Peptide-activated double-negative T cells can prevent autoimmune type-1 diabetes development

Double-Negative T (DNT) Cells in Patients with Systemic Lupus Erythematosus

Double-negative T (DNT) cells are a rare and unconventional T-lymphocyte subpopulation lacking both CD4 and CD8 markers. Their immunopathological roles and clinical relevance have yet to be elucidated. Beyond autoimmune lymphoproliferative syndrome (ALPS), these cells may also play a role in rheumatic disorders, including systemic lupus erythematosus (SLE); indeed, these two diseases share several autoimmune manifestations (including nephritis). Moreover, one of the main experimental murine models used to investigate lupus, namely the MRL/lpr mouse, is characterized by an expansion of DNT cells, which can support the production of pathogenic autoantibodies and/or modulate the immune response in this context. However, lupus murine models are not completely consistent with their human SLE counterpart, of course. In this mini review, we summarize and analyze the most relevant clinical studies investigating the DNT cell population in SLE patients. Overall, based on the present literature review and analysis, DNT cell homeostasis seems to be altered in patients with SLE. Indeed, most of the available clinical studies (which include both adults and children) reported an increased DNT cell percentage in SLE patients, especially during the active phases, even though no clear correlation with disease activity and/or inflammatory parameters has been clearly established. Well-designed, standardized, and longitudinal clinical studies focused on DNT cell population are needed, in order to further elucidate the actual contribution of these cells in SLE pathogenesis and their interactions with other immune cells (also implicated and/or altered in SLE, such as basophils), and clarify whether their expansion and/or immunophenotypic aspects may have any immunopathological relevance (and, then, represent potential disease markers and, in perspective, even therapeutic targets) or are just an unspecific epiphenomenon of autoimmunity.

The value of circulating lymphocytic subpopulations in the diagnosis and repair of ischemic stroke patients with dizziness

Background

To determine whether dizziness can contribute to stroke as a main cause still remains challenging. This study aims to explore clinical biomarkers in the identification of ischemic stroke patients from people with dizziness and the prediction of their long-term recovery.

Methods

From January 2018 to June 2019, 21 ischemic stroke patients with a main complaint of dizziness, 84 non-stroke dizziness patients and 87 healthy volunteers were recruited in this study. Then, their peripheral blood samples were collected, and the percentages of circulating lymphocytes T cells, CD4⁺ T cells, CD8⁺ T cells, T^−/− cells (DNTs), CD4⁺ regulatory T cells (Tregs), CD8⁺ Tregs, B cells and regulatory B cells (Bregs) were examined to identify biomarkers with clinical value.

Results

According to our data, a significant difference in the DNTs proportion was detected between non-stroke dizziness and ischemic stroke patients with dizziness (p = 0.0009). The Bregs proportion in ischemic stroke patients with dizziness was lower than that in non-stroke dizziness patients (p = 0.035). In addition, the percentage of Bregs and DNTs within lymphocytes in patients’ peripheral blood exhibited a significant negative correlation with stroke occurrence (Bregs, p = 0.039; DNTs, p = 0.046). Moreover, the Bregs and DNTs within lymphocytes were negatively related to participants’ age, while presented a weak relationship with clinical risks like smoking, hypertension, and diabetes. Then, area under the receiver operating characteristic curve (AUC) of Bregs and DNTs together was 0.768, the risk factors and Bregs or DNTs ranged from 0.795 and 0.792, respectively, and the AUC value of risk factors, Bregs and DNTs combination was further increased to 0.815. Furthermore, the Bregs percentage within lymphocytes at admission was also a potential predictor of repair at discharge and the following 3 months.

Conclusion

Bregs and DNTs could be the clinical biomarkers together in the identification of ischemic stroke patients from people with dizziness.

Double Negative T Regulatory Cells: An Emerging Paradigm Shift in Reproductive Immune Tolerance?

Immune regulation of female reproductive function plays a crucial role in fertility, as alterations in the relationship between immune and reproductive processes result in autoimmune subfertility or infertility. The breakdown of immune tolerance leads to ovulation dysfunction, implantation failure, and pregnancy loss. In this regard, immune cells with regulatory activities are essential to restore self-tolerance. Apart from regulatory T cells, double negative T regulatory cells (DNTregs) characterized by TCRαβ+/γδ+CD3+CD4–CD8– (and negative for natural killer cell markers) are emerging as effector cells capable of mediating immune tolerance in the female reproductive system. DNTregs are present in the female reproductive tract of humans and murine models. However, their full potential as immune regulators is evolving, and studies so far indicate that DNTregs exhibit features that can also maintain tolerance in the female reproductive microenvironment. This review describes recent progress on the presence, role and mechanisms of DNTregs in the female reproductive system immune regulation and tolerance. In addition, we address how DNTregs can potentially provide a paradigm shift from the known roles of conventional regulatory T cells and immune tolerance by maintaining and restoring balance in the reproductive microenvironment of female fertility.

High-throughput single-сell sequencing in cancer research

With advances in sequencing and instrument technology, bioinformatics analysis is being applied to batches of massive cells at single-cell resolution. High-throughput single-cell sequencing can be utilized for multi-omics characterization of tumor cells, stromal cells or infiltrated immune cells to evaluate tumor progression, responses to environmental perturbations, heterogeneous composition of the tumor microenvironment, and complex intercellular interactions between these factors. Particularly, single-cell sequencing of T cell receptors, alone or in combination with single-cell RNA sequencing, is useful in the fields of tumor immunology and immunotherapy. Clinical insights obtained from single-cell analysis are critically important for exploring the biomarkers of disease progression or antitumor treatment, as well as for guiding precise clinical decision-making for patients with malignant tumors. In this review, we summarize the clinical applications of single-cell sequencing in the fields of tumor cell evolution, tumor immunology, and tumor immunotherapy. Additionally, we analyze the tumor cell response to antitumor treatment, heterogeneity of the tumor microenvironment, and response or resistance to immune checkpoint immunotherapy. The limitations of single-cell analysis in cancer research are also discussed.

CD3+CD4-CD8- (Double-Negative) T Cells in Inflammation, Immune Disorders and Cancer

The crucial role of CD4⁺ and CD8⁺ T cells in shaping and controlling immune responses during immune disease and cancer development has been well established and used to achieve marked clinical benefits. CD3⁺CD4^-CD8^- double-negative (DN) T cells, although constituting a rare subset of peripheral T cells, are gaining interest for their roles in inflammation, immune disease and cancer. Herein, we comprehensively review the origin, distribution and functions of this unique T cell subgroup. First, we focused on characterizing multifunctional DN T cells in various immune responses. DN regulatory T cells have the capacity to prevent graft-versus-host disease and have therapeutic value for autoimmune disease. T helper-like DN T cells protect against or promote inflammation and virus infection depending on the specific settings and promote certain autoimmune disease. Notably, we clarified the role of DN tumor-infiltrating lymphocytes and outlined the potential for malignant proliferation of DN T cells. Finally, we reviewed the recent advances in the applications of DN T cell-based therapy for cancer. In conclusion, a better understanding of the heterogeneity and functions of DN T cells may help to develop DN T cells as a potential therapeutic tool for inflammation, immune disorders and cancer.

