Prostaglandin E2 amplifies IL-17 production by γδ T cells during barrier inflammation

Interleukin-17 (IL-17)-producing γδ (γδ17) T cells are innate-like lymphocytes that contribute to protective anti-microbial responses but are also implicated in pathogenic inflammation at barrier sites. Understanding tissue-specific signals that regulate this subset is important to boost host defense mechanisms, but also to mitigate immunopathology. Here, we demonstrate that prostaglandin E2 (PGE2), a cyclooxygenase-dependent member of the eicosanoid family, directly enhances cytokine production by circulating and tissue-specific γδ17 T cells in vitro. Gain- and loss-of-function in vivo approaches further reveal that although provision of PGE2 amplifies psoriasiform inflammation, ablation of host mPGES1-dependent PGE2 synthesis is dispensable for cutaneous γδ17 T cell activation. By contrast, loss of endogenous PGE2 production or depletion of the gut microbiota compromises intestinal γδ17 T cell responses and increases disease severity during experimental colitis. Together, our results demonstrate how a lipid mediator can synergize with tissue-specific signals to enhance innate lymphocyte production of IL-17 during barrier inflammation.

Chlorpyrifos induces redox imbalance-dependent inflammation in common carp lymphocyte through dysfunction of T-cell receptor γ

Chlorpyrifos is a poisonous pesticide that is highly toxic to fish and aquatic organisms. However, there are fewer reports about how chlorpyrifos influences the redox balance of immune cells. Herein, the head kidney tissue treated with chlorpyrifos to do transcriptome analysis and TCR γ was screened out. Subsequently, we established TCR γ knockdown and overexpression carp head kidney lymphocyte models, respectively, by using RNA interference and pcDNA3.1. Real-time PCR, fluorescent staining, oxidation and antioxidant kit were used to detect the related factors. We found that TCR γ knockdown significantly increased the mRNA expression of HSP70 and HSP90 and decreased the mRNA expression of SOD and CAT. Meanwhile, TCR γ knockdown reduced the activities of GSH, GSG-PX, T-AOC, CAT and SOD and increased the content of MDA and H₂ O₂ and activities of iNOS. Adverse results were obtained in TCR γ overexpression group. Additionally, TCR γ knockdown significantly increased the mRNA expression of IFN-γ, IL-1β, IL-8, IL-10, Nrf2 and NF-κB, but relieved TCR γ overexpression, in which the process of inflammation was activated. Our results reported here indicated that chlorpyrifos induces redox imbalance-dependent inflammation in common carp lymphocyte through dysfunction of T-cell receptor γ, and HSPs play potential protective role in entire process.

In vivo expansion and activation of γδ T cells as immunotherapy for refractory neuroblastoma: A phase 1 study

INTRODUCTION

CD3+ γδ+ T cells comprise 2% to 5% of circulating T cells with Vγ9Vδ2+ cells the dominant circulating subtype. Vγ9Vδ2+ cells recognize non-peptide phosphoantigens and stress-associated NKG2D ligands expressed on malignant cells. Strategies that incorporate the tumoricidal properties of γδ T cells represent a promising immunotherapeutic strategy for treatment of solid malignancies including neuroblastoma (NB). In this prospective, non-randomized Phase I trial, we assessed whether circulating Vγ9Vδ2+ cells could be safely expanded using intravenous ZOL (Zoledronate [Zometa]) and subcutaneous Interleukin-2 (IL-2) in patients with refractory NB.

METHODS

Patients 2 to 21 years of age with refractory neuroblastoma with no known curative therapeutic options received ZOL on day 1, and IL-2 on days 1 to 5 and 15 to 19 of each 28-day cycle (n = 4). Lymphocyte immunophenotyping was assessed weekly. Immunophenotyping studies from the treatment group were compared with healthy pediatric controls (n = 16; range, 5y-15y) and of untreated NB disease controls (n = 9; range, 4m-18y).

RESULTS

Treatment was well tolerated with no unexpected grade 3 and 4 toxicities. Lymphocyte subset counts did not differ significantly between volunteers and disease controls with the exception of γδ+ T cell counts that were significantly higher in healthy volunteers (212 + 93 vs. 89 + 42, P = 0.05). Study patients showed increases in circulating γδ+ T cell count (3-10 fold) after the first week, increasing into the range seen in healthy volunteers (125 + 37, P = 0.1940). Interestingly, all ZOL + IL-2 treated patients showed significant increases in CD3+CD4+CD27CD127 T cells that rose weekly in 2 patients throughout the 4 weeks of observation (maximum 41% and 24% of total CD3+CD4+ T cells, respectively).

CONCLUSIONS

In summary, combined ZOL and IL-2 is well tolerated and restored γδ+ T cell counts to the normal range with a moderate expansion of Natural Killer cells. Progressive increases in circulating CD4+ T cells with a regulatory phenotype cells may offset beneficial effects of this therapy.

CCR6 is required for epidermal trafficking of γδ-T cells in an IL-23-induced model of psoriasiform dermatitis

A subset of CC chemokine receptor-6(+) (CCR6(+)), γδ-low (GDL) T cells that express Th17 cytokines in mouse skin participates in IL-23-induced psoriasiform dermatitis. We use CCR6-deficient (knockout, KO) and wild-type (WT) mice to analyze skin trafficking patterns of GDL T cells and function-blocking mAbs to determine the role of CCR6 in IL-23-mediated dermatitis. Herein, CCL20 was highly upregulated in IL-23-injected WT mouse ear skin as early as 24 hours after initial treatment, and large numbers of CCR6(+) cells were observed in the epidermis of IL-23-injected WT mice. Anti-CCL20 mAbs reduced psoriasiform dermatitis and blocked recruitment of GDL T cells to the epidermis. In CCR6 KO mice, GDL T cells failed to accumulate in the epidermis after IL-23 treatment, but the total numbers of GDL T cells in the dermis of WT and CCR6 KO mice were equivalent. There was an ∼70% reduction in the proportion of IL-22(+) GDL T cells in the dermis of CCR6 KO mice (vs WT mice), suggesting that effector function and epidermal recruitment of GDL T cells are impaired in CCR6-deficient mice. Thus, these data show that CCR6 regulates epidermal trafficking of γδ-T-cell subsets in the skin and suggest the potential of CCR6 as a therapeutic target for psoriasis.

