS

Following ex vivo expansion, ascitic fluid lymphocytes increased by a greater extent in the recurrent group than in the primary group. The proportion of ex vivo-expanded lymphocytes changed as follows; CD4(+) T lymphocytes increased, CD8(+) T lymphocytes decreased, and the proportion of CD3(-)CD16(+)56(+) NK cells was unchanged. The proportion of CD4(+)CD25(high+)Foxp3(+) regulatory T lymphocytes in CD4(+) T lymphocytes increased after ex vivo expansion in both groups, but to a greater degree in the recurrent group.

CONCLUSION

This study showed that regulatory T lymphocytes, neither cytotoxic T lymphocytes nor NK cells, were extensively increased after ex vivo expansion, especially in recurrent ovarian carcinoma. These results may provide information that helps to guide the future development of adoptive immunotherapy against ovarian carcinoma.

Regulatory T cells in transplantation: does extracellular adenosine triphosphate metabolism through CD39 play a crucial role?

Despite tremendous improvements in short-term renal allograft survival, many patients still have chronic rejection or side effects of nonspecific immunosuppression. The discovery of Foxp3(+) regulatory T cells (Tregs) has revolutionized the concepts in immunoregulation and offers perspectives for overcoming rejection. Recently, a subset of Foxp3(+)CD39(+) effector/memory-like Tregs (T(REM)) was identified. The role of CD39(+) Tregs in immunoregulation is supported by the occurrence of alopecia areata and experimental autoimmune encephalomyelitis in CD39-deficient mice and by the failure of CD39(-) Tregs to suppress contact hypersensitivity. In humans, CD39 polymorphisms have been associated with diabetes and nephropathy, and multiple sclerosis patients have reduced numbers of blood CD39(+) Tregs. Preliminary experiments in a murine transplantation model showed that CD39(+) Tregs can determine allograft outcome. CD39 degrades the extracellular adenosine triphosphate (ATP) released during tissue injury, which otherwise would trigger inflammation. Currently, our groups are assessing the role of CD39(+) Tregs and extracellular ATP metabolism in clinical transplantation and whether tolerogenic Treg profiles possess immunopredictive value, envisioning the development of clinical trials using CD39(+) Treg-based vaccination for autoimmunity or transplantation. This is a comprehensive review on the fundamentals of Treg biology, the potential role of ATP metabolism in immunoregulation, and the potential use of Treg-based immunotherapy in transplantation.

Cellular mediators of inflammation: tregs and TH17 cells in gastrointestinal diseases

Human lymphocyte subpopulations were originally classified as T- and B-cells in the 70s. Later, with the development of monoclonal antibodies, it became possible to recognize, within the T-cells, functional populations: CD4⁺ and CD8⁺. These populations were usually referred to as “helper” and “suppressor” cells, respectively. However several investigations within the CD8 cells failed to detect a true suppressor activity. Therefore the term suppressor was neglected because it generated confusion. Much later, true suppressor activity was recognized in a subpopulation of CD4 cells characterized by high levels of CD25. The novel population is usually referred to as T regulatory cells (Tregs) and it is characterized by the expression of FoxP3. The heterogeneity of CD4 cells was further expanded by the recent description of a novel subpopulation characterized by production of IL-17. These cells are generally referred to as T_H17. They contribute to regulate the overall immune response together with other cytokine-producing populations. Treg and T_H17 cells are related because they could derive from a common progenitor, depending on the presence of certain cytokines. The purpose of this review is to summarize recent findings of the role of these novel populations in the field of human gastroenterological disease.

The effect of electroacupuncture on T cell responses in rats with experimental autoimmune encephalitis

Successive electroacupuncture (EA) stimulation on Zusanli ST36 acupoints of rats with experimental autoimmune encephalitis (EAE), which is an inflammatory disease mediated by autoreactive T cells, relieved disease severity, inhibited specific T cell proliferation and rebuilt the CD4+ T cell subset balance. In addition, EA-treated rats had significantly higher ACTH concentrations in vivo compared to untreated EAE rats. These results indicated that EA stimulation could relieve the severity of EAE by restoring balance to the Th1/Th2/Th17/Treg Th cell subset responses by stimulating the hypothalamus to increase ACTH secretion.

