Human gamma delta-T lymphocytes express and synthesize connective tissue growth factor: effect of IL-15 and TGF-beta 1 and comparison with alpha beta-T lymphocytes

T lymphocytes bearing the gammadelta-TCR accumulate during wound healing and inflammation. However, the role of gammadelta-T lymphocytes in fibrogenic tissue reactions is not well understood. Therefore, we addressed the question of whether human gammadelta-T cells express and synthesize connective tissue growth factor (CTGF), a factor known to regulate fibrogenesis and wound healing. In addition, the lymphoblastic leukemia T cell line (Loucy) that possesses characteristics typical of gammadelta-T cells was used as a model to evaluate the regulation of CTGF gene expression. Blood gammadelta-T cells isolated from healthy donors were grown in the presence of IL-15/TGF-beta1 for 48 h and assessed for the expression and synthesis of CTGF. Nonstimulated human blood gammadelta-T cells and Loucy gammadelta-T cells expressed low levels of CTGF mRNA. Costimulation of the cells with IL-15 and TGF-beta1 resulted in a substantially increased level of CTGF mRNA expression within 4-8 h, and it remained elevated for at least 48 h. In contrast, no CTGF mRNA was detected when nonstimulated and stimulated human CD4+ alphabeta-T cells were analyzed. In addition, Western blot analysis of human gammadelta-T cell lysates prepared 4 days following stimulation with IL-15 and TGF-beta1 revealed a 38-kDa CTGF protein in cell lysates of human gammadelta-T cells. Detection was confirmed using Colo 849 fibroblasts, which can constitutively express high levels of CTGF. In conclusion, we herein present novel evidence that in contrast to CD4+ alphabeta-T cells human gammadelta-T cells are capable of expressing CTGF mRNA and synthesizing its corresponding protein, which supports the concept that gammadelta-T cells may contribute to wound healing or tissue fibrotic processes.

Innate T-cell immunity in HIV infection: the role of Vgamma9Vdelta2 T lymphocytes

There is growing interest in the use of innate immune reactions in the therapy and prophylaxis of various diseases. Natural T (NT) lymphocytes that recognize infected cells or microbial compounds without the classical genetic restriction by polymorphic MHC molecules are crucial components of innate immunity. NT cells bearing the Vgamma9Vdelta2 T-cell receptor (TCR) are broadly reactive against intracellular pathogens, can lyse human immunodeficiency virus (HIV) infected cells, and release cytokines capable of regulating HIV replication. The potent antiviral activities of Vgamma9Vdelta2 T cells may help to contain viral spread during acute HIV infection and/or to prevent the establishment of viral persistence. Substantial changes in the composition and function of circulating gammadelta T-cell pools occur in HIV-infected patients. These changes a) may contribute to the etiopathogenesis of opportunistic infections and neoplasms, and b) are partly reversed by highly active anti-retroviral therapy (HAART). In addition to direct antiviral activities, activated gammadelta T cells influence dendritic cell maturation and the adaptive alphabeta T-cell response. Vgamma9Vdelta2 T cells can be stimulated in vivo and in vitro by various nonpeptidic antigens (NpAgs) and recent animal experimental data suggest that activated Vgamma9Vdelta2 T cells may help to control SIV replication. Currently, NpAgs are being assessed as potential therapeutic agents in AIDS, tuberculosis and certain cancers susceptible to Vgamma9Vdelta2 T-cell effector mechanisms.

Emerging role of gammadelta T-cells in health and disease

The majority of T lymphocytes in the peripheral blood bear the alphabeta type of T-cell receptor (TCR) and less than 5% of circulating T lymphocytes bear the gammadelta type of TCR. The alphabeta and gammadelta T-cells contribute differently to the host immune defense. The immunologic function of gammadelta T-cell in humans is gradually unraveling. Pathologic studies have shown a relatively high proportion of gammadelta T-cells in the gastrointestinal mucosa, skin, and splenic red pulp where they appear to have an important immunologic function against pathogens attempting to enter body through the mucosal surfaces and possibly the skin. More data are emerging about the role of gammadelta T-cells in the course of infectious diseases and in the pathogenesis of autoimmunity. The possible role of these cells in immunologic surveillance against cancer has been inferred from their preferential expansion in certain malignancies. In parallel to the low frequency of these cells in normal lymphocytes, lymphomas bearing gammadelta type of T-cell receptors on cell surface are rare. These include hepatosplenic and non-hepatosplenic (including those involving the skin and those involving nasal cavity and upper aero digestive tract) and the rare non-B-cell cases of lymphomas seen in the immunosuppressed organ transplant patients. The limited available clinical data about gammadelta T-cell lymphomas suggest that these lymphomas tend to have an aggressive course particularly the hepatosplenic form with poor response to multi-agent chemotherapy and short median survival.

