CD122+CD8+ Treg suppress vaccine-induced antitumor immune responses in lymphodepleted mice

Circulating CD4+ Treg, CD8+ Treg, and CD3+ γδ T Cell Subpopulations in Ovarian Cancer

Background and Objectives: Regulatory T cells (Tregs) are usually enriched in ovarian cancer (OC), and their immunosuppressive function plays a key role in tumorigenesis and progression. We mainly explored the phenotypical characterization of Treg-related markers on αβ and γδ T cell subsets in patients with OC. Materials and Methods: Thirty-six untreated patients with OC at the Women's Hospital of Nanjing Medical University from September 2019 to August 2021 were enrolled. Phenotypical characterization of Tregs-related markers were detected by flow cytometry (FCM). Enzyme-linked immunosorbent assay was used to detect the levels of carbohydrate antigen (CA125) and transforming growth factor β (TGF-β). The level of human epididymis protein 4 (HE4) was detected by electrochemiluminescence immunoassay. Results: Circulating CD4⁺ Tregs, CD8⁺ Tregs, and CD3⁺γδ T cell subpopulations from OC patients have elevated Foxp3, CD25, CD122, Vδ1, and reduced CD28 expression compared to benign ovarian tumor (BOT) patients and healthy controls (HC). The upregulation of Foxp3 and Vδ1 and the downregulation of CD28 were highly specific for maintaining the immunosuppression function of CD4⁺ Tregs, CD3⁺γδ T cells, and CD8⁺ Tregs in OC patients. These Treg subpopulations were able to discriminate OC from BOT and HC. The levels of CA125, HE4, and TGF-β were increased in OC patients. A significant positive correlation between Treg subpopulations and CA125, HE4, and TGF-β was revealed. Conclusions: Proportions of CD4⁺ Tregs, CD8+ Tregs, and CD3⁺γδ T cell subsets were significantly increased in OC patients and were positively correlated with FIGO stage/metastasis status, CA125, HE4, and TGF-β. These indicators have the potential to be used as immunosurveillance biomarkers for OC.

Vaccination with a shared oncogenic tumor-self antigen elicits a population of CD8+ T cells with a regulatory phenotype

Cancer immunotherapy is a powerful tool for inducing antigen-specific antitumor cytotoxic T lymphocytes (CTLs). Next-generation strategies may include vaccination against overexpressed oncogenic tumor-self antigens. Previously, we reported vaccination against the oncogenic tumor-self antigen D52 (D52) was effective in preventing tumor growth. We recently reported that D52-vaccinated IL-10-deficient mice generated a significant memory response against tumor recurrence compared to wild-type mice and that vaccine-induced CD8+ IL-10+ T cells may possess regulatory function. Herein, we extended these studies by testing the hypothesis that D52-vaccine-elicited CD8+ IL-10+ T cells represent a distinct T cell population with a regulatory phenotype. C57Black/6J mice deficient in IL-10 or IFN-γ were vaccinated with the murine orthologue of D52; vaccination of wild-type (wt) mice served as a control for comparison. T cells were isolated from all three groups of vaccinated mice, and RNA was extracted from purified CD8+ T cells for deep sequencing and expression analysis. Chemokine receptor 8 (CCR8) and inducible co-stimulator (ICOS) were overexpressed in CD8+ T cells that produced IL-10 but not IFN-γ. These surface markers are associated with IL-10 producing CD4+ T regulatory cells thus supporting the possibility that CD8+ IL-10+ T cells elicited by D52 vaccination represent a unique regulatory T cell subset. The current phenotypic analyses of D52 vaccine elicited CD8+ T cells strengthen our premise that CD8+ IL-10+ T cells elicited by D52 tumor-self protein vaccination likely contribute to the suppression of memory CTL responses and inhibition of durable tumor immunity.

Neuroprotection against ischemic stroke requires a specific class of early responder T cells in mice

Immunomodulation holds therapeutic promise against brain injuries, but leveraging this approach requires a precise understanding of mechanisms. We report that CD8⁺CD122⁺CD49d^lo T regulatory-like cells (CD8⁺ TRLs) are among the earliest lymphocytes to infiltrate mouse brains after ischemic stroke and temper inflammation; they also confer neuroprotection. TRL depletion worsened stroke outcomes, an effect reversed by CD8⁺ TRL reconstitution. The CXCR3/CXCL10 axis served as the brain-homing mechanism for CD8⁺ TRLs. Upon brain entry, CD8⁺ TRLs were reprogrammed to upregulate leukemia inhibitory factor (LIF) receptor, epidermal growth factor–like transforming growth factor (ETGF), and interleukin 10 (IL-10). LIF/LIF receptor interactions induced ETGF and IL-10 production in CD8⁺ TRLs. While IL-10 induction was important for the antiinflammatory effects of CD8⁺ TRLs, ETGF provided direct neuroprotection. Poststroke intravenous transfer of CD8⁺ TRLs reduced infarction, promoting long-term neurological recovery in young males or aged mice of both sexes. Thus, these unique CD8⁺ TRLs serve as early responders to rally defenses against stroke, offering fresh perspectives for clinical translation.

