Lysis of a broad range of epithelial tumour cells by human gamma delta T cells: involvement of NKG2D ligands and T-cell receptor- versus NKG2D-dependent recognition

LS. Dynamics of Circulating γδ T Cell Activity in an Immunocompetent Mouse Model of High-Grade Glioma

Human γδ T cells are potent effectors against glioma cell lines in vitro and in human/mouse xenograft models of glioblastoma, however, this effect has not been investigated in an immunocompetent mouse model. In this report, we established GL261 intracranial gliomas in syngeneic WT C57BL/6 mice and measured circulating γδ T cell count, phenotype, Vγ/Vδ repertoire, tumor histopathology, NKG2D ligands expression, and T cell invasion at day 10-12 post-injection and at end stage. Circulating γδ T cells transiently increased and upregulated Annexin V expression at post-tumor day 10-12 followed by a dramatic decline in γδ T cell count at end stage. T cell receptor repertoire showed no changes in Vγ1, Vγ4, Vγ7 or Vδ1 subsets from controls at post-tumor day 10-12 or at end stage except for an end-stage increase in the Vδ4 population. Approximately 12% of γδ T cells produced IFN-γ. IL-17 and IL-4 producing γδ T cells were not detected. Tumor progression was the same in TCRδ-/- C57BL/6 mice as that observed in WT mice, suggesting that γδ T cells exerted neither a regulatory nor a sustainable cytotoxic effect on the tumor. WT mice that received an intracranial injection of γδ T cells 15m following tumor placement showed evidence of local tumor growth inhibition but this was insufficient to confer a survival advantage over untreated controls. Taken together, our findings suggest that an early nonspecific proliferation of γδ T cells followed by their depletion occurs in mice implanted with syngeneic GL261 gliomas. The mechanism by which γδ T cell expansion occurs remains a subject for further investigation of the mechanisms responsible for this immune response in the setting of high-grade glioma.

Harnessing the power of Vδ2 cells in cancer immunotherapy

γδ T cells are a subset of T lymphocytes that have been implicated in immunosurveillance against infections and tumours. In the peripheral blood of humans the γδ T cell pool is made up predominantly of Vδ2 cells, which can detect both foreign and self-metabolites of the isoprenoid biosynthesis pathway. This unique axis of antigen recognition enables Vδ2 cells to respond to a range of pathogenic infections as well as perturbations in endogenous isoprenoid biosynthesis that can occur during cell stress and malignant transformation. There has been growing interest in Vδ2 cells as a potential avenue for cancer immunotherapy, and a number of strategies have been utilized in an attempt to boost the anti-tumour response of Vδ2 cells in patients. In this review we discuss critically the evidence that Vδ2 cells contribute to the cytotoxic response against tumours and evaluate current immunotherapeutic approaches that target these cells in cancer patients, with specific focus on their shortcomings and how they may be improved.

γδ T cells and epigenetic drugs: A useful merger in cancer immunotherapy?

γδ T cell-based immunotherapeutic strategies in cancer patients are as yet of limited success. Drugs targeting epigenetic mechanisms including histone acetylation and DNA methylation trigger cell death in tumor cells but in addition have immunomodulatory activity. Here, we discuss the potential benefit of combining both strategies in cancer immunotherapy.

Modulation of human gamma/delta T-cell activation and phenotype by histone deacetylase inhibitors

Histone deacetylase inhibitors have been shown to possess therapeutic potential in various pathophysiological conditions. Valproic acid (VPA), a known histone deacetylase class I inhibitor, has been studied for its influence on immune cell functions. However, the potential impact of VPA on human γδ T-cells remains unknown. Here we investigated the effects of VPA on the proliferation and the immunophenotype of human γδ T-cells. We observed dose-dependent inhibition of proliferation, associated with significant cell death as revealed by flow cytometry. The cellular response to VPA clearly showed differential modulation of cell surface markers on γδ T-cells when compared to αβ T-cells. Furthermore, histone H3 acetylation was detected in γδ T-cells even at toxic concentrations of VPA. Our investigations focusing on the impact of VPA on human γδ T-cells will be helpful in understanding its safety profile in clinical application, particularly in the context of γδ T-cell-targeted immunotherapy.

Inhibition of human γδ T cell proliferation and effector functions by neutrophil serine proteases

Human peripheral blood γδ T cells expressing the Vγ9Vδ2 T cell receptor are activated by microbial or endogenous pyrophosphate antigens and indirectly by nitrogen-containing bisphosphonates. Apart from proliferation, such phosphoantigens induce proinflammatory cytokine production including TNF-α and IFN-γ and trigger cytotoxic effector function. Neutrophil granulocytes are known to modulate T cell activation. The neutrophil serine proteases proteinase 3, elastase and cathepsin G have multiple potential targets and promote microbial killing. In this study, we investigated the effect of the three serine proteases on the in vitro proliferation and effector functions of γδ T cells cultured in serum-free medium. All three proteases inhibited the proliferative activity, suppressed the cytokine production and decreased the cytotoxicity of γδ T cells. Further studies indicated that proteolytic cleavage of IL-2 and modulation of butyrophilin 3A1 (CD277) expression might contribute to the overall inhibition.

Zoledronic acid causes γδ T cells to target monocytes and down-modulate inflammatory homing

Zoledronic acid (ZA) is a potential immunotherapy for cancer because it can induce potent γδ T-cell-mediated anti-tumour responses. Clinical trials are testing the efficacy of intravenous ZA in cancer patients; however, the effects of systemic ZA on the activation and migration of peripheral γδ T cells remain poorly understood. We found that γδ T cells within ZA-treated peripheral blood mononuclear cells were degranulating, as shown by up-regulated expression of CD107a/b. Degranulation was monocyte dependent because CD107a/b expression was markedly reduced in the absence of CD14(+) cells. Consistent with monocyte-induced degranulation, we observed γδ T-cell-dependent induction of monocyte apoptosis, as shown by phosphatidylserine expression on monocytes and decreased percentages of monocytes in culture. Despite the prevailing paradigm that ZA promotes tumour homing in γδ T cells, we observed down-modulation of their tumour homing capacity, as shown by decreased expression of the inflammatory chemokine receptors CCR5 and CXCR3, and reduced migration towards the inflammatory chemokine CCL5. Taken together our data suggest that ZA causes γδ T cells to target monocytes and down-modulate the migratory programme required for inflammatory homing. This study provides novel insight into how γδ T cells interact with monocytes and the possible implications of systemic use of ZA in cancer.

CD3+ CD4+ and CD3+ CD8+ lymphocyte subgroups and their surface receptors NKG2D and NKG2A in patients with non-small cell lung cancer

BACKGROUND

To explore the prevalence of lymphocyte subgroups CD3+ CD4+ and CD3+ CD8+ and their surface receptors NKG2D and NKG2A in patients with non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

A total of 40 patients with NSCLC were divided into different groups according to different clinical factors (TNM staging, pathological patterns and genders) for assessment of relations with CD3+ CD4+ and CD3+ CD8+ and the surface receptors NKG2D and NKG2A of T lymphocytes in peripheral blood by flow cytometry.

