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γδ T cells represent a substantial fraction of intestinal lymphocytes at homeostasis, but they also constitute a major lymphocyte population infiltrating colorectal cancers (CRCs); however, their temporal contribution to CRC development or progression remains unclear. Using human CRC samples and murine CRC models, we found that most γδ T cells in premalignant or nontumor colons exhibit cytotoxic markers, whereas tumor-infiltrating γδ T cells express a protumorigenic profile. These contrasting T cell profiles were associated with distinct T cell receptor (TCR)-Vγδ gene usage in both humans and mice. Longitudinal intersectional genetics and antibody-dependent strategies targeting murine γδ T cells enriched in the epithelium at steady state led to heightened tumor development, whereas targeting γδ subsets that accumulate during CRC resulted in reduced tumor growth. Our results uncover temporal pro- and antitumor roles for γδ T cell subsets.

Unlike conventional αβ T cells, γδ T cells typically recognize nonpeptide ligands independently of major histocompatibility complex (MHC) restriction. Accordingly, the γδ T cell receptor (TCR) can potentially recognize a wide array of ligands; however, few ligands have been described to date. While there is a growing appreciation of the molecular bases underpinning variable (V)δ1 + and Vδ2 + γδ TCR-mediated ligand recognition, the mode of Vδ3 + TCR ligand engagement is unknown. MHC class I-related protein, MR1, presents vitamin B metabolites to αβ T cells known as mucosal-associated invariant T cells, diverse MR1-restricted T cells, and a subset of human γδ T cells. Here, we identify Vδ1/2 - γδ T cells in the blood and duodenal biopsy specimens of children that showed metabolite-independent binding of MR1 tetramers. Characterization of one Vδ3Vγ8 TCR clone showed MR1 reactivity was independent of the presented antigen. Determination of two Vδ3Vγ8 TCR-MR1-antigen complex structures revealed a recognition mechanism by the Vδ3 TCR chain that mediated specific contacts to the side of the MR1 antigen-binding groove, representing a previously uncharacterized MR1 docking topology. The binding of the Vδ3 + TCR to MR1 did not involve contacts with the presented antigen, providing a basis for understanding its inherent MR1 autoreactivity. We provide molecular insight into antigen-independent recognition of MR1 by a Vδ3 + γδ TCR that strengthens an emerging paradigm of antibody-like ligand engagement by γδ TCRs., Competing Interests: Competing interest statement: J.R. is an inventor on patents describing MR1 tetramers and MR1 ligands.

A minor subset (approximately 5%) of peripheral T cells has their TCR build up from γ and δ chains instead of α and β-those are the γδ T lymphocytes. They can be functionally divided into subsets, e.g., Th1-, Th2-, Th9-, Th17-, Tfh-, and Treg-like γδ T cells. They share some specifics of both innate and adaptive immunity, and are capable of rapid response to a range of stimuli, including some viral and bacterial infections. Atopic diseases, including asthma, are one of major health-related problems of modern western societies. Asthma is one of the most common airway diseases, affecting people of all ages and having potential life-threatening consequences. In this paper, we review the current knowledge about the involvement of γδ T cells in the pathogenesis of asthma and its exacerbations. We summarize both the studies performed on human subjects as well as on the murine model of asthma. γδ T cells seem to be involved in the pathogenesis of asthma, different subsets probably perform opposite functions, e.g., symptom-exacerbating Vγ1 and symptom-suppressing Vγ4 in mice model of asthma.

γδ T cells are enriched at barrier sites such as the gut, skin, and lung, where their roles in maintaining barrier integrity are well established. However, how these cells contribute to homeostasis at the gingiva, a key oral barrier and site of the common chronic inflammatory disease periodontitis, has not been explored. Here we demonstrate that the gingiva is policed by γδ T cells with a T cell receptor (TCR) repertoire that diversifies during development. Gingival γδ T cells accumulated rapidly after birth in response to barrier damage, and strikingly, their absence resulted in enhanced pathology in murine models of the oral inflammatory disease periodontitis. Alterations in bacterial communities could not account for the increased disease severity seen in γδ T cell-deficient mice. Instead, gingival γδ T cells produced the wound healing associated cytokine amphiregulin, administration of which rescued the elevated oral pathology of tcrδ -/- mice. Collectively, our results identify γδ T cells as critical constituents of the immuno-surveillance network that safeguard gingival tissue homeostasis., Competing Interests: The authors declare no conflict of interest., (Copyright © 2018 the Author(s). Published by PNAS.)