Cytolytic CD4+ and CD8+ Regulatory T-Cells and Implications for Developing Immunotherapies to Combat Graft-Versus-Host Disease

Regulatory T-cells (Treg) are critical for the maintenance of immune homeostasis and tolerance induction. While the immunosuppressive mechanisms of Treg have been extensively investigated for decades, the mechanisms responsible for Treg cytotoxicity and their therapeutic potential in regulating immune responses have been incompletely explored and exploited. Conventional cytotoxic T effector cells (Teffs) are known to be important for adaptive immune responses, particularly in the settings of viral infections and cancer. CD4+ and CD8+ Treg subsets may also share similar cytotoxic properties with conventional Teffs. Cytotoxic effector Treg (cyTreg) are a heterogeneous population in the periphery that retain the capacity to suppress T-cell proliferation and activation, induce cellular apoptosis, and migrate to tissues to ensure immune homeostasis. The latter can occur through several cytolytic mechanisms, including the Granzyme/Perforin and Fas/FasL signaling pathways. This review focuses on the current knowledge and recent advances in our understanding of cyTreg and their potential application in the treatment of human disease, particularly Graft-versus-Host Disease (GVHD).

Evolutionary genetic algorithm identifies IL2RB as a potential predictive biomarker for immune-checkpoint therapy in colorectal cancer

Identifying robust predictive biomarkers to stratify colorectal cancer (CRC) patients based on their response to immune-checkpoint therapy is an area of unmet clinical need. Our evolutionary algorithm Atlas Correlation Explorer (ACE) represents a novel approach for mining The Cancer Genome Atlas (TCGA) data for clinically relevant associations. We deployed ACE to identify candidate predictive biomarkers of response to immune-checkpoint therapy in CRC. We interrogated the colon adenocarcinoma (COAD) gene expression data across nine immune-checkpoints (PDL1, PDCD1, CTLA4, LAG3, TIM3, TIGIT, ICOS, IDO1 and BTLA). IL2RB was identified as the most common gene associated with immune-checkpoint genes in CRC. Using human/murine single-cell RNA-seq data, we demonstrated that IL2RB was expressed predominantly in a subset of T-cells associated with increased immune-checkpoint expression (P < 0.0001). Confirmatory IL2RB immunohistochemistry (IHC) analysis in a large MSI-H colon cancer tissue microarray (TMA; n = 115) revealed sensitive, specific staining of a subset of lymphocytes and a strong association with FOXP3+ lymphocytes (P < 0.0001). IL2RB mRNA positively correlated with three previously-published gene signatures of response to immune-checkpoint therapy (P < 0.0001). Our evolutionary algorithm has identified IL2RB to be extensively linked to immune-checkpoints in CRC; its expression should be investigated for clinical utility as a potential predictive biomarker for CRC patients receiving immune-checkpoint blockade.

Galectin-1 fosters an immunosuppressive microenvironment in colorectal cancer by reprogramming CD8+ regulatory T cells

Colorectal cancer (CRC) represents the third most common malignancy and the second leading cause of cancer-related deaths worldwide. Although immunotherapy has taken center stage in mainstream oncology, it has shown limited clinical efficacy in CRC, generating an urgent need for discovery of new biomarkers and potential therapeutic targets. Galectin-1 (Gal-1), an endogenous glycan-binding protein, induces tolerogenic programs and contributes to tumor cell evasion of immune responses. Here, we investigated the relevance of Gal-1 in CRC and explored its modulatory activity within the CD8⁺ regulatory T cell (Treg) compartment. Mice lacking Gal-1 (Lgals1 ^-/- ) developed a lower number of tumors and showed a decreased frequency of a particular population of CD8⁺CD122⁺PD-1⁺ Tregs in the azoxymethane-dextran sodium sulfate model of colitis-associated CRC. Moreover, silencing of tumor-derived Gal-1 in the syngeneic CT26 CRC model resulted in reduced number and attenuated immunosuppressive capacity of CD8⁺CD122⁺PD-1⁺ Tregs, leading to slower tumor growth. Moreover, stromal Gal-1 also influenced the fitness of CD8⁺ Tregs, highlighting the contribution of both tumor and stromal-derived Gal-1 to this immunoregulatory effect. Finally, bioinformatic analysis of a colorectal adenocarcinoma from The Cancer Genome Atlas dataset revealed a particular signature characterized by high CD8⁺ Treg score and elevated Gal-1 expression, which delineates poor prognosis in human CRC. Our findings identify CD8⁺CD122⁺PD-1⁺ Tregs as a target of the immunoregulatory activity of Gal-1, suggesting a potential immunotherapeutic strategy for the treatment of CRC.