A novel human CD4+ T-cell inducer subset with potent immunostimulatory properties

The complexity of immunoregulation has focused attention on the CD4+ T "suppressor" regulatory cell (Treg), which helps maintain balance between immunity and tolerance. An immunoregulatory T-cell population that upon activation amplifies cellular immune responses was described in murine models more than 30 years ago; however, no study has yet identified a naturally occurring T "inducer" cell type. Here, we report that the ectoenzyme CD39/NTPDase1 (ecto-nucleoside triphosphate diphosphohydrolase 1) helps to delineate a novel population of human "inducer" CD4+ T cells (Tind) that significantly increases the proliferation and cytokine production of responder T cells in a dose-dependent manner. Furthermore, this unique Tind subset produces a distinct repertoire of cytokines in comparison to the other CD4+ T-cell subsets. We propose that this novel CD4+ T-cell population counterbalances the suppressive activity of suppressor Treg in peripheral blood and serves as a calibrator of immunoregulation.

Changes of CD4+CD25high regulatory T cells and FOXP3 expression in unexplained recurrent spontaneous abortion patients

OBJECTIVE

To investigate the proportions of CD4+CD25high T cells and forkhead box p3 (FOXP3) expression in peripheral blood and decidua in patients with unexplained recurrent spontaneous abortion (URSA).

DESIGN

Prospective clinical study.

SETTING

University hospital.

PATIENT(S)

125 URSA patients, 35 normal early pregnant women, and 28 normal nonpregnant women.

INTERVENTION(S)

Measurements of CD4+CD25high T cells and FOXP3 expression in peripheral blood and decidua.

MAIN OUTCOME MEASURE(S)

The proportions of CD4+CD25high T cells and FOXP3 expression.

RESULT(S)

In peripheral blood, statistically significantly higher proportions of CD4+CD25high T cells and FOXP3 expression were observed in normal early pregnant women compared with normal nonpregnant women and URSA patients; a statistically significantly lower proportion of CD4+CD25high T cells was observed in nonpregnant URSA patients compared with URSA patients who had early miscarriages and normal nonpregnant women. In the decidua, statistically significantly lower proportions of CD4+CD25high T cells and FOXP3 expression were found in URSA patients with early miscarriages compared with normal early pregnant women.

CONCLUSION(S)

The CD4+CD25high T cells may play an important role in maintaining a normal pregnancy. The reduction in CD4+CD25high T cells may involve in the pathogenesis of URSA, and is correlated with lower FOXP3 expression.

CD127(low) expression in CD4+CD25(high) T cells as immune biomarker of renal function in transplant patients

BACKGROUND

Noninvasive tests measuring cellular immunity could help predict immunologic risk and subsequent allograft dysfunction in transplant patients. CD25 is a promising marker of activation. Recent descriptions of CD127 expression as a discriminating factor between regulatory and activated T cells suggest its potential utility.

METHODS

Expression of CD127 in CD4+CD25 T cells was analyzed by flow cytometry in peripheral blood from 62 renal transplanted patients and 30 healthy controls. Forty patients presented stable graft function and 22 suffered renal failure.

RESULTS

Renal transplant patients showed higher levels of CD127(high) and a lower frequency of CD127(low) than healthy controls (0.63% vs. 0.29% [P<0.001] and 1.4% vs. 2.4% [P<0.001], respectively). However, high frequencies of not only CD127(high) but also CD127(low) showed a significant correlation with serum creatinine levels (P=0.012 and P=0.003, respectively). Allogenic stimulation in vitro increased the frequency of CD127(low) subset in a dose dependent manner. Furthermore, in patients with a high frequency of CD127(low) subset, this consisted mostly of FoxP3 negative cells, discarding their regulatory origin. Median frequency of CD127(low), but not CD127(high), cells showed significant differences between patients with stable function and with renal failure (P<0.005), with 16.7% and 53.1% of individuals above the median CD127(low) value (1.4%), respectively.