Background: Previous studies reported HIV infection alters the distribution and function of γδ T cells and their subsets. γδ T phenotypes in healthy and diseased individuals has received little attention in Ethiopia. We conducted this study to analyze the distribution of γδ T cells, the subsets and levels of expression of activation (CD38), exhaustion or anergy (CD95, PD1), adhesion (N-CAM/CD56 and CD103), among HIV and TB infected patients., Method: The distributions of total γδ T cells, Vδ1 and Vδ2 T cells subsets were analyzed in clinical samples collected from asymptomatic HIV, pulmonary TB patients and apparently healthy controls. Multicolor flow cytometry and IFN-γ ELISA were used to assess surface markers and functional responses of Vδ2 T cells to isopentenyl pyrophosphate stimulation, respectively., Result: A total of 52 study participants were enrolled in this study, 22 HIV + TB-, 10 HIV-TB+ and 20 healthy controls. No significant differences were observed in the distribution of total γδ T cells and in the proportion of Vδ1 subsets in all study groups, though slightly higher proportions were observed in HIV + TB- patients for the latter, of borderline statistical significance (p = 0.07). However, the proportion of Vδ2 T cells, as well as the IFN-γ response to IPP stimulation, was significantly reduced in HIV + TB- patients compared to healthy controls (p < 0.002). Expression of the activation marker CD38 (p < 0.001) and adhesion marker CD103 (αEβ7) were significantly higher in the Vδ1 T cell subset among both HIV + TB- (p = 0.013) and HIV-TB+ (p = 0.006) patients compared to healthy controls. Similarly, exhaustion markers, CD95 and PD1, were significantly higher in these two T cell subsets among both HIV + TB- and HIV-TB+ patients (p < 0.01). Interestingly, we also observed an increased proportion of effector memory (CD45RA-CD27-) and effector cytotoxic (CD45RA + CD27-) Vδ2 T cell subsets in HIV negative pulmonary TB patients., Conclusion: In sum, HIV infection was associated with an increase in Vδ1 and a decrease in the function and frequencies of Vδ2 T cells. Moreover, increased effector Vδ2 T cells were observed among HIV negative pulmonary TB patients suggesting a potential role of these T cells in the host response to TB.

γδ T cells share characteristics of innate and adaptive immune cells and are involved in a broad spectrum of pro-inflammatory functions. Nonetheless, there is accumulating evidence that γδ T cells also exhibit regulatory functions. In this review, we describe the different phenotypes of regulatory γδ T cells in correlation with the identified mechanisms of suppression.

Epithelial tissues line the body providing a protective barrier from the external environment. Maintenance of these epithelial barrier tissues critically relies on the presence of a functional resident T cell population. In some tissues, the resident T cell population is exclusively comprised of γδ T cells, while in others γδ T cells are found together with αβ T cells and other lymphocyte populations. Epithelial-resident γδ T cells function not only in the maintenance of the epithelium, but are also central to the repair process following damage from environmental and pathogenic insults. Key to their function is the crosstalk between γδ T cells and neighboring epithelial cells. This crosstalk relies on multiple receptor-ligand interactions through both the T cell receptor and accessory molecules leading to temporal and spatial regulation of cytokine, chemokine, growth factor, and extracellular matrix protein production. As antigens that activate epithelial γδ T cells are largely unknown and many classical costimulatory molecules and coreceptors are not used by these cells, efforts have focused on identification of novel coreceptors and ligands that mediate pivotal interactions between γδ T cells and their neighbors. In this review, we discuss recent advances in the understanding of functions for these coreceptors and their ligands in epithelial maintenance and repair processes.

Despite evidence that γδ T cells play an important role during malaria, their precise role remains unclear. During murine malaria induced by Plasmodium chabaudi infection and in human P. falciparum infection, we found that γδ T cells expanded rapidly after resolution of acute parasitemia, in contrast to αβ T cells that expanded at the acute stage and then declined. Single-cell sequencing showed that TRAV15N-1 (Vδ6.3) γδ T cells were clonally expanded in mice and had convergent complementarity-determining region 3 sequences. These γδ T cells expressed specific cytokines, M-CSF, CCL5, CCL3, which are known to act on myeloid cells, indicating that this γδ T cell subset might have distinct functions. Both γδ T cells and M-CSF were necessary for preventing parasitemic recurrence. These findings point to an M-CSF-producing γδ T cell subset that fulfills a specialized protective role in the later stage of malaria infection when αβ T cells have declined., (Copyright © 2018. Published by Elsevier Inc.)