A lectin from Chinese mistletoe increases gammadelta T cell-mediated cytotoxicity through induction of caspase-dependent apoptosis

In this study, a mistletoe lectin (ML) was purified from Chinese mistletoe and the effect of this 60 kDa Chinese ML on human gammadelta T cell cytotoxicity, apoptosis and modulation of the cytokine network was studied. The cytotoxic properties of delta T cells was evaluated by using a (51)Cr release test and employed fluorescence-activated cell sorting and enzyme-linked immunosorbent assay analysis to quantify translocation of the cell membrane phospholipid, phosphatidylserine and nuclear DNA fragmentation during apoptosis. It was found that: (i) ML effectively stimulated gammadelta T cell proliferation in a dose- and time-dependent manner; (ii) ML increased gammadelta T cell cytotoxicity; (iii) ML could modulate lipopolysaccharide-induced cytokine release in a pro-inflammatory manner by increasing tumor necrosis factor (TNF)-alpha release and inhibiting the release of anti-inflammatory interleukin (IL)-10; (iv) ML induced apoptosis in caspase-dependent and CD95-independent manner. The results indicated that ML is a potent immunomodulator to human gammadelta T cell cytotoxicity, apoptos is and cytokine production.

Gamma-delta T-cell-mediated dilated cardiomyopathy

Gamma-delta T-cells are usually minor component of peripheral blood and lymphoid tissues, but may play an important role in autoimmune diseases. We here describe the first case of dilated cardiomyopathy (DCM) with heart infiltration by mostly gamma-delta T-cells, who improved significantly by steroid therapy. In general, steroid therapy has only a little effect on DCM, however these findings might have implications with respect to the selection of patients who might respond to immunosuppressive therapy.

Peripheral gammadelta T-lymphocytes as an innovative tool in immunotherapy for metastatic renal cell carcinoma

Renal cell carcinoma represents 3% of solid malignancies in adults and nephrectomy remains the main treatment. Failure of conventional approaches for patients presenting with advanced disease has prompted the exploration of new strategies. This review describes the potential use of peripheral gammadelta (Vgamma9Vdelta2) T-cells in metastatic renal cell carcinoma. This peripheral lymphocyte population from the innate immune system has demonstrated an in vitro antitumor cytotoxicity against primary or established renal cell lines. Moreover, these Vgamma9Vdelta2 lymphocytes undergo a rapid and extensive expansion in vitro as well as in vivo upon stimulation with a synthetic potent agonist, the bromohydrin pyrophosphate molecule. Preclinical results obtained on specific in vitro amplification of Vgamma9Vdelta2 T-cells by bromohydrin pyrophosphate in renal cell carcinoma patients are presented in this review, while Phase I clinical trials are currently running. As there is growing evidence for the low efficiency of monotherapy in cancer patients, innovative approaches combining immunomodulatory gammadelta agonists with classic chemotherapies or administration of antiangiogenic agents are discussed.

Aerosolized anti-T-cell-receptor antibodies are effective against airway inflammation and hyperreactivity

Aerosolized monoclonal antibodies (mAbs) specific for T-cell receptors (TCR) were used to manipulate T-cell function in airways of ovalbumin (OVA)-sensitized and -challenged mice with airway hyperresponsiveness (AHR). The inhaled mAbs were found to be effective at low doses, had little or no systemic effect and specifically abrogated both effector and regulatory functions of the targeted T cells. Specific mAbs targeting alphabeta T cells suppressed and those targeting gammadelta T cells enhanced AHR. Moreover, specific mAbs directed against subsets of gammadelta T cells varied in their effect on AHR. Using this approach of targeting either alphabeta or gammadelta T cells reduced airway eosinophila, although the effect of mAbs specific for alphabeta T cells was stronger. The use of aerosolized anti-TCR mAbs may offer an effective approach for the treatment of airway inflammation and AHR.

Quantitative structure-activity relationships for gammadelta T cell activation by bisphosphonates

gammadelta T cells are the first line of defense against many infectious organisms and are also involved in tumor cell surveillance and killing. They are stimulated by a broad range of small, phosphorus-containing antigens (phosphoantigens) as well as by the bisphosphonates commonly used in bone resorption therapy, such as pamidronate and risedronate. Here, we report the activation of gammadelta T cells by a broad range of bisphosphonates and develop a pharmacophore model for gammadelta T cell activation, in addition to using a comparative molecular similarity index analysis (CoMSIA) approach to make quantitative relationships between gammadelta T cell activation by bisphosphonates and their three-dimensional structures. The CoMSIA analyses yielded R(2) values of approximately 0.8-0.9 and q(2) values of approximately 0.5-0.6 for a training set of 45 compounds. Using an external test set, the activities (IC(50) values) of 16 compounds were predicted within a factor of 4.5, on average. The CoMSIA fields consisted of approximately 40% hydrophobic, approximately 40% electrostatic, and approximately 20% steric interactions. Since bisphosphonates are known to be potent, nanomolar inhibitors of the mevalonate/isoprene pathway enzyme farnesyl pyrophosphate synthase (FPPS), we also compared the pharmacophores for gammadelta T cell activation with those for FPPS inhibition, using the Catalyst program. The pharmacophores for gammadelta T cell activation and FPPS inhibition both consisted of two negative ionizable groups, a positive charge feature and an endocyclic carbon feature, all having very similar spatial dispositions. In addition, the CoMSIA fields were quite similar to those found for FPPS inhibition by bisphosphonates. The activities of the bisphosphonates in gammadelta T cell activation were highly correlated with their activities in FPPS inhibition: R = 0.88, p = 0.002, versus a human recombinant FPPS (N = 9 compounds); R = 0.82, p < 0.0001, for an expressed Leishmania major FPPS (N = 45 compounds). The bisphosphonate gammadelta T cell activation pharmacophore differs considerably, however, from that reported previously for gammadelta T cell activation by phosphoantigens (Gossman, W.; Oldfield, E. J. Med. Chem. 2002, 45, 4868-4874), suggesting different primary targets for the two classes of compounds. The ability to quite accurately predict the activity of bisphosphonates as gammadelta T cell activators by using 3D QSAR techniques can be expected to help facilitate the design of additional bisphosphonates for potential use in immunotherapy.

