Conservation of nonpeptide antigen recognition by rhesus monkey V gamma 2V delta 2 T cells

We have previously found that monkey Vgamma2Vdelta2(+) T cells mount adaptive immune responses in response to Mycobacterium bovis bacillus Calmette-Guérin infections. We have now analyzed rhesus monkey gammadelta T cell responses to nonpeptide Ags and superantigens. Like human Vgamma2Vdelta2(+) T cells, rhesus monkey gammadelta T cells are stimulated when exposed to prenyl pyrophosphate, bisphosphonate, and alkylamine Ags. Responsiveness was limited to gammadelta T cells expressing Vgamma2Vdelta2 TCRs. Rhesus monkey Vgamma2Vdelta2(+) T cells also responded to the superantigen, staphyloccocal enterotoxin A. Sequencing of the rhesus monkey Vgamma2Vdelta2 TCR revealed a strong sequence homology to human Vgamma2Vdelta2 TCR that preserves important sequence motifs. Moreover, chimeric TCRs that pair human Vgamma2 with monkey Vdelta2 and monkey Vgamma2 with human Vdelta2 retain reactivity to nonpeptide Ags and B cell lymphomas. A molecular model of the rhesus monkey Vgamma2Vdelta2 TCR has a basic region in the complementarity-determining region 3 binding groove that is similar to that seen in the human Vgamma2Vdelta2 TCR and preserves the topology of the complementarity-determining region loops. Thus, recognition of nonpeptide prenyl pyrophosphate, bisphosphonate, and alkylamine Ags is conserved in primates suggesting that primates can provide an animal model for human gammadelta T cell Ag responses.     

Infiltration of canonical Vgamma4/Vdelta1 gammadelta T cells in an adriamycin-induced progressive renal failure model

We have previously reported an infiltration of renal interstitial gammadelta T cells in Adriamycin-induced progressive glomerulosclerosis in the rat kidney. The TCR repertoire and sequences used by these gammadelta T cells have now been studied. Two injections of Adriamycin 14 days apart caused segmental glomerulosclerosis, massive interstitial infiltration of mononuclear cells, and end-stage renal failure. Flow cytometry of lymphocyte subpopulations with Abs to CD3, the gammadelta TCR, and the alphabeta TCR showed that gammadelta T cells as a proportion of CD3(+) cells were increased in Adriamycin-treated kidneys (8.5 +/- 5.4%), but not in lymph nodes (1.3 +/- 0.4%). A semiquantitative score of glomerular damage (r = 0.65; p < 0.01) and creatinine (r = 0.62; p < 0.01) correlated significantly with the presence of gammadelta T cells. TCR Vgamma repertoire analysis by RT-PCR and Southern blotting showed that Vgamma2 was the dominant subfamily in lymph nodes, whereas Vgamma4 became the predominant subfamily in advanced stages of the rat Adriamycin-treated kidney. Sequencing of the Vgamma4-Jgamma junctional region showed an invariant sequence. The amino acid sequence of the junctional region of the Vgamma4 TCR was the same as the reported mouse canonical Vgamma4 TCR sequence. Analysis of the kidney Vdelta repertoire showed dominant expression of Vdelta1, and sequencing again revealed the selective expression of a canonical Vdelta1 gene. Semiquantitative RT-PCR for cytokine gene expression showed that gammadelta T cells from the kidneys expressed TGF-beta, but not IL-4, IL-10, or IFN-gamma. These results suggest that the predominant gammadelta T cells in the Adriamycin kidney use an invariant Vgamma4/Vdelta1 receptor.     