RESULTS

Patients in the advanced group had evidently lower levels of CD3+ CD4+ but markedly higher levels of CD3+ CD8+ in peripheral blood than those with early lesions (p<0.05). In addition, NSCLC patients in the advanced group had obviously higher CD3+ CD4+ NKG2D and CD3+ CD8+ NKG2A expression rates but lower CD3+ CD4+ NKG2A and CD3+ CD8+ NKG2D expression rates (p<0.05). However, there were no significant differences between NSCLC patients with different genders and pathological patterns in expression levels of lymphocyte subgroups CD3+ CD4+ and CD3+ CD8+ and their surface receptors NKG2D and NKG2A.

CONCLUSIONS

Unbalanced expression of surface receptors NKG2D and NKG2A in CD3+ CD4+ and CD3+ CD8+ lymphocytes may be associated with a poor prognosis, greater malignancy and immunological evasion by advanced cancers, related to progression of lung cancer.

Novel synthesis of fluorochrome-coupled zoledronate with preserved functional activity on gamma/delta T cells and tumor cells

A novel fluorescent derivative of bisphosphonate zoledronate was synthesized and shown to have comparable functional activity as native zoledronate.

Clinical applications of gamma delta T cells with multivalent immunity

γδ T cells hold promise for adoptive immunotherapy because of their reactivity to bacteria, viruses, and tumors. However, these cells represent a small fraction (1–5%) of the peripheral T-cell pool and require activation and propagation to achieve clinical benefit. Aminobisphosphonates specifically expand the Vγ9Vδ2 subset of γδ T cells and have been used in clinical trials of cancer where objective responses were detected. The Vγ9Vδ2 T cell receptor (TCR) heterodimer binds multiple ligands and results in a multivalent attack by a monoclonal T cell population. Alternatively, populations of γδ T cells with oligoclonal or polyclonal TCR repertoire could be infused for broad-range specificity. However, this goal has been restricted by a lack of applicable expansion protocols for non-Vγ9Vδ2 cells. Recent advances using immobilized antigens, agonistic monoclonal antibodies (mAbs), tumor-derived artificial antigen presenting cells (aAPC), or combinations of activating mAbs and aAPC have been successful in expanding gamma delta T cells with oligoclonal or polyclonal TCR repertoires. Immobilized major histocompatibility complex Class-I chain-related A was a stimulus for γδ T cells expressing TCRδ1 isotypes, and plate-bound activating antibodies have expanded Vδ1 and Vδ2 cells ex vivo. Clinically sufficient quantities of TCRδ1, TCRδ2, and TCRδ1^negTCRδ2^neg have been produced following co-culture on aAPC, and these subsets displayed differences in memory phenotype and reactivity to tumors in vitro and in vivo. Gamma delta T cells are also amenable to genetic modification as evidenced by introduction of αβ TCRs, chimeric antigen receptors, and drug-resistance genes. This represents a promising future for the clinical application of oligoclonal or polyclonal γδ T cells in autologous and allogeneic settings that builds on current trials testing the safety and efficacy of Vγ9Vδ2 T cells.

Plasticity of γδ T Cells: Impact on the Anti-Tumor Response

The tumor immune microenvironment contributes to tumor initiation, progression, and response to therapy. Among the immune cell subsets that play a role in the tumor microenvironment, innate-like T cells that express T cell receptors composed of γ and δ chains (γδ T cells) are of particular interest. γδ T cells can contribute to the immune response against many tumor types (lymphoma, myeloma, melanoma, breast, colon, lung, ovary, and prostate cancer) directly through their cytotoxic activity and indirectly by stimulating or regulating the biological functions of other cell types required for the initiation and establishment of the anti-tumor immune response, such as dendritic cells and cytotoxic CD8+ T cells. However, the notion that tumor-infiltrating γδ T cells are a good prognostic marker in cancer was recently challenged by studies showing that the presence of these cells in the tumor microenvironment was associated with poor prognosis in both breast and colon cancer. These findings suggest that γδ T cells may also display pro-tumor activities. Indeed, breast tumor-infiltrating γδ T cells could exert an immunosuppressive activity by negatively regulating dendritic cell maturation. Furthermore, recent studies demonstrated that signals from the microenvironment, particularly cytokines, can confer some plasticity to γδ T cells and promote their differentiation into γδ T cells with regulatory functions. This review focuses on the current knowledge on the functional plasticity of γδ T cells and its effect on their anti-tumor activities. It also discusses the putative mechanisms underlying γδ T cell expansion, differentiation, and recruitment in the tumor microenvironment.

Human Vδ2 versus non-Vδ2 γδ T cells in antitumor immunity

The Vδ2 and non-Vδ2 (mainly Vδ1) subsets of human γδ T cells have distinct homing patterns and recognize different types of ligands, yet both exert potent antitumor effects. While the T-cell receptor of Vδ2 T cells primarily recognizes tumor cell-derived pyrophosphates, non-Vδ2 γδ T cells preferentially recognize stress-associated surface antigens. Here, we discuss the pros and cons of Vδ2 versus non-Vδ2 γδ T cells as tools for future immunotherapeutic interventions against cancer.

Tumor cell recognition by γδ T lymphocytes: T-cell receptor vs. NK-cell receptors

The dissection of the molecular mechanisms underlying tumor-cell recognition by γδ T-cells is crucial to improve their performance in cancer immunotherapy. Here, we discuss the controversy around the relative contributions of the γδ T-cell receptor (TCR) and natural killer receptors (NKRs) to tumor-cell targeting by γδ T cells.

Murine CD27(-) Vγ6(+) γδ T cells producing IL-17A promote ovarian cancer growth via mobilization of protumor small peritoneal macrophages

Cancer-associated inflammation mobilizes a variety of leukocyte populations that can inhibit or enhance tumor cell growth in situ. These subsets include γδ T cells, which can infiltrate tumors and typically provide large amounts of antitumor cytokines, such as IFN-γ. By contrast, we report here that in a well-established transplantable (ID8 cell line) model of peritoneal/ovarian cancer, γδ T cells promote tumor cell growth. γδ T cells accumulated in the peritoneal cavity in response to tumor challenge and could be visualized within solid tumor foci. Functional characterization of tumor-associated γδ T cells revealed preferential production of interleukin-17A (IL-17), rather than IFN-γ. Consistent with this finding, both T cell receptor (TCR)δ-deficient and IL-17-deficient mice displayed reduced ID8 tumor growth compared with wild-type animals. IL-17 production by γδ T cells in the tumor environment was essentially restricted to a highly proliferative CD27((-)) subset that expressed Vγ6 instead of the more common Vγ1 and Vγ4 TCR chains. The preferential expansion of IL-17-secreting CD27((-)) Vγ6((+)) γδ T cells associated with the selective mobilization of unconventional small peritoneal macrophages (SPMs) that, in comparison with large peritoneal macrophages, were enriched for IL-17 receptor A, and for protumor and proangiogenic molecular mediators, which were up-regulated by IL-17. Importantly, SPMs were uniquely and directly capable of promoting ovarian cancer cell proliferation. Collectively, this work identifies an IL-17-dependent lymphoid/myeloid cross-talk involving γδ T cells and SPMs that promotes tumor cell growth and thus counteracts cancer immunosurveillance.