Celiac disease (CD) is a digestive and autoimmune disorder driven by an immune response to modified gluten peptides. Affected intestines show infiltrates of various T-cell and NK-cell subsets. It is currently unclear if individuals with subclinical CD have systemic abnormalities in immune cells. We here studied whether subclinical CD is associated with changes in blood CD57-expressing and Vδ1-expressing lymphocytes in children, and whether cytomegalovirus (CMV) infection modifies this association. Included were 1068 children from the Generation R Study. Serum Immunoglobulin G (IgG) levels against CMV were measured by ELISA; Tissue transglutaminase type 2 antibody (TG2A) levels with fluorescence enzyme immunoassay (FEIA). Duodenal biopsies, additional Human Leukocyte Antigen (HLA) DQ 2.2, 2.5 and 8 and endomysial antibody (EMA) typing were performed in TG2A positive children. Subclinical CD cases (n=12) had 1.8 fold (95% CI 1.06; 3.1) fewer Vδ1+ T cells which was predominantly observed in CMV seronegative children (p-interaction 0.02), and 2.7 fold (95% CI 1.25; 5.99) more CD57+ T cells than HLA DQ2/-DQ8 positive controls (n=339). Hence, children with subclinical CD have alterations in specific blood T cell subsets that are linked to viral pathology. The observed interaction effect between subclinical CD and CMV may contribute to the understanding of disease pathogenesis., (Copyright © 2017 Elsevier Inc. All rights reserved.)

In the thymus, hematopoietic progenitors commit to the T cell lineage and undergo sequential differentiation to generate diverse T cell subsets, including major histocompatibility complex (MHC)-restricted αβ T cell receptor (TCR) T cells and non-MHC-restricted γδ TCR T cells. The factors controlling precursor commitment and their subsequent maturation and specification into αβ TCR versus γδ TCR T cells remain unclear. Here, we show that the tyrosine phosphatase PTPN2 attenuates STAT5 (signal transducer and activator of transcription 5) signaling to regulate T cell lineage commitment and SRC family kinase LCK and STAT5 signaling to regulate αβ TCR versus γδ TCR T cell development. Our findings identify PTPN2 as an important regulator of critical checkpoints that dictate the commitment of multipotent precursors to the T cell lineage and their subsequent maturation into αβ TCR or γδ TCR T cells., (© 2017 Wiede et al.)

With the promise of T cell-based therapy for cancer finally becoming reality, this Review focuses on the less-studied γδ T cell lineage and its diverse responses to tumours. γδ T cells have well-established protective roles in cancer, largely on the basis of their potent cytotoxicity and interferon-γ production. Besides this, recent studies have revealed a series of tumour-promoting functions that are linked to interleukin-17-producing γδ T cells. Here, we integrate the current knowledge from both human and mouse studies to highlight the potential of γδ T cell modulation to improve cancer immunotherapy.

Background: Rasmussen encephalitis (RE) is a rare neuroinflammatory disease characterized by intractable seizures and progressive atrophy on one side of the cerebrum. Perivascular cuffing and clusters of T cells in the affected cortical hemisphere are indicative of an active cellular immune response., Methods: Peripheral blood mononuclear cells (PBMCs) and brain-infiltrating lymphocytes (BILs) were isolated from 20 RE surgery specimens by standard methods, and CD3(+) T cell populations were analyzed by flow cytometry. Gamma delta T cell receptor spectratyping was carried out by nested PCR of reversed transcribed RNA extracted from RE brain tissue, followed by high resolution capillary electrophoresis. A MiSeq DNA sequencing platform was used to sequence the third complementarity determining region (CDR3) of δ1 chains., Results: CD3(+) BILs from all of the RE brain specimens comprised both αβ and γδ T cells. The median αβ:γδ ratio was 1.9 (range 0.58-5.2) compared with a median ratio of 7.7 (range 2.7-40.8) in peripheral blood from the same patients. The αβ T cells isolated from brain tissue were predominantly CD8(+), and the majority of γδ T cells were CD4(-) CD8(-). Staining for the early activation marker CD69 showed that a fraction of the αβ and γδ T cells in the BILs were activated (median 42%; range 13-91%, and median 47%; range 14-99%, respectively). Spectratyping T cell receptor (TCR) Vδ1-3 chains from 14 of the RE brain tissue specimens indicated that the γδ T cell repertoire was relatively restricted. Sequencing δ1 chain PCR fragments revealed that the same prevalent CDR3 sequences were found in all of the brain specimens. These CDR3 sequences were also detected in brain tissue from 15 focal cortical dysplasia (FCD) cases., Conclusion: Neuroinflammation in RE involves both activated αβ and γδ T cells. The presence of γδ T cells with identical TCR δ1 chain CDR3 sequences in all of the brain specimens examined suggests that a non-major histocompatibility complex (MHC)-restricted immune response to the same antigen(s) is involved in the etiology of RE. The presence of the same δ1 clones in CD brain implies the involvement of a common inflammatory pathway in both diseases.

