The production of cytokines such as interferon-γ and interleukin 17 by αβ and γδ T cells influences the outcome of immune responses. Here we show that most γδ T lymphocytes expressed the tumor necrosis factor receptor family member CD27 and secreted interferon-γ, whereas interleukin 17 production was restricted to CD27- γδ T cells. In contrast to the apparent plasticity of αβ T cells, the cytokine profiles of these distinct γδ T cell subsets were essentially stable, even during infection. These phenotypes were established during thymic development, when CD27 functions as a regulator of the differentiation of γδ T cells at least in part by inducing expression of the lymphotoxin-β receptor and genes associated with trans-conditioning and interferon-γ production. Thus, the cytokine profiles of peripheral γδ T cells are predetermined mainly by a mechanism involving CD27.

Human Vc9Vd2 T cells are potent anti-tumor lymphocytes that specifically respond to pyrophosphate (phospho-) antigens, which constitute the basis of current cd T-cell-based immunotherapy strategies. Despite a clear involvement of the TCR, the costimulation requirements of Vc9Vd2 T cells remain ill-defined. Here, we show that the expression of the CD27 receptor by the vast majority of Vc9Vd2 peripheral blood lymphocytes endows them with enhanced proliferative capacity upon ligation by its unique ligand CD70, a tumor necrosis factor superfamily member expressed on lymphoma B-cells but also on TCRactivated cd T cells. Moreover, Vc9Vd2 T-cell treatment with soluble recombinant CD70 induced calcium signals and increased transcription of anti-apoptotic Bcl2a1 and cell-cyclepromoting Cyclin D2 genes. We further demonstrate that the manipulation of CD70-CD27 interactions significantly impacted on Vc9Vd2 T-cell survival, proliferation and cytokine secretion, in both loss-of-function and gain-of-function experiments. Thus, CD27 coreceptor signals strongly promoted the expansion of Th1-biased, CD27 1 Vc9Vd2 peripheral blood lymphocytes in the context of TCR-mediated stimulation with phosphoantigens. These data collectively establish a novel role for the CD70-CD27 axis in human cd T-cell activation and hence open new perspectives for its modulation in clinical settings.

BackgroundThe unique responsiveness of Vγ9Vδ2 T-cells, the major γδ subset of human peripheral blood, to non-peptidic prenyl pyrophosphate antigens constitutes the basis of current γδ T-cell-based cancer immunotherapy strategies. However, the molecular mechanisms responsible for phosphoantigen-mediated activation of human γδ T-cells remain unclear. In particular, previous reports have described a very slow kinetics of activation of T-cell receptor (TCR)-associated signal transduction pathways by isopentenyl pyrophosphate and bromohydrin pyrophosphate, seemingly incompatible with direct binding of these antigens to the Vγ9Vδ2 TCR. Here we have studied the most potent natural phosphoantigen yet identified, (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMB-PP), produced by Eubacteria and Protozoa, and examined its γδ T-cell activation and anti-tumor properties.Methodology/Principal FindingsWe have performed a comparative study between HMB-PP and the anti-CD3ε monoclonal antibody OKT3, used as a reference inducer of bona fide TCR signaling, and followed multiple cellular and molecular γδ T-cell activation events. We show that HMB-PP activates MEK/Erk and PI-3K/Akt pathways as rapidly as OKT3, and induces an almost identical transcriptional profile in Vγ9+ T-cells. Moreover, MEK/Erk and PI-3K/Akt activities are indispensable for the cellular effects of HMB-PP, including γδ T-cell activation, proliferation and anti-tumor cytotoxicity, which are also abolished upon antibody blockade of the Vγ9+ TCR Surprisingly, HMB-PP treatment does not induce down-modulation of surface TCR levels, and thereby sustains γδ T-cell activation upon re-stimulation. This ultimately translates in potent human γδ T-cell anti-tumor function both in vitro and in vivo upon transplantation of human leukemia cells into lymphopenic mice,Conclusions/SignificanceThe development of efficient cancer immunotherapy strategies critically depends on our capacity to maximize anti-tumor effector T-cell responses. By characterizing the intracellular mechanisms of HMB-PP-mediated activation of the highly cytotoxic Vγ9+ T-cell subset, our data strongly support the usage of this microbial antigen in novel cancer clinical trials.

T cell activation requires the integration of signals that arise from various types of receptors. Although TCR triggering is a necessary condition, it is often not sufficient to induce full T-cell activation, as reflected in cell proliferation and cytokine secretion. This has been firmly demonstrated for conventional αβ T cells, for which a large panel of costimulatory receptors has been identified. By contrast, the area remains more obscure for unconventional, innate-like γδ T cells, as the literature has been scarce and at times contradictory. Here we review the current state of the art on the costimulatory requirements of γδ T cell activation. We highlight the roles of members of the immunoglobulin (like CD28 or JAML) or tumour necrosis factor receptor (like CD27) superfamilies of coreceptors, but also of more atypical costimulatory molecules, such as NKG2D or CD46. Finally, we identify various areas where our knowledge is still markedly insufficient, hoping to provoke future research on γδ T cell costimulation.