Expression of stress ligands of the immunoreceptor NKG2D in melanoma: regulation and clinical significance

Tumor cells, in particular melanoma cells, can be detected as abnormal self by cytotoxic lymphocytes of the innate and adaptive immune system. Of major importance in this process is the activating lymphocyte receptor NKG2D that in humans binds to MIC and ULBP surface molecules on tumor cells. Expression of NKG2D ligands (NKG2DL) is an early event in malignant transformation, induced by stress-associated and oncogene-driven pathways. Thus NKG2DL expression is considered as an innate barrier against tumor development. However, tumor cells can overcome this barrier by shedding of NKG2DL. Ligand shedding leads to elevated levels of soluble ligands in sera of tumor patients that in case of melanoma are of strong prognostic relevance. Here we review important aspects of NKG2DL expression and regulation in tumor cells with a focus on melanoma, and discuss their clinical relevance and potential in immunotherapy.

Human γδ thymocytes are functionally immature and differentiate into cytotoxic type 1 effector T cells upon IL-2/IL-15 signaling

Cytotoxicity and IFN-γ production by human γδ T cells underlie their potent antitumor functions. However, it remains unclear where and how human γδ T cells acquire these key effector properties. Given the recent disclosure of a major contribution of the thymus to murine γδ T cell functional differentiation, in this study we have analyzed a series of human pediatric thymuses. We found that ex vivo-isolated γδ thymocytes produced negligible IFN-γ and lacked cytolytic activity against leukemia cells. However, these properties were selectively acquired upon stimulation with IL-2 or IL-15, but not IL-4 or IL-7. Unexpectedly, TCR activation was dispensable for these stages of functional differentiation. The effects of IL-2/IL-15 depended on MAPK/ERK signaling and induced de novo expression of the transcription factors T-bet and eomesodermin, as well as the cytolytic enzyme perforin, required for the cytotoxic type 1 program. These findings have implications for the manipulation of γδ T cells in cancer immunotherapy.

An unconventional TRAIL to cancer therapy

Cellular immunotherapy offers novel, safe, and effective routes to treating cancer. However, approaches utilizing cytotoxic CD8(+) T cells are hampered by the need to identify suitable target antigens that are expressed by tumor cells but not healthy tissues, and that are recognized with sufficient affinity. Most importantly, the applicability of CD8(+) T-cell-based therapies is governed by the MHC restriction of tumor-specific epitopes, thereby limiting the potential benefit to patients carrying the appropriate MHC haplotype. Alternative approaches to harness the immune system against tumors exploit non-MHC-restricted γδ T cells that recognize stress-induced changes in transformed cells. A new report in this issue of the European Journal of Immunology [Eur. J. Immunol. 2013. 43: 3175-3182] shows that human γδ T cells efficiently kill lung cancer cells through recognition of the NKG2D ligand ULBP2 and secretion of soluble TRAIL. This finding provides new evidence for a TCR-independent cytotoxicity of γδ T cells and supports their promising potential for non-MHC-restricted immunotherapies.

At the Bench: Preclinical rationale for exploiting NK cells and γδ T lymphocytes for the treatment of high-risk leukemias

NK cells and γδ T lymphocytes display potent cytolytic activity against leukemias and CMV-infected cells and are thus, promising immune effector cells in the context of allo-HSCT. NK cells express HLA class I-specific inhibitory receptors and preferentially kill HLA class I(low) tumors or virus-infected cells. Killing occurs upon engagement of activating NKRs with ligands that are up-regulated on tumors and infected cells. A similar activating receptor/ligand interaction strategy is used by γδ T cells, which in addition, use their TCRs for recognition of phosphorylated antigens and still largely undefined ligands on tumor cells. In the haploidentical allo-HSCT setting, alloreactive NK cells, derived from donor HSCs, can exert potent antileukemia activity and kill residual patient DCs and T cells, thus preventing GvHD and graft rejection. However, generation of KIR(+) alloreactive NK cells from HSCs requires many weeks, during which leukemia relapses, and life-threatening infections may occur. Importantly, mature NK cells and γδ T cells can control certain infectious agents efficiently, in particular, limit CMV reactivation, and infusion of such donor cells at the time of HSCT has been implemented. Development of novel, cell-based immunotherapies, allowing improved trafficking and better targeting, will endow NK cells and γδ T lymphocytes with enhanced anti-tumor activity, also making them key reagents for therapies against solid tumors. The clinical aspects of using NK cells and γδ T lymphocytes against hematological malignancies, including the allo-HSCT context, are reviewed in the related side-by-side paper by Locatelli and colleagues [1].

Enhancement effect of dihydroartemisinin on human γδ T cell proliferation and killing pancreatic cancer cells

γδ T cells play important roles in innate immunity against tumors and infections. Inhibitory effect of dihydroartemisinin on growth of cancer cells has been found in recent years. In this study, we investigated the effect of dihydroartemisinin on human γδ T cell proliferation by MTT assay and killing activity against pancreatic cancer cells SW1990, BxPC-3 and PANC-1 by LDH release assay in vitro. Intracellular molecule alterations were verified by flow cytometry. The results suggested that appropriate concentration of dihydroartemisinin favored the expansion of γδ T cells and enhanced γδ T cell mediated killing activity against pancreatic cancer cells. Up-regulation of intracellular perforin, granzyme B expression and IFN-γ production may be the important mechanism of dihydroartemisinin on increased antitumor activity of γδ T cells.

Phenotype and regulation of immunosuppressive Vδ2-expressing γδ T cells

The proliferation and interleukin-2 production of CD4(+)CD25(-) αβ T cells were inhibited in a cell-contact manner by Vδ2 γδ T cells. The transcription factor Helios was constitutively expressed in about one-third of circulating γδ T cells and was upregulated by CD28-signaling. Our data suggest that Helios could serve as a marker for differential activation status rather than for regulatory T cells (Treg). Our findings also indicate that the interaction of CD86 on activated Vδ2 T cells and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) on activated αβ T cells mediated the suppression because the suppressive effect was abolished by blocking the CD86:CTLA-4 interaction. Pre-treatment of Vδ2 T cells with Toll-like receptor 2 ligands enhanced phosphorylation of MAPKs, Akt, and NF-κB and partially abrogated the suppressive capacity, whereas on co-cultured responder T cells inhibitory molecules were downregulated and Akt and NF-κB phosphorylation was restored. Our results suggest that the regulation of αβ T cell proliferation by activated Vδ2 T cells might contribute to fine-tuning of αβ T cell responses.

