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

Immune profiling analysis of double-negative T cells in patients with systemic sclerosis

OBJECTIVE

To construct a molecular immune map of patients with systemic sclerosis (SSc) by mass flow cytometry, and compare the number and molecular expression of double-negative T (DNT) cell subsets between patients and healthy controls (HC).

METHODS

Peripheral blood mononuclear cells (PBMCs) were extracted from the peripheral blood of 17 SSc patients and 9 HC. A 42-channel panel was set up to perform mass cytometry by time of flight (CyTOF) analysis for DNT subgroups. Flow cytometry was used to validate subpopulation functions. The clinical data of patients were collected for correlation analysis.

RESULTS

Compared with HC, the number of total DNT cells decreased in SSc patients. Six DNT subsets were obtained from CyTOF analysis, in which the proportion of cluster1 increased, while the proportion of cluster3 decreased. Further analysis revealed that cluster1 was characterized by high expression of CD28 and CCR7, and cluster3 was characterized by high expression of CD28 and CCR5. After in vitro stimulation, cluster1 secreted more IL-4 and cluster3 secreted more IL-10 in SSc patients compared to HC. Clinical correlation analysis suggested that cluster1 may play a pathogenic role while cluster3 may play a protective role in SSc. ROC curve analysis further revealed that cluster3 may be a potential indicator for determining disease activity in SSc patients.

CONCLUSION

We found a new CCR5+CD28+ DNT cell subset, which played a protective role in the pathogenesis of SSc. Key Points • The number of DNT cells decreased in SSc patients' peripheral blood. • DNT cells do not infiltrate in the skin but secrete cytokines to participate in the pathogenesis of SSc. • A CCR5+CD28+ DNT cell population may play a protective role in SSc.

IL-33 promotes double negative T cell survival via the NF-κB pathway

IL-33, which is a crucial modulator of adaptive immune responses far beyond type 2 response, can enhance the function of several T cell subsets and maintain the immune homeostasis. However, the contribution of IL-33 to double negative T (DNT) cell remains unappreciated. Here, we demonstrated that the IL-33 receptor ST2 was expressed on DNT cells, and that IL-33 stimulation increased DNT cells proliferation and survival in vivo and in vitro. Transcriptome sequencing analysis also demonstrated that IL-33 enhanced the biological function of DNT cells, especially effects on proliferation and survival. IL-33 promoted DNT cells survival by regulating Bcl-2, Bcl-xl and Survivin expression. IL-33-TRAF4/6-NF-κB axis activation promoted the transmission of essential division and survival signals in DNT cells. However, IL-33 failed to enhance the expression of immunoregulatory molecules in DNT cells. DNT cells therapy combined with IL-33 inhibited T cells survival and further ameliorated ConA-induced liver injury, which mainly depended on the proliferative effect of IL-33 on DNT cells in vivo. Finally, we stimulated human DNT cells with IL-33, and similar results were observed. In conclusion, we revealed a cell intrinsic role of IL-33 in the regulation of DNT cells, thereby identifying a previously unappreciated pathway supporting the expansion of DNT cells in the immune environment.

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.

ALPS, FAS, and beyond: from inborn errors of immunity to acquired immunodeficiencies

Autoimmune lymphoproliferative syndrome (ALPS) is a primary immune regulatory disorder characterized by benign or malignant lymphoproliferation and autoimmunity. Classically, ALPS is due to mutations in FAS and other related genes; however, recent research revealed that other genes could be responsible for similar clinical features. Therefore, ALPS classification and diagnostic criteria have changed over time, and several ALPS-like disorders have been recently identified. Moreover, mutations in FAS often show an incomplete penetrance, and certain genotypes have been associated to a dominant or recessive inheritance pattern. FAS mutations may also be acquired or could become pathogenic when associated to variants in other genes, delineating a possible digenic type of inheritance. Intriguingly, variants in FAS and increased TCR αβ double-negative T cells (DNTs, a hallmark of ALPS) have been identified in multifactorial autoimmune diseases, while FAS itself could play a potential role in carcinogenesis. These findings suggest that alterations of FAS-mediated apoptosis could trespass the universe of inborn errors of immunity and that somatic mutations leading to ALPS could only be the tip of the iceberg of acquired immunodeficiencies.