Expression and synthesis of fibroblast growth factor-9 in human γδ T-lymphocytes. Response to isopentenyl pyrophosphate and TGF-β1/IL-15

Gammadelta T-lymphocytes are believed to play a role in maintaining the normal configuration of epithelial tissue. As little is known about the factors mediating this function, we addressed the question of whether gammadelta T-lymphocytes produce fibroblast growth factor (FGF)-9 as well as two other growth factors associated with epithelial tissue reconstitution. Blood gammadelta T cells isolated from healthy donors were grown in the presence of isopentenyl pyrophosphate (IPP) or transforming growth factor-beta1 (TGF-beta1)/interleukin-15 (IL-15) for 24 h and were assessed for the expression and synthesis of FGF-9, keratinocyte growth factor (KGF), and epidermal growth factor (EGF). Resting human gammadelta T cells constitutively expressed KGF and FGF-9 mRNA but no EGF mRNA. In the presence of IPP, FGF-9 mRNA expression significantly increased in a dose-dependent manner, expression of KGF remained unaltered, and EGF mRNA could not be detected. In contrast to IPP, stimulation of the cells with TGF-beta1/IL-15 did not alter FGF-9 expression. Moreover, stimulation with anti-CD3 does not induce FGF-9 expression but triggers a high signal of interferon-gamma mRNA. Western blot analysis of gammadelta T cell lysates, prepared 4 days following stimulation with IPP, showed an increase of FGF-9 protein as compared with control cells. In conclusion, the results demonstrate for the first time that human blood and bronchoalveolar lavage gammadelta T-lymphocytes are capable of expressing FGF-9. The data also provide novel evidence that immunoregulatory cells can synthesize FGF-9.

Effect of immunomodulatory treatment of multiple sclerosis on lymphocyte surface immunomarkers

The aim of this study was to analyze the effect of immunomodulatory treatment of multiple sclerosis (MS) on lymphocyte surface immunomarkers. The special attention was given to TCR alpha/beta, gamma/delta and alpha/beta HLA-DR markers. Peripheral blood was obtained from 39 patients with clinically definite R-R MS, fulfilling the criteria of McDonald et al.[5]. The group of 15 patients was treated with interferon beta-1a (Avonex) intramuscularly once a week. The blood was obtained before and after two years of treatment. The other group of 10 patients was treated every day with 20 mg of glatiramer acetate (Copaxone) intracutaneously. Subsets of lymphocytes were analyzed by the method of flow cytometry, using monoclonal antibodies produced by Ortho Diagnostic System. The relative results were evaluated using Immuno Count II program. The frequency of the studied subsets in MS was markedly different from that in healthy persons. The higher number of CD4, TCR alpha/beta positive cells and higher CD4/CD8 ratio was observed. In comparison to healthy individuals, in MS patients a decreased number of TCR gamma/delta, and alpha/beta HLA-DR was found. After therapy with glatiramer acetate, CD3 and CD8 positive lymphocytes were more frequently observed than before the drug administration. The CD4/CD8 ratio was markedly decreased. The effect of interferon beta-1a treatment was similar as in the previous group, i.e. a slight increase in CD3 and CD8 was noticed after therapy. Despite the differences in action of both immunomodulatory drugs, which was established in several studies, we like to stress some similarity in their effect on CD3, CD8, alpha/beta HLA-DR and gamma/delta HLA-DR immunomarkers frequency in lymphocyte, and on the CD4/CD8 ratio. This may mean that there are some common immunological steps of special importance for the clinical effect in MS.

Differential requirements for proliferation of CD4+ and γδ+ T cells to spirochetal antigens

Alphabeta+ and gammadelta+ T cells have different mechanisms of epitope recognition and are stimulated by antigens of different chemical nature. An immunization model with antigens from the spirochete Brachyspira hyodysenteriae was used to examine the requirements for proliferation of circulating porcine CD4+ and gammadelta+ T cells in mixed lymphocyte cultures. CD4+ T cells only responded to stimulation with B. hyodysenteriae antigens, whereas gammadelta+ T cells proliferated when cultures were stimulated with either spirochetal antigens or interleukin-2 (IL-2). T cells that had proliferated expressed high levels of IL-2-receptor-alpha (IL-2Ralpha). Furthermore, neutralization of IL-2 at the beginning of the culture period was more efficient in blocking gammadelta+ than CD4+ T cell proliferation. Immunization induced interferon-gamma (IFN-gamma) production by CD4+ T cells, whereas only a small fraction of the antigen-stimulated gammadelta+ T cells produced this cytokine. Our results indicate that, under the same environmental conditions, CD4+ T cell functions are more tightly regulated when compared to gammadelta+ T cells. We conclude that these differences are due, in part, to the enhanced gammadelta+ T cell responsiveness to IL-2.