Generation of soluble NKG2D ligands: proteolytic cleavage, exosome secretion and functional implications

The activating natural killer group 2 member D (NKG2D) receptor is expressed on NK cells, cytotoxic T cells and additional T cell subsets. Ligands for human NKG2D comprise two groups of MHC class I-related molecules, the MHC class I chain-related proteins A and B (MICA/B) and 6 UL16-binding proteins (ULBP1-6). While NKG2D ligands are absent from most normal cells, expression is induced upon stress and malignant transformation. In fact, most solid tumours and leukaemia/lymphomas constitutively express at least one NKG2D ligand and thereby are susceptible to NKG2D-dependent immunosurveillance. However, soluble NKG2D ligands are released from tumour cells and can down-modulate NKG2D activation as a means of tumour immune escape. In some tumour entities, levels of soluble NKG2D ligands in the serum correlate with tumour progression. NKG2D ligands can be proteolytically shed from the cell surface or liberated from the membrane by phospholipase C in the case of glycosylphosphatidylinositol (GPI)-anchored molecules. Moreover, NKG2D ligands can be secreted in exosomal microvesicles together with other tumour-derived molecules. Depending on the specific tumour/immune cell setting, these various forms of soluble and/or exosome-bound NKG2D ligands can exert multiple effects on NKG2D/NKG2D ligand interactions. In this review, we focus on the role of various proteases in the shedding of human NKG2D ligands from tumour cells and discuss the not completely unanimous reported functional implications of soluble and exosome-secreted NKG2D ligands for immunosurveillance.

A novel antibody-like TCRγδ-Ig fusion protein exhibits antitumor activity against human ovarian carcinoma

TCRγ9δ2(OT3) is a tumor-specific TCR with an unique complementarity-determining region 3 (CDR3) sequence, referred to as OT3, in its δ2 chain. This region was identified in tumor-infiltrating lymphocytes (TILs) from human ovarian epithelial carcinoma. We demonstrated that TCRγ9δ2(OT3)-Fc, a fusion protein composed of the complete extracellular domains of the γ9 and δ2 chains linked to the Fc domains of human IgG1, exhibited successful binding to multiple human carcinoma cell lines. In vitro, TCRγ9δ2(OT3)-Fc mediated cell killing via antibody-dependent cellular cytotoxicity (ADCC) in a dose-dependent manner. In vivo, TCRγ9δ2(OT3)-Fc significantly inhibited tumor growth and enhanced survival in human ovarian carcinoma xenograft models. Our findings suggest that the TCRγ9δ2(OT3)-Fc fusion protein possesses both the antigen-recognition properties of TCR γδ and the Fc-mediated effector functions of the antibody.

Chemotherapy sensitizes colon cancer initiating cells to Vγ9Vδ2 T cell-mediated cytotoxicity

Colon cancer comprises a small population of cancer initiating stem cells (CIC) that is responsible for tumor maintenance and resistance to anti-cancer therapies, possibly allowing for tumor recapitulation once treatment stops. Combinations of immune-based therapies with chemotherapy and other anti-tumor agents may be of significant clinical benefit in the treatment of colon cancer. However, cellular immune-based therapies have not been experimented yet in the population of colon CICs. Here, we demonstrate that treatment with low concentrations of commonly used chemotherapeutic agents, 5-fluorouracyl and doxorubicin, sensitize colon CICs to Vγ9Vδ2 T cell cytotoxicity. Vγ9Vδ2 T cell cytotoxicity was largely mediated by TRAIL interaction with DR5, following NKG2D-dependent recognition of colon CIC targets. We conclude that in vivo activation of Vγ9Vδ2 T cells or adoptive administration of ex-vivo expanded Vγ9Vδ2 T cells at suitable intervals after chemotherapy may substantially increase anti-tumor activities and represent a novel strategy for colon cancer immunotherapy.

Comparison of γδ T cell responses and farnesyl diphosphate synthase inhibition in tumor cells pretreated with zoledronic acid

Exposing human tumor cells to nitrogen-containing bisphosphonates, such as zoledronic acid (Zol), greatly increases their susceptibility to killing by γδ T cells. Based on this finding and other studies, cancer immunotherapy using γδ T cells and nitrogen-containing bisphosphonates has been studied in pilot clinical trials and has shown benefits. Although Zol treatment can render a wide variety of human tumor cells susceptible to γδ T cell killing, there has not been a systematic investigation to determine which types of tumor cells are the most susceptible to γδ T cell-mediated cytotoxicity. In this study, we determined the Zol concentrations required to stimulate half maximal tumor necrosis factor-α production by γδ T cells cultured with various tumor cell lines pretreated with Zol and compared these concentrations with those required for half maximal inhibition of farnesyl diphosphate synthase (FPPS) in the same tumor cell lines. The inhibition of tumor cell growth by Zol was also assessed. We found that FPPS inhibition strongly correlated with γδ T cell activation, confirming that the mechanism underlying γδ T cell activation by Zol is isopentenyl diphosphate (IPP) accumulation due to FPPS blockade. In addition, we showed that γδ T-cell receptor-mediated signaling correlated with γδ T cell tumor necrosis factor-α production and cytotoxicity. Some lymphoma, myeloid leukemia, and mammary carcinoma cell lines were relatively resistant to Zol treatment, suggesting that assessing tumor sensitivity to Zol may help select those patients most likely to benefit from immunotherapy with γδ T cells.

The multifunctionality of human Vγ9Vδ2 γδ T cells: clonal plasticity or distinct subsets?

The dominant subset of γδ T cells in human peripheral blood expresses Vγ9 paired with Vδ2 as variable TCR elements. Vγ9Vδ2 T cells recognize pyrophosphates derived from the microbial non-mevalonate isoprenoid biosynthesis pathway at pico- to nanomolar concentrations. Structurally related pyrophosphates are generated in eukaryotic cells through the mevalonate pathway involved in protein prenylation and cholesterol synthesis. However, micromolar concentrations of endogenous pyrophosphates are required to be recognized by Vγ9Vδ2 T cells. Such concentrations are not produced by normal cells but can accumulate upon cellular stress and transformation. Therefore, many tumour cells are susceptible to γδ T cell-mediated lysis owing to the overproduction of endogenous pyrophosphates. This explains why Vγ9Vδ2 T cells contribute to both anti-infective and anti-tumour immunity. Ex vivo analysed Vγ9Vδ2 T cells can be subdivided on the basis of additional surface markers, including chemokine receptors and markers for naïve and memory T cells. At the functional level, Vγ9Vδ2 T cells produce a broad range of cytokines, display potent cytotoxic activity, regulate αβ T cell responses, and - quite surprisingly - can act as professional antigen-presenting cells. Thus, an exceptional range of effector functions has been assigned to a population of T cells, which all recognize invariant exogenous or endogenous pyrophosphates that are not seen by any other immune cell. Here, we discuss whether this plethora of effector functions reflects the plasticity of individual Vγ9Vδ2 T cells or can be assigned to distinct subsets.