CONCLUSION

Quantification of CD127(low) subset through staining of CD4+ T cells with the combined markers CD127/CD25/CD45RO has been demonstrated to be a significant tool for monitoring the outcome course of renal transplant patients.

Expansion of FOXP3+ CD8 T cells with suppressive potential in colorectal mucosa following a pathogenic simian immunodeficiency virus infection correlates with diminished antiviral T cell response and viral control

FOXP3(+)CD8(+) T cells are present at low levels in humans; however, the function of these cells is not known. In this study, we demonstrate a rapid expansion of CD25(+)FOXP3(+)CD8(+) regulatory T cells (Tregs) in the blood and multiple tissues following a pathogenic SIV infection in rhesus macaques. The expansion was pronounced in lymphoid and colorectal mucosal tissues, preferential sites of virus replication. These CD8 Tregs expressed molecules associated with immune suppressor function such as CTLA-4 and CD39 and suppressed proliferation of SIV-specific T cells in vitro. They also expressed low levels of granzyme B and perforin, suggesting that these cells do not possess killing potential. Expansion of CD8 Tregs correlated directly with acute phase viremia and inversely with the magnitude of antiviral T cell response. Expansion was also observed in HIV-infected humans but not in SIV-infected sooty mangabeys with high viremia, suggesting a direct role for hyperimmune activation and an indirect role for viremia in the induction of these cells. These results suggest an important but previously unappreciated role for CD8 Tregs in suppressing antiviral immunity during immunodeficiency virus infections. These results also suggest that CD8 Tregs expand in pathogenic immunodeficiency virus infections in the nonnatural hosts and that therapeutic strategies that prevent expansion of these cells may enhance control of HIV infection.

Acute graft-versus-host disease: new treatment strategies

PURPOSE OF REVIEW

Graft-versus-host disease (GVHD) remains a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT), despite improvements in our understanding of its pathophysiology as well as the generation of new monoclonal antibodies, immunomodulatory chemotherapy, cellular therapeutics and supportive care. Herein, we review therapies that have proven effective as well as newer agents that have recently improved GVHD response rates and survival following HCT.

RECENT FINDINGS

Novel approaches to prevent or treat GVHD are often based on evidence from experimental models. Our understanding of the pathophysiology of GVHD may lead to the development of innovative strategies that target both soluble and cellular effectors. Among such agents are sirolimus, anti-tumor necrosis factor antibodies, anti-LFA-3-IgG fusion protein, extracorporeal photopheresis, mesenchymal stem cells and regulatory T cells.

SUMMARY

Obstacles to the improvement of HCT include the tight linkage between GVHD toxicity and the beneficial graft-versus-leukemia (GVL) effect, as well as the impairment of immune reconstitution by immunomodulatory drugs leading to life-threatening infections. The design of newer phase I/II clinical trials are underway. Future therapies are likely to include modulation of cell types that play key roles in the GVH process, including regulatory T cells, dendritic cells, natural killer T cells and B cells.

Birch pollen immunotherapy leads to differential induction of regulatory T cells and delayed helper T cell immune deviation

Correction of an imbalance between allergen-specific T cell subsets is considered a critical event in establishing allergen tolerance by specific immunotherapy (SIT). In a comprehensive, longitudinal study, distinct T cell populations and Ig subtypes were analyzed in subjects allergic to birch pollen during decisive time points of SIT (i.e., induction and maintenance phase), as well as in and out of birch pollen season. An increase in Bet v 1-specific, IL-10-secreting T cells, fulfilling the criteria of inducible type 1 regulatory T (Tr1) cells, was observed by the end of the induction phase; this resulted in a decreased ratio of allergen-specific IL-5(+) Th2/Tr1 cells. In contrast, CD4(+)CD25(+)CD127(low) regulatory T cell numbers did not change. Furthermore, enhanced concentrations of allergen-specific IgG Abs were observed, whereas allergen-specific IgE and IgA levels remained unchanged. After 1 y of SIT, a reduced ratio of allergen-specific Th2/IFN-gamma(+) Th1 cells was apparent. Although untreated and SIT-treated allergic subjects developed enhanced Th2 cell responses during birch pollen season, only SIT-treated patients experienced elevated numbers of allergen-specific Tr1 cells, which were associated with reduced skin prick test reactivity and diminished clinical symptoms. In coculture assays, allergen-specific Tr1 cells showed an IL-10- and dose-dependent inhibition of CD4(+)CD25(-) T effector cells. Thus, SIT has differential effects on regulatory T cell subsets, resulting in an early induction of allergen-specific Tr1 cells associated with an increase in allergen-specific IgG, and it leads to a delayed shift from an allergen-specific Th2- to a Th1-dominated immune response.