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.

Mice lacking the CCR9 CC-chemokine receptor show a mild impairment of early T- and B-cell development and a reduction in T-cell receptor gammadelta(+) gut intraepithelial lymphocytes

CC chemokine receptor (CCR) 9, the receptor for the CC-chemokine CCL25/thymus-expressed chemokine (TECK), is mainly expressed by thymocytes and by intraepithelial (IEL) and lamina propria lymphocytes of the small intestine. To study the biologic role of CCR9, a mouse strain was generated in which the CCR9 gene was deleted. In spite of the high level of CCR9 found in double- and single-positive thymocytes and of the expression of its corresponding ligand on thymic stromal cells, CCR9 deletion had no major effect on intrathymic T-cell development. It was noted that there was only a one-day lag in the appearance of double-positive cells during fetal ontogeny in CCR9(-/-) thymi. When tested in chemotaxis assay, thymocytes isolated from CCR9(-/-) mice failed to respond to TECK/CCL25. Taken together, these results suggest that in thymocytes, CCR9 is the only physiologic receptor for TECK/CCL25, and that it is dispensable for proper T-cell development. Bone marrow pre-pro-B cells migrate in response to TECK/CCL25, but more mature B cells do not. Consistent with this observation, it was shown that there are fewer pre-pro-B cells in CCR9(-/-) mice than in wild-type mice. However, this diminution does not appear to have a detectable effect on the generation of a normal complement of mature B cells. Finally, it was shown that in the small intestine of CCR9-deficient mice, the intraepithelial T-cell-to-epithelial cell ratio is decreased, an observation that can be accounted for by a marked diminution of the T-cell receptor gammadelta(+) compartment.

Human anti-porcine gammadelta T-cell xenoreactivity is inhibited by human FasL expression on porcine endothelial cells

BACKGROUND

The role of gammadelta T cells during an immune response is still elusive and has been proposed to play a first line of defense along with other cells of the innate immune system, such as macrophages and natural killer cells, before alphabeta T-cell activation occurs. Innate cellular immune response plays a major role in xenograft rejection. We investigated the response of human gammadelta T cells to unmodified and human FasL (hFasL)-expressing xenogenic porcine endothelial cells.

METHODS

A 51Cr release assay was used to study the xenoreactivity of human gammadelta T-cell clones against porcine endothelial cells. Stable transfectants of porcine endothelial cells expressing hFasL were established and analyzed for their effectiveness in controlling this response.

RESULTS

Of the gammadelta T-cell clones tested, 38.9% were cytotoxic for porcine endothelial target cells. This cytotoxic response of human gammadelta T-cell clones was significantly inhibited by a monoclonal antibody against human CD3. Incubation of gammadelta T-cell clones with concanamycin A, an inhibitor of the perforin/granzyme B pathway, caused inhibition of lysis of porcine endothelial cells. Inhibition was not observed upon incubation with either anti-FasL or anti-tumor necrosis factor-alpha monoclonal antibodies. Expression of hFasL on porcine endothelial cells significantly reduced lysis by human gammadelta T cells.

CONCLUSION

These results imply that human gammadelta T cells may represent an important obstacle to xenotransplantation. Specific strategies targeted at this subset of T cells could be important in controlling innate cellular response to xenografts and facilitate graft survival.

Modulation of the severity of experimental autoimmune encephalomyelitis by gammadelta T lymphocytes activated by mycobacterial antigens

Immunity to mycobacterial antigens may contribute to the maintenance of self-tolerance. Exposure of the immune system to mycobacterial antigen might well stimulate the immune system to exert control over unwanted self-reactive clones. We demonstrated that in vivo administration of Mycobacterium tuberculosis, PPD, and PPD peptide (180-196) prior to immunization with Myelin Basic Protein (MBP) led to a moderate increase of gammadelta T cells, suppression of the immune response, and reduction in the severity of Experimental Autoimmune Encephalomyelitis. The immunosuppression observed is due, at least in part, to the production of Transforming growth factor-beta (TGFbeta) by the gammadelta T lymphocytes.

Isopentenyl pyrophosphate, a mycobacterial non-peptidic antigen, triggers delayed and highly sustained signaling in human gamma delta T lymphocytes without inducing eown-modulation of T cell antigen receptor

The Vgamma9Vdelta2 T cell subset, which represents up to 90% of the circulating gammadelta T cells in humans, was shown to be activated, via the T cell receptor (TcR), by non-peptidic phosphorylated small organic molecules. These phosphoantigens, which are not presented by professional antigen-presenting cells, induce production of high amounts of interferon-gamma and tumor necrosis factor (TNF-alpha). To date, the specific signals triggered by these antigens have not been characterized. Here we analyze proximal and later intracellular signals triggered by isopentenyl pyrophosphate (IPP), a mycobacterial antigen that specifically stimulates Vgamma9Vdelta2 T cells, and compare these to signals induced by the non-physiological model using an anti-CD3 antibody. During antigenic stimulation we noticed that, except for the proximal p56(lck) signal, which is triggered early, the signals appear to be delayed and highly sustained. This delay, which likely accounts for the delay observed in TNF-alpha production, is discussed in terms of the ability of the antigen to cross-link and recruit transducing molecules mostly anchored to lipid rafts. Moreover, we demonstrate that, in contrast to anti-CD3 antibody, IPP does not induce down-modulation of the TcR.CD3 complex, which likely results in the highly sustained signaling and release of high levels of TNF-alpha.

IL-15 drives the specific migration of CD94+ and TCR-gammadelta+ intraepithelial lymphocytes in organ cultures of treated celiac patients

OBJECTIVES

Celiac disease (CD) is an under-diagnosed but extremely frequent disease, triggered by the ingestion of gliadin. The pathogenic mechanisms of CD are still poorly understood, but intraepithelial lymphocytes are considered to have a key role. We intended to define the subsets of T lymphocytes migrating upon gliadin challenge in organ cultures of treated celiac patients and establish the type of factor(s) driving such an infiltration.

