Human peripheral gamma delta T cells are stimulated by Daudi Burkitt's lymphoma and not by any other Burkitt's lymphoma tested

The cytotoxic molecule granulysin is capable of inducing either chemotaxis or fugetaxis in dendritic cells depending on maturation: a role for Vδ2+ γδ T cells in the modulation of immune response to tumour?

Release of granulysin by γδ T cells contributes to tumour cell killing. A cytolytic 9000 MW isoform of granulysin kills tumour cells directly, whereas a 15 000 MW precursor has been hypothesized to cause both the maturation and migration of dendritic cell (DC) populations. Recruiting DC to a tumour is beneficial as these cells initiate adaptive immune responses, which contribute to the eradication of malignancies. In this study, Vδ2⁺ γδ T cells were activated by stimulation of peripheral blood mononuclear cells with zoledronic acid or Bacillus Calmette-Guérin (BCG), or were isolated and cultured with tumour targets. Although a large proportion of resting Vδ2⁺ γδ T cells expressed 15 000 MW granulysin, 9000 MW granulysin expression was induced only after stimulation with BCG. Increased levels of activation and granulysin secretion were also observed when Vδ2⁺ γδ T cells were cultured with the human B-cell lymphoma line Daudi. High concentrations of recombinant 15 000 MW granulysin caused migration and maturation of immature DC, and also initiated fugetaxis in mature DC. Conversely, low concentrations of recombinant 15 000 MW granulysin resulted in migration of mature DC, but not immature DC. Our data therefore support the hypothesis that Vδ2⁺ γδ T cells can release granulysin, which may modulate recruitment of DC, initiating adaptive immune responses.

The T-cell Response to Epstein-Barr Virus-New Tricks From an Old Dog

Epstein-Barr virus (EBV) infects most people and establishes life-long infection controlled by the host's immune system. The genetic stability of the virus, deep understanding of the viral antigens and immune epitopes recognized by the host's T-cell system and the fact that recent infection can be identified by the development of symptomatic infectious mononucleosis makes EBV a powerful system in which to study human immunology. The association between EBV and multiple cancers also means that the lessons learned have strong translational potential. Increasing evidence of a role for resident memory T-cells and non-conventional γδ T-cells in controlling EBV infection suggests new opportunities for research and means the virus will continue to provide exciting new insights into human biology and immunology into the future.

Gamma Delta T Cell Therapy for Cancer: It Is Good to be Local

Human gamma delta T cells have extraordinary properties including the capacity for tumor cell killing. The major gamma delta T cell subset in human beings is designated Vγ9Vδ2 and is activated by intermediates of isoprenoid biosynthesis or aminobisphosphonate inhibitors of farnesyldiphosphate synthase. Activated cells are potent for killing a broad range of tumor cells and demonstrated the capacity for tumor reduction in murine xenotransplant tumor models. Translating these findings to the clinic produced promising initial results but greater potency is needed. Here, we review the literature on gamma delta T cells in cancer therapy with emphasis on the Vγ9Vδ2 T cell subset. Our goal was to examine obstacles preventing effective Vγ9Vδ2 T cell therapy and strategies for overcoming them. We focus on the potential for local activation of Vγ9Vδ2 T cells within the tumor environment to increase potency and achieve objective responses during cancer therapy. The gamma delta T cells and especially the Vγ9Vδ2 T cell subset, have the potential to overcome many problems in cancer therapy especially for tumors with no known treatment, lacking tumor-specific antigens for targeting by antibodies and CAR-T, or unresponsive to immune checkpoint inhibitors. Translation of amazing work from many laboratories studying gamma delta T cells is needed to fulfill the promise of effective and safe cancer immunotherapy.

Prospects for chimeric antigen receptor (CAR) γδ T cells: A potential game changer for adoptive T cell cancer immunotherapy

Excitement is growing for therapies that harness the power of patients' immune systems to combat their diseases. One approach to immunotherapy involves engineering patients' own T cells to express a chimeric antigen receptor (CAR) to treat advanced cancers, particularly those refractory to conventional therapeutic agents. Although these engineered immune cells have made remarkable strides in the treatment of patients with certain hematologic malignancies, success with solid tumors has been limited, probably due to immunosuppressive mechanisms in the tumor niche. In nearly all studies to date, T cells bearing αβ receptors have been used to generate CAR T cells. In this review, we highlight biological characteristics of γδ T cells that are distinct from those of αβ T cells, including homing to epithelial and mucosal tissues and unique functions such as direct antigen recognition, lack of alloreactivity, and ability to present antigens. We offer our perspective that these features make γδ T cells promising for use in cellular therapy against several types of solid tumors, including melanoma and gastrointestinal cancers. Engineered γδ T cells should be considered as a new platform for adoptive T cell cancer therapy for mucosal tumors.

