Outgrowth of CD4low/negCD25+ T cells with suppressor function in CD4+CD25+ T cell cultures upon polyclonal stimulation ex vivo

Preservation of antigen-specific responses in cryopreserved CD4+ and CD8+ T cells expanded with IL-2 and IL-7

Objectives

We sought to develop medium throughput standard operating procedures for screening cryopreserved human peripheral blood mononuclear cells (PBMCs) for CD4⁺ and CD8⁺ T cell responses to potential autoantigens.

Methods

Dendritic cells were loaded with a peptide cocktail from ubiquitous viruses or full-length viral protein antigens and cocultured with autologous T cells. We measured expression of surface activation markers on T cells by flow cytometry and cytometry by time of flight 24-72 h later. We tested responses among T cells freshly isolated from healthy control PBMCs, cryopreserved T cells, and T cells derived from a variety of T cell expansion protocols. We also compared the transcriptional profile of CD8⁺ T cells rested with interleukin (IL)7 for 48 h after 1) initial thawing, 2) expansion, and 3) secondary cryopreservation/thawing of expanded cells. To generate competent antigen presenting cells from PBMCs, we promoted differentiation of PBMCs into dendritic cells with granulocyte macrophage colony stimulating factor and IL-4.

Results

We observed robust dendritic cell differentiation from human PBMCs treated with 50 ng/mL GM-CSF and 20 ng/mL IL-4 in as little as 3 days. Dendritic cell purity was substantially increased by magnetically enriching for CD14⁺ monocytes prior to differentiation. We also measured antigen-dependent T cell activation in DC-T cell cocultures. However, polyclonal expansion of T cells with anti-CD3/antiCD28 abolished antigen-dependent upregulation of CD69 in our assay despite minimal transcriptional differences between rested CD8⁺ T cells before and after expansion. Furthermore, resting these expanded T cells in IL-2, IL-7 or IL-15 did not restore the antigen dependent responses. In contrast, T cells that were initially expanded with IL-2 + IL-7 rather than plate bound anti-CD3 + anti-CD28 retained responsiveness to antigen stimulation and these responses strongly correlated with responses measured at initial thawing.

Significance

While screening techniques for potential pathological autoantibodies have come a long way, comparable full-length protein target assays for screening patient T cells at medium throughput are noticeably lacking due to technical hurdles. Here we advance techniques that should have broad applicability to translational studies investigating cell mediated immunity in infectious or autoimmune diseases. Future studies are aimed at investigating possible CD8⁺ T cell autoantigens in MS and other CNS autoimmune diseases.

Small Heterodimer Partner Regulates Dichotomous T Cell Expansion by Macrophages

The involvement of small heterodimer partner (SHP) in the inhibition of hepatic bile acid synthesis from cholesterol has been established. However, extrahepatic expression of SHP implies that SHP may have regulatory functions other than those in the liver. Here, we find that SHP mRNA expression is high in murine bone marrow cells, suggesting a physiological role within macrophages. Indeed, expression of SHP in macrophages decreases the transcriptional activity and nuclear localization of nuclear factor κB, whereas downregulation of SHP has the opposite effects. Expression of genes associated with macrophage-T cell crosstalk were altered by overexpression or downregulation of SHP. Intriguingly, increasing SHP expression in macrophages resulted in decreased T cell expansion, a hallmark of T cell activation, whereas knockdown of SHP resulted in increased expansion. Analyses of the expanded T cells revealed a dichotomous skewing between effector T cells and regulatory T cells (Tregs), with SHP overexpression reducing Tregs and downregulation of SHP increasing their expansion. The expanded Tregs were confirmed to be suppressive via adoptive transfers. IL-2 and TGF-β, known inducers of Treg differentiation, were found to be regulated by SHP. Furthermore, SHP occupancy at the promoter region of IL-2 was increased after macrophages were challenged with lipopolysaccharide. Neutralizing antibodies to IL-2 and TGF-β inhibited the expansion of Tregs mediated by downregulation of SHP. This study demonstrates that expression and activity of SHP within macrophages can alter T cell fate and identifies SHP as a potential therapeutic target for autoimmune diseases or solid cancers.