METHODS

Duodenum biopsies from 10 treated celiacs and 7 controls were cultured in vitro with/without gliadin digest (1 mg/ml) or interleukin (IL)-15 (10 ng/ml). In 7 treated celiacs IL-7, IL-4, and IL-2 were similarly tested. Intraepithelial CD3, CD8, TCR-gammadelta, and CD94 were detected by immunohistochemistry and numbered per mm epithelium.

RESULTS

IL-15 but not IL-7, IL-4, or IL-2 induced intraepithelial increase of CD3+ and CD8+ cells in celiac and control intestine (p < 0.001 vs cultures with medium). IL-15 induced increases in the number of intraepithelial TCR- gammadelta+ and CD94+ cells only in celiacs (p < 0.001). IL-7 was also effective in increasing intraepithelial TCR-gammadelta+ (but not CD94+) cells in celiac biopsies (p < 0.001). Gliadin induced intraepithelial migration of CD3+, CD8+ (p < 0.001), and CD94+ (p < 0.05) cells in celiacs, but not in controls.

CONCLUSIONS

The results we describe in this report indicate that IL-15 might have a key role in modulating and driving intraepithelial infiltration and ultimately in the pathogenesis of CD.

Defective T cell function for inhibition of growth of Mycobacterium avium-intracellulare complex (MAC) in patients with MAC disease: restoration by cytokines

To define the immunopathologic mechanism underlying pulmonary Mycobacterium avium-intracellulare complex (MAC) disease in patients without AIDS, the ability of CD4(+) and gammadelta T cells to induce growth inhibition of MAC in monocytes was compared between patients and healthy control subjects. T cell-dependent growth inhibition and production of interferon-gamma and macrophage colony-stimulating factor decreased in patients. CD4(+) T and gammadelta T cells from patients were equally defective in inducing anti-MAC activity. The combination of these cytokines restored the ability of patients' T cells to control MAC growth. In experiments with allogeneic cocultures of gammadelta T cells and infected monocytes from patients and control subjects, healthy control T cells could augment growth inhibition of MAC in monocytes from patients, whereas patients' T cells could not, even in the presence of healthy control monocytes. These results indicate that the defect in T cells may be associated with impaired protective immunity against MAC in these patients.

In vivo gammadelta T cell priming to mycobacterial antigens by primary Mycobacterium tuberculosis infection and exposure to nonpeptidic ligands

BACKGROUND

The recognition of phosphorylated nonpeptidic microbial metabolites by Vgamma9Vdelta2 T cells does not appear to require the presence of MHC molecules or antigen processing, permitting rapid responses against microbial pathogens. These may constitute an important area of natural anti-infectious immunity. To provide evidence of their involvement in immune reactivities against mycobacteria, we measured the responsiveness of peripheral blood Vgamma9Vdelta2 T cells in children with primary Mycobacterium tuberculosis (MTB) infections.

MATERIALS AND METHODS

Peripheral blood mononuclear cells from 22 children with MTB infections and 16 positivity of tuberculin (PPD)-negative healthy children were exposed to nonpeptidic antigens in vitro and the reactivity of the Vgamma9Vdelta2 T cell subset with these antigens was determined using proliferation and cytokine assays. Also, responses of gammadelta T cells from rhesus monkeys stimulated with phosphoantigens in vivo were measured.

RESULTS

The Vgamma9Vdelta2 T cell responses were highly increased in infected children in comparison with age-matched controls. This augmented Vgamma9Vdelta2 T cell reactivity subsided after successful antibiotic chemotherapy, suggesting that persistent exposure to mycobacterial antigens is required for the maintenance of gammadelta T cell activation in vivo. The in vivo reactivity of Vgamma9Vdelta2 T cells to phosphoantigens was also analyzed in a rhesus monkey model system. Intravenous injections of phosphoantigens induced an activated state of simian Vgamma9Vdelta2 T cells which decreased after 2 months, i.e., with a time course similar to that seen in MTB-infected children.

CONCLUSIONS

The increased reactivity of Vgamma9Vdelta2 T cells to phosphoantigens appears to be dependent on constant antigenic exposure. Consequently, the assessment of Vgamma9Vdelta2 responses may be useful for monitoring the efficacy of antimycobacterial therapies.

Major histocompatibility complex class I molecules modulate activation threshold and early signaling of T cell antigen receptor-gamma/delta stimulated by nonpeptidic ligands

Killer cell inhibitory receptors and CD94-NKG2-A/B heterodimers are major histocompatibility complex class I-specific inhibitory receptors expressed by natural killer cells, T cell antigen receptor (TCR)-gamma/delta cells, and a subset of TCR-alpha/beta cells. We studied the functional interaction between TCR-gamma/delta and CD94, this inhibitory receptor being expressed on the majority of gamma/delta T cells. When engaged by human histocompatibility leukocyte antigen class I molecules, CD94 downmodulates activation of human TCR-gamma/delta by phosphorylated ligands. CD94-mediated inhibition is more effective at low than at high doses of TCR ligand, which may focus T cell responses towards antigen-presenting cells presenting high amounts of antigen. CD94 engagement has major effects on TCR signaling cascade. It facilitates recruitment of SHP-1 phosphatase to TCR-CD3 complex and affects phosphorylation of Lck and ZAP-70 kinase, but not of CD3 zeta chain upon TCR triggering. These events may cause abortion of proximal TCR-mediated signaling and set a higher TCR activation threshold.