Differential Leukocyte MicroRNA Responses Following Pan T Cell, Allorecognition and Allosecretome-Based Therapeutic Activation

Effective immunomodulation of T-cell responses is critical in treating both autoimmune diseases and cancer. Our previous studies have demonstrated that secretomes derived from control or methoxypolyethylene glycol mixed lymphocyte alloactivation assays exerted potent immunomodulatory activity that was mediated by microRNAs (miRNA). The immunomodulatory effects of biomanufactured miRNA-based allo-secretome therapeutics (SYN, TA1, IA1 and IA2) were compared to Pan T-cell activators (PHA and anti-CD3/CD28) and lymphocyte alloactivation. The differential effects of these activation strategies on resting peripheral blood mononuclear cells (PBMC) were assessed via T-cell proliferation, subset analysis and miRNA expression profiles. Mitogen-induced PBMC proliferation (> 85%) significantly exceeded that arising from either allostimulation (~ 30%) or the pro-inflammatory IA1 secretome product (~ 12%). Consequent to stimulation, the ratio of CD4 to CD8 cells of the resting PBMC (CD4:CD8; 1.7 ± 0.1) decreased in the Pan T cell, allrecognition and IA1 activated cells (averages of 1.1 ± 0.2; 1.2 ± 0.1 and 1.0 ± 0.1). These changes arose consequent to the expansion of both CD4⁺CD8⁺ and CD4^–CD8^– populations as well as the shrinkage of the CD4 subset and the expansion of the CD8 T cells. Importantly, these activation strategies induced vastly different miRNA expression profiles which were associated with significant differences in cellular differentiation and biological function. These findings support the concept that the “differential patterns of miRNA expression” regulate the biologic immune response in a “lock and key” manner. The biomanufacturing of miRNA-enriched secretome biotherapeutics may be a successful therapeutic approach for the systemic treatment of autoimmune diseases (TA1) and cancer (IA1).

Lymphocytes: Versatile Participants in Acute Kidney Injury and Progression to Chronic Kidney Disease

Background: Acute kidney injury (AKI) remains a major global public health concern due to its high morbidity and mortality. The progression from AKI to chronic kidney disease (CKD) makes it a scientific problem to be solved. However, it is with lack of effective treatments.

Summary: Both innate and adaptive immune systems participate in the inflammatory process during AKI, and excessive or dysregulated immune responses play a pathogenic role in renal fibrosis, which is an important hallmark of CKD. Studies on the pathogenesis of AKI and CKD have clarified that renal injury induces the production of various chemokines by renal parenchyma cells or resident immune cells, which recruits multiple-subtype lymphocytes in circulation. Some infiltrated lymphocytes exacerbate injury by proinflammatory cytokine production, cytotoxicity, and interaction with renal resident cells, which constructs the inflammatory environment and induces further injury, even death of renal parenchyma cells. Others promote tissue repair by producing protective cytokines. In this review, we outline the diversity of these lymphocytes and their mechanisms to regulate the whole pathogenic stages of AKI and CKD; discuss the chronological responses and the plasticity of lymphocytes related to AKI and CKD progression; and introduce the potential therapies targeting lymphocytes of AKI and CKD, including the interventions of chemokines, cytokines, and lymphocyte frequency regulation in vivo, adaptive transfer of ex-expanded lymphocytes, and the treatments of gut microbiota or metabolite regulations based on gut-kidney axis.

Key Message: In the process of AKI and CKD, T helper (Th) cells, innate, and innate-like lymphocytes exert mainly pathogenic roles, while double-negative T (DNT) cells and regulatory T cells (Tregs) are confirmed to be protective. Understanding the mechanisms by which lymphocytes mediate renal injury and renal fibrosis is necessary to promote the development of specific therapeutic strategies to protect from AKI and prevent the progression of CKD.

NKG2D Enhances Double-Negative T Cell Regulation of B Cells

Numerous studies reported a small subpopulation of TCRαβ+CD4-CD8- (double-negative) T cells that exert regulatory functions in the peripheral lymphocyte population. However, the origin of these double-negative T (DNT) cells is controversial. Some researchers reported that DNT cells originated from the thymus, and others argued that these cells are derived from peripheral immune induction. We report a possible mechanism for the induction of nonregulatory CD4+ T cells to become regulatory double-negative T (iDNT) cells in vitro. We found that immature bone marrow dendritic cells (CD86+MHC-II- DCs), rather than mature DCs (CD86+MHC-II+), induced high levels of iDNT cells. The addition of an anti-MHC-II antibody to the CD86+MHC-II+ DC group significantly increased induction. These iDNT cells promoted B cell apoptosis and inhibited B cell proliferation and plasma cell formation. A subgroup of iDNT cells expressed NKG2D. Compared to NKG2D- iDNT cells, NKG2D+ iDNT cells released more granzyme B to enhance B cell regulation. This enhancement may function via NKG2D ligands expressed on B cells following lipopolysaccharide stimulation. These results demonstrate that MHC-II impedes induction, and iDNT cells may be MHC independent. NKG2D expression on iDNT cells enhanced the regulatory function of these cells. Our findings elucidate one possible mechanism of the induction of peripheral immune tolerance and provide a potential treatment for chronic allograft rejection in the future.

Evidence of genetic epistasis in autoimmune diabetes susceptibility revealed by mouse congenic sublines

Susceptibility to autoimmune diabetes is a complex genetic trait. Linkage analyses exploiting the NOD mouse, which spontaneously develops autoimmune diabetes, have proved to be a useful tool for the characterization of some of these traits. In a linkage analysis using 3A9 TCR transgenic mice on both B10.BR and NOD.H2^k backgrounds, we previously determined that both the Idd2 and Idd13 loci were linked to the proportion of immunoregulatory CD4^-CD8^- double negative (DN) T cells. In addition to Idd2 and Idd13, five other loci showed weak linkage to the proportion of DN T cells. Of interest, in an interim analysis, a locus on chromosome 12 is linked to DN T cell proportion in both the spleen and the lymph nodes. To determine the impact of this locus on DN T cells, we generated two congenic sublines, which we named Chr12P and Chr12D for proximal and distal, respectively. While 3A9 TCR:insHEL NOD.H2^k-Chr12D mice were protected from diabetes, 3A9 TCR:insHEL NOD.H2^k-Chr12P showed an increase in diabetes incidence. Yet, the proportion of DN T cells was similar to the parental 3A9 TCR NOD.H2^k strain for both of these congenic sublines. A genome-wide two dimensional LOD score analysis reveals genetic epistasis between chromosome 12 and the Idd13 locus. Altogether, this study identified further complex genetic interactions in defining the proportion of DN T cells, along with evidence of genetic epistasis within a locus on chromosome 12 influencing autoimmune susceptibility.