γδ T cells present a minor population of the T cell family which basically differs in construction of their T cell receptor (TCR). Thanks to the features of γδ TCR, these cells can acquire unique effector functions and play a specific role (not only) in antitumor immune response. In this article, we describe the basic characteristics of this cell population and their connection to cancer. In the experimental part we performed exploratory analysis of circulating γδ T cells in reference population and comparison with melanoma and breast carcinoma patients. The median percentage of γδ T cells from all lymphocytes was 2.9% (interquartile range-IQR 1.7-4%). The median absolute numbers of γδ cells per liter of blood was 5.05×10(7) (IQR 2.9-7.84×10(7)). The median percentage of γδ cells between all CD3 T cells was 3.9% (IQR 2.3-5.6%). No correlation between γδ T cells levels and gender or age was observed in reference population. Detailed immunophenotyping was also conducted describing representation of memory subsets (using CD45RO and CD27 markers) and presence of surface markers HLADr, CD69, CD25, CD28, CCR7, CTLA 4, ICOS, PD 1L and PD 1 between γδ T cells of the controls and breast carcinoma patients. From this analysis, it is evident that γδ T cells do not represent a uniform population but they differ in surface markers as well as in their effector functions.

Atopic dermatitis (AD) is generally regarded as a type 2 helper T (Th2)-mediated inflammatory skin disease. Although the number of IL-17A-producing cells is increased in the peripheral blood and in acute skin lesion of AD patients, the role of IL-17A in the pathogenesis of AD remains unclear. To clarify this issue, we used murine AD models in an IL-17A-deficient condition. In a repeated hapten application-induced AD model, skin inflammation, IL-4 production in the draining lymph nodes (LNs), and hapten-specific IgG1 and IgE induction were suppressed in IL-17A-deficient mice. Vγ4(+) γδ T cells in the skin-draining LNs and Vγ5(-) dermal γδ T cells in the skin were the major sources of IL-17A. Consistently, in flaky-tail (Flg(ft/ft) ma/ma) mice, spontaneous development of AD-like dermatitis and IgE induction were attenuated by IL-17A deficiency. Moreover, Th2 differentiation from naive T cells was promoted in vitro by the addition of IL-17A. Taken together, our results suggest that IL-17A mediates Th2-type immune responses and that IL-17A signal may be a therapeutic target of AD.

UVB is a component of solar radiation primarily responsible for causing damage and cancer in irradiated skin, and disrupting immune homeostasis. The immediate harm and long-term health risks of excessive sunlight exposure are affecting the lives of nearly all people worldwide. Inflammation is a key mechanism underlying UVB's various detrimental effects. Here we show that activation of the protein kinase p38α is restricted to the epidermis in UVB-exposed skin, and that p38α ablation targeted to the epithelial compartment is sufficient to suppress UVB-induced inflammation. Mechanistically, loss of epithelial p38α signaling attenuates the expression of genes required to induce vascular leakage and edema, and also increases the steady-state abundance of epidermal γδ T cells, which are known to promote the repair of damaged epidermis. These effects of p38α deficiency delineate a molecular network operating at the organism-environment interface, and reveal conditions crucial to preventing the pathology resulting from sun-damaged skin.

A central role for T cells and their cytokines in the pathogenesis of psoriasis has been proposed; however, there are controversies over the details of this issue. The goal of this study is to summarise currently available data on the importance of T cells in psoriasis pathogenesis. A systematic review of the English medical literature was conducted by searching PubMed, Embase, ISI Web of Knowledge, and Iranian databases including Iranmedex, and SID for studies on associations between the involvement of T cell subsets and psoriasis. The results of the present study indicate that alterations in the number and function of different subsets of T-cells are associated with psoriasis. It appears that studies on T cell subsets contributed to understanding the immunopathogenesis of psoriasis. In addition, it may have provided novel therapeutic opportunities in ameliorating immunopathologies.