Biology and clinical observations of regulatory T cells in cancer immunology

This review specifically examines the role of regulatory T cells (Tregs) in cancer in both mice and the clinic. Due to the rapid refinement of the definition of Tregs and their heterogeneity, emphasis is given to research findings over the past three years. For clarity, this review is broadly divided into three short sections that outline the basic biology of Tregs - (1) Treg lineage and development, (2) Treg subsets, and (3) mechanisms of Treg-mediated immune suppression; followed by two more comprehensive sections that cover; (4) clinical observations of Tregs and cancer, and (5) modifications of Treg biology as cancer immunotherapies. The latter two sections discuss the measurement of function and frequency of Treg in model systems and clinical trials and possible ways to interfere with Treg-mediated immune suppression with the focus on recent pre-clinical and clinical findings.

Memory T cells in Rhesus macaques

The Rhesus macaque (Macaca mulatta) is one of the best studied species of Old World monkeys. DNA sequencing of the entire Rhesus macaque genome, completed in 2007, has demonstrated that humans and macaques share about 93% of their nucleotide sequence. Rhesus macaques have been widely used for medical research including drug testing, neurology, behavioral and cognitive science, reproduction, xenotransplantation and genetics. Because of the Rhesus macaque's sensitivity to bacteria, parasites and viruses that cause similar disease in humans, these animals represent an excellent model to study infectious diseases. The recent pandemic of HIV and the discovery of SIV, a lentivirus genetically related to HIV Type 1 that causes AIDS in Rhesus macaques, have prompted the development of reagents that can be used to study innate and adaptive immune responses in macaques at the single cell level. This review will focus on the distribution of memory cells in the different immunologic compartments of Rhesus macaques. In addition, the strategies available to manipulate memory cells in Rhesus macaques to understand their trafficking and function will be discussed. Emphasis is placed on studies of memory cells in macaques infected with SIV because many studies are available. Lastly, we highlight the usefulness of the Rhesus macaque model in studies related to the aging of the immune system.

The role of tregs in glioma-mediated immunosuppression: potential target for intervention

The role of regulatory T cells (Tregs) in mediating immune suppression of anti-tumor immune responses is increasingly appreciated in patients with malignancies-especially within the malignant glioma patient population. This article discuss the role and prognostic significance of Tregs within glioma patients and delineates potential approaches for their inhibition that can be used alone or in combination with other immune therapeutics in clinical trials and in the clinical settings of recurrent or residual disease.

Increased Th17 cells are accompanied by FoxP3(+) Treg cell accumulation and correlated with psoriasis disease severity

Both T-helper 17 cells (Th17) and CD4(+)CD25(+) regulatory T cells (Treg) play important roles in the pathogenesis of psoriasis. However, the relationship between Th17 and Treg cells and their dynamic variations in psoriasis remain unclear. In this study, we found that both Th17 and FoxP3(+) Treg cells were increased in psoriasis patients both in the peripheral circulation and skin tissue lesions and were positively correlated with disease severity. The ratio of Th17 to Treg cells in skin tissue lesions was inversely correlated with PASI scores, while it was positively correlated with PASI scores in the circulation. IL-17 secretion by CD4(+) T cells was not regulated by Treg cells, even though Treg cells exhibited significant inhibition on CD4(+) T cells proliferation and IFN-gamma production. These findings provide new information regarding the association between Th17 and Treg cells, which will further our understanding of the pathogenesis of psoriasis.