Interleukin-15 preferentially promotes the growth of intestinal intraepithelial lymphocytes bearing gamma delta T cell receptor in mice

Several cytokines including stem cell factor (SCF) and interleukin (IL)-7 are known to be required for development of gamma delta T cell receptor (TCR) intestinal intraepithelial lymphocytes (i-IEL) in mice. We show here the effects of IL-15 on the proliferation and maintenance of murine gamma delta i-IEL in vitro. gamma delta i-IEL constitutively expressed a high level of IL-15 receptor alpha mRNA and proliferated in response to IL-15 more vigorously than alpha beta i-IEL. V gamma/delta repertoire analysis revealed that IL-15, like IL-2, induced polyclonal expansion of gamma delta i-IEL, whereas gamma delta i-IEL responding to IL-7 showed a V gamma/delta repertoire skewed towards V gamma 1/V delta 4, V delta 5. IL-15 efficiently prevented gamma delta i-IEL from apoptosis induced by growth factor deprivation. This rescue was accompanied by up-regulation of Bcl-2 expression. These results suggest that IL-15 plays important roles in proliferation and maintenance of gamma delta i-IEL.

Human gamma delta T cell subset-proliferative response to malarial antigen in vitro depends on CD4+ T cells or cytokines that signal through components of the IL-2R

We examined the cellular and molecular basis of the proliferative response of human gamma delta T cells in cultures of PBMC stimulated with blood-stage Plasmodium falciparum malarial Ag. Flow cytometry revealed that maximal gamma delta T cell proliferation occurs after maximal CD4+ alpha beta T cell proliferation. Depletion of CD4+ T cells from PBMC before stimulation with malarial Ag markedly reduces the number of proliferating gamma delta T cells, which suggests that CD4+ T cells function in providing help to gamma delta T cells to respond to this parasite Ag. Removal of gamma delta T cells, however, did not alter the expansion of the CD4+ T cell subset. The addition of exogenous IL-2, IL-4, or IL-15 restored the capacity of gamma delta T cells to proliferate in Ag-stimulated cultures of PBMC depleted of CD4+ T cells. mAbs specific for the alpha- and beta-subunits of the IL-2 receptor inhibit the gamma delta T cell subset expansion in cultures stimulated with malarial Ag. Taken together, these findings suggest that the proliferation of gamma delta T cells in response to malarial Ag is dependent on the presence of CD4+ alpha beta T cells, but the requirement for CD4+ alpha beta T cells can be met by cytokines that use the IL-2R.

Induction of V gamma 2 V delta 2 T cell proliferation by activated antigen-specific CD4+ T cells and IL-2

Human gamma delta T cells respond to a wide range of ligands including some T lymphocyte cellular antigens associated with viral infection. In the present study we examined the participation of gamma delta T cells in the proliferative response that is induced in human peripheral blood mononuclear cells (PBMC) by activated, antigen-reactive, CD4+ T cells. Activated, irradiated, myelin basic protein (MBP)-specific T cells stimulate brisk proliferation when cultured with freshly isolated, autologous PBMC. Determination of the phenotype of the responding PBMC T cells revealed a prominent expansion of gamma delta T cells, principally of the V gamma 2 subset. There was only minimal proliferation of PBMC following culture with irradiated, MBP-specific T cells that had not been recently activated. However, addition of rIL-2 to cultures of PBMC and nonstimulated MBP-specific T cells restored proliferation and the expansion of the gamma delta T cells. IL-2 alone did not mediate this effect. While MBP was a convenient antigen to use in these experiments, similar gamma delta T cell expansion in vitro was noted using activated, CD4+ T cells reactive with an exogenous antigen, Candida. In additional experiments, gamma delta-enriched T cell lines and certain V gamma 2 T cell clones continued to respond to activated but not to nonstimulated, CD4+ T cells. Overall, this study suggests that V gamma 2 V delta 2 T cells may proliferate as a consequence of the activation of CD4+ T cells. At least one ligand associated with T cell activation is required in addition to IL-2.

Role of IL-7 in the shaping of the pulmonary gamma delta T cell repertoire

Gamma delta T cells bearing the canonical fetal-type V gamma 6/V delta 1 rearrangements are the predominant gamma delta T cells in the lungs of adult mice. In contrast, these V gamma 6/V delta 1 T cells are virtually absent in the pulmonary epithelia of nude mice. The intraepithelial dominance of gamma delta T cells that express this particular TCR is thought to result from a preferred thymic pathway of gene rearrangement and not from TCR-mediated positive selection. We now show that gamma delta T cell precursors in the lung epithelium of both euthymic and athymic neonatal mice generate this rearrangement in situ. In athymic mice, these clonotypes do not survive, but can be rescued in vitro and in vivo by the lymphokine IL-7.

Erythropoietin induces activation of Stat5 through association with specific tyrosines on the receptor that are not required for a mitogenic response

The cytoplasmic domain of the erythropoietin receptor (EpoR) contains a membrane-distal region that is dispensable for mitogenesis but is required for the recruitment and tyrosine phosphorylation of a variety of signaling proteins. The membrane-proximal region of 96 amino acids is necessary and sufficient for mitogenesis as well as Jak2 activation, induction of c-fos, c-myc, cis, the T-cell receptor gamma locus (TCR-gamma), and c-pim-1. The studies presented here demonstrate that this region is also necessary and sufficient for the activation of Stat5A and Stat5B. The membrane-proximal domain contains a single tyrosine, Y-343, which when mutated eliminates the ability of the receptor to couple Epo binding to the activation of Stat5. Furthermore, peptide competitions demonstrate that this site, when phosphorylated, can disrupt Stat5 DNA binding activity, consistent with a role of Y-343 as a site of recruitment to the receptor. Cells expressing the truncated, Y343F mutant (a mutant with a Y-to-F alteration at position 343) proliferate in response to Epo in a manner comparable to that of the controls. However, in these cells, Epo stimulation does not induce the appearance of transcripts for cis, TCR-gamma, or c-fos, suggesting a role for Stat5 in their regulation.

