The Plasticity of γδ T Cells： Innate Immunity,Antigen Presentation and New Immunotherapy

Several signals influence dendritic cell （DC） functions and consequent the immune responses to infectious pathogens. Our recent findings provide a new model of intervention on DCs implicating human γδ T cell stimuli. Vγ/9Vδ2 T cells represent the major subset of circulating human γδ T cells and can be activated by non-peptidic molecules derived from different microorganisms or abnormal metabolic routes. With activated-Vγ/9Vδ2 T cell co-culture, immature DCs acquire features of mature DCs, such as increasing the migratory activity, up-regulating the chemokine receptors, and triggering the Thl immune response. Similar to the NK-derived signals, DC activation is mediated by soluble factors as well as cell-to-cell contact. Many non-peptidic molecules including nitrogen- containing bisphosphonates and pyrophosphomonoester drugs, can stimulate the activity of Vγ/9Vδ2 T cells in vitro and in vivo. The relatively low in vivo toxicity of many of these drugs makes possible novel vaccine and immune-based strategies against infectious diseases.     

The Anti-tumor Immunity of Dendritic Cells Modified by IFN γ Gene on Mice Bearing Ascite Hepatoma Cell H22

1 Introduction Dendritc cell (DC)-based cancer vaccines have shown to been effective both in clinical trials and in animal tumor models. Some clinical trials have been on the phase Ⅲ , but some problems are challenging now. The functions of DC from patient with malignant tumor were depressed by tumor-secreting cytokines such as IL-10. it is critical to find out some methods to improve DC differentiation maturation for priming naive T cells and initiating the specific anti-tumor immunity effectively. IFNγ is a pluripotent cytokine that can exert more the expressions of different molecules in various cells. Now, some data have shown that DCs can produce IFNγ and IFNγ can promote the maturation of DCs, which plays very important roles in promoting protective immune response as the same as IFNγ produced in NK and NKT cells. In our research,we transfected IFNγ gene into DCs in order to investigate the effect of IFNγ on DCs and monitor the anti-tumor response of the tumor bearing mice after vaccination by IFNγ-modified DCs.     

Interferon γ Stimulates Cellular Maturation of Dendritic Cell Line DC2.4 Leading to Induction of Efficient Cytotoxic T Cell Responses and Antitumor Immunity

Dendritic cells （DCs） are the most potent antigen-presenting cells （APCs） for the initiation of antigen （Ag）-specific immune responses. In most studies, mature DCs are generated from bone marrow cells or peripheral monocytes; in either case, the harvested cells are then cultured in medium containing recombinant GM-CSF, IL-4 and TNF-α for 7-10 days and stimulated with lipopolysaccharide （LPS）. However, this approach is time-consuming and expensive. There is another less cost approach of using immobilized DC cell lines, which can easily grow in the medium. A disadvantage with the immobilized DC cell lines, however, is that they are immature DCs and lack expression of MHC class Ⅱ and costimulatory CD40 and CD80 molecules. This, therefore, limits their capacity for inducing efficient antitumor immunity. In the current study, we investigated the possible efficacy of various stimuli （IL-1β, IFN-γ, TNF-α CpG and LPS） in converting the immature dendritic cell line DC2.4 to mature DCs. Our findings were quite interesting since we demonstrated for the first time that IFN-γ was able to stimulate the maturation of DC2.4 cells. The IFN-γ-activated ovalbumin （OVA）-pulsed DC2.4 cells have capacity to upregulate MHC class Ⅱ, CD40, CD80 and CCR7, and to more efficiently stimulate in vitro and in vivo OVA-specific CD8^＋ T cell responses and antitumor immunity. Therefore, IFN-γ-activated immortal DC2.4 ceils may prove to be useful in the study of DC biology and antitumor immunity.     