[Regulatory T cells and systemic autoimmune diseases: systemic lupus erythematosus, rheumatoid arthritis, primary Sjögren's syndrome]

Regulatory/suppressor T cells (Tregs) maintain immunologic homeostasis and prevent autoimmunity. They are the guardians of dominant tolerance. Recent research reveals quantitative and/or functional defect of Tregs in systemic autoimmune diseases. In this article, past and recent studies of Tregs in human systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and primary Sjögren's syndrome (pGSS) are reviewed. Most studies report that Tregs are decreased in peripheral blood of subjects with active SLE. A population of CD4+CD25-Foxp3+ is specifically described in SLE. Tregs functions are still discussed. Tregs counts in peripheral blood of RA patients vary across studies. Enrichment of synovial fluid in Tregs contrasts with inflammation. Tregs suppressive effects are altered in vivo in RA secondary to proinflammatory cytokines environment and resistance of effector T cells to Tregs. In pGSS, the conflicting place of Tregs in the balance prevention of autoimmunity/antitumor immunity is unspecified. Immunosuppressive treatments, like corticosteroids and anti-TNF, modulate Tregs cells population. There is increasing interest in the use of Tregs as a biological therapy to preserve and restore tolerance to self-antigen. However, difficulties to characterize these lymphocytes and controversies in the results of studies refrain their use in current clinical practice.

Ethylene-Diamine-Tetra-Acetate (EDTA) mimics the effect of regulatory T cells in suppression assays: a potential pitfall when using AutoMACS-separated cells

CD4+CD25+ regulatory T cells (Tregs) mediate tolerance towards self antigens and prevent the development of autoimmunity. Treg function is typically evaluated by the ability to suppress proliferation and cytokine production of co-cultured CD4+CD25- T cells in Treg suppression assays. Purified Tregs are often obtained using the "Regulatory T Cell isolation kit" from Miltenyi Biotech. Separation can be performed manually using single columns or automated using the AutoMACS Cell Separator. In this Technical Note we present a serious pitfall in Treg suppression assays when evaluating magnetically separated CD4+CD25+ T cells obtained by the "Regulatory T Cell isolation kit" and AutoMACS Cell Separator. The AutoMACS Running Buffer recommended by the manufacturer for separation contains Ethylene-Diamine-Tetra-Acetate (EDTA). Here we show that even minute traces of EDTA in the CD4+CD25+ T cell fraction mediate significant suppression of CD4+CD25- T cell proliferation. The suppressive effect of EDTA is dose-dependent and mimics Treg mediated suppression of CD4+CD25- T cell proliferation. The influence of EDTA can be eliminated by thorough washing of the CD4+CD25+ T cell fraction following the separation. Our observation may have implications for other cell separation methods using EDTA-containing buffers.

New perspectives on the biology of acute GVHD

The use of allogeneic hematopoietic cell transplantation (HCT) has increased as new techniques have been developed for transplantation in patients who previously would not have been considered HCT candidates. However, its efficacy continued to be limited by the development of frequent and severe acute GVHD. The complex and intricate pathophysiology of acute GVHD is a consequence of interactions between the donor and host innate and adaptive immune responses. Multiple inflammatory molecules and cell types are implicated in the development of GVHD that can be categorized as: (1) triggers that initiate GVHD by therapy-induced tissue damage and the antigen disparities between host and graft tissue; (2) sensors that detect the triggers, that is, process and present alloantigens; (3) mediators such as T-cell subsets (naive, memory, regulatory, Th17 and natural killer T cells) and (4) the effectors and amplifiers that cause damage of the target organs. These multiple inflammatory molecules and cell types that are implicated in the development of GVHD have been described with models that use stepwise cascades. Herein, we provide a novel perspective on the immunobiology of acute GVHD and briefly discuss some of the outstanding questions and limitations of the model systems.