The Immunoregulatory Role of the Signal Regulatory Protein Family and CD47 Signaling Pathway in Type 1 Diabetes

Background

The pathogenesis of type 1 diabetes (T1D) involves complex genetic susceptibility that impacts pathways regulating host immunity and the target of autoimmune attack, insulin-producing pancreatic β-cells. Interactions between risk variants and environmental factors result in significant heterogeneity in clinical presentation among those who develop T1D. Although genetic risk is dominated by the human leukocyte antigen (HLA) class II and insulin (INS) gene loci, nearly 150 additional risk variants are significantly associated with the disease, including polymorphisms in immune checkpoint molecules, such as SIRPG.

Scope of Review

In this review, we summarize the literature related to the T1D-associated risk variants in SIRPG, which include a protein-coding variant (rs6043409, G>A; A263V) and an intronic polymorphism (rs2281808, C>T), and their potential impacts on the immunoregulatory signal regulatory protein (SIRP) family:CD47 signaling axis. We discuss how dysregulated expression or function of SIRPs and CD47 in antigen-presenting cells (APCs), T cells, natural killer (NK) cells, and pancreatic β-cells could potentially promote T1D development.

Major Conclusions

We propose a hypothesis, supported by emerging genetic and functional immune studies, which states a loss of proper SIRP:CD47 signaling may result in increased lymphocyte activation and cytotoxicity and enhanced β-cell destruction. Thus, we present several novel therapeutic strategies for modulation of SIRPs and CD47 to intervene in T1D.

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.

Double-negative T cells in autoimmune diseases

PURPOSE OF REVIEW

TCRαβ+CD4-CD8- double-negative T (DNT) cells, a principal subset of mature T lymphocytes, have been closely linked with autoimmune/inflammatory conditions. However, controversy persists regarding their ontogeny and function. Here, we present an overview on DNT cells in different autoimmune diseases to advance a deeper understanding of the contribution of this population to disease pathogenesis.

RECENT FINDINGS

DNT cells have been characterized in various chronic inflammatory diseases and they have been proposed to display pathogenic or regulatory function. The tissue location of DNT cells and the effector cytokines they produce bespeak to their active involvement in chronic inflammatory diseases.

SUMMARY

By producing various cytokines, expanded DNT cells in inflamed tissues contribute to the pathogenesis of a variety of autoimmune inflammatory diseases. However, it is unclear whether this population represents a stable lineage consisting of different subsets similar to CD4+ T helper cell subset. Better understanding of the possible heterogeneity and plasticity of DNT cells is needed to reveal interventional therapeutic opportunities.

CD4 derived double negative T cells prevent the development and progression of nonalcoholic steatohepatitis

Hepatic inflammation is the driving force for the development and progression of NASH. Treatment targeting inflammation is believed to be beneficial. In this study, adoptive transfer of CD4+ T cells converted double negative T cells (cDNT) protects mice from diet-induced liver fat accumulation, lobular inflammation and focal necrosis. cDNT selectively suppress liver-infiltrating Th17 cells and proinflammatory M1 macrophages. IL-10 secreted by M2 macrophages decreases the survival and function of cDNT to protect M2 macrophages from cDNT-mediated lysis. NKG2A, a cell inhibitory molecule, contributes to IL-10 induced apoptosis and dampened suppressive function of cDNT. In conclusion, ex vivo-generated cDNT exert potent protection in diet induced obesity, type 2 diabetes and NASH. The improvement of outcome is due to the inhibition on liver inflammatory cells. This study supports the concept and the feasibility of potentially utilizing this autologous immune cell-based therapy for the treatment of NASH.