Formation of a Unique Population of CD8+ T Lymphocytes after Adoptive Transfer of Syngeneic Splenocytes to Mice with Lymphopenia

Under conditions of lymphopenia, T lymphocytes proliferate and acquire a surface activation phenotype, which in many respects is similar to the phenotype of true memory T cells. We investigated the phenotypic features of the CD8+ T-cell population formed from donor lymphocytes after adoptive transfer of syngeneic splenocytes to sublethally irradiated mice. This population expresses markers CD44, CD122, CD5, CD49d and the chemokine receptor CXCR3. Thus, for the first time, the phenomenon of the formation of a population of T cells with signs of suppressive CD8+ T lymphocytes and true memory cells was demonstrated.

Suppression of the Immune Response by Syngeneic Splenocytes Adoptively Transferred to Sublethally Irradiated Mice

The peripheral T-cell pool consists of several, functionally distinct populations of CD8⁺ T cells. CD44 and CD62L are among the major surface markers that allow us to define T-cell populations. The expression of these molecules depends on the functional status of a T lymphocyte. Under lymphopenic conditions, peripheral T cells undergo homeostatic proliferation and acquire the memory-like surface phenotype CD44hiCD62Lhi. However, the data on the functional activity of these cells remains controversial. In this paper, we analyzed the effects of the adoptive transfer of syngeneic splenocytes on the recovery of CD8⁺ T cells in sublethally irradiated mice. Our data demonstrate that under lymphopenia, donor lymphocytes form a population of memory-like CD8⁺ T cells with the phenotype CD122+CD5+CD49dhiCXCR3+ that shares the phenotypic characteristics of true memory cells and suppressive CD8⁺ T cells. Ex vivo experiments showed that after adoptive transfer in irradiated mice, T cells lacked the functions of true effector or memory cells; the allogeneic immune response and immune response to pathogens were greatly suppressed in these mice.

Regulatory T Cells: Concept, Classification, Phenotype, and Biological Characteristics

Regulatory T cells (Treg) play an indispensable role in maintaining the body's immune nonresponse to self-antigens and suppressing the body's unwarranted and potentially harmful immune responses. Their absence, reduction, dysfunction, transformation, and instability can lead to numerous autoimmune diseases. There are several distinct subtypes of the Treg cells, although they share certain biological characteristics and have unique phenotypes with different regulatory functions, as well as mechanistic abilities. In this book chapter, we introduce the latest advances in Treg cell subtypes pertaining to classification, phenotype, biological characteristics, and mechanisms. We also highlight the relationship between Treg cells and various diseases, including autoimmune, infectious, as well as tumors and organ transplants.

Resveratrol exerts antitumor effects by downregulating CD8+CD122+ Tregs in murine hepatocellular carcinoma

CD4⁺Foxp3⁺ regulatory T cells (Tregs) in the tumor microenvironment restrain antitumor immunity, resulting in tumor aggression and poor survival in hepatocellular carcinoma (HCC). CD8⁺CD122⁺ Tregs have been previously shown to be more potent in immunosuppression than are CD4⁺Foxp3⁺ Tregs. Previous studies have demonstrated that resveratrol exerts its anti-cancer effects by downregulating CD4⁺Foxp3⁺ and M2-like macrophages, two key immunoregulatory cells that maintain the immunosuppressive tumor microenvironment. In this study, we found that resveratrol inhibited the tumor growth in a subcutaneous Hepa1-6 HCC model and decreased the frequency of CD8⁺CD122⁺ Tregs in the tumor as well as lymph nodes and spleen of the tumor-bearing mice. It also increased the percentage of IFN-γ-expressing CD8⁺ T cells in the tumor and peripheral lymphoid organs. The antitumor effects of resveratrol were partially reversed by the adoptive transfer of exogenous CD8⁺CD122⁺ Tregs into the tumor-bearing mice. Meanwhile, resveratrol treatment downregulated immunosuppressive cytokines, including TGF-β1 and interleukin-10, in the tumor while elevating antitumor cytokines, TNF-α and IFN-γ. It also inhibited the activation of STAT3 signaling in the tumor. As expected, resveratrol reduced the percentage of M2-like macrophages in the mice. Importantly, resveratrol suppressed orthotopic H22 tumor growth and decreased the frequency of CD8⁺CD122⁺ Tregs and M2-like macrophages in the tumor-bearing mice. Furthermore, our studies showed that resveratrol, at non-cytotoxic concentrations, inhibited CD8⁺CD122⁺ Treg differentiation from CD8⁺CD122⁻ T cells in vitro. Thus, our studies unveiled a new immune mechanism underlying the immunosuppressive tumor microenvironment and demonstrated that resveratrol could help reverse it by diminishing CD8⁺CD122⁺ Tregs.