Mechanisms of Vdelta1 gammadelta T cell activation by microbial components

There are two major subsets of gammadelta T cell in humans. Vgamma2Vdelta2 T cells predominate in the circulation and significantly expand in vivo during a variety of infectious diseases. Ags identified for the Vdelta2 T cells are nonpeptide phosphate, amine, and aminobisphosphonate compounds. In contrast, Vdelta1-encoded TCRs account for the vast majority of gammadelta T cells in tissues such as intestine and spleen. Some of these T cells recognize CD1c and MHC class I-related chain (MICA/B) molecules [correction]. These T cells are cytotoxic and use both perforin- and Fas-mediated cytotoxicity. A fundamental question is how these gammadelta T cells are activated during microbial exposure to carry out effector functions. In this study, we provide evidence for a mechanism by which Vdelta1 gammadelta T cells are activated by inflammatory cytokines in the context of the Vdelta1 TCR. Dendritic cells are necessary as accessory cells for microbial Ag-mediated Vdelta1 gammadelta T cell activation. Cytokine (IL-12), adhesion (LFA3/CD2, LFA1/ICAM1) and costimulatory (MHC class I-related chain (MICA/B) molecules/NK-activating receptor G2D) molecules play a significant role along with Vdelta1 TCR in this activation.     

An autoreactive gamma delta TCR derived from a polymyositis lesion

To investigate the role of gammadelta T cells in human autoimmune disease we expressed and characterized a gammadelta TCR from an autoimmune tissue lesion. The TCR was first identified in a rare form of polymyositis characterized by a monoclonal infiltrate of gammadelta T cells which invaded and destroyed skeletal muscle fibers. The Vgamma1.3-Jgamma1-Cgamma1/Vdelta2-Jdelta3 TCR cDNA of the original muscle invasive gammadelta T cell clone was reconstructed from unrelated cDNA and transfected into the mouse hybridoma BW58alpha(-)beta(-). Appropriate anti-human gammadelta TCR Abs stimulated the TCR transfectants to produce IL-2, thus demonstrating that the human gammadelta TCR functionally interacted with murine signaling components. The transfected Vgamma1.3/Vdelta2 TCR recognized a cytosolic protein expressed in cultured human myoblasts and TE671 rhabdomyosarcoma cells. The Ag was recognized in the absence of presenting cells. Using a panel of control gammadelta TCR transfectants with defined exchanges in different positions of both TCR chains, we showed that the gammadelta TCR recognized its Ag in a TCR complementarity-determining region 3-dependent way. To our knowledge, this is the first example of a molecularly defined gammadelta TCR directly derived from an autoimmune tissue lesion. The strategy used in this study may be applicable to other autoimmune diseases.     

Vdelta1 T cell receptor binds specifically to MHC I chain related A: molecular and biochemical evidences

Human MHC class I chain-related A (MICA) is a tumor-associated antigen that can be recognized by Vdelta1 subset of tumor-infiltrating gammadelta T cells. We previously reported that immobilized recombinant MICA protein could induce the proliferation of tumor-infiltrating Vdelta1 gammadelta T cells in vitro. But there has been no direct evidence showing the engagement of gammadelta T cell receptors (TCR) of the induced cells with MICA. In the current investigation, we show that MICA induces specific cytolytic activity of the expanded gammadelta T cells. We expressed the coupled V domains from the MICA-induced T cells as a single polypeptide chain Vdelta Vgamma TCR (gammadelta scTCR). Such scTCR can specifically bind MICA of HeLa cells. Direct interaction of gammadelta scTCRs with in vitro expressed MICA was monitored using an IAsys biosensor. We found that the Vdelta1 scTCR can specifically bind to immobilized MICA molecule and MICA alpha1alpha2 domains are responsible for the binding reaction.     

Functional and structural similarity of V gamma 9V delta 2 T cells in humans and Aotus monkeys, a primate infection model for Plasmodium falciparum malaria.