Defining the nature of human γδ T cells: a biographical sketch of the highly empathetic

The elusive task of defining the character of γδ T cells has been an evolving process for immunologists since stumbling upon their existence during the molecular characterization of the α and β T cell receptor genes of their better understood brethren. Defying the categorical rules used to distinctly characterize lymphocytes as either innate or adaptive in nature, γδ T cells inhabit a hybrid world of their own. At opposing ends of the simplified spectrum of modes of antigen recognition used by lymphocytes, natural killer and αβ T cells are particularly well equipped to respond to the 'missing self' and the 'dangerous non-self', respectively. However, between these two reductive extremes, we are chronically faced with the challenge of making peace with the 'safe non-self' and dealing with the inevitable 'distressed self', and it is within this more complex realm γδ T cells excel thanks to their highly empathetic nature. This review gives an overview of the latest insights revealing the unfolding story of human γδ T cells, providing a biographical sketch of these unique lymphocytes in an attempt to capture the essence of their fundamental nature and events that influence their life trajectory. What hangs in their balance is their nuanced ability to differentiate the friends from the foe and the pathological from the benign to help us adapt swiftly and efficiently to life's many stresses.

Role of gamma-delta T-cells in cancer: another opening door to immunotherapy

The gamma-delta (γδ) T-cells are a subset of T-lymphocytes characterized by the presence of a surface antigen recognition complex type 2. Those γδ T-cells represent 2-5 % of peripheral T-cells only, but they are common in organs and mucosae, acting as a first defense system in the entries to the organism. The γδ T-cells take part on immune response by direct cytolysis, development of memory phenotypes, and modulation of immune cells, and they have been implied in autoimmune disorders, immune deficiencies, infections, and tumor diseases. We reported the role of γδ T-cells in oncology, focusing in their potential applications for cancer treatment. Experimental designs and clinical trials in the treatment of solid malignancies are extensively reviewed.

Immunomodulation at epithelial sites by obesity and metabolic disease

Obesity and related type 2 diabetes are increasing at epidemic proportions globally. It is now recognized that inflammatory responses mediated within the adipose tissue in obesity are central to the development of disease. Once initiated, chronic inflammation associated with obesity leads to the modulation of immune cell function. This review will focus specifically on the impact of obesity on γδ T cells, a T-cell subset that is found in high concentrations in epithelial tissues such as the skin, intestine, and lung. Epithelial γδ T cell function is of particular concern in obesity as they are the guardians of the epithelial barrier and mediate repair. A breakdown in their function, and subsequently the deterioration of the epithelium can result in dire consequences for the host. Obese patients are more prone to non-healing injuries, infection, and disease. The resulting inflammation from these pathologies further perpetuates the disease condition already present in obese hosts. Here we will provide insight into the immunomodulation of γδ T cells that occurs in the epithelial barrier during obesity and discuss current therapeutic options.

Lung cancer: a classic example of tumor escape and progression while providing opportunities for immunological intervention

Lung cancers remain one of the most common and deadly cancers in the world today (12.5% of newly diagnosed cancers) despite current advances in chemo- and radiation therapies. Often, by the time these tumors are diagnosed, they have already metastasized. These tumors demonstrate the classic hallmarks of cancer in that they have advanced defensive strategies allowing them to escape various standard oncological treatments. Immunotherapy is making inroads towards effectively treating other fatal cancers, such as melanoma, glioblastoma multiforme, and castrate-resistant prostate cancers. This paper will cover the escape mechanisms of bronchogenic lung cancer that must be overcome before they can be successfully treated. We also review the history of immunotherapy directed towards lung cancers.

Human Vdelta1 gamma-delta T cells exert potent specific cytotoxicity against primary multiple myeloma cells

BACKGROUND AIMS

Human gamma-delta (γδ) T cells are potent effector lymphocytes of innate immunity involved in anti-tumor immune surveillance. However, the Vδ1 γδ T-cell subset targeting multiple myeloma (MM) has not previously been investigated.

METHODS

Vδ1 T cells were purified from peripheral blood mononuclear cells of healthy donors and patients with MM by immunomagnetic sorting and expanded with phytohemagglutinin (PHA) together with interleukin (IL)-2 in the presence of allogeneic feeders. Vδ1 T cells were phenotyped by flow cytometry and used in a 4-h flow cytometric cytotoxicity assay. Cytokine release and blocking studies were performed. Primary myeloma cells were purified from MM patients' bone marrow aspirates.

RESULTS

Vδ1 T cells expanded from healthy donors displayed prominent cytotoxicity by specific lysis against patients' CD38 (+) CD138 (+) bone marrow-derived plasma cells. Vδ1 T cells isolated from MM patients showed equally significant killing of myeloma cells as Vδ1 T cells from normal donors. Vδ1 T cells showed similarly potent cytotoxicity against myeloma cell lines U266 and RPMI8226 and plasma cell leukemia ARH77 in a dose-dependent manner. The interferon (IFN)-γ secretion and Vδ1 T-cell cytotoxicity against myeloma cells was mediated in part through the T-cell receptor (TCR) in addition to involvement of Natural killer-G2D molecule (NKG2D), DNAX accessory molecule-1 (DNAM-1), intracellular cell adhesion molecule (ICAM)-1, CD3 and CD2 receptors. In addition, Vδ1 T cells were shown to exert anti-myeloma activity equal to that of Vδ2 T cells.

CONCLUSIONS

We have shown for the first time that Vδ1 T cells are highly myeloma-reactive and have therefore established Vδ1 γδ T cells as a potential candidate for a novel tumor immunotherapy.

Mycobacteria activate γδ T-cell anti-tumour responses via cytokines from type 1 myeloid dendritic cells: a mechanism of action for cancer immunotherapy

Attenuated and heat-killed mycobacteria display demonstrable activity against cancer in the clinic; however, the induced immune response is poorly characterised and potential biomarkers of response ill-defined. We investigated whether three mycobacterial preparations currently used in the clinic (BCG and heat-killed Mycobacterium vaccae and Mycobacterium obuense) can stimulate anti-tumour effector responses in human γδ T-cells. γδ T-cell responses were characterised by measuring cytokine production, expression of granzyme B and cytotoxicity against tumour target cells. Results show that γδ T-cells are activated by these mycobacterial preparations, as indicated by upregulation of activation marker expression and proliferation. Activated γδ T-cells display enhanced effector responses, as shown by upregulated granzyme B expression, production of the T_H1 cytokines IFN-γ and TNF-α, and enhanced degranulation in response to susceptible and zoledronic acid-treated resistant tumour cells. Moreover, γδ T-cell activation is induced by IL-12, IL-1β and TNF-α from circulating type 1 myeloid dendritic cells (DCs), but not from type 2 myeloid DCs or plasmacytoid DCs. Taken together, we show that BCG, M. vaccae and M. obuense induce γδ T-cell anti-tumour effector responses indirectly via a specific subset of circulating DCs and suggest a mechanism for the potential immunotherapeutic effects of BCG, M. vaccae and M. obuense in cancer.