Effect of IFN-beta therapy on the frequency and function of CD4(+)CD25(+) regulatory T cells and Foxp3 gene expression in relapsing-remitting multiple sclerosis (RRMS): a preliminary study

Interferon-beta (IFN-beta) is an immunomodulatory drug of choice to control relapsing-remitting multiple sclerosis (RR-MS), although its function is still unclear. A reduced suppressive function of CD4(+)CD25(+) regulatory T cells (T(reg)) has been shown in RR-MS patients. In this study, to understand the effect of IFN-ss on CD4(+)CD25(+) regulatory T cells, we analyzed the frequency and function of these cells and Foxp3 gene expression before and after treatment. We evaluated the frequency and function of CD4(+)CD25(+)Foxp3(+) regulatory T cells by flow cytometry and co-culture inhibition test respectively and gene expression of Foxp3 by real-time PCR in a longitudinal follow-up study in 18 relapsing-remitting MS patients. Our data revealed that IFN-beta significantly improved frequency and suppressive function of T(reg) cells (P<0.05) without any significant effect on gene expression of Foxp3 after 6 months. The results of the present study indicate that IFN-beta therapy in some of patients with RR-MS may restore function of regulatory T cells and control the unchecked immune cascade activity. Larger longitudinal studies on more MS patients are required to confirm our findings.

Understanding dendritic cell biology and its role in immunological disorders through proteomic profiling

Dendritic cells (DC) have always been present on the bright spot of immune research. They have been extensively studied for the last 35 years, and much is known about their different phenotypes, stimulatory capacity, and role in the immune system. During the last 15 years, great attention has been given to studies on global gene and protein expression profiles during the differentiation and maturation processes of these cells. It is well understood that studying the proteome, together with information on the role of protein post-translational modifications (PTM), will reveal the real dynamics of a living cell. The rapid increase of proteomic studies during the last decade describing the differentiation and maturation process in DCs, as well as modifications brought by the use of different compounds that either increase or decrease their immunogenicity, reflects the importance of understanding the molecular processes behind the functional properties of these cells. In the present review, we will give an overview of proteomic studies focusing on DCs. Thereby we will concentrate on the importance of these studies in understanding DC behavior from a molecular point of view and how these findings have aided in understanding the differences in functional properties of these cells.

Translational mini-review series on Th17 cells: induction of interleukin-17 production by regulatory T cells

Uncommitted (naive) CD4(+) T helper cells (Thp) can be induced to differentiate to specific lineages according to the local cytokine milieu, towards T helper type 1 (Th1), Th2, Th17 and regulatory T cell (T(reg)) phenotypes in a mutually exclusive manner. Each phenotype is characterized by unique signalling pathways and expression of specific transcription factors, notably T-bet for Th1, GATA-3 for Th2, forkhead box P3 (FoxP3) for T(regs) and receptor-related orphan receptor (ROR)alpha and RORgammat for Th17 cells. T(regs) and Th17 cells have been demonstrated to arise from common precursors in a reciprocal manner based on exposure to transforming growth factor (TGF)-beta or TGF-beta plus interleukin (IL)-6 and carry out diametrically opposing functions, namely suppression or propagation of inflammation, respectively. However, while epigenetic modifications in Th1 and Th2 differentiated cells prevents their conversion to other phenotypes, Th17 cells generated in vitro using TGF-beta and IL-6 are unstable and can convert to other phenotypes, especially Th1, both in vitro and in vivo. T(regs) are generated from naive precursors both in the thymus (natural, nT(regs)) and in the periphery (induced, iT(regs)). The highly suppressive function of T(regs) enables them to control many inflammatory diseases in animals and makes them particularly attractive candidates for immunotherapy in humans. The stability of the T(reg) phenotype is therefore of paramount importance in this context. Recent descriptions of T(reg) biology have suggested that components of pathogens or inflammatory mediators may subvert the suppressive function of T(regs) in order to allow propagation of adequate immune responses. Unexpectedly, however, a number of groups have now described conversion of T(regs) to the Th17 phenotype induced by appropriate inflammatory stimuli. These observations are particularly relevant in the context of cell therapy but may also explain some of the dysregulation seen in autoimmune diseases. In this paper, we review T(reg) to Th17 conversion and propose some potential mechanisms for this phenomenon.