Gammadelta T cells are implicated to play crucial roles during early immune responses to pathogens. A subset of human gammadelta T cells carrying the Vgamma9Vdelta2 TCR recognize small, phosphorylated nonpeptidic Ags. However, the precise role of these cells and the ligands recognized in human immune responses against pathogens remains unclear because of the lack of suitable animal models. We have analyzed the reactivity of spleen cells of the New World monkey Aotus nancymaae against isopentenyl pyrophosphate (IPP), a phosphorylated microbial metabolite selectively activating Vgamma9Vdelta2 T cells. Spleen cells were stimulated by IPP and the expanding cell population expressed the Vgamma9 TCR. TRGV-J and TRDV-D-J rearrangements expressed by IPP-stimulated cells of Aotus were analyzed by RT-PCR and DNA sequencing. The TRGV-J and TRDV-D-J rearrangements expressed by IPP-stimulated Aotus and human gammadelta T cells were similar with respect to 1) TCR gene segment usage, 2) a high degree of germline sequence homology of the TCR gene segments used, and 3) the diversity of the CDR3 regions. Phylogenetic analysis of human, Pan troglodytes, and A. nancymaae TRGV gene segments showed that the interspecies differences are smaller than the intraspecies differences with TRGV9 gene segments located on a distinct clade of the phylogenetic tree. The structural and functional conservation of Vgamma9Vdelta2 T cells in A. nancymaae and humans implicates a functionally important and evolutionary conserved mechanism of recognition of phosphorylated microbial metabolites.     

In vivo immunomanipulation of V gamma 9V delta 2 T cells with a synthetic phosphoantigen in a preclinical nonhuman primate model

Vgamma9Vdelta2(+) cells represent the major population of gammadelta T cells in primate blood and react in an MHC-unrestricted fashion to a set of low m.w. nonpeptide phosphoantigens. Two types of structurally related agonists have been discovered so far: the natural phosphoantigens (hydroxydimethyl allyl-pyrophosphate or isopentenyl-pyrophosphate (IPP)) acting directly on Vgamma9Vdelta2(+) TCR and aminobisphosphonates, which block the mevalonate pathway in target cells, leading to accumulation of natural phosphoantigens that in turn activate Vgamma9Vdelta2(+) cells. We demonstrate in the cynomolgus monkey that Vgamma9Vdelta2 can be manipulated in vivo with bromohydrin pyrophosphate (BrHPP)/Phosphostim, a potent synthetic agonist for which the mechanism of action is similar to natural phosphoantigens. Although of very short half-life, injection of BrHPP leads to strong activation of Vgamma9Vdelta2, inducing production of a high level of Th1 cytokines. Combination of BrHPP with low-dose rhIL-2 induces specific amplification of effector-memory peripheral Vgamma9Vdelta2 in blood in a dose-dependant manner. This transient response returns to baseline within 10-15 days. Successive infusions of BrHPP and rhIL-2 induce less vigorous expansions, suggesting a progressive exhaustion of the response. As no toxicity is detected with or without IL-2, this scheme represents a promising immunotherapeutic strategy for induction of systemic Th1 cytokines and massive expansion of gammadelta T cell subset with antitumor and anti-infectious properties.     

Missing HLA class I expression on Daudi cells unveils cytotoxic and proliferative responses of human gammadelta T lymphocytes

The major subset of human blood gammadelta T lymphocytes expresses the variable-region genes Vgamma9 and Vdelta2. These cells recognize non-peptidic phosphoantigens that are present in some microbial extracts, as well as the beta(2)-microglobulin-deficient Burkitt's lymphoma Daudi. Most cytotoxic human Vgamma9/Vdelta2 T cells express inhibitory natural killer cell receptors for HLA class I that downmodulate the responses of the gammadelta T lymphocytes against HLA class I expressing cells. In this study we show that transfection of the human beta(2)-microglobulin cDNA into Daudi cells markedly inhibits the cytotoxic and proliferative responses of human Vgamma9/Vdelta2 T cells. This provides direct evidence that the "innate" specificity of human Vgamma9/Vdelta2 T-lymphocytes for Daudi cells is uncovered by the loss of beta(2)m by Daudi. However, Daudi cells that express HLA class I in association with mouse beta(2)m at the cell surface are recognized by human Vgamma9/Vdelta2 T cells close to the same degree as the parental HLA class I deficient Daudi cell line. Thus, proper conformation of the HLA class I molecules is required for binding to natural killer cell receptors. Cloning of the HLA class I A, B, and C molecules of Daudi cells and transfer of the individual HLA class I molecules of Daudi cells into the HLA class I deficient recipient cell lines.221 and C1R demonstrate that for some human gammadelta T-cell clones cytolysis can be entirely inhibited by single HLA class I alleles while for other clones single HLA class I alleles only partially inhibit cytotoxicity. Thus, most human Vgamma9/Vdelta2 T cells represent a population of killer cells that evolved like NK cells to destroy target cells that have lost expression of individual HLA class I molecules but with a specificity that is determined by the Vgamma9/Vdelta2 TCR.     