T cell vaccination as an immunotherapy for autoimmune diseases

Immunization with inactivated autoreactive T cells(T cell vaccination) selected from individual's own T cellrepertoire provides a unique in vivo setting for testing immune regulation that is known to involve interactionsof a variety of related surface molecules(1).It induces regulatory immune responses that closely resemble thein vivo situation where the immune system is challenged by clonal activation and expansion of given T cellpopulations in various autoimmune diseases.T cell vaccination provides a powerful means of eliciting naturalreactions of the immune system in response to clonal expansion of T cells,which can be used as a therapeuticapproach to suppress or eliminate specific pathogenic autoreactive T cells in autoimmune conditions.Clinicaltrials using T cell vaccination to deplete autoreactive T cells in human autoimmune conditions have begun toreveal the pathologic relevance of various autoimmune T cell populations in the disease processes,providing aunique opportunity to test the autoimmune theories in a clinical setting.Cellular & Molecular Immunology.2004;1(5):321-327.     

Distinct Pattern of Human Vδ/51 γδ/5 T Cells Recognizing MICA

γδ T cells represent one unique recognition pattern, the limited recognition, which distinguishes from the specific recognition for αβ T cells and pattern recognition for macrophages. Vδ1 γδT cell is the major subset of human γδT cells, which predominates in mucosal tissue including the intestinal epithelia. Presently, a few antigens that human Vδ1TCR can recognize have been identified. Among them, MHC class I chain-related molecules A （MICA） have been studied most intensively. Besides Vδ1TCR, MICA is also the ligand of NKG2D, a C-type lectin-like activating immunoreceptor. In human, only Vδ1 cells can simultaneously express both types of receptors of MICA while NK cells, αβ T cells and other subsets of γδT cells likewise express NKG2D. Although the precise mechanisms are still enigmatic, this distinct pattern of Vδ1 cells recognizing MICA predicts unique biological significance of Vδ1 cells in immune defense. Recent years, some progresses have been made in this issue. In this review we summarize the related reports and put forward some novel views based on our group＇s studies.     

自然杀伤T细胞在抗感染免疫中的作用研究进展

Natural killer T cell(NKT) are a unique T cell lineage expressing T cell receptor(TCR)and natural killer cell(NK) lineage receptors, and can recognize glycolipids presented by CD1d molecules expressed on antigen presenting cell through cell recognition pathway. After activated, NKT cells can release large amounts of cytokines, such as IL-4 and IFN-γ, and play a regulatory role in both innate and adaptive immune response. NKT cells can also act as direct effector cells via cytolysis or granulysin. NKT cells play an important role in infectious diseases, autoimmune disease,and cancer.     

自然杀伤T细胞在抗感染免疫中的作用研究进展

Natural killer T cell(NKT) are a unique T cell lineage expressing T cell receptor(TCR)and natural killer cell(NK) lineage receptors, and can recognize glycolipids presented by CD1d molecules expressed on antigen presenting cell through cell recognition pathway. After activated, NKT cells can release large amounts of cytokines, such as IL-4 and IFN-γ, and play a regulatory role in both innate and adaptive immune response. NKT cells can also act as direct effector cells via cytolysis or granulysin. NKT cells play an important role in infectious diseases, autoimmune disease,and cancer.     

Distinct effect of CD40 and TNF-signaling on the chemokine/chemokine receptor expression and function of the human monocyte-derived dendritic cells