Adaptive Immunity Regulation and Cerebral Ischemia

Stroke is a disease that occurs due to a sudden interruption of the blood supply to the brain. It is a leading cause of death and disability worldwide. It is well-known that the immune system drives brain injury following an episode of ischemic stroke. The innate system and the adaptive system play distinct but synergistic roles following ischemia. The innate system can be activated by damage-associated molecular patterns (DAMPs), which are released from cells in the ischemic region. Damaged cells also release various other mediators that serve to increase inflammation and compromise the integrity of the blood–brain barrier (BBB). Within 24 h of an ischemic insult, the adaptive immune system is activated. This involves T cell and B cell-mediated inflammatory and humoral effects. These cells also stimulate the release of various interleukins and cytokines, which can modulate the inflammatory response. The adaptive immune system has been shown to contribute to a state of immunodepression following an ischemic episode, and this can increase the risk of infections. However, this phenomenon is equally important in preventing autoimmunity of the body to brain antigens that are released into the peripheral system as a result of BBB compromise. In this review, we highlight the key components of the adaptive immune system that are activated following cerebral ischemia.

Double-negative T cells remarkably promote neuroinflammation after ischemic stroke

CD3⁺CD4^-CD8^- T cells (double-negative T cells; DNTs) have diverse functions in peripheral immune-related diseases by regulating immunological and inflammatory homeostasis. However, the functions of DNTs in the central nervous system remain unknown. Here, we found that the levels of DNTs were dramatically increased in both the brain and peripheral blood of stroke patients and in a mouse model in a time-dependent manner. The infiltrating DNTs enhanced cerebral immune and inflammatory responses and exacerbated ischemic brain injury by modulating the FasL/PTPN2/TNF-α signaling pathway. Blockade of this pathway limited DNT-mediated neuroinflammation and improved the outcomes of stroke. Our results identified a critical function of DNTs in the ischemic brain, suggesting that this unique population serves as an attractive target for the treatment of ischemic stroke.

Infusion of ex-vivo expanded human TCR-αβ+ double-negative regulatory T cells delays onset of xenogeneic graft-versus-host disease

Despite the demonstration of potent immunosuppressive function of T cell receptor (TCR)-αβ⁺ double-negative regulatory T cells (DN T_regs ), scarce numbers and lack of effective expansion method limit their clinical applications. Here we describe an approach that allows for ∼3500-fold ex-vivo expansion of human DN T_regs within 3 weeks with > 97% purity. Ex-vivo-expanded DN T_regs suppress proliferation of polyclonally stimulated autologous T and B cells in vitro through direct cell-to-cell contact. In vivo, we demonstrate for the first time that infusion of human DN T_regs delayed an onset of xenogeneic graft-versus-host disease (GVHD) significantly in a humanized mouse model. Furthermore, preincubation of ex-vivo-expanded DN T_regs with a mechanistic target of rapamycin (mTOR) inhibitor rapamycin enhanced their immune regulatory function further. Taken together, this study demonstrates that human DN T_regs can be expanded ex vivo to therapeutic numbers. The expanded DN T_regs can suppress proliferation of T and B cells and attenuate GVHD, highlighting the potential clinical use of DN T_regs to mitigate GVHD.

Critical role of OX40 in the expansion and survival of CD4 T-cell-derived double-negative T cells

CD4⁺ T-cell-converted CD4⁻CD8⁻ double negative (cDNT) have strong suppressive activity in the maintenance of immune tolerance, whereas IL-2 promotes cDNT proliferation and enhances cDNT resistance to apoptosis. However, the intrinsic mechanisms that regulate the survival of cDNT are still unknown. Here we demonstrate that the OX40 molecule was highly expressed on cDNT. The expression of OX40 was necessary to promote proliferation and inhibit apoptosis of cDNT in vivo and in vitro. OX40 promoted the survival of cDNT by regulating the expression of Bcl-2, Bcl-xL, Survivin, and BCL2L11. Canonical NF-κB cell signaling played an important role in the transmission of essential division and survival signals through OX40 in cDNT. IL-2 promoted the survival of cDNT in part via elevating the expression of the OX40 molecule. IL-2 promoted OX40 expression via downregulating the PPARα expression. In conclusion, we elucidated that OX40 is a key molecule that regulates cDNT proliferation and survival. IL-2 promoted OX40 expression by downregulating the PPARα binding to the OX40 promoter, leading to the elevated expression of Bcl-2, Bcl-xL, and Survivin in cDNT, which finally resulted in the promoted proliferation and decreased apoptosis of cDNT.

Genetic interaction between two insulin-dependent diabetes susceptibility loci, Idd2 and Idd13, in determining immunoregulatory DN T cell proportion

Several immune regulatory cell types participate in the protection against autoimmune diseases such as autoimmune diabetes. Of these immunoregulatory cells, we and others have shown that peripheral CD4^-CD8^- double negative (DN) T cells can induce antigen-specific immune tolerance. Particularly, we have described that diabetes-prone mice exhibit a lower number of peripheral DN T cells compared to diabetes-resistant mice. Identifying the molecular pathways that influence the size of the DN T cell pool in peripheral lymphoid organs may thus be of interest for maintaining antigen-specific immune tolerance. Hence, through immunogenetic approaches, we found that two genetic loci linked to autoimmune diabetes susceptibility, namely Idd2 and Idd13, independently contribute to the partial restoration of DN T cell proportion in secondary lymphoid organs. We now extend these findings to show an interaction between the Idd2 and Idd13 loci in determining the number of DN T cells in secondary lymphoid organs. Using bioinformatics tools, we link potential biological pathways arising from interactions of genes encoded within the two loci. By focusing on cell cycle, we validate that both the Idd2 and Idd13 loci influence RAD51 expression as well as DN T cell progression through the cell cycle. Altogether, we find that genetic interactions between Idd2 and Idd13 loci modulate cell cycle progression, which contributes, at least in part, to defining the proportion of DN T cells in secondary lymphoid organs.