Stem Cell-Derived Regulatory T Cells for Therapeutic Use in Arthritis

Pluripotent stem cells (PSCs) can be utilized to obtain a renewable source of healthy regulatory T cells (T_regs) to treat autoimmune arthritis as they have the ability to produce almost all cell types in the body, including T_regs. However, the right conditions for the development of antigen (Ag)-specific T_regs from PSCs (i.e., PSC-T_regs) remain unknown. An ongoing project will determine the mechanisms underlying the Ag-specific PSC-T_reg treatments that aim to modulate tolerance in autoimmune arthritis. The knowledge gained from these studies will provide new insights into cell-based therapies in autoimmune arthritis, and advance the understanding of fundamental mechanisms underlying T_reg differentiation.

Development of Auto Antigen-specific Regulatory T Cells for Diabetes Immunotherapy

CD4⁺ regulatory T cells (Tregs) are essential for normal immune surveillance, and their dysfunction can lead to the development of autoimmune diseases, such as type-1 diabetes (T1D). T1D is a T cell-mediated autoimmune disease characterized by islet β cell destruction, hypoinsulinemia, and severely altered glucose homeostasis. Tregs play a critical role in the development of T1D and participate in peripheral tolerance. Pluripotent stem cells (PSCs) can be utilized to obtain a renewable source of healthy Tregs to treat T1D as they have the ability to produce almost all cell types in the body, including Tregs. However, the right conditions for the development of antigen (Ag)-specific Tregs from PSCs (i.e., PSC-Tregs) remain undefined, especially molecular mechanisms that direct differentiation of such Tregs. Auto Ag-specific PSC-Tregs can be programmed to be tissue-associated and infiltrate to local inflamed tissue (e.g., islets) to suppress autoimmune responses after adoptive transfer, thereby avoiding potential overall immunosuppression from non-specific Tregs. Developing auto Ag-specific PSC-Tregs can reduce overall immunosuppression after adoptive transfer by accumulating inflamed islets, which drives forward the use of therapeutic PSC-Tregs for cell-based therapies in T1D.

Alloreactive regulatory T cells generated with retinoic acid prevent skin allograft rejection

CD4(+) CD25(+) Foxp3(+) regulatory T (Treg) cells mediate immunological self-tolerance and suppress immune responses. Retinoic acid (RA), a natural metabolite of vitamin A, has been reported to enhance the differentiation of Treg cells in the presence of TGF-β. In this study, we show that the co-culture of naive T cells from C57BL/6 mice with allogeneic antigen-presenting cells (APCs) from BALB/c mice in the presence of TGF-β, RA, and IL-2 resulted in a striking enrichment of Foxp3(+) T cells. These RA in vitro-induced regulatory T (RA-iTreg) cells did not secrete Th1-, Th2-, or Th17-related cytokines, showed a nonbiased homing potential, and expressed several cell surface molecules related to Treg-cell suppressive potential. Accordingly, these RA-iTreg cells suppressed T-cell proliferation and inhibited cytokine production by T cells in in vitro assays. Moreover, following adoptive transfer, RA-iTreg cells maintained Foxp3 expression and their suppressive capacity. Finally, RA-iTreg cells showed alloantigen-specific immunosuppressive capacity in a skin allograft model in immunodeficient mice. Altogether, these data indicate that functional and stable allogeneic-specific Treg cells may be generated using TGF-β, RA, and IL-2. Thus, RA-iTreg cells may have a potential use in the development of more effective cellular therapies in clinical transplantation.

Helper T cells down-regulate CD4 expression upon chronic stimulation giving rise to double-negative T cells

Double-negative T (DNT) cells are αβTCR(+)CD3(+)CD4(-)CD8(-)NK1.1(-) cells that constitute a small but significant proportion of the αβTCR(+) T cells. Their developmental pathway and pathological significance remain unclear. In the present study, we utilized chronic in vitro stimulation of CD4(+) T cells to mimic immune hyper-activation of autoimmune lymphoproliferative syndrome and systemic lupus erythematosus, conditions characterized by DNT cells accumulation. After approximately 4-5 rounds of stimulation, the CD3(+)CD4(-) population became apparent. These cells did not express CD8, NK1.1, γδTCR, or B220, exhibited a highly proliferative effector phenotype, and were dependent on T cell receptor (TCR) stimulation for survival. Moreover, CD3(+)CD4(-) cells expressed MHC class II-restricted αβTCR, indicative of their origin from a CD4(+) T cell population. The results presented herein illustrate a novel method of DNT cell generation in vitro and suggest that immune hyper-activation could also be implicated in the genesis of the disease-associated DNT cells in vivo.