Regulatory T Cells in children with intestinal parasite infection

Chronic intestinal parasite infection can induce both persistent immune activation and defective responsiveness of T cells. This study aimed to assess the number and function of T regulatory (Treg) cells in children with intestinal parasite infection. We have studied the peripheral blood from 93 children, 53 of them parasitized with protozoa, helminths, or both; the remainder were non parasitized, healthy controls. The number and function of CD4(+) CD25(high) and CD4(+) Foxp3(+) cells were similar in parasitized and control children. In contrast, there was a significant increase in the levels of CD3(+) CD69(+), CD4(+) CTLA-4(+), and CD8(+) CD28(-) T cells in helminth infected children. Moreover, some of these patients showed a diminished response to CD3/CD28 stimulation in comparison with the control children. Our data strongly suggest that whilst Treg cells are not affected by intestinal parasite infection, CD3(+) CD69(+), CD4(+) CTLA-4(+) and CD8(+) CD28(-) lymphocytes may play an important, but as yet undetermined role in the diminished immune competence observed in parasitized children.

Generation and accumulation of immunosuppressive adenosine by human CD4+CD25highFOXP3+ regulatory T cells

Naturally occurring regulatory T cells (nTreg) are crucial for maintaining tolerance to self and thus preventing autoimmune diseases and allograft rejections. In cancer, Treg down-regulate antitumor responses by several distinct mechanisms. This study analyzes the role the adenosinergic pathway plays in suppressive activities of human nTreg. Human CD4(+)CD25(high)FOXP3(+) Treg overexpress CD39 and CD73, ectonucleotidases sequentially converting ATP into AMP and adenosine, which then binds to A(2a) receptors on effector T cells, suppressing their functions. CD4(+)CD39(+) and CD4(+)CD25(high) T cells express low levels of adenosine deaminase (ADA), the enzyme responsible for adenosine breakdown, and of CD26, a surface-bound glycoprotein associated with ADA. In contrast, T effector cells are enriched in CD26/ADA but express low levels of CD39 and CD73. Inhibitors of ectonucleotidase activity (e.g. ARL67156) and antagonists of the A(2a) receptor (e.g. ZM241385) blocked Treg-mediated immunosuppression. The inhibition of ADA activity on effector T cells enhanced Treg-mediated immunosuppression. Thus, human nTreg characterized by the presence of CD39 and the low expression of CD26/ADA are responsible for the generation of adenosine, which plays a major role in Treg-mediated immunosuppression. The data suggest that the adenosinergic pathway represents a potential therapeutic target for regulation of immunosuppression in a broad variety of human diseases.

Increased ectonucleotidase expression and activity in regulatory T cells of patients with head and neck cancer

PURPOSE

Regulatory T cell (Treg) frequency and activity are increased in cancer patients and play a major role in tumor escape. Although disease progression is favored by the presence of Treg, mechanisms used by Treg to suppress antitumor immunity are unknown. The ectonucleotidases CD39 and CD73 are expressed in Treg and convert ATP into immunosuppressive adenosine. In this study, the involvement of the adenosinergic pathway in Treg-mediated suppression in head and neck squamous cell carcinoma (HNSCC) patients was evaluated.

EXPERIMENTAL DESIGN

HNSCC patients with an active disease (n = 19) and patients with no evident disease after therapy (n = 14) were studied. Ectonucleotidase expression on CD4(+) T cells and CD4(+)CD25(high) Treg was evaluated by flow cytometry and compared with normal controls. Ectonucleotidase activity was also compared within these three groups. The data were analyzed for associations of ectonucleotidase expression/function with disease stage.