A key and limiting step in the process of human monocyte-derived dendritic cells （mDCs） for clinical use is their in vitro maturation and in vivo migration. We previously observed that CD40 signal facilitated human mDC growth and maturation. To further explore this process, mDCs generated with GM-CSF and IL-4 were co-cultured with apoptotic tumor cells for 24 hours, followed by incubating with anti-CD40 monoclonal antibody or TNF-a for 48 hours to generate mature DCs. The chemokine/chemokine receptor expression and functions of mature DCs upon various stimuli were determined. The expression of costimulatory molecules on apoptotic tumor cell-loaded mature DCs co-cultured with either anti-CD40 antibody （anti-CD40-DCs） or TNF-a （TNF-DCs） were up-regulated compared to immature DCs, consistent with the abilities of these cytokine to drive DC maturation in vitro. The mRNA levels of chemokines such as stromal cell-derived factor-1a （SDF-1a）, EBV-induced molecule 1 ligand chemokine （ELC）, and IFN inducible protein-10 （IP-10） in anti-CD40 activated DCs were increased and the dendritic cell-specific chemokine 1 （DC-CK1） was moderately up-regulated as compared with other mature DCs. The corresponding chemokine receptors CXCR4 and CCR7 of anti-CD40-DCs were significantly expressed. The CXCR3 expression on activated T cells stimulated by anti-CD40-DCs was also increased. Moreover, the anti-CD40-DCs had a stronger ability to stimulate T cell proliferation than any other DCs. The NF-xB activity was much higher in anti-CD40-DCs than that of TNF-DCs. These results offer further evidence of the importance of the CD40 signal in developing efficient human DC vaccines for cancer immune therapy. Cellular ＆ Molecular Immunology.     

Distinct Pattern of Human Vδ1 γδ T Cells Recognizing MICA

γδT cells represent one unique recognition pattern,the limited recognition,which distinguishes from the specificrecognition for αβT cells and pattern recognition for macrophages.Vδ1 γδT cell is the major subset of human γδT cells,which predominates in mucosal tissue including the intestinal epithelia.Presently,a few antigens thathuman Vδ1TCR can recognize have been identified.Among them,MHC class I chain-related molecules A (MICA)have been studied most intensively.Besides Vδ1TCR,MICA is also the ligand of NKG2D,a C-type lectin-likeactivating immunoreceptor.In human,only Vδ1 cells can simultaneously express both types of receptors of MICAwhile NK cells,αβT cells and other subsets of γδT cells likewise express NKG2D.Although the precisemechanisms are still enigmatic,this distinct pattern of Vδ1 cells recognizing MICA predicts unique biologicalsignificance of Vδ1 cells in immune defense.Recent years,some progresses have been made in this issue.In thisreview we summarize the related reports and put forward some novel views based on our group's studies.Cellular& Molecular Immunology.2005;2(4):253-258.     

Antitumor activity and immune enhancement of murine interleukin-23 expressed in murine colon carcinoma cells

Interleukin （IL）-23, a cytokine composed of p19 and the p40 subunit of IL-12, can enhance the proliferation of memory T cells and production of IFN-γ from activated T cells. It can also induce antitumor effects in murine model. To further evaluate the antitumor activity and immune enhancement of IL-23 in vivo, murine colon carcinoma cells retrovirally transduced with mIL-23 gene were injected subcutaneously （s.c.） into BALB/c mice. Survival time and tumor volume were observed. LDH release assay, [^3H]-TdR incorporation assay and ELISA were used to determine CTL activity, proliferation of splenocytes and level of cytokines, respectively. Number of dendritic cells （DCs） was analyzed by flow cytometry （FCM）. IL-23 secreted by Colon26/IL-23 cells suppressed the growth of tumor and prolonged the survival time of mice, enhanced proliferation of splenocytes, CTL activity, and number of DCs. IL-23 also promoted the production of Thl cytokines such as IFN-γ, IL-12 and TNF-α. However, the level of IL-4 was not enhanced significantly. These data suggested that IL-23 secreted by tumor cells can induce antitumor activitv bv enhancing immune resnonse.     