DNT Cell-based Immunotherapy: Progress and Applications

Cancer immunotherapy has firmly established a dominant status in recent years. Adoptive cellular immunotherapy (ACI) is the main branch of immunotherapy. Recently, the immune effector cells of ACI, such as T cells, NK cells, and genetically engineered cells, have been used to achieve significant clinical benefits in the treatment of malignant tumors. However, the clinical applications have limitations, including toxicity, unexpectedly low efficiency, high costs and strict technical requirements. More exploration is needed to optimize ACI for cancer patients. CD3+CD4-CD8- double negative T cells (DNTs) have emerged as functional antitumor effector cells, according to the definition of adoptive immunotherapy. They constitute a kind of T cell subset that mediates nontumor antigen-restricted immunity and has important immune regulatory functions. Preclinical experiments showed that DNTs had a dual effect by killing tumor cells and inhibiting graft-versus-host disease. Notably, DNTs can be acquired from healthy donors and expanded in vitro; thus, allogeneic DNTs may be provided as “off-the-shelf” cellular products that can be readily available for direct clinical application. We review the progress and application of DNTs in immunotherapy. DNTs may provide some novel perspectives on cancer immunotherapy.

Alteration of liver-infiltrated and peripheral blood double-negative T-cells in primary biliary cholangitis

BACKGROUND & AIMS

Double-negative (DN) T-cell is a unique regulatory T-cell, which is essential for maintaining immune system homoeostasis. However, the role of DN T-cells in the pathogenesis of primary biliary cholangitis (PBC) is still unknown.

METHODS

We investigated the number and function of DN T-cells in peripheral blood and liver biopsy specimens of PBC patients.

RESULTS

The number and frequency of DN T-cells significantly decreased in peripheral blood and liver tissue of PBC patients. Furthermore, the frequency of DN T-cells in PBC was negatively correlated with disease severity and positively correlated with ursodeoxycholic acid response. In vitro assays showed that perforin expression and the suppressive capability of DN T-cells on the proliferation of CD4⁺ and CD8⁺ T-cells were impaired in PBC. Finally, lithocholic acid, the most hydrophobic acid, could downregulate the proliferation and perforin expression of DN T-cells.

CONCLUSIONS

Decreased quantity and function of DN T-cells in PBC may result in the loss of immune regulations on effector CD4⁺ and cytotoxic CD8⁺ T-cells, and thereby may break the immune tolerance and promote the pathogenesis of PBC.

Reparative T lymphocytes in organ injury

Acute organ injuries such as acute cerebrovascular accidents, myocardial infarction, acute kidney injury, acute lung injury, and others are among the leading causes of death worldwide. Dysregulated or insufficient organ repair mechanisms limit restoration of homeostasis and contribute to chronic organ failure. Studies reveal that both humans and mice harness potent non-stem cells that are capable of directly or indirectly promoting tissue repair. Specific populations of T lymphocytes have emerged as important reparative cells with context-specific actions. These T cells can resolve inflammation and secrete reparative cytokines and growth factors as well as interact with other immune and stromal cells to promote the complex and active process of tissue repair. This Review focuses on the major populations of T lymphocytes known to mediate tissue repair, their reparative mechanisms, and the diseases in which they have been implicated. Elucidating and harnessing the mechanisms that promote the reparative functions of these T cells could greatly improve organ dysfunction after acute injury.

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.

The effect of ethephon on immune system in male offspring of mice

Ethephon can liberate ethylene which could interfere the plant growth process. The aim of the present study was to determine the effect of ethephon on developing immune system of male offspring. Ethephon could enhance NK cell activity in male mice. For 4-week-old male mice, lymphocytes of peripheral blood increased while the hemolytic plaque number decreased. Delayed type hypersensitivity(DTH) was inhibited in all groups. The expression of protein Bcl11b and p-p38 in thymus of treatment groups were lower than control group. Our results indicated that cellular immunity of male offspring is more sensitive to ethephon when exposed in pregnancy and lactation period. It should be emphasized that exposure to ethephon during the in utero stage and lactation stage still could damage the immune function of animal in the period before fully mature even in the dosage that could not influence the immune function of adult animal.