CD8+ T cells: The past and future of immune regulation

Regulation of the adaptive immune response is critical for health. Regulatory activity can be found in multiple components of the immune system, however, the focus on particular components of the immune regulatory network has left many aspects of this critical immune component understudied. Here we review the evidence for activities of CD8+ T cells in immune homeostasis and regulation of autoimmune reactivity. The heterogeneous nature of identified CD8+ cell types are examined, and common phenotypes associated with functional activities are defined. The varying types of antigen signal crucial for CD8+ T cell regulatory activity are identified and the implications of these activation pathways for control of adaptive responses is considered. Finally, the promising capacity for transgenic antigen receptor directed cytotoxicity as a mechanism for modulation of autoimmunity is detailed.

Analysis of the CD8+ IL-10+ T cell response elicited by vaccination with the oncogenic tumor-self protein D52

Development of cancer vaccines targeting tumor self-antigens is complex and challenging due to the difficulty of overcoming immune tolerance to self-proteins. Vaccination against tumor self-protein D52 (D52) has been successful, although complete protection appears impaired by immune regulation. Our previous studies suggest that vaccine elicited CD8 + T cells producing interleukin 10 (IL-10) may have a negative impact on tumor protection. Understanding the role CD8+ IL-10 + T cells play in the immune response following vaccination with D52 could result in a more potent vaccine. To address this, we vaccinated IL-10 deficient mice with the murine orthologue of D52; vaccination of wild type (wt) C57BL/6J served as a control for comparison. In separate experiments, D52 vaccinated wt mice were administered IL-10R-specific mAb to neutralize IL-10 function. Interestingly, we observed similar protection against primary tumor challenge in the experimental groups compared to the controls. However, individual IL-10 deficient mice that rejected the primary tumor challenge were re-challenged 140 days post-primary challenge to access vaccine durability and immunologic memory against tumor recurrence. Mice deficient in IL-10 demonstrated a memory response in which 100% of the mice were protected from secondary tumor challenge, while wt mice had diminished recall response (25%) against tumor recurrence. These results with analysis of vaccine-elicited CD8 + T cells for tumor-specific killing and regulatory cell marker expression, add further support to our premise that CD8+ IL-10 + T cells elicited by D52 tumor-self protein vaccine contribute to the suppression of a memory CTL responses and durable tumor immunity.

Future prospects for CD8+ regulatory T cells in immune tolerance

CD8⁺ Tregs have been long described and significant progresses have been made about their phenotype, their functional mechanisms, and their suppressive ability compared to conventional CD4⁺ Tregs. They are now at the dawn of their clinical use. In this review, we will summarize their phenotypic characteristics, their mechanisms of action, the similarities, differences and synergies between CD8⁺ and CD4⁺ Tregs, and we will discuss the biology, development and induction of CD8⁺ Tregs, their manufacturing for clinical use, considering open questions/uncertainties and future technically accessible improvements notably through genetic modifications.

Description of CD8+ Regulatory T Lymphocytes and Their Specific Intervention in Graft-versus-Host and Infectious Diseases, Autoimmunity, and Cancer

Gershon and Kondo described CD8⁺ Treg lymphocytes as the first ones with regulating activity due to their tolerance ability to foreign antigens and their capacity to inhibit the proliferation of other lymphocytes. Regardless, CD8⁺ Treg lymphocytes have not been fully described-unlike CD4⁺ Treg lymphocytes-because of their low numbers in blood and the lack of specific and accurate population markers. Still, these lymphocytes have been studied for the past 30 years, even after finding difficulties during investigations. As a result, studies have identified markers that define their subpopulations. This review is focused on the expression of cell membrane markers as CD25, CD122, CD103, CTLA-4, CD39, CD73, LAG-3, and FasL as well as soluble molecules such as FoxP3, IFN-γ, IL-10, TGF-β, IL-34, and IL-35, in addition to the lack of expression of cell activation markers such as CD28, CD127 CD45RC, and CD49d. This work also underlines the importance of identifying some of these markers in infections with several pathogens, autoimmunity, cancer, and graft-versus-host disease as a strategy in their prevention, monitoring, and cure.

Suppression of allograft rejection by CD8+CD122+PD-1+ Tregs is dictated by their Fas ligand-initiated killing of effector T cells versus Fas-mediated own apoptosis

Mounting evidence has shown that naturally occurring CD8+CD122+ T cells are regulatory T cells (Tregs) that suppress both autoimmunity and alloimmunity. We have previously shown that CD8+CD122+PD-1+ Tregs not only suppress allograft rejection, but also are more potent in suppression than conventional CD4+CD25+ Tregs. However, the mechanisms underlying their suppression of alloimmunity are not well understood. In an adoptive T-cell transfer model of mice lacking lymphocytes, we found that suppression of skin allograft rejection by CD8+CD122+PD-1+ Tregs was mostly dependent on their expression of Fas ligand as either lacking Fas ligand or blocking it with antibodies largely abolished their suppression of allograft rejection mediated by transferred T cells. Their suppression was also mostly reversed when effector T cells lacked Fas receptor. Indeed, these FasL+ Tregs induced T cell apoptosis in vitro in a Fas/FasL-dependent manner. However, their suppression of T cell proliferation in vitro was dependent on IL-10, but not FasL expression. Furthermore, adoptive transfer of CD8+CD122+PD-1+ Tregs significantly extended allograft survival even in wild-type mice if Tregs lacked Fas receptor or if recipients received recombinant IL-15, as these two measures synergistically expanded adoptively-transferred Tregs in recipients. Thus, this study may have important implications for Treg therapies in clinical transplantation.