Specific activation of CD4- CD8- double-negative T cells by Trypanosoma cruzi-derived glycolipids induces a proinflammatory profile associated with cardiomyopathy in Chagas patients

Cardiomyopathy is the most severe outcome of Chagas disease, causing more than 12 000 deaths/year. Immune cells participate in cardiomyopathy development either by direct tissue destruction, or by driving inflammation. We have shown that CD4^- CD8^- [double-negative (DN)] T cells are major sources of inflammatory and anti-inflammatory cytokines, associated with the cardiac (CARD) and indeterminate (IND) forms of Chagas disease, respectively. Here, we sought to identify Trypanosoma cruzi-derived components that lead to activation of DN T cells in Chagas patients. Glycolipid (GCL), lipid (LIP) and protein-enriched (PRO) fractions derived from trypomastigote forms of T. cruzi were utilized to stimulate cells from IND and CARD patients to determine DN T cell activation by evaluating CD69 and cytokine expression. We observed that GCL, but not LIP or PRO fractions, induced higher activation of DN T cells, especially T cell receptor (TCR)-γδ DN T, from IND and CARD. GCL led to an increase in tumour necrosis factor (TNF) and interleukin (IL)-10 expression by TCR-γδ DN T cells from IND, while inducing IFN-γ expression by TCR-γδ DN T cells from CARD. This led to an increase in the ratio IFN-γ/IL-10 in TCR-γδ DN T cells from CARD, favouring an inflammatory profile. These results identify GCL as the major T. cruzi component responsible for activation of DN T cells in chronic Chagas disease, associated predominantly with an inflammatory profile in CARD, but not IND. These findings may have implications for designing new strategies of control or prevention of Chagas disease cardiomyopathy by modulating the response to GCL.

Weight loss independent changes in adipose tissue macrophage and T cell populations after sleeve gastrectomy in mice

OBJECTIVE

In addition to adipocytes, adipose tissue contains large numbers of immune cells. A wide range of evidence links the activity of these cells to regulation of adipocyte and systemic metabolic function. Bariatric surgery improves several aspects of metabolic derangements and at least some of these effects occur in a weight-loss independent manner. We sought to investigate the impact of vertical sleeve gastrectomy (VSG) on adipose immune cell frequencies.

METHODS

We analyzed the frequencies of immune cells within distinct adipose tissue depots in obese mice that had VSG or sham surgery with a portion of the latter group pair-fed such that their body mass was matched to the VSG animals.

RESULTS

We demonstrate that VSG induced a shift in the epididymal adipose tissue leukocyte profile including increased frequencies of CD11c- macrophages, increased frequencies of T cells (CD4+, CD8+, and CD4-/CD8- T cells all increased), but a significantly decreased frequency of adipose tissue dendritic cells (ATDC) that, despite the continued high fat feeding of the VSG group, dropped below control diet levels.

CONCLUSIONS

These results indicate that VSG induces substantial changes in the immune populations residing in the adipose depots independent of weight loss.

Superagonistic CD28 Protects against Renal Ischemic Injury by Expansion of Regulatory T-Cell

BACKGROUND

Regulatory T (Treg) cells are a highly suppressive subset of CD4+ lymphocytes and have recently been proved to be crucial to suppress the inflammatory responses of ischemic kidney injury. CD28 superagonists (CD28sa) are monoclonal antibodies that preferentially expand Treg cells without a T-cell receptor and a costimulatory signal. This study aims to test the protection and discover the mechanisms of CD28sa treatment against renal ischemia-reperfusion (IR) injury (IRI).

METHODS

Male C57BL/6N mice were treated with CD28sa via peritoneal injection (0.1 mg) 6 days before the induction of IRI, or with 18-min ischemic precondition (IPC). IRI was induced by bilateral clamping of renal pedicles for 35 min followed by reperfusion. The role of Treg expansion in renal protection conferred by CD28sa treatment was examined using anti-CD25 antibody.

RESULTS

CD28sa treatment alone significantly increased the percentage of Treg cells in the spleen (18.10 ± 2.00 vs. 6.64 ± 0.86%, p < 0.01), peripheral blood (16.43 ± 5.94 vs. 2.57 ± 1.09%, p < 0.01), and kidney (2.69 ± 0.90 vs. 0.53 ± 0.14%, p < 0.01) of C57BL/6N mice 6 days after the administration. Mice pretreated with CD28sa or IPC had less renal injury at 24 h after IRI with attenuation of renal tubular damage and lower serum creatinine compared with the mice that underwent renal IRI alone. The number of infiltrating macrophages in the kidney and IFN-γ secreting CD4+ T cells in peripheral blood were diminished in the CD28sa-IR group and the IPC-IR group. The renal protection bestowed by CD28sa or IPC was abolished by anti-CD25 antibody administration.

CONCLUSIONS

Treg expansion induced by CD28sa ameliorated renal IRI.

Blocking of CD1d Decreases Trypanosoma cruzi-Induced Activation of CD4-CD8- T Cells and Modulates the Inflammatory Response in Patients With Chagas Heart Disease

The control of inflammatory responses to prevent the deadly cardiac pathology in human Chagas disease is a desirable and currently unattained goal. Double-negative (DN) T cells are important sources of inflammatory and antiinflammatory cytokines in patients with Chagas heart disease and those with the indeterminate clinical form of Chagas disease, respectively. Given the importance of DN T cells in immunoregulatory processes and their potential as targets for controlling inflammation-induced pathology, we studied the involvement of CD1 molecules in the activation and functional profile of Trypanosoma cruzi-specific DN T cells. We observed that parasite stimulation significantly increased the expression of CD1a, CD1b, CD1c, and CD1d by CD14(+) cells from patients with Chagas disease. Importantly, among the analyzed molecules, only CD1d expression showed an association with the activation of DN T cells, as well as with worse ventricular function in patients with Chagas disease. Blocking of CD1d-mediated antigen presentation led to a clear reduction of DN T-cell activation and a decrease in the expression of interferon γ (IFN-γ) by DN T cells. Thus, our results showed that antigen presentation via CD1d is associated with activation of DN T cells in Chagas disease and that CD1d blocking leads to downregulation of IFN-γ by DN T cells from patients with Chagas heart disease, which may be a potential target for preventing progression of inflammation-mediated dilated cardiomyopathy.

Maintenance of peripheral tolerance to islet antigens

Reestablishment of immune tolerance to the insulin-producing beta cells is the desired goal for type 1 diabetes (T1D) treatment and prevention. Immune tolerance to multiple islet antigens is defective in individuals with T1D, but the mechanisms involved are multifaceted and may involve loss of thymic and peripheral tolerance. In this review we discuss our current understanding of the varied mechanisms by which peripheral tolerance to islet antigens is maintained in healthy individuals where genetic protection from T1D is present and how this fails in those with genetic susceptibility to disease. Novel findings in regards to expression of neo-islet antigens, non-classical regulatory cell subsets and the impact of specific genetic variants on tolerance induction are discussed.