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.

HLA-DR*0401 expression in the NOD mice prevents the development of autoimmune diabetes by multiple alterations in the T-cell compartment

Several human HLA alleles have been found associated with type 1 diabetes (T1D), but their precise role is not clearly defined. Herein, we report that a human MHC class II (HLA-DR*0401) allele transgene that has been expressed into NOD (H-2(g7)I-E(null)) mice prone to T1D rendered the mice resistant to the disease. T1D resistance occurred in the context of multi-point T-cell alterations such as: (i) skewed CD4/CD8 T-cell ratio, (ii) decreased size of CD4(+)CD44(high) T memory pool, (iii) aberrant TCR Vβ repertoire, (iv) increased neonatal number of Foxp3(+) and TR-1(+) regulatory cells, and (v) reduced IFN-γ inflammatory response vs. enhanced IL-10 suppressogenic response of T-cells upon polyclonal and antigen-specific stimulation. The T-cells from NOD/DR4 Tg mice were unable to induce or suppress diabetes in NOD/RAG deficient mice. This study describes a multifaceted regulatory function of the HLA-DR*0401 allele strongly associated with the lack of T1D development in NOD mice.

Regulation of IgE production and airway reactivity by CD4⁻CD8⁻ regulatory T cells

The mechanisms of tolerance induction occurring in the course of allergen-specific immunotherapy have not been elucidated in full detail. Our study aimed to characterize high zone tolerance in mouse models of type I allergy and of allergic airway inflammation induced by subcutaneous sensitization of mice with high doses of the model allergen ovalbumin (OVA) without the use of adjuvant. Mice were immunized by subcutaneous injection of high doses (HD) of OVA or, for comparison, low doses (LD) of OVA in saline. HD-mice showed lower specific IgE, but augmented IgG in sera than LD-mice. Pre-treatment of mice with HD-OVA antigen-specifically inhibited IgE production subsequently induced by LD-OVA. OVA-restimulated splenocytes from HD-mice revealed hypoproliferation and impaired production of Th2-associated cytokines. HD-mice exhibited lower airway reactivity, goblet cell hyperplasia and mucus production, as well as IL-5 and IL-13 production in the lungs than LD-mice following local provocation. Recruitment of inflammatory cells into the airways was comparable, while the number of eosinophils in the bronchoalveolar lavage was substantially higher in HD-mice. Adoptive transfer of dnTC from HD-mice into naïve mice, which were subsequently sensitized with LD-OVA, suppressed IgE production in the recipients. The number of dnTC was higher in the spleens of HD-mice than LD-mice. In conclusion, our study demonstrates that subcutaneous sensitization of mice with high doses of allergen in the absence of adjuvant results in attenuated airway reactivity as compared with LD-sensitization and induces CD4(-)CD8(-) dnTC with regulatory function on IgE production.

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.

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.

Spi6 protects alloreactive CD4(+) but not CD8 (+) memory T cell from granzyme B attack by double-negative T regulatory cell

Memory T (Tm) cells pose a major barrier to long-term transplant survival. Whether regulatory T cells (Tregs)can control them remains poorly defined. Previously,we established that double-negative (DN) Tregs suppress effector T (Teff) cells. Here, we demonstrate that DNTregs effectively suppress CD4+/CD8+Teff and CD8+Tm but not CD4+Tm cells, whereas the suppression on CD8+Tm is abrogated by perforin (PFN) deficiency in DNTregs. Consistently, in a BALB/c to B6-Rag1-/-skin transplantation, transfer of DN Tregs suppressed the rejection mediated by CD4þ/CD8+Teff and CD8+Tmcells (76.0±4.9, 87.5±5.0 and 63.0±4.7 days, respectively)but not CD4þTmcells (25.3±1.4 days). Both CD8þ effector memory T and central memory T compartments significantly reduced after DN Treg transfer. CD4+Tm highly expresses granzyme B (GzmB) inhibitor serine protease inhibitor-6 (Spi6). Spi6 deficiency renders CD4þTm susceptible to DN Treg suppression. In addition,transfer of WT DN Tregs, but not PFN-/-DN Tregs,inhibited the skin allograft rejection mediated by Spi6-/-CD4þTm(75.5±7.9 days). In conclusion, CD4+ and CD8+Tm cells differentially respond toDNTregs’ suppression.The GzmB resistance conferred by Spi6 in CD4þTm cells might hint at the physiological significance of Tmpersistence