Herbal Components of a Novel Formula PSORI-CM02 Interdependently Suppress Allograft Rejection and Induce CD8+CD122+PD-1+ Regulatory T Cells

A recipient usually rejects a transplanted organ and thus needs immunosuppressive treatments to prevent rejection. Achieving long-term allograft survival without continuous global immunosuppression is highly desirable in transplantation as long-term immunosuppression causes various side effects. Therefore, it is necessary to search for medicine with potentially less side effects. Traditional Chinese medicine PSORI-CM01 (Yin Xie Ling), a formula with seven natural herbs, has been used to treat patients with psoriasis. Here, we investigated a “sharpened” formula, PSORI-CM02 consisting of only five herbs from PSORI-CM01: Curcumae rhizoma, Radix paeoniae rubra, Rhizoma smilacis glabrae, Mume fructus, and Sarcandrae herba. We examined whether or not PSORI-CM02 would suppress alloimmunity and found that PSORI-CM02 significantly inhibited murine skin allograft rejection and reduced graft-infiltration of CD3+ T cells. Interestingly, omitting any single herbal component rendered the whole formula ineffective in suppression, indicating that these herbal components exert their effects cooperatively as a whole. Moreover, PSORI-CM02 increased CD8+CD122+PD-1+ Treg frequency with CD4+FoxP3+ Tregs remaining unchanged in recipient mice, whereas CsA reduced CD4+FoxP3+ Treg frequency. PSORI-CM02 also hindered CD11c+ DC maturation posttransplantation. Importantly, PSORI-CM02-induced CD8+CD122+PD-1+ Tregs were more potent in suppression of allograft rejection in Rag-/- mice than control Tregs. On the other hand, PSORI-CM02 suppressed T cell proliferation in vitro and reduced their phosphorylation of P70S6K and P50/P65, suggesting that it inhibits both mTOR and NFκB signaling pathways. It also increased IL-10 production while reducing IFNγ level in the supernatant of activated T cells co-cultured with CD8+CD122+PD-1+ Tregs. Furthermore, HPLC fingerprinting ruled out that PSORI-CM02 contained CsA or rapamycin. PSORI-CM02 also did not cause any illness and toxic injury in recipient mice. Thus, we demonstrate that PSORI-CM02 formula suppresses allograft rejection without toxicity.

Targeting of CD122 enhances antitumor immunity by altering the tumor immune environment

Mounting evidence demonstrates that CD8⁺CD122⁺ T cells have suppressive properties with the capacity to inhibit T cell responses. Therefore, these cells are rational targets for cancer immunotherapy. Here, we demonstrate that CD122 monoclonal antibody (mAb; aCD122) therapy significantly suppressed tumor growth and improved long-term survival in tumor-bearing mice. This therapeutic effect correlated with enhanced polyfunctional, cytolytic intratumoral CD8⁺ T cells and a decrease in granulocytic myeloid-derived suppressor cells (G-MDSCs). In addition, aCD122 treatment synergized with a vaccine to augment vaccine-induced antigen (Ag)-specific CD8⁺ T cell responses, reject established tumors and generate memory T cells. Furthermore, aCD122 mAb synergized with an anti-GITR (aGITR) mAb to confer significant control of tumor growth. These results suggest CD122 might be a promising target for cancer immunotherapy, either as a single agent or in combination with other forms of immunotherapy.

Modification of anti-tumor immunity by tolerogenic dendritic cells

Immunosuppressive functions of glucocorticoids (GC) can be mediated via various mechanisms, including the modulation of dendritic cells (DC). Our study investigates the effects of tolerogenic GC-treated DCs on NK and T cell anti-tumor responses in OT-1/Rag^-/- mice, expressing a transgenic TCR in CD8⁺ T cells. The effects caused by GC-treated DCs were compared to the responses to immunogenic, CpG-activated DCs. The effects of DCs on anti-tumor immune responses were analyzed using the EG7 tumor model, where the tumor cells express the peptide epitope recognized by OT-1 T cells. We observed that immunization with CpG and peptide-treated DCs protected against tumor growth by activation of NK cell response. Also, immunogenic DCs induced the expansion of cytotoxic CD8⁺OT-1 cells, expressing activation markers CD44 and CD69 and producing IFNγ. In contrast, the peptide and GC-treated DCs in OT-1 mice increased the numbers of immature Mac-1⁺CD27^- NK cells as well as Foxp3⁺ and IL-10 secreting CD8⁺OT-1 cells with suppressive properties. We conclude that the generation of tolerogenic DCs is one of many immunosuppressive mechanisms that can be induced by GC. Our study demonstrated that tolerogenic DCs modify anti-tumor immune response by suppressing NK cell activity and stimulating the formation of IL-10-secreting CD8⁺ Tregs.