Interleukin (IL)-17A is expressed in the tumor microenvironment where it appears to contribute to tumor development, but its precise role in tumor immunity remains controversial. Here, we report mouse genetic evidence that IL-17A is critical for tumor growth. IL-17A-deficient mice exhibited reduced tumor growth, whereas systemic administration of recombinant mouse IL-17A promoted the growth of hepatocellular carcinoma. The tumor-promoting effect of IL-17A was mediated through suppression of antitumor responses, especially CD8(+) T-cell responses. Furthermore, we found that IL-17A was produced mainly by Vγ4 γδ T cells, insofar as depleting Vγ4 γδ T cells reduced tumor growth, whereas adoptive transfer of Vγ4 γδ T cells promoted tumor growth. Mechanistic investigations showed that IL-17A induced CXCL5 production by tumor cells to enhance the infiltration of myeloid-derived suppressor cells (MDSC) to tumor sites in a CXCL5/CXCR2-dependent manner. IL-17A also promoted the suppressive activity of MDSC to reinforce suppression of tumoral immunity. Moreover, we found that MDSC could induce IL-17A-producing γδ T cells via production of IL-1β and IL-23. Conversely, IL-17A could also enhance production of IL-1β and IL-23 in MDSC as a positive feedback. Together, our results revealed a novel mechanism involving cross-talk among γδ T cells, MDSCs, and tumor cells through IL-17A production. These findings offer new insights into how IL-17A influences tumor immunity, with potential implications for the development of tumor immunotherapy., (©2014 AACR.)

Vγ9Vδ2 (also termed Vγ2Vδ2) T cells, a major human peripheral blood γδ T cell subset, recognize microbial (E)-4-hydroxy-3-methylbut-2-enyl diphosphate and endogenous isopentenyl diphosphate in a TCR-dependent manner. The recognition does not require specific accessory cells, antigen uptake, antigen processing, or MHC class I, class II, or class Ib expression. This subset of T cells plays important roles in mediating innate immunity against a wide variety of infections and displays potent and broad cytotoxic activity against human tumor cells. Because γδT cells express both natural killer receptors such as NKG2D and γδ T cell receptors, they are considered to represent a link between innate and adaptive immunity. In addition, activated γδ T cells express a high level of antigen-presenting cell-related molecules and can present peptide antigens derived from destructed cells to αβ T cells. Utilizing these antimicrobial and anti-tumor properties of γδ T cells, preclinical and clinical trials have been conducted to develop novel immunotherapies for infections and malignancies. Here, we review the immunological properties of γδ T cells including the underlying recognition mechanism of nonpeptitde antigens and summarize the results of γδ T cell-based therapies so far performed. Based on the results of the reported trials, γδ T cells appear to be a promising tool for novel immunotherapies against certain types of diseases.

γδ T cell comprises about 5% of the overall T cell population, and they differ from conventional αβ T cells. Previous studies have indicated the contribution of γδ T cell to acute allograft rejection, but the role of γδ T cell in cardiac allograft vasculopathy (CAV) is not investigated. Hearts of adult B6.C-H-2(bm12) KhEg were heterotopically transplanted into major histocompatibility complex (MHC) class II-mismatched C57BL/6 mice (wild-type, γδ TCR(-/-)), which is an established murine model of chronic allograft rejection without immunosuppression. The survival of grafts was monitored daily by abdominal palpation until the complete cessation of cardiac contractility. Our current study demonstrated that γδ T cell receptor (TCR) deficiency significantly attenuated CAV, and this effect coincides with low expression of Hmgb1, IFN-γ and IL-17 while increased number of CD4(+) CD25(+) Foxp3(+) regulatory T cells, and depletion of regulatory T cells abrogated the prolonged allograft survival induced by γδ TCR deficiency. γδ TCR deficiency resulted in attenuated CAV and prolonged graft survival in murine models of cardiac transplantation, and this effect was associated with enhanced expansion of regulatory T cells., (© 2013 John Wiley & Sons Ltd.)