Combination of double negative T cells and anti-thymocyte serum reverses type 1 diabetes in NOD mice

Background

Double-negative (DN) T cells could delay the onset and the progression of autoimmune diabetes, yet they were less efficient on reversing autoimmune diabetes. The aim of this study was to investigate whether the combination of DN T cells and anti-thymocyte serum (ATS) could reverse new-onset diabetes in NOD mice.

Methods

The regulation of different subsets of T cells in vitro and in vivo by ATS and DN T cells were examined using flow cytometry. At the day of diabetes onset, ATS was administered on the same day and 2 days later, and DN T cells were transferred at day 7. The reversion of diabetes was assessed by monitoring blood glucose levels.

Results

The efficacy of inhibition of DN T cells on CD8⁺ T cells was lower than that on CD4⁺ T cells both in vitro and in vivo. ATS resulted in a significant depletion of CD8⁺ T cells, while DN T cells were less sensitive to ATS depletion. 80 % diabetic NOD mice achieved long term (6 months) reversion of diabetes by combined ATS and DN T cells treatment, compared to 16 % in ATS single treatment and none in DN T cell single treatment. DN T cells preferentially resided in spleen and pancreatic draining lymph nodes in ATS plus DN T cells treated NOD mice.

Conclusions

DN T cells plus ATS therapy show promising reversion effects on diabetic NOD mice due to a shift of balance from a destructive T cell response to one that favors DN T cell regulation.

The role of intrahepatic CD3+/CD4-/CD8- double negative T (DN T) cells in enhanced acetaminophen toxicity

The role of the immune system, specifically NK, NKT and CD3 cells, in acetaminophen (APAP) induced liver injury remains inconsistently defined. In the present study, wild type (C57BL/6J) mice and granzyme B deficient (GrB -/-) mice were treated with acetaminophen to assess the role of the immune system in acute liver injury. Doses of acetaminophen that induced sub lethal liver injury in wild type mice unexpectedly produced fatal hepatotoxicity in granzyme B deficient (GrB -/-) mice. Analysis revealed that GrB -/- mice had an increased population of intrahepatic CD3 (+), CD4 (-), and CD8 (-) lymphocytes expressing the CD69 activation marker and Fas ligand. Depletion of these cells in the GrB -/- and wild type mice made them less susceptible to APAP injury, while depletion of NK1.1 (+) cells or both CD4 (+) and CD8 (+) T cells failed to provide the same hepatoprotection. Transfer of the GrB -/- IHLs further exacerbated liver injury and increased mortality in wild type mice but not in LRP/LPR mice, lacking fas expression.

CONCLUSIONS

Acetaminophen toxicity is enhanced by the presence of activated, FasL expressing intrahepatic CD3 (+), CD4 (-), CD8 (-), NK1.1 (-) T cells. Depletion of these cells from GrB -/- mice and wild type mice greatly reduces mortality and improves the course of liver injury recovery.

MHC class II restricted innate-like double negative T cells contribute to optimal primary and secondary immunity to Leishmania major

Although it is generally believed that CD4⁺ T cells play important roles in anti-Leishmania immunity, some studies suggest that they may be dispensable, and that MHC II-restricted CD3⁺CD4⁻CD8⁻ (double negative, DN) T cells may be more important in regulating primary anti-Leishmania immunity. In addition, while there are reports of increased numbers of DN T cells in Leishmania-infected patients, dogs and mice, concrete evidence implicating these cells in secondary anti-Leishmania immunity has not yet been documented. Here, we report that DN T cells extensively proliferate and produce effector cytokines (IFN-γ, TNF and IL-17) and granzyme B (GrzB) in the draining lymph nodes and spleens of mice following primary and secondary L. major infections. DN T cells from healed mice display functional characteristics of protective anti-Leishmania memory-like cells: rapid and extensive proliferation and effector cytokines production following L. major challenge in vitro and in vivo. DN T cells express predominantly (> 95%) alpha-beta T cell receptor (αβ TCR), are Leishmania-specific, restricted mostly by MHC class II molecules and display transcriptional profile of innate-like genes. Using in vivo depletion and adoptive transfer studies, we show that DN T cells contribute to optimal primary and secondary anti-Leishmania immunity in mice. These results directly identify DN T cells as important players in effective and protective primary and secondary anti-L. major immunity in experimental cutaneous leishmaniasis.

Although it is generally believed that CD4⁺ T cells mediate anti-Leishmania immunity, some studies suggest that CD3⁺CD4⁻CD8⁻ (double negative, DN) T cells may play a more important role in regulating primary anti-Leishmania immunity. Here, we report that DN T cells extensively proliferate and produce effector cytokines in mice following primary and secondary L. major infections. Leishmania-reactive DN T cells utilize αβ T cell receptor (TCR) and are restricted by MHC class II molecules. Strikingly, DN T cells from healed mice display functional characteristics of protective anti-Leishmania memory-like cells: rapid and extensive proliferation, effector cytokine production in vitro and in vivo, and accelerated parasite control following secondary L. major challenge. These results directly identify DN T cells as important players in protective primary and secondary anti-L. major immunity in experimental cutaneous leishmaniasis.

The mouse idd2 locus is linked to the proportion of immunoregulatory double-negative T cells, a trait associated with autoimmune diabetes resistance

Autoimmune diseases result from a break in immune tolerance. Various mechanisms of peripheral tolerance can protect against autoimmunity, including immunoregulatory CD4(-)CD8(-) double-negative (DN) T cells. Indeed, we have previously shown that diabetes-prone mouse strains exhibit a low proportion of DN T cells relative to that of diabetes-resistant mice, and that a single autologous transfer of DN T cells can impede autoimmune diabetes development, at least in the 3A9 TCR transgenic setting. In this study, we aim to understand the genetic basis for the difference in DN T cell proportion between diabetes-resistant and diabetes-prone mice. We thus perform an unbiased linkage analysis in 3A9 TCR F2 (NOD.H2(k) × B10.BR) mice and reveal that a locus on chromosome 9, which coincides with Idd2, is linked to the proportion of DN T cells in the lymph nodes. We generate two NOD.H2(k).B10-Chr9 congenic mouse strains and validate the role of this genetic interval in defining the proportion of DN T cells. Moreover, we find that the increased proportion of DN T cells in lymphoid organs is associated with a decrease in both diabetes incidence and serum IgG Ab levels. Together, the data suggest that Idd2 is linked to DN T cell proportion and that a physiological increase in DN T cell number may be sufficient to confer resistance to autoimmune diabetes. Altogether, these findings could help identify new candidate genes for the development of therapeutic avenues aimed at modulating DN T cell number for the prevention of autoimmune diseases.