Flanking V and J sequences of complementary determining region 3 of T cell receptor (TCR) δ1 (CDR3δ1) determine the structure and function of TCRγ4δ1

The γδ T cell receptor (TCR) differs from immunoglobulin and αβ TCR in its overall binding mode. In human, genes δ1, δ2, and δ3 are used for TCRδ chains. Previously, we have studied antigen binding determinants of TCRδ2 derived from dominant γδ T cells residing in peripheral blood. In this study we have investigated the critical determinants for antigen recognition and TCR function in TCRδ1 originated from gastric tumor-infiltrating γδ T lymphocytes using three independent experimental strategies including complementary determining region 3 (CDR3) of TCRδ1 (CDR3δ1)-peptide mediated binding, CDR3δ1-grafted TCR fusion protein-mediated binding, and TCRγ4δ1- and mutant-expressing cell-mediated binding. All three approaches consistently showed that the conserved flanking V and J sequences but not the diverse D segment in CDR3δ1 determine the antigen binding. Most importantly, we found that mutations in the V and J regions of CDR3δ1 also abolish the assembly of TCR and TCR-CD3 complexes in TCRγ4δ1-transduced J.RT3-T3.5 cells. Together with our previous studies on CDR3δ2 binding, our finding suggests that both human TCRδ1 and TCRδ2 recognize antigen predominately via flanking V and J regions. These results indicate that TCRγδ recognizes antigens using conserved parts in their CDR3, which provides an explanation for a diverse repertoire of γδTCRs only recognizing a limited number of antigens.

Large scale expansion of Vgamma9Vdelta2 T lymphocytes from human peripheral blood mononuclear cells after a positive selection using MACS "TCR gamma/delta+ T cell isolation kit"

Interest in gamma9delta2 T cells has increased greatly in the past decade. While several protocols allowed the amplification of a large proportion of these cells in vitro, the purity of the final preparation is usually heterogeneous between different donors. Functional studies of this population are often controversial due to the presence of other populations such as NK cells which share a wide range of characteristics. Here, the gamma9delta2 T cells labelled-fraction is purified and mixed with the irradiated unlabelled fraction followed by a single stimulation with phosphoantigen, in turn followed by a classical step of amplification in the presence of interleukin 2. In this study, we describe a straightforward protocol to amplify pure populations of gamma9delta2 T cells which could be useful in fundamental research or in the development of a new generation of gammadelta cell therapy protocol.

Individual Vgamma2-Jgamma1.2+ T cells respond to both isopentenyl pyrophosphate and Daudi cell stimulation: generating tumor effectors with low molecular weight phosphoantigens

Human Vgamma2Vdelta2 T cells exhibit T cell receptor-dependent, MHC-unrestricted recognition of antigen and play important roles in tumor and pathogen immunity. To characterize antigen recognition by the Vgamma2Vdelta2 TCR, we used the combined approach of spectratyping and CDR3 sequence analysis that measures changes in the TCR repertoire before and after stimulation with a phosphoantigen (isopentenyl pyrophosphate) or an irradiated tumor cell line (Daudi B lymphoma). Here we describe common Vgamma2 chains that are substantially involved in the response to both phosphoantigens and tumor cells. The recognition properties of common Vgamma2 chains explains the observation that Vgamma2Vdelta2 T cells expanded by phosphoantigen stimulation specifically recognize and kill some but not all tumor cell lines. Our studies further justify efforts to stimulate tumor immunity by administering low molecular weight phosphoantigens and boosting the frequency and tumor effector functions of circulating Vgamma2Vdelta2 T cells.