Sphingobacterium spiritivorum has five unusual sphingophospholipids (SPLs). Our previous study determined the complete chemical structures of these SPLs. The compositions of the long-chain bases/fatty acids in the ceramide portion, isoheptadecasphingosine/isopentadecanoate or isoheptadecasphingosine/2-hydroxy isopentadecanoate, are characteristic. The immune response against bacterial lipid components is considered to play important roles in microbial infections. It is reported that several bacterial sphingolipids composed of ceramide are recognized by CD1-restricted T and NKT cells and that a non-peptide antigen is recognized by γδ T cells. In this study, we demonstrated that these bacterial SPLs activated murine bone marrow macrophages (BMMs) via Toll-like receptor (TLR) 4 but not TLR2, although they slightly activated CD1d-restricted NKT and γδT cells. Interestingly, this TLR 4-recognition pathway of bacterial SPLs involves the fatty acid composition of ceramide in addition to the sugar moiety. A non-hydroxy fatty acid composed of ceramide was necessary to activate murine BMMs. The bacterial survival was significantly higher in TLR4-KO mice than in TLR2-KO and wild-type mice. The results indicate that activation of the TLR4-dependent pathway of BMMs by SPLs induced an innate immune response and contributed to bacterial clearance., (Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.)

Background & Aims: The immunosuppressive network within the tumor microenvironment is one of the major obstacles to the success of cancer immunotherapy. γδ T cells are attractive effectors for cancer immunotherapy. Nevertheless, the promising anti-tumor effect in vitro is partially if not totally mitigated in vivo. Thus, understanding the immune status of tumor-infiltrating γδ T cells is essential for orchestrating effective immunotherapy strategies. In this study, we have investigated the immunophenotype and function of γδ T cells in hepatocellular carcinoma (HCC) patients., Methods: The phenotype of γδ T cells in peripheral blood, and peritumoral and tumoral tissues of HCC patients (n=61) was characterized by flow cytometry. Functional analysis of the HCC-infiltrating γδ T cells was conducted directly after γδ T cell isolation., Results: The infiltration of γδ T cells in tumoral tissues was significantly reduced compared to paired peritumoral tissues. Impairment in degranulation of the granule pathway and downregulation of IFN-γ secretion were also demonstrated in HCC-infiltrating γδ T cells, which was in agreement with the results of gene microarray analysis, and further strengthened by the compromised specific cytotoxicity and IFN-γ secretion in vitro. Moreover, isolated HCC-infiltrating CD4(+)CD25(+) regulatory T cells (Treg cells) directly suppressed the cytotoxic function and IFN-γ secretion of γδ T cells in a TGFβ- and IL-10-dependent manner., Conclusions: The effector function of γδ T cells was substantially impaired in HCC, which is partially mediated by Treg cells. We propose a new mechanism by which immune privilege develops within the tumor milieu., (Copyright © 2012 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.)

In order to understand how tumor cells can escape immune surveillance mechanisms and thus develop antitumor therapies, it is critically important to investigate the mechanisms by which the immune system interacts with the tumor microenvironment. In our current study, IL-17 deficiency results in reduced melanoma tumor size, diminished numbers of proliferating cells and blood vessels, and decreased percentage of CD11b(+)Gr-1(+) MDSCs in tumor tissues. IL-17 promotes IL-6 induction and Stat3 activation. Treatment of Stat3 inhibitor WP1066 in B16-F10 tumor cells inoculated wild-type mice inhibits tumor growth. Additional administration of recombinant IL-6 into B16-F10 tumor-bearing IL-17(-/-) mice results in markedly increased tumor size and p-Stat3 expression, whereas additional recombinant IL-17 administration into B16-F10 tumor-bearing wild-type mice treated with anti-IL-6 mAb does not significantly alter the tumor growth and p-Stat3 expression. In our further study, blockade of Hmgb1-RAGE pathway inhibits melanoma tumor growth and reduces production of IL-23 and IL-17. All these data suggest that Hmgb1-IL-23-IL-17-IL-6-Stat3 axis plays a pivotal role in tumor development in murine models of melanoma, and blocking any portion of this axis will attenuate melanoma tumor growth.

γ9δ2 T cells are a primate-specific γδ T cell subtype that expand and become activated during infection, responding directly to phosphoantigens which are by-products of essential metabolic pathways in both bacteria and mammals. Analogues of natural phosphoantigens have been developed as potential immunotherapeutics for treatment of tumours and infectious diseases. Several non-human primate models have been used in preclinical studies, however, little is known about marmoset γ9δ2 T cell responses. We identified γ9(+) T cells in various tissues in the marmoset and determined that these cells respond to phosphoantigen in a similar manner to human γ9δ2 T cells in vitro. Both human γ9δ2 T cells and marmoset γ9(+) T cells were able to reduce growth of the intracellular bacterium Burkholderia pseudomallei in vitro following expansion with phosphoantigen. This suggests that the marmoset is an appropriate model for examining the immunotherapeutic potential of compounds which target γ9δ2 T cells., (Crown Copyright © 2013. Published by Elsevier Inc. All rights reserved.)