Ex vivo converted double negative T cells suppress activated B cells

Although the ability of endogenous CD4(-)CD8(-) double negative (DN) T cells to suppress B cells has been documented, the extent to which ex vivo converted DN T cells suppress B cells activity is still being explored. The aim of this study was to determine whether and what extent ex vivo converted CD4(-)CD8(-) DN T cells suppress B cell activation and antibody production. We found that ex vivo converted DN T cells suppressed proliferation of activated B cells in a perforin and cell-cell contact dependent manner. In addition, ex vivo converted DN T cells significantly inhibited the production of IgG by stimulated B cells. This study provides evidence that ex vivo converted CD4(-)CD8(-) double negative T cells can down-regulate immune responses by suppressing B cell proliferation and IgG production, and supports efforts to develop ex vivo DN T cell therapies.

Idd13 is involved in determining immunoregulatory DN T-cell number in NOD mice

Immunoregulatory T cells have been identified as key modulators of peripheral tolerance and participate in preventing autoimmune diseases. CD4(-)CD8(-) (double negative, DN) T cells compose one of these immunoregulatory T-cell subsets, where the injection of DN T cells confers protection from autoimmune diabetes progression. Interestingly, genetic loci defining the function and number of CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) coincide with at least some autoimmune disease susceptibility loci. Herein, we investigate the impact of major insulin-dependent diabetes (Idd) loci in defining the number of DN T cells. We demonstrate that although Idd3, Idd5 and Idd9 loci do not regulate DN T-cell number, NOD mice congenic for diabetes resistance alleles at the Idd13 locus show a partial restoration in DN T-cell number. Moreover, competitive and non-competitive bone marrow chimera experiments reveal that DN T-cell number is defined by a bone marrow-intrinsic, but DN T-cell-extrinsic, factor. This suggests that non-autonomous candidate genes define DN T-cell number in secondary lymphoid organs. Together, our results show that the regulation of DN T-cell number in NOD mice is at least partially conferred by alleles at the Idd13 locus.

Pretransplant infusion of donor B cells enhances donor-specific skin allograft survival

Pretransplant donor lymphocyte infusion (DLI) has been shown to enhance donor-specific allograft survival in rodents, primates and humans. However, the cell subset that is critical for the DLI effect and the mechanisms involved remain elusive. In this study, we monitored donor cell subsets after DLI in a murine MHC class I L^d-mismatched skin transplantation model. We found that donor B cells, but not DCs, are the major surviving donor APCs in recipients following DLI. Infusing donor B, but not non-B, cells resulted in significantly enhanced donor-specific skin allograft survival. Furthermore, mice that had received donor B cells showed higher expression of Ly6A and CD62L on antigen-specific TCRαβ⁺CD3⁺CD4⁻CD8⁻NK1.1⁻ double negative (DN) regulatory T cells (Tregs). B cells presented alloantigen to DN Tregs and primed their proliferation in an antigen-specific fashion. Importantly, DN Tregs, activated by donor B cells, showed increased cytotoxicity toward anti-donor CD8⁺ T cells. These data demonstrate that donor B cells can enhance skin allograft survival, at least partially, by increasing recipient DN Treg-mediated killing of anti-donor CD8⁺ T cells. These findings provide novel insights into the mechanisms underlying DLI-induced transplant tolerance and suggest that DN Tregs have great potential as an antigen-specific immune therapy to enhance allograft survival.

Identification of CD3+CD4-CD8- T cells as potential regulatory cells in an experimental murine model of graft-versus-host skin disease (GVHD)

We have developed K14-mOVA transgenic (Tg) mice that express membrane-associated ovalbumin (mOVA) under the control of a K14 promoter as well as double Tg mice by crossing them with OT-I mice that have a T cell receptor (TCR) recognizing OVA peptide. When injected with CD8⁺ OT-I cells, K14-mOVATg mice develop graft-vs-host disease (GvHD), whereas double Tg mice are protected. This suggests that, in double Tg mice, regulatory mechanisms may prevent infused OT-I cells from inducing GvHD. We demonstrated that, after adoptive transfer, TCRαβ⁺CD3⁺CD4^-CD8^-NK1.1^- double negative (DN) T cells are increased in the peripheral lymphoid organs and skin of double Tg mice and exhibit a Vα2⁺Vβ5⁺TCR that is the same TCR specificity as OT-I cells. These DN T cells isolated from tolerant double Tg mice proliferated in response to OVA peptide and produced IFN-γ in the presence of IL-2. These cells could also suppress the proliferation of OT-I cells and were able to specifically kill activated OT-I cells through Fas/Fas ligand interaction. These findings suggest that DN T cells that accumulate in double Tg mice have regulatory functions and may play a role in the maintenance of peripheral tolerance in vivo.

Immunoregulatory CD4(-)CD8(-) T cells as a potential therapeutic tool for transplantation, autoimmunity, and cancer

A central objective in organ transplantation and the treatment or prevention of autoimmune disease is the achievement of antigen-specific immune tolerance. An additional challenge in bone marrow transplantation for the treatment of hematological malignancies is the prevention of graft-vs-host disease (GVHD) while maintaining graft-vs-tumor activity. Interestingly, CD4^-CD8^- (double negative, DN) T cells, which exhibit a unique antigen-specific immunoregulatory potential, appear to exhibit all of the properties to respond to these challenges. Herein, we review the therapeutic potential of immunoregulatory DN T cells in various immunopathological settings, including graft tolerance, GVHD, cancer, and autoimmunity.

Autocrine IFNγ controls the regulatory function of lymphoproliferative double negative T cells

TCRαβ⁺ CD4⁻CD8⁻NK⁻ double negative T cells (DN T cells) can act as regulatory T cells to inhibit allograft rejection and autoimmunity. Their role in graft-versus-host disease and mechanisms of suppression remain elusive. In this study, we demonstrate that DN T cells can inhibit CD4⁺ T cell-mediated GVHD in a semi-allogeneic model of bone marrow transplantation. Furthermore, we present evidence of a novel autocrine IFNγ signaling pathway in Fas-deficient C57BL/6.lpr (B6.lpr) DN T cells. B6.lpr DN T cells lacking IFNγ or its receptor were impaired in their ability to suppress syngeneic CD4⁺ T cells responding to alloantigen stimulation both in vitro and in vivo. Autocrine IFNγ signaling was required for sustained B6.lpr DN T cell IFNγ secretion in vivo and for upregulation of surface Fas ligand expression during TCR stimulation. Fas ligand (FasL) expression by B6.lpr DN T cells permitted lysis of activated CD4⁺ T cells and was required for suppression of GVHD. Collectively, our data indicate that DN T cells can inhibit GVHD and that IFNγ plays a critical autocrine role in controlling the regulatory function of B6.lpr DN T cells.