Bovine gamma delta T cell subsets express distinct patterns of chemokine responsiveness and adhesion molecules: a mechanism for tissue-specific gamma delta T cell subset accumulation

Subsets of gammadelta T cells localize to distinct tissue sites in the absence of exogenous Ag stimulation or development of effector/memory cells. Selective lymphocyte homing from the blood into tissues is controlled by a multistep process involving vascular and lymphocyte adhesion molecules, and G protein-linked chemokine receptors. The role of these mechanisms in the tissue tropism of gammadelta T cells is still poorly understood. In this study, we demonstrate that a subset of gammadelta T cells, most of which express an antigenically distinct TCR and are characterized by coexpression of CD8, selectively accumulated in tissues that expressed high levels of the mucosal vascular addressin, mucosal addressin cell adhesion molecule 1. These cells expressed higher levels of alpha(4)beta(7) integrins than other gammadelta T cell subsets and selectively migrated to the CCR7 ligand secondary lymphoid-tissue chemokine (CCL21). Integrin activation by CCL21 selectively increased CD8(+)gammadelta T cell binding to recombinant mucosal addressin cell adhesion molecule 1. These results suggest that the tropism of circulating CD8(+)gammadelta T cells for mucosal tissues is due, at least in part, to selective developmental expression of adhesion molecules and chemokine receptors.

Requirement for the p75 TNF-alpha receptor 2 in the regulation of airway hyperresponsiveness by gamma delta T cells

In a recent study, we found that TNF-alpha negatively regulates airway responsiveness through the activation of gammadelta T cells. The biological activities of TNF-alpha are mediated by two structurally related but functionally distinct receptors, p55 (TNFR1) and p75 (TNFR2), which are independently expressed on the cell surface. However, the relative importance of either TNFR in airway hyperresponsiveness (AHR) is unknown. To investigate the importance of these TNFRs in the development of allergen-induced AHR, p55-deficient and p75-deficient mice were sensitized to OVA by i.p. injection and subsequently challenged with OVA via the airways; airway responsiveness to inhaled methacholine was monitored. p75-deficient mice developed AHR to a similar degree as control mice. In contrast, p55-deficient mice, which were sensitized and challenged with OVA, failed to develop AHR. In p55-deficient mice, both the numbers of eosinophils and levels of IL-5 in bronchoalveolar lavage fluid were significantly lower than in sensitized/challenged control mice (p < 0.05). However, depletion of gammadelta T cells resulted in significant increases in AHR in the p55-deficient mice, whereas no significant effect of gammadelta T cell depletion was evident in the p75-deficient mice. These data indicate that, in the absence of TNFR1 (p55), where TNF-alpha uses the p75 pathway exclusively, the development of AHR is regulated by gammadelta T cells.

Gamma/delta T cell-deficient mice exhibit reduced disease severity and decreased inflammatory response in the brain in murine neurocysticercosis

In a recently developed mouse model for neurocysticercosis, the immune response was characterized by a massive influx of gammadelta T cells and a type 1 pathway of cytokine expression. To understand the role of gammadelta T cells during this infection, the cellular and cytokine response was analyzed in mice that lack gammadelta T cells (TCRdelta(-/-)). In TCRdelta(-/-) mice, Mesocestoides corti metacestodes preferentially invaded the extraparenchymal areas of the brain. Furthermore, parasites were able to escape from the brain and establish a systemic infection with liver and peritoneal involvement. Immunopathological studies indicated that TCRdelta(-/-) mice develop little inflammatory response and less neurological symptomatology. Significantly reduced numbers of T cells, macrophages, dendritic cells, and mast cells were present in the brain. The cytokine response in the brain of TCRdelta(-/-) mice appears to be a mixed type1/type 2 response with low levels of IL-2, IL-4, IL-10, IL-12, IL-13, IL-15, and IFN-gamma. To further investigate the immunological significance of this cell population, gammadelta T cells were adoptively transferred into intracranially infected TCRdelta(-/-) mice. gammadelta T cells were specifically recruited into the CNS in response to this parasitic infection, and they were able to target the infected brain within 12 h after transfer. These results suggest that gammadelta T cells are key players in the immune response elicited during this CNS infection and direct a type 1 response in wild-type mice upon infection.