RESULTS

The percentages and expression levels of CD39 and CD73 in CD4(+) T cells and Treg were greater in HNSCC than in normal controls and highest in patients with no evident disease. Patients' Treg hydrolyzed ATP at higher rates and produced higher levels of adenosine than normal controls' Treg. The increased frequency and enzymatic activity of CD4(+)CD39(+) cells corresponded to increased adenosine-mediated suppression of effector T cells, which was partly inhibited by ARL67156, an ectonucleotidase inhibitor, and by ZM241385, a selective A(2a)/A(2b) receptor antagonist.

CONCLUSIONS

CD39(+) Treg frequency and adenosine-mediated suppression are significantly increased in HNSCC patients. The adenosinergic pathway is involved in Treg-mediated immunosuppression in cancer and its attenuation could be a promising immunotherapeutic strategy for patients with HNSCC.

The number of Foxp3-positive regulatory T cells is increased in Helicobacter pylori gastritis and gastric cancer

Helicobacter pylori (H. pylori) colonization induces vigorous innate and specific immune responses; however, the infection is not removed, a state of chronic active gastritis persists for life if untreated. Recent studies have shown that CD4(+) CD25(+) Foxp3-positive regulatory T cells (Tregs) suppress the immune response to H. pylori. Persistent H. pylori-associated gastritis is closely associated with gastric carcinogenesis. We investigated the number of Tregs in the context of H. pylori colonization in chronic gastritis, examined the relationship between it and histopathological findings and compared it with that of gastric dysplasia and adenocarcinoma. This study was based on the analysis of gastric biopsy specimens from 126 cases of H. pylori-associated gastritis, 16 cases of H. pylori-negative gastritis, 17 cases of gastric dysplasia, and 25 cases of gastric adenocarcinoma. The number of Tregs was elevated in H. pylori-associated gastritis, where it was positively correlated with the grade of chronic inflammation and the number of lymphoid follicles. It was significantly elevated in adenocarcinomas compared to chronic gastritis and gastric dysplasia. In summary, the number of Tregs is increased in H. pylori-associated gastritis and gastric cancer.

HOZOTs, novel human regulatory T-cell lines, exhibit helper or suppressor activities depending on dendritic cell or anti-CD3 stimulation

OBJECTIVE

HOZOT cell lines (HOZOTs) are a new type of regulatory T cells established from human umbilical cord blood without using cytokines. In addition to their unique FOXP3(+)CD4(+)CD8(+)CD25(+) phenotype, HOZOTs are bifunctional and can exert either suppressor or cytotoxic activities. To further characterize HOZOTs, we cocultured HOZOTs with responder T cells under different stimulation conditions and found another function of HOZOTs.

MATERIALS AND METHODS

Naïve CD4(+)T cells as responder cells were stimulated with dendritic cells or plate bound anti-CD3 antibody. As effector cells, HOZOTs were added to this culture and proliferation of the responder cells were monitored by (3)H-thymidine incorporation or carboxyfluorescein succinimidyl ester dilution method. To investigate the molecular mechanisms, antibodies specific for interleukin (IL)-2/IL-2R or cell surface molecules were used for blocking experiments.

RESULTS

The proliferation of naïve CD4(+)T cells was suppressed by one HOZOT line, HOZOT-4, when the responder cells were stimulated with dendritic cells. However, responder cell proliferation was augmented by HOZOT-4 when these cells were stimulated with anti-CD3 antibody. This opposing function to responder cells was unique to HOZOTs because naturally occurring regulatory T cells suppressed proliferation of both dendritic cell- and anti-CD3-antibody-stimulated cells. IL-2 was not involved in the mechanism of the helper activity of HOZOT-4 as blocking antibodies for IL-2 and IL-2R did not abrogate the helper activity. Moreover, this helper activity could not be reduced by blocking costimulatory pathways such as CD28/B7, CD4/human leukocyte antigen-DR, and intercellular adhesion molecule-1/lymphocyte function-associated antigen-1.

CONCLUSION

We demonstrated a new function of HOZOTs as helper T cells in addition to suppressor and cytotoxic activities, characterizing HOZOTs as multifunctional T cells.