Purinergic signaling plays a key role in a variety of physiological functions, including regulation of immune responses. Conventional αβ T cells release ATP upon TCR cross-linking; ATP binds to purinergic receptors expressed by these cells and triggers T cell activation in an autocrine and paracrine manner. Here, we studied whether similar purinergic signaling pathways also operate in the "unconventional" γδ T lymphocytes. We observed that γδ T cells purified from peripheral human blood rapidly release ATP upon in vitro stimulation with anti-CD3/CD28-coated beads or IPP. Pretreatment of γδ T cells with (10)panx-1, CBX, or Bf A reversed the stimulation-induced increase in extracellular ATP concentration, indicating that panx-1, connexin hemichannels, and vesicular exocytosis contribute to the controlled release of cellular ATP. Blockade of ATP release with (10)panx-1 inhibited Ca(2+) signaling in response to TCR stimulation. qPCR revealed that γδ T cells predominantly express purinergic receptor subtypes A2a, P2X1, P2X4, P2X7, and P2Y11. We found that pharmacological inhibition of P2X4 receptors with TNP-ATP inhibited transcriptional up-regulation of TNF-α and IFN-γ in γδ T cells stimulated with anti-CD3/CD28-coated beads or IPP. Our data thus indicate that purinergic signaling via P2X4 receptors plays an important role in orchestrating the functional response of circulating human γδ T cells.

Behçet's disease (BD) is a recurrent systemic inflammatory disorder of unknown origin characterized by oral and genital mucous ulcer, uveitis, and skin lesions. Involvement of large vessels, central nervous system (CNS), gastrointestinal tract and thrombotic events are less frequent but can be life threatening. The aim of this review is to provide new insights into the pathogenesis of BD. Over the past year substantial advances have been done in the understanding of the genetic [1,2] and immunology [3] of BD. BD is at the crossroad between autoimmune and autoinflammatory syndromes. In common with autoimmune diseases BD shares class I MHC association. However, in contrast to autoimmune disorders, BD has clinical features that seem to be mostly autoinflammatory. The pathogenesis of BD is still unknown, but major determinants of the genetic and immune system abnormalities have been reported recently. Triggering infectious factors are supposed to participate in the outbreak of BD in genetically predisposed patients. Two recent large genome-wide association study (GWAS) conducted in Turkey and Japan reported association between single nucleotide polymorphism (SNP) of interleukin (IL)-10 and IL-23R/IL-12RB2 genes and BD. New insights into the perturbations of T cell homeostasis of BD recently emerged. We have recently demonstrated the promotion of Th17 responses and the suppression of regulatory T cells (Tregs) that were driven by interleukin (IL)-21 production and that correlates with BD activity. Inflammatory cells within BD inflammatory lesions included mostly neutrophils, Th1 and Th17 cells, and cytotoxic CD8+ and γδ T cells. Altogether, the recent progresses in the knowledge of BD pathogenesis pave the way for innovative therapy., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Although IL-17A (commonly referred to as IL-17) has been implicated in the pathogenesis of central nervous system (CNS) autoimmune disease, its role during CNS bacterial infections remains unclear. To evaluate the broader impact of IL-17 family members in the context of CNS infection, we utilized IL-17 receptor (IL-17R) knockout (KO) mice that lack the ability to respond to IL-17, IL-17F and IL-17E (IL-25). In this article, we demonstrate that IL-17R signaling regulates bacterial clearance as well as natural killer T (NKT) cell and gamma-delta (γδ) T cell infiltrates during Staphylococcus aureus-induced brain abscess formation. Specifically, when compared with wild-type (WT) animals, IL-17R KO mice exhibited elevated bacterial burdens at days 7 and 14 following S. aureus infection. Additionally, IL-17R KO animals displayed elevated neutrophil chemokine production, revealing the ability to compensate for the lack of IL-17R activity. Despite these differences, innate immune cell recruitment into brain abscesses was similar in IL-17R KO and WT mice, whereas IL-17R signaling exerted a greater influence on adaptive immune cell recruitment. In particular, γδ T cell influx was increased in IL-17R KO mice at day 7 post-infection. In addition, NK1.1high infiltrates were absent in brain abscesses of IL-17R KO animals and, surprisingly, were rarely detected in the livers of uninfected IL-17R KO mice. Although IL-17 is a key regulator of neutrophils in other infection models, our data implicate an important role for IL-17R signaling in regulating adaptive immunity during CNS bacterial infection.