Regulatory role of gammadelta T cells in the recruitment of CD4+ and CD8+ T cells to lung and subsequent pulmonary fibrosis

The mechanisms by which T cells accumulate in the lungs of patients with pulmonary fibrosis are poorly understood. Because the lung is continually exposed to microbial agents from the environment, we repeatedly exposed C57BL/6 mice to the ubiquitous microorganism, Bacillus subtilis, to determine whether chronic exposure to an inhaled microorganism could lead to T cell accumulation in the lungs and subsequent pulmonary fibrosis. C57BL/6 mice repeatedly treated with B. subtilis for 4 consecutive weeks developed a 33-fold increase in the number of CD4+ T cells and a 354-fold increase in gammadelta T cells in the lung. The gammadelta T cells consisted almost entirely of Vgamma6/Vdelta1+ cells, a murine subset bearing an invariant TCR the function of which is still unknown. Treatment of C57BL/6 mice with heat-killed vs live B. subtilis resulted in a 2-fold increase in the number of CD4+ T cells in the lung but no expansion of gammadelta T cells indicating that gammadelta cells accumulate in response to live microorganisms. In addition, mice treated with heat-killed B. subtilis developed significantly increased pulmonary fibrosis compared with mice treated with the live microorganism. Mice deficient in Vgamma6/Vdelta1+ T cells when treated with B. subtilis had a 231-fold increase in lung CD4+ T cells and significantly increased collagen deposition compared with wild-type C57BL/6 mice, consistent with an immunoregulatory role for the Vgamma6/Vdelta1 T cell subset. These findings indicate that chronic inhalation of B. subtilis can result in T cell accumulation in the lung and fibrosis, constituting a new model of immune-mediated pulmonary fibrosis.     

Phosphostim-activated gamma delta T cells kill autologous metastatic renal cell carcinoma

Metastatic renal cell carcinoma, inherently resistant to conventional treatments, is considered immunogenic. Indeed, partial responses are obtained after treatment with cytokines such as IL-2 or IFN-alpha, suggesting that the immune system may control the tumor growth. In this study, we have investigated the ability of the main subset of peripheral gammadelta lymphocytes, the Vgamma9Vdelta2-TCR T lymphocytes, to induce an effective cytotoxic response against autologous primary renal cell carcinoma lines. These gammadelta T cells were expanded ex vivo using a Vgamma9Vdelta2 agonist, a synthetic phosphoantigen called Phosphostim. From 11 of 15 patients, the peripheral Vgamma9Vdelta2 T cells were amplified in vitro by stimulating PBMCs with IL-2 and Phosphostim molecule. These expanded Vgamma9Vdelta2 T cells express activation markers and exhibit an effector/memory phenotype. They display a selective lytic potential toward autologous primary renal tumor cells and not against renal NC. The lytic activity involves the perforin-granzyme pathway and is mainly TCR and NKG2D receptor dependent. Furthermore, an increased expression of MHC class I-related molecule A or B proteins, known ligands of NKG2D, are detected on primary renal tumor cells. Interestingly, from 2 of the 11 positive cultures in response to Phosphostim, expanded-Vgamma9Vdelta2 T cells present an expression of killer cell Ig-like receptors, suggesting their prior recruitment in vivo. Unexpectedly, on serial frozen sections from three tumors, we observe a gammadelta lymphocyte infiltrate that was mainly composed of Vgamma9Vdelta2 T cells. These results outline that Vgamma9Vdelta2-TCR effectors may represent a promising approach for the treatment of metastatic renal cell carcinoma.     

Predominance of Vgamma9/Vdelta2 T lymphocytes in the cerebrospinal fluid of children with tuberculous meningitis: reversal after chemotherapy.