Identification of an ionomycin/cyclosporin A-responsive element within the human T cell receptor gamma enhancer

Activation through the Ca2+/calcineurin pathway is essential to the transcription of many cytokine genes. The conserved cis-acting sequence, GGAAAA, and transcription factors binding to this sequence are involved in the response to increased intracellular Ca2+ concentrations. Here we report the identification and importance of the same sequence in a non-cytokine gene, the human T cell receptor gamma (TCRG) enhancer. Results from site-directed mutations and electrophoretic mobility shift assays strongly suggest that this sequence mediates the ionomycin-induced activation of the TCRG enhancer. Our studies provide an explanation for a previous observation that TCRG mRNA levels, but not mRNA levels for T cell receptor alpha and -beta, are increased by ionomycin treatment.

Development of TCR-gamma delta CD4-CD8+ alpha alpha but not TCR-alpha beta CD4-CD8+ alpha alpha i-IEL is resistant to cyclosporin A

Present evidence suggests that cyclosporin A (CSA) inhibits the development of both alpha beta and gamma delta T cells in the thymus. However, whether CSA can inhibit the development of murine intestinal intraepithelial lymphocytes (i-IEL) is unknown as most i-IEL are clearly derived from a different lineage than the conventional thymus-derived T cells found in the periphery. Using the adult thymectomized, lethally irradiated bone-marrow reconstituted chimera (ATXBM mice) as a model for the development of extrathymically derived i-IEL and the fetal thymus-grafted (FTG) nude mice as a model for the development of thymically derived i-IEL, we demonstrate that CSA nearly completely inhibited the development of extrathymically, and possibly thymically, derived TCR-alpha beta i-IEL. Most of the TCR-alpha beta i-IEL whose development was inhibited by CSA belonged to the CD4-CD8+ alpha alpha subset. In contrast, the development of extrathymically and thymically derived TCR-gamma delta i-IEL was completely resistant to CSA. The phenotype of CSA-resistant TCR-gamma delta i-IEL in these models was not different from those in control mice, and the TCR-gamma delta i-IEL in CSA-treated mice appear to be mature and activated as most were large, granular, and CD69+. Lastly, we demonstrate that CSA does not affect the extrathymic positive selection of V delta 4 i-IEL in C3H hosts. These results suggest that despite their similarity, the intracellular activation cascade involved after TCR stimulation between TCR-alpha beta CD4-CD8+ alpha alpha and TCR-gamma delta CD4-CD8+ alpha alpha i-IEL are markedly different.

Cytokine dependence of V gamma 3 thymocytes: mature but not immature V gamma 3 cells require endogenous IL-2 and IL-7 to survive--evidence for cytokine redundancy

It has previously been described that V gamma 3 cells can proliferate extensively in vitro in the presence of different cytokines. Here, the role of cytokines in the maintenance of V gamma 3 cells in the thymus has been determined. Culture of fetal thymocytes in cell suspension for 24 h showed that, whereas immature TCRlowHSAhigh V gamma 3 cells remained viable, all mature TCRhighHSAlow V gamma 3 cells died. These cells died by apoptosis since protein synthesis was required and flow cytometric analysis as well as DNA gel electrophoresis showed that the DNA was degraded to oligonucleosomal bands. Addition of IL-2, IL-4 or IL-7 to suspension cultures of fetal thymocytes rescued V gamma 3 cells from dying. Addition of IL-1, IL-3, IL-5, IL-6, IL-9, TNF-alpha or IFN-gamma was without effect. Phenotypic analysis showed that the alpha-chain of the IL-2 receptor (IL-2R alpha) was expressed by part of the immature V gamma 3 thymocytes, all mature V gamma 3 cells expressed the beta-chain of the IL-2 receptor (IL-2R beta). Addition of anti-IL-2R beta mAb to fetal thymic organ culture (FTOC) resulted in a moderate reduction of the cell number of mature V gamma 3 thymocytes. Addition of anti-IL-2R alpha, anti-IL-4 or anti-IL-7 mAb had no effect. The cell number of mature V gamma 3 cells was highly reduced when both anti-IL-2R beta and anti-IL-7 mAb were added to FTOC.(ABSTRACT TRUNCATED AT 250 WORDS)

Transient immunomodulation by intravenous methylprednisolone treatment of multiple sclerosis

The extent and duration of immunomodulation induced by high-dose corticosteroid treatment of clinical relapse of multiple sclerosis was investigated. Ten patients treated with a 5 day course of intravenous methylprednisolone (IVMP) (500 mg daily) were studied. Circulating lymphocyte subpopulations and mitogen-induced interleukin 2 (IL-2) and gamma-interferon (gamma-IFN) production were determined immediately before initiation of therapy (day 1), during therapy (24 h after first dose, day 2) and at 24 h and 1 week post therapy (days 6 and 12 respectively). T-cell subpopulation (CD3, CD4, CD8, CD4CD45RA, CD4CD45RO) levels fell within 24 h of initiation of therapy, rebounded above pretreatment levels at day 6 and normalised 1 week post therapy. Despite a reduction in total T-cell numbers during treatment, the gamma delta T-cell subpopulation was not significantly altered. HLA-DR expression on B cells and monocytes declined transiently on day 2 to approximately 50% of pretherapy levels. IL-2 and gamma-IFN production were reduced during therapy but returned to baseline levels by 24 h post therapy. The effects of IVMP on lymphocyte distribution and function appear to be short-lived and, therefore, may not be responsible for the rapid improvement associated with this form of treatment.