T cell antigen receptor engagement and specificity in the recognition of stress-inducible MHC class I-related chains by human epithelial gamma delta T cells

Human gamma delta T cells with the TCR variable region V(delta)1 occur mainly in epithelia and respond to stress-induced expression of the MHC class I-related chains A and B, which have no function in Ag presentation. MIC function as ligands for NKG2D-DAP10, an activating receptor complex that triggers NK cells, costimulates CD8 alpha beta and V(gamma)9V(delta)2 gamma delta T cells, and is required for stimulation of V(delta)1 gamma delta T cells. It is unresolved, however, whether triggering of V(delta)1 gamma delta TCRs is also mediated by MIC or by unidentified cell surface components. Soluble MICA tetramers were used as a binding reagent to demonstrate specific interactions with various V(delta)1 gamma delta TCRs expressed on transfectants of a T cell line selected for lack of NKG2D. Tetramer binding was restricted to TCRs derived from responder T cell clones classified as reactive against a broad range of MIC-expressing target cells and was abrogated when TCRs were composed of mismatched gamma- and delta-chains. These results and the inability of V(delta)1 gamma delta T cells to respond to target cells expressing the ULBP/N2DL ligands of NKG2D, which are highly divergent from MIC, indicate that MIC delivers both the TCR-dependent signal 1 and the NKG2D-dependent costimulatory signal 2. This dual function may serve to prevent erroneous gamma delta T cell activation by cross-reactive cell surface determinants.

Distinct structure and signaling potential of the gamma delta TCR complex

Alpha beta and gamma delta T cells are distinguished by the clonotypic subunits contained within their TCRs. Although the alpha beta TCR has been well characterized, much less is known about the gamma delta TCR. Here, we report that, unlike alpha beta T CRs, most gamma delta TCRs expressed on ex vivo gamma delta T cells lack CD3 delta. Despite this structural difference, signal transduction by the gamma delta TCR is superior to that of the alpha beta TCR, as measured by its ability to induce calcium mobilization, ERK activation, and cellular proliferation. Additionally, the TCR complexes expressed on primary gamma delta T cells contain only zeta zeta homodimers; however, following activation and expansion, Fc epsilon R1 gamma is expressed and is included in the gamma delta TCR complex. These results reveal fundamental differences in the primary structure and signaling potential of the alpha beta- and gamma delta TCR complexes.

Phenotypic analysis of oral tolerance to alloantigens: evidence that the indirect pathway of antigen presentation is involved

BACKGROUND

Oral administration of alloantigens induces down-regulation of Th1 immune responses and reduces the incidence of corneal graft rejection. This study examined the role of Th1 and Th2 cytokines, accessory cells, and lymphoid organs that are known to be instrumental in other forms of antigen-specific tolerance.

METHODS

Allogeneic dendritic cells (DC) were administered orally using a protocol that is known to reduce the incidence of corneal allograft rejection and prevent the generation of allospecific delayed-type hypersensitivity (DTH). Hosts included normal mice and gene knockout (KO) mice, including B cell-deficient (mu)MT, interleukin (IL)-4 KO, IL-10 KO, and interferon (IFN)-gamma KO mice. The requirement for either an intact spleen or thymus was also examined. Orally administered paraformaldehyde-fixed, UVB-treated, or sonicated allogeneic cells were tested to determine if dead cells were capable of inducing tolerance.

RESULTS

Studies on gene KO mice indicated that a Th1 cytokine (IFN-gamma) and a Th2 cytokine (IL-4) were needed for the development of oral tolerance to alloantigens. By contrast, IL-10 was not required. Although an intact spleen was necessary for the development of tolerance, removal of the thymus did not affect down-regulation of DTH.

CONCLUSIONS

Oral tolerance induced with allogeneic cells shares characteristics with antigen-specific unresponsiveness induced by other routes, yet there are some noteworthy differences. The capacity of killed or sonicated allogeneic cells to induce oral tolerance and enhance corneal graft survival indicates that oral tolerance to alloantigens can occur via the indirect pathway of alloantigen presentation. These results also emphasize the remarkable redundancy in the mechanisms that the immune system employs to produce antigen-specific unresponsiveness.