Chinese medicine Ginseng and Astragalus granules ameliorate autoimmune diabetes by upregulating both CD4+FoxP3+ and CD8+CD122+PD1+ regulatory T cells

Type 1 diabetes mellitus (T1DM) is an autoimmune disease mainly mediated by effector T cells that are activated by autoantigen, thereby resulting in the destruction of pancreatic islets and deficiency of insulin. Cyclosporine is widely used as an immunosuppressant that suppresses autoimmunity in clinic. However, continuous treatments with conventional immunosuppressive drugs may cause severe side effects. Therefore it is important to seek alternative medicine. Chinese medicine Ginseng and Astragalus granule (GAG) was used to successfully treat type 2 diabetes mellitus in clinic in China. Here we found that GAG ameliorated T1DM in autoimmune NOD mice by increasing the level of insulin and reducing the level of blood glucose. Treatments with both GAG and CsA further decreased the blood glucose level. Moreover, GAG increased both CD4+FoxP3+ and CD8+CD122+PD-1+ Treg numbers in both spleens and lymph nodes of NOD mice. In particular, GAG could reverse a decline in CD4+FoxP3+ Tregs resulted from CsA treatments. The percentage of effector/memory CD8+ T cells (CD44^highCD62L^low) was significantly reduced by GAG, especially in the presence of low-doses of CsA. Histopathology also showed that GAG attenuated cellular infiltration and lowered CD3+ T cell numbers around and in islets. Thus, we demonstrated that GAG ameliorated autoimmune T1DM by upregulating both CD4+FoxP3+ and CD8+CD122+PD-1+ Tregs while GAG synergized with CsA to further suppress autoimmunity and T1DM by reversing the decline in CD4+FoxP3+ Tregs resulted from CsA treatments. This study may have important clinical implications for the treatment of T1DM using traditional Chinese medicine.

CD8(+)CD122(+) T-Cells: A Newly Emerging Regulator with Central Memory Cell Phenotypes

CD8(+)CD122(+) T-cells have been traditionally described as antigen-specific memory T-cells that respond to previously encountered antigens more quickly and vigorously than their naïve counterparts. However, mounting evidence has demonstrated that murine CD8(+)CD122(+) T-cells exhibit a central memory phenotype (CD44(high)CD62L(high)), regulate T cell homeostasis, and act as regulatory T-cells (Treg) by suppressing both autoimmune and alloimmune responses. Importantly, naturally occurring murine CD8(+)CD122(+) Tregs are more potent in immunosuppression than their CD4(+)CD25(+) counterparts. They appear to be acting in an antigen-non-specific manner. Human CD8(+)CXCR3(+) T-cells are the equivalent of murine CD8(+)CD122(+) Tregs and also exhibit central memory phenotypes. In this mini-review article, we will summarize recent progresses in their phenotypes, homeostatic expansion, antigen-specificity, roles in the suppression of alloimmune and autoimmune responses, and the mechanisms underlying their inhibitory function.

A naturally occurring CD8(+)CD122(+) T-cell subset as a memory-like Treg family

Despite extensive studies on CD4(+)CD25(+) regulatory T cells (Tregs) during the past decade, the progress on their clinical translation remains stagnant. Mounting evidence suggests that naturally occurring CD8(+)CD122(+) T cells are also Tregs with the capacity to inhibit T-cell responses and suppress autoimmunity as well as alloimmunity. In fact, they are memory-like Tregs that resemble a central memory T cell (TCM) phenotype. The mechanisms underlying their suppression are still not well understood, although they may include IL-10 production. We have recently demonstrated that programmed death-1 (PD-1) expression distinguishes between regulatory and memory CD8(+)CD122(+) T cells and that CD8(+)CD122(+) Tregs undergo faster homeostatic proliferation and are more potent in the suppression of allograft rejection than conventional CD4(+)CD25(+) Tregs. These findings may open a new line of investigation for accelerating effective Treg therapies in the clinic. In this review, we summarize the significant progress in this promising field of CD8(+)CD122(+) Treg research and discuss their phenotypes, suppressive roles in autoimmunity and alloimmunity, functional requirements, mechanisms of action and potential applications in the clinic.