BACKGROUND: We analyzed the gammadelta T cell composition and responses in the peripheral blood and cerebrospinal fluid (CSF) of children affected by tuberculous meningitis (TBM) and in control children. MATERIALS AND METHODS: Peripheral blood and CSF samples were stimulated with different phosphoantigens and IL-2, and expansion of Vgamma9/Vdelta2 T cells assessed by FACS analysis. Vgamma9/Vdelta2 lines were obtained by culturing CSF or peripheral blood mononuclear cells (PBMC) in vitro with phosphoantigens and IL-2 for 2 months, and tested for proliferation and cytokine production in response to phosphoantigens. Vdelta2(D)Jdelta junctional sequence length was assessed by PCR. RESULTS: The repertoire of gammadelta T cells from the CSF of TBM patients was characterized by the predominance of Vgamma9/Vdelta2 T lymphocytes, which accounted for >80% of gammadelta T cells. Vgamma9/Vdelta2 cells from the CSF of TBM children responded to different synthetic and natural (mycobacterial) phosphoantigens and produced discrete amounts of IFN-gamma and TNF-alpha. The in vitro expansion of Vgamma9/Vdelta2 T cells from CSF and peripheral blood of TBM patients prominently decreased following chemotherapy, and similarly, the proportion of ex vivo unstimulated Vgamma9/Vdelta2 T cells in CSF of TBM patients decreased to levels detected in the CSF of control subjects. Vdelta2 CDR3 TCR analysis showed that the remaining Vdelta2 cells in the CSF of TBM patients were still polyclonal. CONCLUSIONS: These findings are consistent with an involvement of Vgamma9/Vdelta2 T cells in TBM. http://link. springer-ny.com/link/service/journals/00020/bibs/5n5p301. html     

Exacerbation of collagen-induced arthritis by oligoclonal, IL-17-producing gamma delta T cells

Murine gammadelta T cell subsets, defined by their Vgamma chain usage, have been shown in various disease models to have distinct functional roles. In this study, we examined the responses of the two main peripheral gammadelta T cell subsets, Vgamma1(+) and Vgamma4(+) cells, during collagen-induced arthritis (CIA), a mouse model that shares many hallmarks with human rheumatoid arthritis. We found that whereas both subsets increased in number, only the Vgamma4(+) cells became activated. Surprisingly, these Vgamma4(+) cells appeared to be Ag selected, based on preferential Vgamma4/Vdelta4 pairing and very limited TCR junctions. Furthermore, in both the draining lymph node and the joints, the vast majority of the Vgamma4/Vdelta4(+) cells produced IL-17, a cytokine that appears to be key in the development of CIA. In fact, the number of IL-17-producing Vgamma4(+) gammadelta T cells in the draining lymph nodes was found to be equivalent to the number of CD4(+)alphabeta(+) Th-17 cells. When mice were depleted of Vgamma4(+) cells, clinical disease scores were significantly reduced and the incidence of disease was lowered. A decrease in total IgG and IgG2a anti-collagen Abs was also seen. These results suggest that Vgamma4/Vdelta4(+) gammadelta T cells exacerbate CIA through their production of IL-17.     

Synthetic phosphoantigens enhance human Vgamma9Vdelta2 T lymphocytes killing of non-Hodgkin's B lymphoma.

BACKGROUND: Non-Hodgkin's B lymphomas (NHL) are often resistant to conventional treatments and, until now, immunotherapeutic approaches against NHL only aimed at inducing anti-tumor effectors. Nevertheless, human blood Vgamma9Vdelta2 T lymphocytes represent an abundant pool of cytotoxic tumor-reactive cells. Vgamma9Vdelta2 T cells are strongly activated by natural compounds, from which powerful synthetic ligands have been derived. These synthetic antigens induce efficient Vgamma9Vdelta2 T cell responses in vitro. MATERIALS AND METHODS: We set up a series of Vgamma9Vdelta2 T cell-activation experiments, including cytotoxic activity and amplification from whole blood cells. Several types of Vgamma9Vdelta2 effectors were challenged against a panel of 16 B lymphoma cell lines. These tests have been performed in the absence and presence of -specific synthetic ligands to evaluate the effect of such molecules on anti-tumor activity. RESULTS: We report here that Vgamma9Vdelta2 T cells recognize B lymphomas. This recognition is associated with the cytotoxic activity against B-lymphoma cells and/or proliferative responses, and appears to be T-cell antigen receptor (TCR)-dependent. Because few B lymphoma induce a complete set of Vgamma9Vdelta2 cell responses, a chemical ligand of Vgamma9Vdelta2 T cells was used to enhance both proliferation and cytotoxic activity of anti-B lymphoma effectors. We show that such synthetic compound improves Vgamma9Vdelta2 CTL numbers and lysis of B lymphoma lines, especially when the targets are already spontaneously recognized by these effectors. CONCLUSIONS: We report here that human Vgamma9Vdelta2 T cells anti-B lymphoma response can be improved by use of specific synthetic ligands, which enhance their cytotoxic activity and allows their rapid expansion ex vivo.     