T cells expressing the gammadelta receptor are essential for Th2-mediated inflammation in patients with acute exacerbation of asthma

OBJECTIVE

T lymphocytes have a central regulatory role in the pathogenesis of asthma. The objective of this study was to characterize immunologically the activation stage of asthma and the functional profile of lymphocytes from induced sputum, with particular emphasis on gammadelta T cells.

METHODS

Induced sputum was collected from 10 patients with acute exacerbation of asthma, and from healthy controls. The expression of activation markers on freshly isolated induced sputum lymphocytes and T-cell subsets was analyzed by double immunofluorescent staining and flow cytometry. Fas ligand (FasL) was determined by reverse transcriptase-polymerase chain reaction analysis. The phenotype of gammadelta T-cell subpopulations was tested by A13 and BB3 monoclonal antibodies. In this context, the functional profile of gammadelta T cells was tested in a chromium releasing test.

RESULTS

A significantly decreased proportion of alphabeta T cells and an increased proportion of gammadelta T cells, CD56+ cells and CD8+ gammadelta T cells were found in asthma patients compared with healthy controls. In asthmatic patients, there is a significantly increased proportion of T cells expressing CD69 and CD25 antigen. After stimulation of gammadelta T cells, an increased expression of intracellular tumour necrosis factor-alpha, interleukin (IL)-4 and IL10 cytokines were found at higher levels than controls. Interferon-gamma was observed at similar levels in asthma patients and healthy controls. Freshly isolated T-cell receptor (TCR) gammadelta+ cells exhibited an increased percentage of FasL in our patient group. FasL mRNA was detected in TCR gammadelta+ cells before and after IL2 stimulation. TCR gammadelta+ cells were cytotoxic against the K562 cell line. This natural killer activity was mediated by the A13-positive subpopulation.

CONCLUSION

The presence of cytokines producing gammadelta cells in induced sputum of asthmatic patients is consistent with regulatory activities. These cells display also cytotoxic function.

The influence of gammadelta T cells on the CD4+ T cell and antibody response during a primary Plasmodium chabaudi chabaudi infection in mice

A primary infection with Plasmodium chabaudi chabaudi (AS) is characterized by an expansion of gammadelta cells after the acute phase of infection in mice. This is particularly marked during chronic infections in B cell-deficient mice. Infections in gammadelta T cell-deficient mice suggest that, although these cells play some role in the control of parasitaemia and can produce interferon-gamma, they do not appear to be involved in the development of hypoglycaemia, loss of weight and temperature during a P. c. chabaudi infection. However, gammadelta T cells do influence the nature of the CD4+ T cell response during infection since, in their absence, Th2-like responses, such as interleukin (IL)-4 production and help for malaria-specific antibody responses, are more pronounced. This alteration in CD4+ T cells is reflected in a more rapid and greater immunoglobulin (Ig)G1 and IgG3 antibody response to the parasite. The large gammadelta T cell expansion normally observed in infected B cell-deficient mice did not take place in the absence of IL-2, and double-knockout mice lacking both B cells and functional IL-2 were highly susceptible to lethal infection with P. c. chabaudi. The majority of the single IL-2 knockout mice, in contrast, were able to control and clear a primary infection, suggesting that for the CD4+ T cell and antibody response, IL-2 could be replaced by other cytokines.

Escherichia coli produces phosphoantigens activating human gamma delta T cells

Human Vgamma9delta2 T lymphocytes are suggested to play an important role in the immune response to various microbial pathogens. In contrast to alphabeta T cells, gammadelta T lymphocytes recognize small, non-protein, phosphate-bearing antigens (phosphoantigens) in a major histocompatibility complex-independent manner. Four different phosphoantigens termed TUBag1 to TUBag4 with a common 3-formyl-1-butyl-pyrophosphate moiety and isopentenyl-pyrophosphate have been isolated and identified from mycobacteria. However, natural occurring gammadelta T cell ligands from other bacterial species were not characterized so far. Here, we describe the structural identification of the two compounds responsible for the gammadelta T cell-stimulating capacity of Escherichia coli as similar to the mycobacterial phosphoantigens 3-formyl-1-butyl-pyrophosphate and its M(r) 275 homologue TUBag2. In addition, E. coli phosphoantigens exert bioactivities on gammadelta T cells with similar potencies to the mycobacterial phosphoantigens at 5-15 nm concentration. Furthermore, our results clearly prove that the deoxyxylulose 5-phophate pathway (also referred to as Rohmer metabolic route of isoprenoid biosynthesis) is essential for the biosynthesis of the phosphoantigens in E. coli. Because this pathway is absent from human cells, it proves an ideal target for focusing efficiently the antimicrobial selectivity of human gammadelta T lymphocytes.