FOXP3 expression is upregulated in CD4T cells in progressive HIV-1 infection and is a marker of disease severity

Background

Understanding the role of different classes of T cells during HIV infection is critical to determining which responses correlate with protective immunity. To date, it is unclear whether alterations in regulatory T cell (Treg) function are contributory to progression of HIV infection.

Methodology

FOXP3 expression was measured by both qRT-PCR and by flow cytometry in HIV-infected individuals and uninfected controls together with expression of CD25, GITR and CTLA-4. Cultured peripheral blood mononuclear cells were stimulated with anti-CD3 and cell proliferation was assessed by CFSE dilution.

Principal Findings

HIV infected individuals had significantly higher frequencies of CD4⁺FOXP3⁺ T cells (median of 8.11%; range 1.33%–26.27%) than healthy controls (median 3.72%; range 1.3–7.5%; P = 0.002), despite having lower absolute counts of CD4⁺FOXP3⁺ T cells. There was a significant positive correlation between the frequency of CD4⁺FOXP3⁺ T cells and viral load (rho = 0.593 P = 0.003) and a significant negative correlation with CD4 count (rho = −0.423 P = 0.044). 48% of our patients had CD4 counts below 200 cells/µl and these patients showed a marked elevation of FOXP3 percentage (median 10% range 4.07%–26.27%). Assessing the mechanism of increased FOXP3 frequency, we found that the high FOXP3 levels noted in HIV infected individuals dropped rapidly in unstimulated culture conditions but could be restimulated by T cell receptor stimulation. This suggests that the high FOXP3 expression in HIV infected patients is likely due to FOXP3 upregulation by individual CD4⁺ T cells following antigenic or other stimulation.

Conclusions/Significance

FOXP3 expression in the CD4⁺ T cell population is a marker of severity of HIV infection and a potential prognostic marker of disease progression.

Dendritic cells and B cells cooperate in the generation of CD4(+)CD25(+)FOXP3(+) allogeneic T cells

BACKGROUND

CD4(+)CD25(+)Foxp3(+) regulatory T cells (Treg) play an essential role in immune tolerance, suppressing responses against self-antigens. Additionally, Treg play an important role in maintaining immunosuppression to alloantigens as well as to other antigens. It is well known that in the gut, a subset of dendritic cells produces retinoic acid (RA), which together with transforming growth factor (TGF-beta) is able to differentiate naïve T cells into Treg. The aim of this study was to establish the role of antigen-presenting cells (APC) in the differentiation of allogeneic Tregs under the effect of RA and TGF-beta.

METHODS

Splenic CD4(+)CD25(-) naïve T cells from C57BL/6 mice were co-cultured with splenic CD11c-enriched APC from Balb/c mice in the presence of TGF-beta, RA, and interleukin (IL-2). After 6 days of culture, cells were analyzed for the expression of Foxp3 by flow cytometry. Additionally, we investigated the role of B cells and dendritic cells (DCs) and their stimulatory capacity in the generation of Tregs.

RESULTS

Our results showed that co-culture of naive T cells with the appropriate level of stimulation by APC in the presence of TGF-beta, RA, and IL-2 provided a new powerful approach to generate allogeneic Treg cells. We demonstrated that although B cells and DCs can generate Tregs by themselves, a mixure of both APC improved their capacity to efficiently generate Tregs. Also, we observed that although the addition of IL-2 to the cultures was not crucial to generate Tregs, it was required to optimize their expansion and cell survival.