A comprehensive review of the phenotype and function of antigen-specific immunoregulatory double negative T cells

Double negative T cells that lack the expression of both CD4 and CD8 T cell co-receptors exhibit a most unique antigen-specific immunoregulatory potential first described over a decade ago. Due to their immunoregulatory function, this rare T cell population has been studied in both mice and humans for their contribution to peripheral tolerance and disease prevention. Consequently, double negative cells are gaining interest as a potential cellular therapeutic. Herein, we review the phenotype and function of double negative T cells with emphasis on their capacity to induce antigen-specific immune tolerance. While the phenotypic and functional similarities between double negative T cells identified in mouse and humans are highlighted, we also call attention to the need for a specific marker of double negative T cells, which will facilitate future studies in humans. Altogether, due to their unique properties, double negative T cells present a promising therapeutic potential in the context of various disease settings.

Tumour suppressor Fus1 provides a molecular link between inflammatory response and mitochondrial homeostasis

Fus1, encoded by a 3p21.3 tumour suppressor gene, is down-regulated, mutated or lost in the majority of inflammatory thoracic malignancies. The mitochondrial localization of Fus1 stimulated us to investigate how Fus1 modulates inflammatory response and mitochondrial function in a mouse model of asbestos-induced peritoneal inflammation. Asbestos treatment resulted in a decreased Fus1 expression in wild-type (WT) peritoneal immune cells, suggesting that asbestos exposure may compromise the Fus1-mediated inflammatory response. Untreated Fus1(-/-) mice had an ~eight-fold higher proportion of peritoneal granulocytes than Fus1(+/+) mice, pointing at ongoing chronic inflammation. Fus1(-/-) mice exhibited a perturbed inflammatory response to asbestos, reflected in decreased immune organ weight and peritoneal fluid protein concentration, along with an increased proportion of peritoneal macrophages. Fus1(-/-) immune cells showed augmented asbestos-induced activation of key inflammatory, anti-oxidant and genotoxic stress response proteins ERK1/2, NFκB, SOD2, γH2AX, etc. Moreover, Fus1(-/-) mice demonstrated altered dynamics of pro- and anti-inflammatory cytokine expression, such as IFNγ, TNFα, IL-1A, IL-1B and IL-10. 'Late' response cytokine Ccl5 was persistently under-expressed in Fus1(-/-) immune cells at both basal and asbestos-activated states. We observed an asbestos-related difference in the size of CD3(+) CD4(-) CD8(-) DN T cell subset that was expanded four-fold in Fus1(-/-) mice. Finally, we demonstrated Fus1-dependent basal and asbestos-induced changes in major mitochondrial parameters (ROS production, mitochondrial potential and UCP2 expression) in Fus1(-/-) immune cells and in Fus1-depleted cancer cells, thus supporting our hypothesis that Fus1 establishes its immune- and tumour-suppressive activities via regulation of mitochondrial homeostasis.

Double negative regulatory T cells in transplantation and autoimmunity: recent progress and future directions

T lymphocytes bearing the αβ T cell receptor (TCR) but lacking CD4, CD8, and markers of natural killer (NK) cell differentiation are known as 'double-negative' (DN) T cells and have been described in both humans and rodent models. We and others have shown that DN T cells can act as regulatory T cells (Tregs) that are able to prevent allograft rejection, graft-versus-host disease, and autoimmune diabetes. In the last few years, new data have revealed evidence of DN Treg function in vivo in rodents and humans. Moreover, significant advances have been made in the mechanisms by which DN Tregs target antigen-specific T cells. One major limitation of the field is the lack of a specific marker that can be used to distinguish truly regulatory DN T cells (DN Tregs) from non-regulatory ones, and this is the central challenge in the coming years. Here, we review recent progress on the role of DN Tregs in transplantation and autoimmunity, and their mechanisms of action. We also provide some perspectives on how DN Tregs compare with Foxp3(+) Tregs.

Regulation of antigen-expressing dendritic cells by double negative regulatory T cells

TCRαβ(+) CD3(+) CD4(-) CD8(-) NK1.1(-) double negative (DN) Tregs comprise 1-3% of peripheral T lymphocytes in mice and humans. It has been demonstrated that DN Tregs can suppress allo-, xeno- and auto-immune responses in an Ag-specific fashion. However, the mechanisms by which DN Tregs regulate immune responses remain elusive. Whether DN Tregs can regulate DCs has not been investigated previously. In this study, we demonstrate that DN Tregs express a high level of CTLA4 and are able to down-regulate costimulatory molecules CD80 and CD86 expressed on Ag-expressing mature DCs (mDCs). DN Tregs from CTLA4 KO mice were not able to downregulate CD80 and CD86 expression, indicating that CTLA4 is critical for DN Treg-mediated downregulation of costimulatory molecule expression on Ag-expressing mature DCs. Furthermore, DN Tregs could kill both immature and mature allogeneic DCs, as well as Ag-loaded syngeneic DCs, in an Ag-specific manner in vitro and in vivo, mainly through the Fas-FasL pathway. These data demonstrate, for the first time, that DN Tregs are potent regulators of DCs and may have the potential to be developed as a novel immune suppression treatment.

Adoptive cell therapy using antigen-specific CD4⁻CD8⁻T regulatory cells to prevent autoimmune diabetes and promote islet allograft survival in NOD mice

AIMS/HYPOTHESIS

A new differentiation pathway for CD4(-)CD8(-) (DN) T cells has recently been identified that exhibits the potent function of peripheral converted DN T cells in suppressing immune responses and provides the potential to treat autoimmune diseases. The aim of this study was to determine if the DN T cells converted from CD4(+) T cells of NOD mice retain the antigen-specific regulatory capacity and prevent autoimmune diabetes in vivo. We also sought to determine if the combination of DN T cells with rapamycin promotes islet allograft survival in autoimmune diabetic NOD recipients.

METHODS

NOD CD4(+) T cells were converted to DN T cells in an in vitro mixed-lymphocyte reaction, with or without GAD65 peptide, as previously reported. The antigen-specific DN T cells were adoptively transferred to NOD/SCID mice, new-onset diabetic NOD mice or islet-allograft-recipient NOD mice as the part of cell-based therapy. The development of diabetes and allograft survival was assessed by monitoring blood glucose levels.