Activated gammadelta T cells express the natural cytotoxicity receptor natural killer p 44 and show cytotoxic activity against myeloma cells

gammadelta T cells account for up to 10% of T lymphocytes in the peripheral blood of healthy donors. They can be activated by cytokines such as interleukin (IL)-2, IL-12 and IL-15, express natural killer (NK) cell markers such as NKG2D and show cytotoxic activity against several tumour cells, including multiple myeloma. Here, we present activated polyclonal gammadelta T cells from healthy donors with an NK T cell-like phenotype expressing the natural cytotoxicity receptor NKp44. Natural cytotoxicity receptors NKp30, NKp44 and NKp46 have been regarded as specific NK receptors; only two gammadelta T cell clones described so far expressed NKp 44. Isolated polyclonal gammadelta T cells cultured for 7 days according to the cytokine-induced killer cell (CIK) protocol with additional IL-15 revealed a surface expression of NKp44 of 8+/-7% (n=22). This could be confirmed by detection of NKp 44 mRNA by reverse transcription-polymerase chain reaction (RT-PCR). gammadelta T cells exhibited a marked cytotoxic activity against myeloma cells, which could be reduced by inhibition of NKp44. To our knowledge, this is the first description of the expression of NKp44 on polyclonal gammadelta T cells.

Distinct subpopulations of gamma delta T cells are present in normal and tumor-bearing human liver

Gamma delta T cells are thought to mediate immune responses at epithelial surfaces. We have quantified and characterized hepatic and peripheral blood gamma delta T cells from 11 normal and 13 unresolved tumor-bearing human liver specimens. gamma delta T cells are enriched in normal liver (6.6% of T cells) relative to matched blood (0.9%; P = 0.008). The majority express CD4(-)CD8(-) phenotypes and many express CD56 and/or CD161. In vitro, hepatic gamma delta T cells can be induced to kill tumor cell lines and release interferon-gamma, tumor necrosis factor-alpha, interleukin-2 and interleukin-4. Analysis of V gamma and V delta chain usage indicated that V delta 3(+) cells are expanded in normal livers (21.2% of gamma delta T cells) compared to blood (0.5%; P = 0.001). Tumor-bearing livers had significant expansions and depletions of gamma delta T cell subsets but normal cytolytic activity. This study identifies novel populations of liver T cells that may play a role in immunity against tumors.

Targeting of tumor cells for human gammadelta T cells by nonpeptide antigens

Human Vgamma2/Vdelta2(+) gammadelta T cells respond to low molecular-mass nonpeptide Ags in a gammadelta TCR-dependent manner. Although requirements of Ag presentation have remained controversial, we have indicated that specific responses of the primary gammadelta T cells to pamidronate were dependent on monocytic adherent cells for Ag presentation. Here, we show that human tumor cells can efficiently present aminobisphosphonate and pyrophosphomonoester compounds to gammadelta T cells, inducing specific proliferation and IFN-gamma production. gammadelta TCR dependency of the response to Ag-pulsed tumor cells was confirmed by using a Jurkat line transfected with a Vgamma2/Vdelta2 gammadelta TCR. Furthermore, gammadelta T cells exhibited markedly enhanced cytotoxicity against the Ag-pulsed tumor cells as compared with untreated tumor cells. Survey of a number of human tumor cell lines of different origins revealed that the majority of them became susceptible for gammadelta T cell-mediated cytotoxicity following the Ag pulsing except for breast cancer lines so far examined, while normal PHA blast cells remained resistant. The results not only imply a unique mode of nonpeptide Ag recognition by human gammadelta T cells but also may provide a novel strategic clue for immunotherapy of human malignancy.

The expansion of human gammadelta T cells in response to Daudi cells requires the participation of CD4+ T cells

The Burkitt's lymphoma cell line Daudi is a potent inducer of human gammadelta T-cell expansion. Using an in vitro culture system comprised of irradiated Daudi cells as stimulators and normal human lymphocytes as responders, the cellular determinants of this response were investigated. Three of four monoclonal antibodies (mAbs 1-1C4, L243, and 9.3F10) directed against disparate epitopes of human major histocompatibility complex (MHC) class II, as well as a mAb with specificity for CD4 (OKT4), inhibited the expansion of gammadelta T cells in response to Daudi cell stimulators. mAbs with a specificity for CD74 and CD8 were non-inhibitory. Lymphocyte depletion experiments demonstrated a critical role for the CD4+ T-cell subset in the expansion of gammadelta T cells. Other data pointed towards requirements for direct cell contact in this system, and the addition of exogenous recombinant interleukin (IL)-2, IL-4, and IL-12 failed to reconstitute gammadelta T-cell expansion in CD4+ lymphocyte-depleted cultures. These results complement previous findings in murine infectious disease and mycobacterial systems, providing a direct demonstration that CD4+ T cells play a role in gammadelta T-cell expansion through an interaction with human leucocyte antigen (HLA) class II on Daudi cells. The data point towards important functional links between the acquired and natural immune systems.