Transforming growth factor beta 1 (TGF-beta1) and rapamycin synergize to effectively suppress human T cell responses via upregulation of FoxP3+ Tregs

BACKGROUND

The major obstacle faced by patients with type 1 diabetes who undergo islet transplantation is a gradual decline in insulin independence. This decline may reflect alloimmune rejection, autoimmune recurrence and toxicity of drugs such as rapamycin to islet beta cells. Thus, there is a pressing need to refine immunosuppressive protocols in order to reduce toxicity to islet grafts and yet prevent rejection. Recent studies demonstrated that TGF-beta1 is a critical cytokine for the regulation of immune responses. In naive T cells, TGF-beta1 induces FoxP3(+) regulatory T cells and thus could promote transplant tolerance. In this study, in vitro experiments were performed to determine whether TGF-beta1 could synergize with low-dose rapamycin and inhibit T cell activation and production of inflammatory cytokines, as well as enhance FoxP3 expression for potential application in islet transplantation.

METHODS

Human peripheral blood mononuclear cells were stimulated with either anti-CD3/CD28 or anti-CD3 during TGF-beta1 and rapamycin treatment.

RESULTS

TGF-beta1 inhibited T cell proliferation induced with anti-CD3 stimulation, but not with anti-CD3/CD28 stimulation. The combination of these reagents produced a synergistic inhibition of T cell proliferation induced with both anti-CD3/CD28 and anti-CD3 stimulations. Moreover, TGF-beta1 and rapamycin significantly suppressed cytokine production and induced regulatory T cells by upregulating FoxP3 expression.

CONCLUSIONS

These results suggest that the combination of TGF-beta1 and low-dose rapamycin can potently inhibit T cell responses in vivo and would be beneficial in supporting islet graft survival by limiting toxicity and preventing immune rejection.

The worldwide gradient of autoimmune conditions

Among the numerous consequences of globalization, the dissemination of scientific research allows real-time comparisons of clinical and basic experimental data between different geographical areas. As a result, the field of geoepidemiology is now vigorously supported by multiple lines of evidence. This special issue of Autoimmunity Reviews is dedicated to the 2010 International Congress on Autoimmunity and aims to provide a state-of-the-art representation of what is currently known in the field of geoepidemiology for autoimmune diseases. The obvious implications of these observations is a role for environmental factors. We will herein review selected publications from prominent scientific journals to provide the bases to understand some of the lines of evidence proposed in the subsequent papers of this comprehensive volume. The ultimate goal is thus to define whether geoepidemiology should be considered a new challenge for autoimmunologists.

Toll-like receptor signaling in uterine natural killer cells--role in embryonic loss

Embryonic development is a complex process that is regulated by many cell types and signaling pathways. This review focuses on the role of NK cells and regulatory T-cells (Treg cells) in embryonic loss. Approximately 70% of uterine leukocytes until the time of mid-gestation are found to be CD16(-)CD56(bright) NK cells. This subset of NK cells, along with Treg cells, has been shown to regulate fetal development. We recently found a population of NK cells in the pregnant mouse uterus with a unique CD3(-)CD49b(+)CD25(+)Foxp3(+) phenotype. This review summarizes the studies indicating critical roles for expression of IL-10 by CD3(-)CD49b(+)CD25(+)Foxp3(+) cells and CXCR4 expression on CD16(-)CD56(bright) NK cells in preventing embryonic loss. In addition, the roles of toll-like receptors (TLRs) and CXCR4 in NK cell migration and functional modulation are discussed.

Regulatory T cells: how do they suppress immune responses?

Regulatory T cells (Tregs), either natural or induced, suppress a variety of physiological and pathological immune responses. One of the key issues for understanding Treg function is to determine how they suppress other lymphocytes at the molecular level in vivo and in vitro. Here we propose that there may be a key suppressive mechanism that is shared by every forkhead box p3 (Foxp3)(+) Treg in vivo and in vitro in mice and humans. When this central mechanism is abrogated, it causes a breach in self-tolerance and immune homeostasis. Other suppressive mechanisms may synergistically operate with this common mechanism depending on the environment and the type of an immune response. Further, Treg-mediated suppression is a multi-step process and impairment or augmentation of each step can alter the ultimate effectiveness of Treg-mediated suppression. These findings will help to design effective ways for controlling immune responses by targeting Treg suppressive functions.