Functional expression of NOD2 in freshly isolated human peripheral blood γδ T cells

γδ T cells play an important role in anti-infective immunity. The major subset of human γδ T cells selectively recognizes phosphorylated bacterial metabolites of the isoprenoid biosynthesis pathway, so-called phosphoantigens. The activation of γδ T cells is modulated by functionally expressed innate immune receptors, notably Toll-like receptor 2 and 3. It was also reported that in vitro expanded γδ T cells respond to muramyl dipeptide (MDP), the minimal peptidoglycan motif activating the nucleotide-binding oligomerization domain containing 2 (NOD2) receptor, although it is unknown whether ex vivo isolated human γδ T cells express functional NOD2. Here, we report that freshly isolated, highly purified peripheral blood γδ T cells express NOD2 mRNA and detectable amounts of NOD2 protein. The biologically active MDP L-D isomer but not the inactive D-D isomer augmented the interferon-γ (IFN-γ) secretion in phosphoantigen-stimulated peripheral blood mononuclear cells. Moreover, a moderate but reproducible and statistically significant increase in IFN-γ secretion was also observed when highly purified peripheral blood γδ T cells were activated by T cell receptor cross-linking in the presence of MDP. Taken together, our results indicate that in addition to the T cell receptor and Toll-like receptors, circulating human γδ T cells express NOD2 as a third class of pattern recognition receptor for sensing bacterial products.

Redirecting αβ T cells against cancer cells by transfer of a broadly tumor-reactive γδT-cell receptor

Major limitations of currently investigated αβT cells redirected against cancer by transfer of tumor-specific αβTCR arise from their low affinity, MHC restriction, and risk to mediate self-reactivity after pairing with endogenous α or βTCR chains. Therefore, the ability of a defined γ9δ2TCR to redirect αβT cells selectively against tumor cells was tested and its molecular interaction with a variety of targets investigated. Functional analysis revealed that a γ9δ2TCR efficiently reprograms both CD4(+) and CD8(+) αβT cells against a broad panel of cancer cells while ignoring normal cells, and substantially reduces but does not completely abrogate alloreactivity. γ9δ2TCR-transduced αβT cells reduced colony formation of progenitor cells of primary acute myeloid leukemia blasts and inhibited leukemia growth in a humanized mouse model. Thereby, metabolites of a dysregulated mevalonate pathway are targeted and the additional application of widely used biphosphonates is crucial for in vivo efficacy most likely because of its modulating effect on cytokine secretion of γ9δ2TCR-transduced αβT cells. Expression of NKG2D ligands and F1-ATPase contributed to the activity of γ9δ2TCR-transduced αβT cells but were not mandatory. In summary, γ9δ2 TCRs are an attractive alternative to broadly redirect αβT cells against cancer cells with both an improved efficacy and safety profile compared with currently used αβTCRs.

γδ T cells attenuate bleomycin-induced fibrosis through the production of CXCL10

γδ T cells are a subset of T cells associated with epithelial mucosal tissues and play a prominent role in both promoting and dampening inflammatory responses to pathogens; in addition, they strongly mediate epithelial repair. By using a bleomycin model of pulmonary fibrosis, we found that γδ T-cell populations dramatically increased after bleomycin administration. To determine the importance of these cells, we exposed mice lacking the δ chain of the γδ T-cell receptor (γδ knockout [KO]) to bleomycin. Pulmonary fibrosis was more severe in γδ KO mice, as measured by collagen deposition (hydroxyproline) and histopathological features. Furthermore, there was no evidence of resolution of the fibrotic response up to 45 days after bleomycin therapy. In contrast to control mice, γδ KO mice had decreased concentrations of IL-6, granulocyte colony stimulating factor, chemokine CXC ligand (CXCL) 1, and interferon inducible protein 10/CXCL10. In vitro culture of γδ T cells purified from lungs 17 days after bleomycin exposure (a time of peak influx of these cells) demonstrated that γδ T cells produced substantial quantities of all four of these cytokines, suggesting that γδ T cells are a predominant source of these proteins. To demonstrate that γδ T cells are effector cells in the fibrotic response, we performed adoptive transfer experiments with γδ T cells sorted from bleomycin-treated lungs; these cells were sufficient to resolve fibrosis in γδ KO mice and restore CXCL10 levels comparable to wild-type mice. Furthermore, overexpression of CXCL10 in the lung decreased the severity of fibrosis seen in the γδ KO mice. Finally, adoptive transfer of γδ T cells from CXCL10(-/-) mice failed to reverse the severe fibrosis in γδ KO mice. These results indicate that γδ T cells promote the resolution of fibrosis through the production of CXCL10.

Generation of human regulatory gammadelta T cells by TCRgammadelta stimulation in the presence of TGF-beta and their involvement in the pathogenesis of systemic lupus erythematosus

As a component of the innate immune cell population, γδ T cells are involved in tumor immunosurveillance and host defense against viral invasion. In this study, we demonstrated a novel function of human γδ T cells as regulatory cells by detecting their suppressive effect on the proliferation of autologous naive CD4(+) T cells. These regulatory γδ T cells (γδ Tregs) could be generated in vitro by stimulating with anti-TCRγδ in the presence of TGF-β and IL-2. Similar to CD4(+)Foxp3(+) Tregs, γδ Tregs also expressed Foxp3. Additionally, they primarily belonged to the Vδ1 subset with a CD27(+)CD25(high) phenotype. Furthermore, these γδ Tregs showed an immunoregulatory activity mainly through cell-to-cell contact. Importantly, this γδ regulatory population decreased in the peripheral blood of systemic lupus erythematosus patients, suggesting a potential mechanism in understanding the pathogenesis of systemic lupus erythematosus.

Expression of MICA, MICB and NKG2D in human leukemic myelomonocytic and cervical cancer cells

BACKGROUND

Cancer cells are known to secrete the stress molecules MICA and MICB that activate cytotoxicity by lymphocytes and NK cells through their NKG2D receptor as a mechanism of immunological defense. This work was undertaken to evaluate if cancer cells can also express this receptor as a possible mechanisms of depletion of MIC molecules and thus interfere with their immune recognition.

METHODS

Myelomonocytic leukemic (TPH-1 and U-937) and cervical cancer (CALO and INBL) cell lines were evaluated by Western Blot, ELISA, flow cytometry and immunocytochemistry to evaluate their capacity to express and secrete MICA and MICB and to be induced to proliferate by these molecules as well as to express their receptor NKG2D. Statistical analysis was performed by two-way ANOVA for time course analysis and Student's t-test for comparison between groups. Values were considered significantly different if p < 0.05.