Physiological organization of immune response based on the homeostatic mechanism of matrix reprogramming: implication in tumor and biotechnology

It is accepted that the immune system responds to pathogens with activation of antigen-independent innate and antigen-dependent adaptive immunity. However many immune events do not fit or are even inconsistent with this notion. We developed a new homeostatic model of the immune response. This model consists of four units: a sensor, a regulator, an effector and a rehabilitator. The sensor, macrophages or lymphocytes, recognize pathogenic cells and generate alarm signals. The regulator, antigen-presenting cells, Тregs and myeloid-derived suppressor cells, evaluate the signals and together with sensor cells program the effector. The effector, programmed macrophages and lymphocytes, eliminate the pathogenic cells. The rehabilitator, M2 macrophages, restrict inflammation, provide angiogenesis and reparation of tissue damage, and restore the homeostasis. We suggest the terms "immune matrix" for a biological template of immune responses to pathogens and "matrix reprogramming" for the interdependent reprogramming of different cells in the matrix. In an adequate immune response, the matrix forms a negative feedback mechanism to support the homeostasis. We defined the cellular and phenotypic composition of a tumor immune matrix. A tumor reprograms the homeostatic negative feedback mechanism of matrix into a pathogenic positive feedback mechanism. M2 macrophages play a key role in this transformation. Therefore, macrophages are an attractive target for biotechnology. Based on our hypotheses, we are developing a cell biotechnology method for creation of macrophages with a stable antitumor phenotype. We have shown that such macrophages almost doubled the survival time of mice with tumor.

Role of CD8(+) regulatory T cells in organ transplantation

CD8⁺ T cells are regulatory T cells (Tregs) that suppress both alloimmunity and autoimmunity in many animal models. This class of regulatory cells includes the CD8⁺CD28⁻, CD8⁺CD103⁺, CD8⁺FoxP3⁺ and CD8⁺CD122⁺ subsets. The mechanisms of action of these regulatory cells are not fully understood; however, the secretion of immunosuppressive cytokines, such as interleukin (IL)-4, IL-10 and transforming growth factor beta (TGF-β) as well as the direct killing of target cells via Fas L/Fas and the perforin/granzyme B pathways have been demonstrated in various models. Further studies are necessary to fully understand the mechanisms underlying the suppressive effects of Tregs and to provide experimental support for potential clinical trials. We recently observed that CD8⁺CD122⁺ Tregs more potently suppressed allograft rejection compared to their CD4⁺CD25⁺ counterparts, supporting the hypothesis that CD8⁺ Tregs may represent a new and promising Treg family that can be targeted to prevent allograft rejection in the clinic. In this review, we summarize the progress in the field during the past 7–10 years and discuss CD8⁺ Treg phenotypes, mechanisms of action, and their potential clinical applications; particularly in composite tissue transplants in burn and trauma patients.

Natural CD8+CD122+ T cells are more potent in suppression of allograft rejection than CD4+CD25+ regulatory T cells

Despite extensive studies on CD4+CD25+ regulatory T cells (Tregs), their application in adoptive transfer therapies is still not optimal in immune-competent wild-type (WT) animal models. Therefore, it is compelling to search for more potent Tregs for potential clinical application. Mounting evidence has shown that naturally occurring CD8+CD122+ T cells are also Tregs. However, their suppression in allograft rejection, efficiency in suppression and underlying mechanisms remain unclear. Using a murine allotransplantation model, we reported here that CD8+CD122+ Tregs were actually more potent in suppression of allograft rejection and underwent more rapid homeostatic proliferation than their CD4+CD25+ counterparts. Moreover, they produced more IL-10 and were more potent in suppressing T cell proliferation in vitro. Deficiency in IL-10 in CD4+CD25+ and CD8+CD122+ Tregs resulted in their reduced but equal suppression in vivo and in vitro, suggesting that IL-10 is responsible for more effective suppression by CD8+CD122+ than CD4+CD25+ Tregs. Importantly, transfer of CD8+CD122+ Tregs together with the administration of recombinant IL-15 significantly prolonged allograft survival in WT mice. Thus, for the first time, we demonstrate that naturally arising CD8+CD122+ Tregs not only inhibit allograft rejection but also exert this suppression more potently than their CD4+CD25+ counterparts. This novel finding may have important implications for tolerance induction.

Injection site and regulatory T cells influence durable vaccine-induced tumor immunity to an over-expressed self tumor associated antigen

Tumor protein D52 (D52) is constitutively expressed in healthy tissues and overexpressed in multiple cancers, including (but not limited to) breast, prostate and ovarian carcinomas. Although the normal functions of D52 are unknown, it is clear that increased D52 expression levels not only stimulate cell proliferation and metastasis, but also correlate with poor prognosis in a subset of breast cancer patients. The murine orthologs of D52 (mD52) shares 86% identity with its human counterpart (hD52) and mirrors hD52 expression patterns. The forced overexpression of mD52 induces anchorage-independent growth in vitro and promotes tumor formation as well as spontaneous metastasis in vivo. We have previously reported that the intramuscular administration of recombinant mD52 elicits immune responses capable of rejecting a challenge with tumor cells and preventing spontaneous metastasis only in 50% of mice. We hypothesized that mechanisms of peripheral tolerance dampen immune responses against mD52, thus limiting the protective effects of vaccination. To test this hypothesis, mice were depleted of CD25⁺ regulatory T cells (Tregs) and subcutaneously immunized with mD52 prior to a tumor challenge. The subcutaneous immunization failed to induce protective antitumor immunity unless accompanied by Treg depletion, which resulted in a rate of protection of 70% as compared with