Increased IL-17 and IL-21 producing TCRαβ+CD4−CD8− T cells in Chinese systemic lupus erythematosus patients

Background: Increased numbers of TCRαβ+CD4−CD8− T cells in the peripheral blood of systemic lupus erythematosus (SLE) patients in the United States and United Kingdom have been reported. However, the proportions of TCRαβ+CD4−CD8− T cells and their involvement in the pathogenesis of SLE in Chinese populations are yet to be determined. Methods: A total of 120 SLE patients, 38 rheumatoid arthritis (RA) patients and 43 normal control subjects were examined. The proportion of TCRαβ+CD4−CD8− T cells in the peripheral blood, Fas expression on these cells, and intracellular cytokine levels in these cells were assessed using flow cytometry. Plasma cytokine concentrations were measured using enzyme-linked immunosorbent assay. Results: The percentages of TCRαβ+CD4−CD8− T cells were increased in Chinese SLE patients, particularly in active SLE patients, correlated with decreased Fas expression on these cells. IL-17 and IL-21 levels in the blood and in TCRαβ+CD4−CD8− T cells from SLE patients were increased. Moreover, a positive correlation was evident between IL-17- and IL-21-producing TCRαβ+CD4−CD8− T cells. Conclusions: Increased TCRαβ+CD4−CD8− T cells expressing inflammatory cytokines, such as IL-17 and IL-21, may be implicated in the pathogenesis of SLE in patients. Appropriate IL-17- and/or IL-21 blockage may be utilized as a novel immunotherapeutic strategy for SLE patients.

Interleukin-4-induced loss of CD8 expression and cytolytic function in effector CD8 T cells persists long term in vivo

Activation of naive CD8(+) T cells in the presence of interleukin-4 modulates their CD8 co-receptor expression and functional differentiation, resulting in the generation of CD8(low) cells that produce type 2 cytokines and display poor cytolytic and anti-tumour activity. Although this CD8(low) phenotype becomes stable after about a week and can persist with further stimulation in vitro, it is not known whether it can be maintained long term in vivo. Here we report that CD8(low) cells derived from oval-bumin(257-264) -specific T-cell receptor-transgenic CD8(+) T cells activated in the presence of interleukin-4 could be detected in the spleen for at least 4 months after adoptive transfer into normal mice. A significant proportion of the long-term surviving cells retained their CD8(low) phenotype in vivo and after clonal re-activation in vitro. Although long-term surviving CD8(low) cells lacked detectable cytolytic activity or perforin expression, they showed some anti-tumour function in vivo. The persistence of functional cells with a CD8(low) phenotype in vivo raises the possibility that such cells can contribute to effector or regulatory responses to tumours or pathogens.

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.

CD4-CD8-T cells contribute to the persistence of viral hepatitis by striking a delicate balance in immune modulation

Viral hepatitis remains the most common cause of liver disease and a major public health problem. Here, we focus on the role of CD4 CD8 double negative T (DN T) cells involved in the mechanisms of viral persistence in hepatitis. C3H/HeJ mice infected with murine hepatitis virus strain 3 (MHV-3) were used to display chronic viral hepatitis. DN T cells dramatically increased in MHV-3 infected mice. Adoptive transfer of DN T cells from MHV-3 infected mice led to a significant increase in mice survival. The DN T cells with production of IFN-γ and IL-2 are able to kill virus-specific CD8⁺ T cells via the Fas/FasL dependent pathway. The delicate balance of multiple effects of DN T cells may lead to viral persistence in MHV-3 induced hepatitis. In short, our study identified DN T cells contributing to viral persistence in MHV-3 induced hepatitis in C3H/HeJ mice, which provides a rationale for modulating DN T cells for the management of viral hepatitis.