RESULTS

THP-1 and U-937 produce and secrete the stress MICA and MICB as shown by Western Blot of lysed cells and by ELISA of their conditioned media. By Western Blot and flow cytometry we found that these cells also express the receptor NKG2D. When THP-1 and U-937 were cultured with recombinant MICA and MICB they exhibited a dose dependent induction for their proliferation. CALO and INBL also produce MICA and MICB and were induced to proliferate by these stress molecules. By Western Blot, flow cytometry and immunocytochemistry we also found that these cells express NKG2D.

CONCLUSIONS

Our novel results that tumor cells can simultaneously secrete MIC molecules and express their receptor, and to be induced for proliferation by these stress molecules, and that tumor epithelial cells can also express the NKG2D receptor that was thought to be exclusive of NK and cytotoxic lymphocytes is discussed as a possible mechanism of immunological escape and of tumor growth induction.

Preferential Th1 cytokine profile of phosphoantigen-stimulated human Vγ9Vδ2 T cells

Human Vγ9Vδ2 T cells recognise pyrophosphate-based antigens (phosphoantigens) and have multiple functions in innate and adaptive immunity, including a unique ability to activate other cells of the immune system. We used flow cytometry and ELISA to define the early cytokine profiles of Vγ9Vδ2 T cells stimulated in vitro with isopentenyl pyrophosphate (IPP) and (E)-4-hydroxy-3-methyl-but-2 enyl pyrophosphate (HMB-PP) in the absence and presence of IL-2 and IL-15. We show that fresh Vγ9Vδ2 T cells produce interferon-γ (IFN-γ) and tumour necrosis factor-α (TNF-α) within 4 hours of stimulation with phosphoantigen, but neither IL-10, IL-13, nor IL-17 was detectable up to 72 hours under these conditions. Cytokine production was not influenced by expression or lack, thereof, of CD4 or CD8. Addition of IL-2 or IL-15 caused expansion of IFN-γ-producing Vγ9Vδ2 T cells, but did not enhance IFN-γ secretion after 24–72 hours. Thus, phosphoantigen-stimulated Vγ9Vδ2 T cells have potential as Th1-biasing adjuvants for immunotherapy.

gammadelta T cells in cancer immunotherapy: current status and future prospects

gammadelta T lymphocytes are a distinct T-cell subset that display unique features with respect to T-cell receptor (TCR) gene usage, tissue tropism and antigen recognition. Phosphoantigens contributed by a dysregulated mevalonate pathway or the bacterial nonmevalonate pathway and aminobisphosphonates are capable of activating Vgamma9Vdelta2 T cells. With the aid of synthetic phosphoantigens, large-scale expansion of gammadelta T cells and their adoptive transfer into human hosts is now possible. The present review summarizes triumphs and tribulations of clinical trials using gammadelta T-cell immunotherapy. Adoptive transfer of phosphoantigen-activated gammadelta T cells or coadministration with aminobisphosphonates/cytokines/monoclonal antibodies appear to be promising approaches for cancer immunotherapy. It can be predicted that a comprehensive understanding of the molecular interactions of this unique T-cell subset with other key immune regulators (dendritic cells and regulatory T cells) will provide an impetus to bring this modality of treatment from bench to bedside.

γδ T cells cross-link innate and adaptive immunity in Mycobacterium tuberculosis infection

Protective immunity against mycobacterial infections such as Mycobacterium tuberculosis is mediated by interactions between specific T cells and activated antigen presenting cells. To date, many aspects of mycobacterial immunity have shown that innate cells could be the key elements that substantially may influence the subsequent adaptive host response. During the early phases of infection, innate lymphocyte subsets play a pivotal role in this context. Here we summarize the findings of recent investigations on γδ T lymphocytes and their role in tuberculosis immunity.

Histamine modulates γδ-T lymphocyte migration and cytotoxicity, via Gi and Gs protein-coupled signalling pathways

BACKGROUND AND PURPOSE

The biogenic amine, histamine plays a pathophysiological regulatory role in cellular processes of a variety of immune cells. This work analyses the actions of histamine on γδ-T lymphocytes, isolated from human peripheral blood, which are critically involved in immunological surveillance of tumours.

EXPERIMENTAL APPROACH

We have analysed effects of histamine on the intracellular calcium, actin reorganization, migratory response and the interaction of human γδ T cells with tumour cells such as the A2058 human melanoma cell line, the human Burkitt's Non-Hodgkin lymphoma cell line Raji, the T-lymphoblastic lymphoma cell line Jurkat and the natural killer cell-sensitive erythroleukaemia cell line, K562.

KEY RESULTS

γδ T lymphocytes express mRNA for different histamine receptor subtypes. In human peripheral blood γδ T cells, histamine stimulated Pertussis toxin-sensitive intracellular calcium increase, actin polymerization and chemotaxis. However, histamine inhibited the spontaneous cytolytic activity of γδ T cells towards several tumour cell lines in a cholera toxin-sensitive manner. A histamine H(4) receptor antagonist abolished the histamine induced γδ T cell migratory response. A histamine H(2) receptor agonist inhibited γδ T cell-mediated cytotoxicity.

CONCLUSIONS AND IMPLICATIONS

Histamine activated signalling pathways typical of chemotaxis (G(i) protein-dependent actin reorganization, increase of intracellular calcium) and induced migratory responses in γδ T lymphocytes, via the H(4) receptor, whereas it down-regulated γδ T cell mediated cytotoxicity through H(2) receptors and G(s) protein-coupled signalling. Our data suggest that histamine activated γδ T cells could modulate immunological surveillance of tumour tissue.

Phase I study of bromohydrin pyrophosphate (BrHPP, IPH 1101), a Vgamma9Vdelta2 T lymphocyte agonist in patients with solid tumors

PURPOSE

Vgamma9Vdelta2 (gammadelta) T lymphocytes, a critical peripheral blood lymphocyte subset, are directly cytotoxic against many solid and hematologic tumor types. Vgamma9Vdelta2 T lymphocytes can be selectively expanded in vivo with BrHPP (IPH1101) and IL-2. The present phase I trial was conducted with the aim of determining the maximum-tolerated dose (MTD) and safety of IPH1101 combined with a low dose of IL-2 in patients with solid tumors.

EXPERIMENTAL DESIGN

A 1-h intravenous infusion of IPH11 was administered alone at cycle 1, combined with a low dose of SC IL-2 (1 MIU/M(2) d1 to d7) in the subsequent cycles (day 1 every 3 weeks). The dose of IPH1101 was escalated from 200 to 1,800 mg/m(2).