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.

Distinct CpG oligonucleotide sequences activate human gamma delta T cells via interferon-alpha/-beta

Oligodeoxynucleotides with CpG motifs (CpG ODN) mimic microbial DNA and activate effectors of innate immunity including NK cells. Human gamma delta T cells (Vgamma9/Vdelta2) are antigen specific "natural memory" T cells in a preactivated stage, which respond to common non-protein phosphoantigens. Among several CpG ODN tested, distinct CpG ODN sequences characterized by inducing high amounts of IFN-alpha/-beta in PBMC elicited strong gamma delta T cell and NK cell responses, as determined by CD69 expression, IFN-gamma production, perforin content and lytic activity. These CpG ODN activated gamma delta T cells and NK cells in the absence of an additional stimulus and synergistically increased responsiveness to cell-type-specific antigens like isopentenylpyrophosphate for gamma delta T cells and NK-sensitive tumor cells for NK cells. NK cells and gamma delta T cells were activated via IFN-alpha/-beta released by CpG ODN-stimulated PBMC. Purified gamma delta T cells and NK cells did not respond to CpG ODN but to recombinant IFN-alpha/-beta. In conclusion, CpG ODN sequences were identified which, based on their ability to induce high amounts of IFN-alpha/-beta, represent strong adjuvants for "natural memory" cells including responses of gamma delta T cells to non-protein antigens. Early IFN-alpha/-beta dependent stimulation of IFN-gamma synthesis in NK cells and gamma delta T cells may contribute to the CpG ODN-induced Th1 bias of an evolving immune response.

T cell receptor specificity is critical for the development of epidermal gammadelta T cells

A particular feature of gammadelta T cell biology is that cells expressing T cell receptor (TCR) using specific Vgamma/Vdelta segments are localized in distinct epithelial sites, e.g., in mouse epidermis nearly all gammadelta T cells express Vgamma3/Vdelta1. These cells, referred to as dendritic epidermal T cells (DETC) originate from fetal Vgamma3+ thymocytes. The role of gammadelta TCR specificity in DETC's migration/localization to the skin has remained controversial. To address this issue we have generated transgenic (Tg) mice expressing a TCR delta chain (Vdelta6.3-Ddelta1-Ddelta2-Jdelta1-Cdelta), which can pair with Vgamma3 in fetal thymocytes but is not normally expressed by DETC. In wild-type (wt) Vdelta6.3Tg mice DETC were present and virtually all of them express Vdelta6.3. However, DETC were absent in TCR-delta(-/-) Vdelta6.3Tg mice, despite the fact that Vdelta6.3Tg gammadelta T cells were present in normal numbers in other lymphoid and nonlymphoid tissues. In wt Vdelta6.3Tg mice, a high proportion of in-frame Vdelta1 transcripts were found in DETC, suggesting that the expression of an endogenous TCR-delta (most probably Vdelta1) was required for the development of Vdelta6.3+ epidermal gammadelta T cells. Collectively our data demonstrate that TCR specificity is essential for the development of gammadelta T cells in the epidermis. Moreover, they show that the TCR-delta locus is not allelically excluded.

Role for T cell-independent B cell activity in the resolution of primary rotavirus infection in mice

We examined the importance of T cell-independent B cell activity in the resolution of primary murine (EDIM) rotavirus infection in adult mice. We showed that Rag 1 (C57BL / 6 background) and Rag 2 (BALB / c background) knockout mice, which lack both T and B cells, chronically shed high levels of rotavirus Ag in stool samples following oral inoculation. However, nude mice (BALB / c and C57BL / 6 backgrounds) and alpha beta TCR knockout mice (C57BL / 6 background) chronically shed 100-fold lower levels of virus in stool samples. Thus, B cells appeared to sharply reduce the level of chronic rotavirus shedding by a T cell-independent mechanism. C57BL / 6 mice depleted of CD4(+) cells or both CD4(+) and CD8(+) cells were also unable to resolve primary rotavirus infection but chronically shed equally low levels of rotavirus Ag in stool samples, whereas mice depleted of only CD8(+) cells resolved infection. Similar results were obtained with a second rotavirus strain (EC(w)) in which virus was shed chronically in stool samples at low levels in alpha beta TCR knockout mice and at high levels in Rag 1 knockout mice. Virus-specific intestinal IgA was readily detected in mice lacking thymic T cells and alpha beta T cells and in mice depleted of CD4(+) cells but levels were 95 % reduced in comparison to immunocompetent control mice. Together, these results show that B cells lacking CD4(+) T cell help have the capacity to substantially reduce rotavirus shedding, possibly through the production of T cell-independent IgA to rotavirus, but full resolution requires alpha beta T cells.