Fas-Fas ligand interactions are essential for the binding to and killing of activated macrophages by gamma delta T cells

Gammadelta T cells have a direct role in resolving the host immune response to infection by eliminating populations of activated macrophages. Macrophage reactivity resides within the Vgamma1/Vdelta6.3 subset of gammadelta T cells, which have the ability to kill activated macrophages following infection with Listeria monocytogenes (Lm). However, it is not known how gammadelta T cell macrophage cytocidal activity is regulated, or what effector mechanisms gammadelta T cells use to kill activated macrophages. Using a macrophage-T cell coculture system in which peritoneal macrophages from naive or Lm-infected TCRdelta-/- mice were incubated with splenocytes from wild-type and Fas ligand (FasL)-deficient mice (gld), the ability of Vgamma1 T cells to bind macrophages was shown to be dependent upon Fas-FasL interactions. Combinations of anti-TCR and FasL Abs completely abolished binding to and killing of activated macrophages by Vgamma1 T cells. In addition, confocal microscopy showed that Fas and the TCR colocalized on Vgamma1 T cells at points of contact with macrophages. Collectively, these studies identify an accessory or coreceptor-like function for Fas-FasL that is essential for the interaction of Vgamma1 T cells with activated macrophages and their elimination during the resolution stage of pathogen-induced immune responses.     

V gamma 9V delta 2 T cell response to colon carcinoma cells

During analysis of CD8 T cells derived from ascites of a colon cancer patient, we isolated a Vgamma9Vdelta2 T cell clone showing strong reactivity against autologous tumor cell lines. This clone killed a large fraction of allogeneic colon carcinoma and melanoma cell lines, but did not affect a normal colon cell line, colon fibroblasts, or melanocytes. Tumor cell recognition was TCR and NKG2D dependent and induced TNF-alpha and IFN-gamma secretion by the clone; accordingly, tumor targets expressed several NKG2D ligands, such as MHC class I chain-related gene A and UL16-binding protein molecules. Colon tumor recognition by Vgamma9Vdelta2 T cells was highly dependent on isopentenyl pyrophosphate production and ICAM-1 expression by target cells. Finally, similar reactivity patterns against colon carcinoma cell lines were observed using polyclonal Vgamma9Vdelta2 T cells of various origins, and Vgamma9Vdelta2 lymphocytes were present in the majority of colon tumor samples studied. Together, these results suggest that Vgamma9Vdelta2 T cells contribute to the natural immune surveillance against colon cancers. Therefore, this study provides a strong rationale for the use of Vgamma9Vdelta2 T cell agonists in immunotherapies targeting colon 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.     

Lack of CD27-CD45RA-V gamma 9V delta 2+ T cell effectors in immunocompromised hosts and during active pulmonary tuberculosis.

In humans, the circulating pool of mycobacteria-reactive Vgamma9Vdelta2+ T cells is expanded with age and may contribute to Mycobacterium tuberculosis immunosurveillance. We observed that two subsets of Vgamma9Vdelta2+ T cells could be identified on the basis of CD27 expression in immunocompetent adults, showing that functionally differentiated gammadelta T cells have lost CD27 expression. In contrast, the CD27-CD45RA-Vgamma9Vdelta2+ T cell subset of effector cells was absent in cord blood cells from healthy newborns and lacking in the peripheral blood from HIV-infected patients. Moreover, circulating Vgamma9Vdelta2+ T cell effectors were significantly reduced in patients with acute pulmonary tuberculosis, resulting in a reduced frequency of IFN-gamma-producing cells after stimulation with nonpeptidic mycobacterial ligands. These observations indicate that monitoring and boosting gammadelta T cell effectors could be clinically relevant both in immunocompromised hosts and during active tuberculosis disease.     