RESULTS

As much as 28 patients with solid tumors underwent a total of 109 treatment cycles. Pharmacodynamics data demonstrate that gammadelta T lymphocyte amplification in humans requires the co-administration of IL-2 and is dependent on IPH 1101 dose. Dose-limiting toxicity occurred in two patients at a dose of 1,800 mg/m(2): one grade 3 fever (1 patient) and one grade 3 hypotension (1 patient) suggesting cytokine release syndrome immediately following the first infusion. At lower doses the treatment was well tolerated; the most frequent adverse events were mild fever, chills and abdominal pain, without exacerbation in the IL-2 combined cycles.

CONCLUSION

IPH1101 in combination with SC low-dose IL-2 is safe, well tolerated and induces a potent gammadelta T lymphocyte expansion in patients. Its clinical activity will be evaluated in phase II clinical trials.

(E)-4-hydroxy-3-methyl-but-2 enyl pyrophosphate-stimulated Vgamma9Vdelta2 T cells possess T helper type 1-promoting adjuvant activity for human monocyte-derived dendritic cells

Vgamma9Vdelta2 T cells respond to pyrophosphate antigens and display potent antitumour activity in vitro. We have investigated the potential of the most potent phosphoantigen known to activate Vgamma9Vdelta2 T cells, (E)-4-hydroxy-3-methyl-but-2 enyl pyrophosphate (HMB-PP), as an adjuvant for dendritic cell (DC)-based vaccines. A single stimulation of peripheral blood mononuclear cells with HMB-PP and IL-2 was sufficient to generate lines of effector memory Vgamma9Vdelta2 T cells that retained their cytolytic and cytokine secretion activities. These cells induced differentiation of DC into semi-mature antigen-presenting cells expressing CD86, CD11c, CD54, HLA-DR, CD83 and CD40, which secreted low levels of bioactive IL-12 but no IL-10. Vgamma9Vdelta2 T cells also strongly costimulated IL-12 release but inhibited IL-10 production by lipopolysaccharide (LPS)-stimulated DC. When substituted for Vgamma9Vdelta2 T cells, IFN-gamma did not induce full DC maturation but it augmented IL-12 and inhibited IL-10 release by LPS-stimulated DC, in a manner similar to HMB-PP-activated Vgamma9Vdelta2 T cells. Our findings indicate that Vgamma9Vdelta2 T cells, stimulated with nanomolar concentrations of HMB-PP, strongly promote T helper type 1 (Th1) responses through their ability to induce DC maturation and IL-12 secretion. This adjuvant activity may prove useful in DC-based cancer therapies.

Human γδ T lymphocytes for immunotherapeutic strategies against cancer

γδ T lymphocytes are a numerically small subset of T cells with potent cytotoxic activity against a variety of tumor cells. Human γδ T cells expressing the Vγ9Vδ2 T cell antigen receptor recognize endogenous pyrophosphate molecules that are overproduced in transformed cells. Moreover, the intracellular accumulation of such pyrophosphates is strongly enhanced by aminobisphosphonates used in the treatment of osteoporosis and bone metastasis in certain cancer patients. A new concept of cancer immunotherapy is based on the endogenous activation of γδ T cells with aminobisphosphonates plus low-dose interleukin-2.

Aging related changes of circadian rhythmicity of cytotoxic lymphocyte subpopulations

Background

Immunosenescence is a process that affects all cell compartments of the immune system and the contribution of the immune system to healthy aging and longevity is still an open question. Lymphocyte subpopulations present different patterns of circadian variation and in the elderly alteration of circadian rhythmicity has been evidenced. The aim of our study was to analyze the dynamics of variation of specific cytotoxic lymphocyte subsets in old aged subjects.

Methods

Lymphocyte subpopulation analyses were performed and cortisol serum levels were measured on blood samples collected every four hours for 24 hours from fifteen healthy male young-middle aged subjects (age range 36-55 years) and fifteen healthy male old aged subjects (age range 67-79 years).

Results

In healthy young-middle aged subjects CD20 were higher and at 06:00 h CD8+ dim correlated positively with CD16+ and positively with γδTCR+ cells, CD16 correlated positively with γδTCR+ cells At 18:00 h CD8+ dim correlated positively with CD16+ and positively with γδTCR+ cells, CD16+ correlated positively with γδTCR+ cells and a clear circadian rhythm was validated for the time-qualified changes of CD3+, CD4+, CD20+, CD25+ and HLA-DR+ cells with acrophase during the night and for the time-qualified changes of CD8+, CD8+ bright, CD8+ dim, CD16+ and γδTCR+ cells with acrophase during the day. In old aged subjects CD25, DR+ T cells and cortisol serum levels were higher, but there was no statistically significant correlation among lymphocyte subpopulations and a clear circadian rhythm was evidenced for time-qualified changes of CD3+ and CD25+ cells with acrophase during the night and for the time-qualified changes of CD8+ cells and cortisol with acrophase during the day.

Conclusion

Our study has evidenced aging-related changes of correlation and circadian rhythmicity of variation of cytotoxic lymphocyte subpopulations that might play a role in the alteration of immune system function in the elderly.

MICA polymorphism identified by whole genome array associated with NKG2D-mediated cytotoxicity in T-cell large granular lymphocyte leukemia

BACKGROUND

Large granular lymphocyte leukemia is a semi-autonomous clonal proliferation of cytotoxic T cells accompanied by immune cytopenias and various autoimmune conditions. Due to the rarity of this disease and its association with autoimmune diseases, a theoretical germline or somatic mutation might have significant penetrance, thus enabling detection, even from samples of suboptimal size, through genome-wide association studies.

DESIGN AND METHODS

To investigate a non-mendelian genetic predisposition to large granular lymphocyte leukemia, we used a step-wise method for gene discovery. First, a modified 'random forests' technique was used for candidate gene identification: this was followed by traditional allele-specific polymerase chain reaction, sequencing modalities, and mechanistic assays.

RESULTS

Our analysis found an association with MICA, a non-peptide-presenting, tightly regulated, stress-induced MHC-like molecule and cognate receptor for NKG2D, found abundantly on large granular lymphocyte leukemia cells. Sequencing of germline DNA revealed a higher frequency of MICA*00801/A5.1 in patients with large granular lymphocyte leukemia than in matched controls (64% versus 41%, P<0.001, homozygous 40% versus 15%, P<0.001). Flow cytometry was employed to determine the expression of MICA within hematologic compartments, showing that the signal intensity of MICA was increased in granulocytes from neutropenic patients with large granular lymphocyte leukemia in comparison with that in controls (P=0.033). Furthermore, neutrophil counts were inversely correlated with MICA expression (R(2)=0.50, P=0.035). Finally, large granular lymphocyte leukemia cells were able to selectively kill MICA(+) Ba/F3 lymphocytes transfected with human MICA*019 in a dose-dependent manner compared to naïve cells (P<0.001), an effect mitigated by administration of an anti-NKG2D antibody (P=0.033).

CONCLUSIONS

Our results illustrate that MICA-NKG2D played a role in disease pathogenesis in the majority of patients in our cohort of cases of large granular lymphocyte leukemia and further investigation into this signaling axis may provide potent therapeutic targets.