Enhancing effect of tumor necrosis factor (TNF)-alpha, but not IFN-gamma, on the tumor-specific cytotoxicity of gammadeltaT cells from glioblastoma patients

Adoptive immunotherapy using tumor-specific killer cells can be beneficial in inducing regression of advanced cancer. The roles of cytokines on effector cells in inducing maximal killing activity and the accompanying side-effects should be investigated in vitro and fully understood prior to their clinical use. The present study indicates that the gammadeltaT cells involved in autologous tumor-specific killing consist of several populations in terms of their T cell receptor (TCR) repertoire, but predominantly express the products of the Vgamma9/Vdelta2 gene locus of the TCR. We then examined the effect of TNF-alpha and IFN-gamma on these tumor-specific gammadeltaT cells for possible clinical use in cancer patients. TNF-alpha alone, at concentrations of 0.01-1.0 microg/ml, caused increased gammadeltaT cell cytotoxicity against autologous glioblastoma cells, whereas IFN-gamma alone had no effect. The combination of TNF-alpha (1 microg/ml) with IL-2 (50 units/ml) resulted in further enhancement of cytotoxicity. TNF-alpha, but not IFN-gamma, marginally inhibited the proliferative response of gammadeltaT cells; a similar result was seen when the cytokines were combined. TNF-alpha may, therefore, be one cytokine capable of inducing increased autologous tumor-specific activity in gammadeltaT cells, bearing mainly Vgamma9/Vdelta2 chains, which can be enhanced when combined with other cytokines.

gamma delta T-cell-human glial cell interactions. II. Relationship between heat shock protein expression and susceptibility to cytolysis

gamma delta T-cells have been implicated in the immunopathogenesis of multiple sclerosis (MS), possibly through interaction with heat shock proteins (hsp). We have previously demonstrated that human oligodendrocytes (OGC) express hsp on their surface and induce the proliferation and expansion of gamma delta T-cells. We also showed that gamma delta T-cells are highly cytolytic to OGC in vitro. The current study addresses whether gamma delta T-cell-induced cytotoxicity to OGC involves the recognition of hsp on OGC or some other ligand. We first compared the lytic potential for different human glial cells and found that gamma delta T-cells lysed OGC, microglia and human fetal astrocytes to the same extent, despite the preferential expression of hsp only on OGC. This suggested that either hsp was not involved in cytolytic recognition or that more than one ligand exists. To address this we used cell lines that either shared OGC properties of hsp expression and the ability to stimulate gamma delta T-cells (RPMI 8226, Daudi) or did not (U937) in cold target competition assays with OGC. Results demonstrated that although all the cell lines were effectively killed by gamma delta T-cells, only the RPMI 8226 and Daudi cells were able to effectively compete for lysis with the OGC. These results support the notion that probably more than one ligand for gamma delta T-cell cytotoxic recognition exists but hsp could still be involved in gamma delta T-cell-induced lysis of OGC. Regulating the expression of hsp on OGC might therefore be a way of interfering with potential gamma delta T-cell-induced damage in MS.

gamma delta T-cell-human glial cell interactions. I. In vitro induction of gammadelta T-cell expansion by human glial cells

gamma delta T-cells are found in increased proportion in multiple sclerosis (MS) white matter plaque infiltrates compared with peripheral blood or spleen, raising the possibility that they are either specifically attracted to lesion sites or, once present, are stimulated to expand. We have previously shown that human oligodendrocytes (OGC) preferentially express heat shock proteins (hsp), molecules to which gamma delta T-cells have been known to react and that in vitro expanded gamma delta T-cells can lyse OGC. We therefore investigated whether human glial cells, that differentially express hsp, could stimulate gamma delta T-cell expansion from peripheral blood. We compared the glial cell-induced expansion to cell lines which also differentially express hsp and have been shown to selectively stimulate gamma delta T-cell expansion (e.g. RPMI 8226, Daudi). We found that both OGC and human fetal astrocytes (hFA) expressed hsp and stimulated the preferential expansion of gamma delta T-cells to about the same extent as the hsp expressing cell lines RPMI 8226 or Daudi, in the presence of exogenous interleukin-2 (IL-2) but without any T-cell mitogen. Furthermore, the type of gamma delta T-cells expanded were of the V delta 2 subtype known to be particularly reactive to hsp. Microglia, U937 cell lines or purified myelin membranes, which express little or no hsp, did not support gamma delta T-cell growth. These results therefore suggest that OGC may contribute to the local expansion of gamma delta T-cells within MS plaques. Potential harmful effects of gamma delta T-cells on OGC may thereby contribute to the immunopathogenesis of MS demyelination.