Production of TNF-alpha by human V gamma 9V delta 2 T cells via engagement of Fc gamma RIIIA, the low affinity type 3 receptor for the Fc portion of IgG, expressed upon TCR activation by nonpeptidic antigen

Human lymphocytes expressing the gammadelta TCR represent a minor T cell subpopulation found in blood. The majority of these cells express Vgamma9Vdelta2 determinants and respond to nonpeptidic phosphoantigens. Several studies have shown that, in vivo, the percentage of Vgamma9Vdelta2 T cells dramatically increases during pathological infection, leading to the hypothesis that they play an important role in the defense against pathogens. However, the specific mechanisms involved in this response remain poorly understood. It has been established that Vgamma9Vdelta2 T cells display potent cytotoxic activity against virus-infected and tumor cells, thereby resembling NK cells. In this study, we show that, upon stimulation by nonpeptidic Ags, Vgamma9Vdelta2 T cells express FcgammaRIIIA (CD16), a receptor that is constitutively expressed on NK cells. CD16 appears to be an activation Ag for Vgamma9Vdelta2 T cells. Indeed, ligation of CD16 on Vgamma9Vdelta2 T cells leads to TNF-alpha production. This TNF-alpha production, which is dependent (like that induced via the TCR-CD3 complex) on the activation of the p38 and extracellular signal-regulated kinase-2 mitogen-activated protein kinases, can be modulated by CD94 NK receptors. Therefore, it appears that Vgamma9Vdelta2 T cells can be physiologically activated by two sequential steps via two different cell surface Ags: the TCR-CD3 complex and the FcgammaRIIIA receptor, which are specific cell surface Ags for T lymphocytes and NK cells, respectively. This strongly suggests that, in the general scheme of the immune response, Vgamma9Vdelta2 T cells represent an important subpopulation of cells that play a key role in the defense against invading pathogens.     

Patterns of chemokine receptor expression on peripheral blood gamma delta T lymphocytes: strong expression of CCR5 is a selective feature of V delta 2/V gamma 9 gamma delta T cells

Gammadelta T lymphocytes play an important role in the immune defense against infection, based on the unique reactivity of human Vdelta2Vgamma9 gammadelta T cells toward bacterial phosphoantigens. Chemokines and their corresponding receptors orchestrate numerous cellular reactions, including leukocyte migration, activation, and degranulation. In this study we investigated the expression of various receptors for inflammatory and homeostatic chemokines on peripheral blood gammadelta T cells and compared their expression patterns with those on alphabeta T cells. Although several of the analyzed receptors (including CCR6, CCR7, CXCR4, and CXCR5) were not differentially expressed on gammadelta vs alphabeta T cells, gammadelta T cells expressed strongly increased levels of the RANTES/macrophage inflammatory protein-1alpha/-1beta receptor CCR5 and also enhanced levels of CCR1-3 and CXCR1-3. CCR5 expression was restricted to Vdelta2 gammadelta T cells, while the minor subset of Vdelta1 gammadelta T cells preferentially expressed CXCR1. Stimulation with heat-killed extracts of Mycobacterium tuberculosis down-modulated cell surface expression of CCR5 on gammadelta T cells in a macrophage-dependent manner, while synthetic phosphoantigen isopentenyl pyrophosphate and CCR5 ligands directly triggered CCR5 down-modulation on gammadelta T cells. The functionality of chemokine receptors CCR5 and CXCR3 on gammadelta T cells was demonstrated by Ca(2+) mobilization and chemotactic response to the respective chemokines. Our results identify high level expression of CCR5 as a characteristic and selective feature of circulating Vdelta2 gammadelta T cells, which is in line with their suspected function as Th1 effector T cells.