Increased tumor-infiltrating CD8(+)Foxp3(+) T lymphocytes are associated with tumor progression in human gastric cancer

BACKGROUND

CD8(+)Foxp3(+) T lymphocytes have been detected in tumors. However, the distribution, phenotypic features, and regulation of these cells in gastric cancer remain unknown.

METHODS

The levels of CD8(+)Foxp3(+) T lymphocytes in the peripheral blood, tumor-draining lymph nodes, non-tumor tissues, and tumor tissues of patients with gastric cancer were detected by flow cytometry. Foxp3 induction in CD8(+)Foxp3(-) T cells was investigated in vitro. The suppressive function of CD8(+)Foxp3(+) T lymphocytes was analyzed by their effect on CD4(+) T-cell proliferation and IFN-γ production. The percentages of CD8(+)Foxp3(+) T lymphocytes were evaluated for the association with tumor stage.

RESULTS

The frequency of CD8(+)Foxp3(+) T lymphocytes in tumor tissues was significantly higher than that in non-tumor tissues, and similar results were also observed in tumor-draining lymph nodes compared with peripheral blood. Most intratumoral CD8(+)Foxp3(+) T lymphocytes were activated effector cells (CD45RA(-)CD27(-)). TGF-β1 levels were positively correlated with the frequency of CD8(+)Foxp3(+) T lymphocytes in tumor tissues, and in vitro TGF-β1 could induce the generation of CD8(+)Foxp3(+) T lymphocytes in a dose-dependent manner. Furthermore, intratumoral CD8(+)Foxp3(+) T lymphocytes suppressed the proliferation and IFN-γ production of CD4(+) T cells. Finally, intratumoral CD8(+)Foxp3(+) T lymphocytes were significantly increased with tumor progression in terms of tumor-node-metastasis (TNM) stage.

CONCLUSIONS

Our data have shown that increased intratumoral CD8(+)Foxp3(+) T lymphocytes are associated with tumor stage and potentially influence CD4(+) T-cell functions, which may provide insights for developing novel immunotherapy protocols against gastric cancer.

Regulation of self-tolerance by Qa-1-restricted CD8(+) regulatory T cells

Mounting an efficient immune response to pathogens while avoiding damage to host tissues is the central task of the immune system. Emerging evidence has highlighted the contribution of the CD8(+) lineage of regulatory T cells to the maintenance of self-tolerance. Specific recognition of the MHC class Ib molecule Qa-1 complexed to peptides expressed by activated CD4(+) T cells by regulatory CD8(+) T cells triggers an inhibitory interaction that prevents autoimmune responses. Conversely, defective Qa-1-restricted CD8(+) regulatory activity can result in development of systemic autoimmune disease. Here, we review recent research into the cellular and molecular basis of these regulatory T cells, their mechanism of suppressive activity and the potential application of these insights into new treatments for autoimmune disease and cancer.

Multiple vaccinations: friend or foe

Few immunotherapists would accept the concept of a single vaccination inducing a therapeutic anticancer immune response in a patient with advanced cancer. But what is the evidence to support the "more-is-better" approach of multiple vaccinations? Because we are unaware of trials comparing the effect of a single vaccine versus multiple vaccinations on patient outcome, we considered that an anticancer immune response might provide a surrogate measure of the effectiveness of vaccination strategies. Because few large trials include immunologic monitoring, the majority of information is gleaned from smaller trials in which an evaluation of immune responses to vaccine or tumor, before and at 1 or more times following the first vaccine, was performed. In some studies, there is convincing evidence that repeated administration of a specific vaccine can augment the immune response to antigens contained in the vaccine. In other settings, multiple vaccinations can significantly reduce the immune response to 1 or more targets. Results from 3 large adjuvant vaccine studies support the potential detrimental effect of multiple vaccinations as clinical outcomes in the control arms were significantly better than that for treatment groups. Recent research has provided insights into mechanisms that are likely responsible for the reduced responses in the studies noted above, but supporting evidence from clinical specimens is generally lacking. Interpretation of these results is further complicated by the possibility that the dominant immune response may evolve to recognize epitopes not present in the vaccine. Nonetheless, the Food and Drug Administration approval of the first therapeutic cancer vaccine and recent developments from preclinical models and clinical trials provide a substantial basis for optimism and a critical evaluation of cancer vaccine strategies.