RESULTS

NOD CD4(+) T cells were converted in vitro to DN T cells at a rate of 50% and expressed unique cell features. The DN T cells from NOD donors blocked autoimmunity and prevented diabetes in NOD models, and these effects were even greater for GAD65-peptide-primed DN T cells. DN T cells acted in conjunction with rapamycin to suppress alloantigen-triggered T cell proliferation, promoted apoptosis and prolonged islet allograft survival in NOD recipients.

CONCLUSIONS/INTERPRETATION

Administration of the islet beta cell antigen-specific DN T cells can prevent the development of autoimmune diabetes and promote islet allograft survival in NOD mice.

Making sense of regulatory T cell suppressive function

Several types of regulatory T cells maintain self-tolerance and control excessive immune responses to foreign antigens. The major regulatory T subsets described over the past decade and novel function in transplantation will be covered in this review with a focus on CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells. Multiple mechanisms have been proposed to explain how Treg cells inhibit effector cells but none can completely explain the observed effects in toto. Proposed mechanisms to explain suppressive activity of Treg cells include the generation of inhibitory cytokines, induced death of effector cells by cytokine deprivation or cytolysis, local metabolic perturbation of target cells mediated by changes in extracellular nucleotide/nucleoside fluxes with alterations in intracellular signaling molecules such as cyclic AMP, and finally inhibition of dendritic cell functions. A better understanding of how Treg cells operate at the molecular level could result in novel and safer therapeutic approaches in transplantation and immune-mediated diseases.

Regulatory CD4(-)CD8(-) double negative T cells

Peripheral αβTCR(+)CD3(+)CD4(-)CD8(-) NK1.1/CD56(-) double-negative (DN) Treg cells are a relatively rare subset of regulatory cells found in both humans and mice, typically comprising less than 5% of the total peripheral T-cell pool. Numerous studies have shown that DN Tregs can inhibit CD4(+) and CD8(+) T-cell responses in vitro and in vivo using a variety of model systems [Zhang et al., Nature Medicine 6:782, 2000; Young et al., Blood 100:3408, 2002; Ford et al., Experimental Medicine 196:261, 2002; Young et al., Journal of Immunology 171:134, 2003; Ford et al., European Journal of Immunology 37:2234, 2007; Zhang et al., Blood 109:4071, 2007; Fischer et al., Blood 105:2828, 2005]. This chapter describes published methods for the phenotypic identification of DN Tregs, their isolation from secondary lymphoid organs of mice or human peripheral blood, activation and expansion, and assays for their ability to suppress T-cell proliferation, induce apoptosis, and promote tolerance to allografts in vivo.

Double negative (CD3+ 4- 8-) TCR alphabeta splenic cells from young NOD mice provide long-lasting protection against type 1 diabetes

BACKGROUND

Double negative CD3(+)4(-)8(-) TCR alphabeta splenic cells (DNCD3) can suppress the immune responses to allo and xenografts, infectious agents, tumors, and some autoimmune disorders. However, little is known about their role in autoimmune diabetes, a disease characterized by the reduction of insulin production subsequent to destruction of pancreatic beta-cells by a polyclonal population of self-reactive T-cells. Herein, we analyzed the function and phenotype of DNCD3 splenic cells in young NOD mice predisposed to several autoimmune disorders among which, the human-like autoimmune diabetes.

METHODOLOGY/PRINCIPAL FINDINGS

DNCD3 splenic cells from young NOD mice (1) provided long-lasting protection against diabetes transfer in NOD/Scid immunodeficient mice, (2) proliferated and differentiated in the spleen and pancreas of NOD/Scid mice and pre-diabetic NOD mice into IL-10-secreting T(R)-1 like cells in a Th2-like environment, and (3) their anti-diabetogenic phenotype is CD3(+)(CD4(-)CD8(-))CD28(+)CD69(+)CD25(low) Foxp3(-) iCTLA-4(-)TCR alphabeta(+) with a predominant Vbeta13 gene usage.

CONCLUSIONS/SIGNIFICANCE

These findings delineate a new T regulatory component in autoimmune diabetes apart from that of NKT and CD4(+)CD25(high) Foxp3(+)T-regulatory cells. DNCD3 splenic cells could be potentially manipulated towards the development of autologous cell therapies in autoimmune diabetes.

The effect of murine anti-thymocyte globulin on experimental kidney warm ischemia-reperfusion injury in mice

Kidney ischemia-reperfusion injury (IRI) is an important contributor to delayed graft function (DGF) and poor outcome of allografts. Small clinical studies suggest a beneficial role for human anti-thymocyte globulin (ATG) in DGF. We investigated the short-term effect of mouse anti-thymocyte globulin (mATG) on kidney warm IRI in mice. We administered either mATG, rabbit immunoglobulin (RIgG), or saline with different dosing schedules in three different IRI models: 30 min bilateral, 60 min bilateral, and 45min unilateral IRI. mATG effectively depleted circulating T cells but had less effect on kidney-infiltrating T cells. There was no difference in serum creatinine levels between groups in each study. Scoring of renal tubular damage and regenerating tubules revealed no difference between groups. The percentage of CD3(+)CD4(-)CD8(-) double-negative (DN) T cells, which were reported to contribute to the pathogenesis of lupus nephritis, increased and the percentages of regulatory T cells and NK cells decreased in the post-ischemic kidneys of mATG treated mice. mATG did not alter the expression of pro-inflammatory cytokines such as IFN-gamma or anti-inflammatory cytokines such as IL-10 in post-ischemic kidneys. mATG treatment, whether initiated before ischemia or immediately after reperfusion, had minimal effects on renal injury following warm IRI in mice.

Cutting edge: in vivo trogocytosis as a mechanism of double negative regulatory T cell-mediated antigen-specific suppression

Recent data have demonstrated that treatment with alphabeta-TCR(+)CD3(+)CD4(-)CD8(-)NK1.1(-) double negative (DN) regulatory T cells (Tregs) inhibits autoimmune diabetes and enhances allotransplant and xenotransplant survival in an Ag-specific fashion. However, the mechanisms whereby DN Tregs suppress Ag-specific immune responses remain largely unknown. In this study, we demonstrate that murine DN Tregs acquire alloantigen in vivo via trogocytosis and express it on their cell surface. Trogocytosis requires specific interaction of MHC-peptide on APCs and Ag-specific TCR on DN Tregs, as blocking this interaction prevents DN Treg-mediated trogocytosis. Acquisition of alloantigen by DN Tregs was required for their ability to kill syngeneic CD8(+) T cells. Importantly, DN Tregs that had acquired alloantigen were cytotoxic toward Ag-specific, but not Ag-nonspecific, syngeneic CD8(+) T cells. These data provide new insight into how Tregs mediate Ag-specific T cell suppression and may enhance our ability to use DN Tregs as a therapy for transplant rejection and autoimmune diseases.