Hepatitis B Virus Down-Regulates Expressions of MHC Class Ⅰ Molecules on Hepatoplastoma Cell Line

Chronic HBV infection is associated with a 100-fold high risk of developing hepatocellular carcinoma. Tumor recognition is of the most importance during the immune surveillance process that prevents cancer development in humans. In the present study, the expressions of MHC class Ⅰ molecules on hepatoplastoma cell line HepG2.2.15 were investigated to indicate the possible effects of HBV on the immune recognition during HBV-associated hepatocellular carcinoma. It was found that the expressions of MHC class Ⅰ molecules HLA-ABC, HLA-E and MICA were much lower in HepG2.2.15 cells compared with HepG2 cells. The expressing HBV in human hepatoplastoma cell line significantly down-regulated the expressions of MHC class Ⅰ molecules. Additionally, it was observed that in murine chronic HBsAg carriers the expression of classical MHC-I molecule on hepatocytes was down-regulated. These results demonstrated that HBV might affect the immune recognition during HBV- associated hepatocellular carcinoma such as the recognition of CD8^＋ T, NK-CTL and NK cells and prevent the immune surveillance against tumors. However, the effects of HBV down-regulation of MHC class I molecules on the target cells in vivo should be further studied. Cellular ＆ Molecular Immunology.     

Selective Function of PKC-θ in T cells

T cell activation is a critical process in initiating adaptive immune response since only through this process the naive antigen specific T cells differentiate into armed effector T cells that mediate the actual immune response. During T cell activation, naive T cells undergo clonal expansion and acquire the capability to kill target cells infected with pathogens or produce cytokines essential for regulating immune response. Inappropriate activation or inactivation of T cells leads to autoimmunity or severe immunodeficiencies. PKC-θ is selectively expressed in T cells and required for mediating T cell activation process. Mice deficient in PKC-θ exhibit defects in T cell activation, survival and activation-induced cell death. PKC-θ selectively translocates to immunological synapse and mediates the signals required for activation of NF-κB, AP1 and NFAT that are essential for T cell activation. Furthermore, PKC-θ^-│- mice displayed multiple defects in the development of T cell-mediated immune responses in vivo. PKC-θ is thus a critical molecule that regulates T cell function at multiple stages in T cell-mediated immune responses in vivo.     

Dendritic Cells Transduced with SOCS1 Gene Exhibit Regulatory DC Properties and Prolong Allograft Survival

SOCS1 is a key regulator of cytokine signaling and is important for maintaining balance in the immune system. It is thought to participate in negative feedback loops in cytokine signaling and may be an important signal for the regulation of dendritic cell （DC） maturation. However, it remains unclear whether DCs transduced with SOCS1 exhibit characteristics of regulatory DCs and induce allogeneic T-cell hyporesponsiveness. In this study, we constructed adenovirai vector coding SOCS1 （Ad-SOCS1） that can efficiently increase SOCS1 gene expression in bone marrow-derived dendritic cells. DCs transduced with Ad-SOCS1 （DC-SOCS1） expressed low levels of costimulatory and MHC molecules, were resistant to maturation and activation stimulation, induced allogeneic T-cell hyporesponsiveness, and promoted the generation of regulatory-like T cells in vitro. DC-SOCS1 pretreatment significantly prolonged the survival of ailografts and led to a substantial increase in the generation of regulatory T cells. Our data suggest that SOCS1 inhibits DC maturation and induces regulatory DC generation, therefore possessing therapeutic potential to prevent rejection in organ transplantation.     

The interaction of influenza H5N1 viral hemagglutinin with sialic acid receptors leads to the activation of human γδT cells

Highly pathogenic avian influenza H5N 1 epidemics are a significant public health hazard. Genetically engineered H5N 1 viruses with mammalian transmission activity highlight the potential risk of a human influenza H5N 1 pandemic. Understanding the underlying principles of the innate immune system in response to influenza H5N 1 viruses will lead to improved prevention and control of these potentially deadly viruses, γδT cells act as the first line of defense against microbial infection and help initiate adaptive immune responses during the early stages of viral infection. In this study, we investigated the molecular mechanisms of γδ T cells in response to influenza H5N1 viral infection, We found that recombinant hemagglutinin （rHA） derived from three different strains of influenza H5N 1 viruses elicited the activation of γδ T cells cultured in peripheral blood mononuclear cells （PBMCs）. Both the cell surface expression of CD69, an early activation marker on γδ T cells, and the production of interferon-y （IFN-y） were significantly increased. Notably, the rHA protein-induced γδ T-cell activation was not mediated by TCRγδ, NKG2D or pattern recognition receptors （PRRs） or NKp46 receptors. The interaction of rHA proteins with sialic acid receptors may play a critical role in γδ T-cell activation. Our data may provide insight into the mechanisms underlyingγδT-cell activation in response to infection with H5N1 viruses.     