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.

Impaired humoral immunity and tolerance in K14-VEGFR-3-Ig mice that lack dermal lymphatic drainage

Lymphatic vessels transport interstitial fluid, soluble Ag, and immune cells from peripheral tissues to lymph nodes (LNs), yet the contribution of peripheral lymphatic drainage to adaptive immunity remains poorly understood. We examined immune responses to dermal vaccination and contact hypersensitivity (CHS) challenge in K14-VEGFR-3-Ig mice, which lack dermal lymphatic capillaries and experience markedly depressed transport of solutes and dendritic cells from the skin to draining LNs. In response to dermal immunization, K14-VEGFR-3-Ig mice produced lower Ab titers. In contrast, although delayed, T cell responses were robust after 21 d, including high levels of Ag-specific CD8+ T cells and production of IFN-γ, IL-4, and IL-10 upon restimulation. T cell-mediated CHS responses were strong in K14-VEGFR-3-Ig mice, but importantly, their ability to induce CHS tolerance in the skin was impaired. In addition, 1-y-old mice displayed multiple signs of autoimmunity. These data suggest that lymphatic drainage plays more important roles in regulating humoral immunity and peripheral tolerance than in effector T cell immunity.

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.

Double-negative T cells during HIV/SIV infections: potential pinch hitters in the T-cell lineup

PURPOSE OF REVIEW

This review summarizes the role of CD3+CD4-CD8- double-negative T cells, which have both regulatory and helper T-cell functions and may have the potential to compensate for the reduced levels of CD4 T cells during SIV/HIV infection.

RECENT FINDINGS

Double-negative T cells have been characterized in several human diseases and in murine models of autoimmunity and transplantation, where they exhibit both immunoregulatory and helper T-cell-like function. During the natural nonpathogenic SIV infection of African nonhuman primates, the lack of clinical disease progression is associated with the presence of double-negative T cells that maintain helper T-cell functions while remaining refractory to viral infection. Moreover, DN T cells may compensate for very low levels of CD4+ T cells observed in a cohort of SIV-infected sooty mangabeys that have remained free of clinical AIDS for over 10 years. These studies identify a potential for double-negative T cells to provide critical helper function during HIV infection.

SUMMARY

Double-negative T cells with some CD4+ T-cell functions are associated with a nonpathogenic outcome during SIV infection and represent a potential immune therapeutic target in HIV-infected patients.

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.

CD3+CD4-CD8- (double negative) T cells: saviours or villains of the immune response?

Recent studies have shown that T cells are not just the latecomers in inflammation but might also play a key role in the early phase of this response. In this context, a number of T cell subsets including NKT cells, mucosal-associated invariant T cells and γ/δ T cells have been shown, together with classical innate immune cells, to contribute significantly to the development and establishment of acute and chronic inflammatory diseases. In this commentary we will focus our attention on a somewhat neglected class of T cells called CD3(+)CD4(-)CD8(-) double negative T cells and on their role in inflammation and autoimmunity. We will summarize the most recent views on their origin at the thymic and peripheral levels as well as their tissue localization in immune and non-lymphoid organs. We will then outline their potential pathogenic role in autoimmunity as well as their homeostatic role in suppressing excessive immune responses deleterious to the host. Finally, we will discuss the potential therapeutic benefits or disadvantages of targeting CD3(+)CD4(-)CD8(-) double negative T cells for the treatment of autoimmune disease. We hope that this overview will shed some light on the function of these immune cells and attract the interest of investigators aiming at the design of novel therapeutic approaches for the treatment of autoimmune and inflammatory conditions.