Immature thymocytes that fail to express TCRbeta and/or TCRgamma delta proteins die by apoptotic cell death in the CD44(-)CD25(-) (DN4) subset

Pre-TCR/CD3 signals are essential for survival and maturation of (CD44(-)25(+)) DN3 thymocytes via the (CD44(-)25(-)) DN4 stage to CD4(+)CD8(+) (DP) cells, a process termed beta-selection. The exact developmental stages of apoptosis resulting from lack of pre-TCR/CD3 signals have so far not been determined. Here we analyzed apoptotic cell death in relation to expression of clonotypic TCR polypeptides and to cell cycle status in immature thymocyte subpopulations of wild type (wt) mice and of several strains of mice with compromised pre-TCR/CD3 signaling complexes. In wt mice or pre-TCR/CD3-deficient mice, apoptotic cells could not be detected among DN3 cells but accumulated in a subset of DN4 expressing CD69. Apoptotic CD69(+)DN4 cells were rare in wt mice and were found among DN4 cells that were negative or low for intracellular TCRbeta and negative for TCRgamma delta polypeptide chains. Apoptotic CD69(+)DN4 cells were abundant in pre-TCR/CD3 signaling-deficient mice in which most DN4 cells failed to express clonotypic TCR polypeptides. Survival of DN4 cells, but not maturation of DN3 cells to DN4, was found to depend on the expression of clonotypic TCR polypeptides in the same cell. The results suggest that thymocytes unsuccessful in alpha beta or in gamma delta lineage development die by apoptosis in the DN4 subset.

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.

Does Parkinson's disease have an immunological basis? The evidence and its therapeutic implications

Parkinson's disease (PD) is an age-related neurodegenerative movement disorder of unknown aetiology. Immune abnormalities have been described in PD including the occurrence of autoantibodies against neuronal structures and high numbers of microglia cells expressing the histocompatibility glycoprotein human leucocyte antigen-DR in the substantia nigra. An infectious cause for PD has been discussed for years. Disturbed cellular and humoral immune functions in peripheral blood of patients with PD have been also reported. An elevated gammadelta(+) T cell population and increased immunoglobulin G immunity in CSF to heat shock proteins have been found in PD. Cytokines and apoptosis-related proteins were elevated in the striatum in patients with PD. Activated glial cells may participate in neuronal cell death in PD by providing toxic substances. We may conclude that the immune system is involved in the pathogenesis of PD. However, we are not able to determine whether the disturbances described above constitute a primary or secondary phenomenon. Immunomodulatory agents may have important applications in the development of new therapies for PD.

Requirement for tyrosine residues 315 and 319 within zeta chain-associated protein 70 for T cell development

Engagement of the T cell antigen receptor (TCR) induces the transphosphorylation of the zeta chain-associated protein of 70,000 Mr (ZAP-70) protein tyrosine kinase (PTK) by the CD4/8 coreceptor associated Lck PTK. Phosphorylation of Tyr 493 within ZAP-70's activation loop results in the enzymatic activation of ZAP-70. Additional tyrosines (Tyrs) within ZAP-70 are phosphorylated that play both positive and negative regulatory roles in TCR function. Phosphorylation of Tyr residues (Tyrs 315 and 319) within the Interdomain B region of the ZAP-70 PTK plays important roles in the generation of second messengers after TCR engagement. Here, we demonstrate that phosphorylation of these two Tyr residues also play important roles in mediating the positive and negative selection of T cells in the thymus.

Cloning a new allele form of bovine TNF-a

Although little is known on the function of gammadelta T lymphocytes, there is increasing evidence that gammadelta T lymphocytes are early responders and modulators of immune responses against pathogens and cytokines such as IL-2, IL-7, IL-15 and TNF-a. To study the role TNF-a on gammadelta T lymphocytes, we cloned bovine TNF-a. Sequence analysis revealed that a new allele form of bovine TNF-a was cloned which has 3 additional nucleotide sequences as well as 3 nucleotide substitutions compared with previously reported bovine TNF-a. Further studies are needed to document the functional significance of a new allele form of TNF-a in cattle.