Dysfunction of murine dendritic cells induced by incubation with tumor cells

In vivo studies showed that dendritic cell （DC） dysfunction occurred in tumor microenvironment. As tumors were composed of many kinds of cells, the direct effects of tumor cells on immature DCs （imDCs） are needed for further studies in vitro. In the present study, bone marrow-derived imDCs were incubated with lymphoma, hepatoma and menaloma cells in vitro and surface molecules in imDCs were determined by flow cytometry. Then, imDCs incubated with tumor cells or control imDCs were further pulsed with tumor lysates and then incubated with splenocytes to perform mixed lymphocyte reaction. The DC-dependent tumor antigen-specific T cell proliferation, and IL-12 secretion were determined by flow cytometry, and enzyme-linked immunosorbent assay respectively. Finally, the DC-dependent tumor-associated antigen-specific CTL was determined by enzyme-linked immunospot assay. The results showed that tumor cell-DC incubation down-regulated the surface molecules in imDCs, such as CD80, CD54, CDIIb, CDIIa and MHC class II molecules. The abilities of DC-dependent antigen-specific T cell proliferation and IL-12 secretion were also decreased by tumor cell incubation in vitro. Most importantly, the ability for antigenic-specific CTL priming of DCs was also decreased by incubation with tumor cells. In the present in vitro study demonstrated that the defective abilities of DCs induced by tumor cell co-incubation and the co-incubation system might be useful for future study of tumor-immune cells direct interaction and for drug screen of immune-modulation. Cellular ＆ Molecular Immunology.     

Intratumoral Expression of MIP-1β Induces Antitumor Responses in a Pre-Established Tumor Model through Chemoattracting T Cells and NK Cells

Direct intratumoral introduction of therapeutic or regulatory genes is a developing technology with potential application for cancer gene therapy. Macrophage inflammatory protein-1 beta (MIP-1β) is a chemokine which can chemoattract immune cells such as T cells. In the present study, murine colorectal adenocarcinoma CT26 cells were transfected with a recombinant adenovirus (AdhMIP-1β) carrying the human MIP-1β gene. 24h post-transfection, hMIP-1β levels reached approximately 980 pg/ml in supernatants of 10^6 hMIP-1β-transfected CT26 cells. Moreover, the supernatants exhibited chemotactic activity for CD8^ T cells, CD4^ T cells, NK cells and immature DCs. Intratumoral injection of AdhMIP-1β significantly inhibited tumor growth and prolonged the survival time of tumor-bearing mice. Intratumoral hMIP-1β gene transfer also induced powerful tumor-specific CTL responses in vivo. The therapeutic effects of hMIP-1β gene therapy were greatly reduced following in vivo depletion of both CD4^ and CD8~ T cells, but were unaffected by depletion of single T cell subsets. Immune cell depletion experiments also revealed that NK cells played an important role in hMIP-1β-induced antitumor responses. These results suggest that intratumoral expression of hMIP-1β has the potential effect to induce host antitumor immunity and may prove to be a useful form of cancer gene therapy.     