γδ T cells play key nonredundant roles in immunity to infections and tumors. Thus, it is critical to understand the molecular mechanisms responsible for γδ T cell activation and expansion in vivo. In striking contrast to their αβ counterparts, the costimulation requirements of γδ T cells remain poorly understood. Having previously described a role for the TNFR superfamily member CD27, we since screened for other nonredundant costimulatory receptors in γδ T cell activation. We report in this article that the Ig superfamily receptor CD28 (but not its related protein ICOS) is expressed on freshly isolated lymphoid γδ T cells and synergizes with the TCR to induce autocrine IL-2 production that promotes γδ cell survival and proliferation in both mice and humans. Specific gain-of-function and loss-of-function experiments demonstrated a nonredundant function for CD28 interactions with its B7 ligands, B7.1 (CD80) and B7.2 (CD86), both in vitro and in vivo. Thus, γδ cell proliferation was significantly enhanced by CD28 receptor agonists but abrogated by B7 Ab-mediated blockade. Furthermore, γδ cell expansion following Plasmodium infection was severely impaired in mice genetically deficient for CD28. This resulted in the failure to mount both IFN-γ–mediated and IL-17–mediated γδ cell responses, which contrasted with the selective effect of CD27 on IFN-γ–producing γδ cells. Our data collectively show that CD28 signals are required for IL-2–mediated survival and proliferation of both CD27+ and CD27− γδ T cell subsets, thus providing new mechanistic insight for their modulation in disease models.

cd T cells are highly cytolytic lymphocytes that produce large amounts of pro-inflammatory cytokines during immune responses to multiple pathogens. Furthermore, their ability to kill tumor cells has fueled the development of cd-T-cell-based cancer therapies. Thus, the regulation of cd-T-cell activity is of great biological and clinical relevance. Here, we show that murine CD4 1 CD25 1 ab T cells, the vast majority of which express the Treg marker, Foxp3, abolish key effector functions of cd T cells, namely the production of the pro-inflammatory cytokines, IFN-c and IL-17, cytotoxicity, and lymphocyte proliferation in vitro and in vivo. We further show that suppression is dependent on cellular contact between Treg and cd T cells, results in the induction of an anergic state in cd lymphocytes, and can be partially reversed by manipulating glucocorticoid-induced TNF receptor-related protein (GITR) signals. Our data collectively dissect a novel mechanism by which the expansion and pro-inflammatory functions of cd T cells are regulated. IntroductionThe integration of multiple effector and regulatory mechanisms dictates the course of immune responses to self and non-self antigens. gd T cells are innate-like lymphocytes known to mount robust responses to infectious pathogens [1] and tumors [2], while also regulating tissue homeostasis and repair [3]. Importantly, several of these functions are non-redundant, as demonstrated by the immunopathology phenotypes of TCR-d-deficient mice [4]. It is also well documented that upon pathogen challenge (for example, with Plasmodium falciparum, Mycobacterium tuberculosis, Haemophilus influenzae, or Streptococcus pneumoniae), gd T cells are one of the immune populations that expands most dramatically in human peripheral blood [1,5,6].In contrast with adaptive ab T cells, activated gd lymphocytes are capable of ''immediate'' cytotoxicity and cytokine secretion [5]. In fact, we have recently shown that murine gd T cells become functionally competent in the thymus, particularly regarding the production of pro-inflammatory cytokines . Furthermore, several reports have demonstrated the crucial contributions of gd T cells to the reservoirs of such cytokines in the context of anti-tumor immunity [8], immune responses to infection [9], and autoimmunity [9,10]. While these data highlight the importance of understanding how the [17], and monocytes/macrophages [18]. As a result, CD4 1 CD25 1 ab T cells, and particularly those that develop in the thymus through a Foxp3-dependent genetic program [19,20], so-called ''naturally occurring '' Treg (nTreg), are pivotal to maintaining immune homeostasis and preventing inflammatory and autoimmune diseases [21]. On the other hand, Treg-suppressive functions are also known to diminish immunity to pathogens and to tumors [22,23]. Provocatively, an inverse correlation between circulating human Treg frequencies and gd-T-cell numbers in cancer patients has been recently reported [24].Building on these foundations, we show here that Treg suppress gd-T-cell ...

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<p>S1. LDL-cholesterol does not affect the viability of human γÎ' T cells. S2. Effects of LDL-cholesterol on Vï�¤2+ T cells after 36 or 48 hours of culture. S3. Effects of LDL-cholesterol on additional immune functions of γÎ' T cells. S4. Effect of LDL-cholesterol on expanded Vγ9VÎ'2 T cells cultured in the presence of human plasma. S5. Effects of receptor blockade on breast cancer cell targeting by γÎ' T lymphocytes. S6: Cholesterol-rich diet reduces multifunctional anti-tumour γÎ' infiltrating lymphocytes.</p>