Nonpeptide ligands for human gamma delta T cells

gamma delta T cells respond to a variety of microbial pathogens and transformed cells. Their limited receptor repertoire and activation by mycobacterial antigens resistant to proteases suggest that they may recognize nonpeptide antigens. We have tested a variety of nonpeptide molecules for stimulation of human gamma delta T cells. Synthetic alkyl phosphates, particularly monoethyl phosphate (MEP), selectively activated gamma delta T cells and stimulated their proliferation in vitro. All gamma delta T cells stimulated by MEP expressed V gamma 2/V delta 2 receptors. The purified natural ligand of mycobacteria is chemically similar to, though distinct from, MEP and contains a phosphate residue that is critical for biological activity. Recognition and expansion of a specific T-cell receptor-bearing population to non-peptide ligands is unprecedented among T cells. We suggest that MEP mimics small natural ligands capable of expanding one subset of gamma delta T cells and that this recognition of nonpeptide antigens may play an important role in human immunity to pathogens.

Androgen-induced expression of the peripheral blood gamma delta T cell population in the chicken

Unlike alpha beta T cells, the physiologic significance of gamma delta T cells has remained elusive. In avian species they comprise a large circulating T cell subset. Here we report that in chicken around the time of sexual maturation (4 to 6 mo of age) a significant increase of the gamma delta T cells takes place in male but not in female chickens. The frequency of gamma delta T cells increases both in peripheral blood and spleen, but not in intestinal epithelium. This expansion is independent of MHC haplotype, being observed in various inbred and MHC-recombinant strains. Furthermore, administration of testosterone to young female chickens induces an equivalent increase in the frequency of gamma delta T cells in peripheral blood. These results indicate that sex, through androgens, has an effect on the gamma delta T cell numbers in a species, in which these cells form a major subset of peripheral lymphocytes.

Brefeldin A blocks the cytotoxicity of T cell receptor alpha/beta and gamma/delta cytotoxic T lymphocyte clones reacting against human autologous cancer cells

We studied the effector mechanism of T cell receptor (TCR) alpha/beta- and gamma/delta-type cytotoxic T lymphocyte (CTL) clones that react with human autologous tumor cells. Treatment of tumor cells with a fungal antibacterial reagent, brefeldin A (BFA), resulted in the inhibition of cytotoxicity of an autologous tumor (HST-2)-specific CD8+ TCR alpha/beta-type CTL, TcHST-2. Other anti-metabolites such as chloroquine, cycloheximide and colchicine did not affect the cytotoxicity. The cell-surface antigen expression, including MHC class I molecules, was not influenced by BFA treatment. Furthermore, BFA did not influence the cytotoxicity of lymphokine-activated killer cells and natural killer cells. Since BFA blocks the transport of peptides from endoplasmic reticulum to the Golgi apparatus, the above data suggest that BFA could affect washing out of the peptide fragments from the MHC class I groove. Consequently, target tumor cells were protected from killing by CTL. Moreover, we obtained a CD4-, 8-, TCR gamma/delta-type (V delta 1+) CTL clone, TcHOT, that reacts against an autologous ovarial carcinoma, HOT. BFA could also inhibit this cytotoxicity, and it is likely that different presenting molecules other than MHC class I proteins participate in the cytotoxicity of this TCR gamma/delta-type CTL. These studies suggest that both TCR alpha/beta- and gamma/delta-type CTL may require antigenic peptides that are most likely derived from the BFA-sensitive, intracellular endogenous target proteins.

Exposure to tetrachlorodibenzo-p-dioxin (TCDD) alters fetal thymocyte maturation

We previously reported that thymic atrophy and reduced thymic cellularity associated with prenatal exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in mice are characterized by quantitative alerations in the number of thymocytes expressing CD4 and CD8 surface antigens. In the present study, these observations have been extended to establish the specific thymocyte maturation processes affected by TCDD through an examination of cell size distributions, alpha beta and gamma delta T cell receptor (TCR) expression, peanut agglutinin (PNA) binding, and J11d marker analysis in murine thymocytes exposed prenatally to TCDD. Pregnant mice were administered vehicle, 1.5 or 3.0 micrograms/kg body wt TCDD by gavage on gestational Days (gd) 6-14. Flow cytometry analysis of gd 18 fetal thymocytes revealed a reduction in the number of small CD4+CD8+ double positive (DP) and PNA+, small thymocytes in the TCDD-exposed groups. The large cell population was reduced by TCDD to approximately 70% of control values. There was also a significant shift in TCR expression of thymocytes with a decrease in alpha beta TCR and a concommitant increase in gamma delta TCR expression from TCDD-exposed fetuses. The CD4-CD8+J11d+ thymocytes were increased in TCDD-treated mice while the more mature CD4-CD8+J11d- thymocyte numbers were similar to controls. Taken together, these data indicate that TCDD inhibits thymocyte maturation at the transition phase between the CD4-CD8+J11d+ phenotype and the DP/J11d+ thymocytes.

CD8 gamma delta cells: presence in the adult rat thymus and generation in vitro from CD4-/CD8- thymocytes in the presence of interleukin 2

Three to fifteen percent of peripheral T cells in adults express the recently described gamma delta T-cell antigen receptor (TcR) heterodimer. A small subpopulation of gamma delta cells express the CD8 accessory molecule. In this study, we analyzed the potential of highly purified CD4-/CD8-, double negative (DN) rat precursor thymocytes to give rise to gamma delta cells. We observed that in the presence of interleukin 2 (IL-2) and concanavalin A (ConA), both DN and CD8 cells expressing the gamma delta TcR were generated in vitro. We then examined the rat thymus for these cells and confirmed the presence of a previously undescribed CD8 TcR-alpha beta- subset in the rat thymus, expressing high levels of TcR-gamma and delta messages with no detectable TcR-alpha transcripts, similar to the cells generated in vitro in the presence of IL-2 and ConA.