DC-SIGN and immunoregulation

Dendritic cells （DCs） are known to be the most powerful professional antigen-presenting cells so far. It could activate primary immune response, and also downregulate immune response. DCs have a unique character of immunoregulation. DC-SIGN, a molecule designated as CD209, is one member of the C-type lectin superfamily. It is not only a pattern recognition receptor but implicated in immunoregulation of DCs. DC-SIGN has become hotspot of recent studies because of its important role in mediating DC adhesion, migration, inflammation, activating primary T cell, triggering immune response and participating in immune escape of pathogens and tumors. These studies on DC-SIGN involved in primary and secondary immune response and relevant mechanism will certainly provide us with a new method in treating and preventing certain diseases.     

Dendritic cells as a pharmacological target of traditional Chinese medicine

Dendritic cells （DCs） represent a heterogeneous population of professional antigen-presenting cells （APCs） that play a central role in the initiation and regulation of immune responses. There is considerable evidence that DCs can be used as therapeutic targets for pharmacological modulation of immune responses. Traditional Chinese medicine （TCM） has a long-standing history of using herbal medicine in the treatment of variety of human diseases. Many of the clinical effects of TCM have reportedly been attributed to the up- or down-regulation of immune responses. Accumulating evidence indicates that TCM and its components can interfere with immune responses at the earliest stage by targeting key functions of DCs. Here, we review those published studies of TCM with respect to their effects on immunobiological functions of DCs. Investigations based on both chemical entities derived from TCM as well as TCM herbal mixtures are presented. These studies suggest that various TCM herbal medicines have the capacity to inhibit or promote major functions of DCs, such as differentiation, maturation, cytokine production, survival, antigen uptake and presentation as well as trafficking. These studies have revealed novel biological effects of TCM and documented the utility of this approach to discover novel biological modifier of DC functions derived from natural sources.     

Liaison between natural killer cells and dendritic cells in human gestation

A successful pregnancy relies on immunological adaptations that allow the fetus to grow and develop in the uterus, despite being recognized by maternal immune cells. Among several immunocompetent cell types present within the human maternal/fetal interface, DC-SIGN~ dendritic cells （DCs） and CD56＋ natural killer （NK） cells are of major importance for early pregnancy maintenance, not only generating maternal immunological tolerance but also regulating stromal cell differentiation. Previous reports show the presence of NK-DC cell conjugates in first trimester human decidua, suggesting that these cells may play a role in the modulation of the local immune response within the uterus. While effective immunity is necessary to protect the mother from harmful pathogens, some form of tolerance must be activated to avoid an immune response against fetal antigens. This review article discusses current evidence concerning the functions of DC and NK cells in pregnancy and their liaison in human decidua.     

Interleukin 17-Producing γδT Cells Increased in Patients with Active Pulmonary Tuberculosis

Although it has been known that y8 T cells may play an important role in the immune response to infection of Mycobacterium tuberculosis (M. tb), the mechanisms by which the T8 T cells participate in the innate and/or acquired immunity to tuberculosis (TB) have not been full elucidated. In the present study, 27 patients with active pulmonary TB and 16 healthy donors (HD) were performed. We found that proportion of IL-17-producing cells among lymphocyte was similar between TB patients and HD, whereas the proportions of γδ T cells in IL-17- producing cells (59.2%) and IL-17-producing cells in γδ T cells (19.4%) in peripheral blood were markedly increased in TB patients when compared to those in HD (43.9% and 7.7%, respectively). In addition, the proportions of IFN-γ-producing γδ T cells in TB patients were obviously lower than that in HD. Upon re-stimulated with M. tb heat-treated antigen (M. tb-HAg) in vitro, fewer IL-17-producing γδ T cells were generated from HD and TB patients, whereas IFN-γ-producing γδ T cells were increased in TB patients compared to that in HD. Our findings in TB patients and healthy human were consistent with other murine investigation that the IL-17- producing γδ T cells were main source of IL-17 in mouse model of BCG infection, suggesting that γδ T cells might be involved in the formation of tubercular granuloma in pulmonary TB patients, but need further identification. Cellular & Molecular Immunology. 2008;5(3):203-208.