IL-27 and TCRγδ(+) T lymphocytes play critical roles in both innate and adaptive immune responses in health and disease, including infection and tumors. Although the activity of IL-27 is well characterized in different human immune cells, no information is available on the role of IL-27 in human TCRγδ(+) T lymphocytes. Here, we provide the first evidence that TCRγδ(+) T lymphocytes express both gp130 and WSX-1 chains of IL-27R, and that IL-27 may function in TCRγδ(+) T cells by (i) inducing STAT1 and STAT3 phosphorylation, (ii) stimulating cytotoxicity against tumor cells through upregulation of cytotoxic granules production, (iii) reducing the release of Th2-related cytokines, such as IL-5 and IL-13, and inducing IFN-γ production, and (iv) upregulating the expression of CD62L. These results highlighted a novel immunoregulatory property of human IL-27 that may be relevant in the immune response against tumors. Our results may offer new perspectives for the development of future clinical trials using IL-27 and TCRγδ(+) cells for cancer immunotherapy., (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The corpus luteum (CL) is a transient endocrine organ composed of a heterogeneous mixture of cells. Functional interactions exist between peripheral T cells and luteal cells in vitro; however, the precise role of resident T cells (RTC) remains unknown. The goals of the present study were to isolate RTC from within the CL and determine if alteration of luteal function resulted in changes in RTC phenotypes. Functional lymphocyte phenotypes identified in the bovine CL by using quantitative flow cytometric analysis were clearly different from those in the peripheral circulation. The proportion of CD8(+) RTC was greater than CD4(+) RTC. These proportions were opposite in peripheral blood. The proportion of γδ(+) lymphocytes was not different in the CL compared to that in peripheral blood nor was it altered during luteal regression. There was a significant increase in CD8αα(+) and γδ(+)CD8αα(+) RTC during luteal regression. The proportion of FOXP3(+) lymphocytes in the CL was greater than that isolated from peripheral blood, and this proportion of lymphocytes was dramatically reduced by induction of luteolysis. Within the CL of early pregnancy, there was an increase in the CD8αβ(+) and γδ(+)CD8αβ(+) populations compared to those in the CL of nonpregnant animals. Based on these data, we concluded that the functional state of the CL creates a microenvironment that regulates the recruitment of or differentiation into specific lymphocyte types. Understanding the interactions between steroidogenic cells and ovarian lymphocytes within CL will not only enhance understanding of reproductive function but may provide vital clues to lymphocyte regulation within tissues.

West Nile virus (WNV)-induced encephalitis has been a public health concern in North America over the past decade. No therapeutics or vaccines are available for human use. Studies in animal models have provided important information for investigations of WNV pathogenesis and the host immune response in humans. This article will give an overview of the role of γδ T cells, one of the non-classical T cell subsets in the murine model of WNV encephalitis., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Con A-induced fulminant hepatitis is a well-known animal model for acute liver failure. However, the role of γδ T cells in this model is undefined. In this report, using TCR δ(-/-) mice, we demonstrated a protective role of γδ T cells in Con A-induced hepatitis model. TCR δ(-/-) mice showed significantly decreased levels of IL-17A and IL-17F in the Con A-treated liver tissue, and reconstitution of TCR δ(-/-) mice with wild-type (Wt), but not IL-17A(-/-), γδ T cells significantly reduced hepatitis, strongly suggesting a critical role of IL-17A in mediating the protective effect of γδ T cells. Interestingly, only Vγ4, but not Vγ1, γδ T cells exerted such a protective effect. Furthermore, depletion of NKT cells in TCR δ(-/-) mice completely abolished hepatitis, and NKT cells from Con A-challenged liver tissues of TCR δ(-/-) mice expressed significantly higher amounts of proinflammatory cytokine IFN-γ than those from Wt mice, indicating that γδ T cells protected hepatitis through targeting NKT cells. Finally, abnormal capacity of IFN-γ production by NKT cells of TCR δ(-/-) mice could only be downregulated by transferring Wt, but not IL-17(-/-), Vγ4 γδ T cells, confirming an essential role of Vγ4-derived IL-17A in regulating the function of NKT cells. In summary, our report thus demonstrated a novel function of Vγ4 γδ T cells in mediating a protective effect against Con A-induced fulminant hepatitis through negatively regulating function of NKT cells in an IL-17A-dependent manner, and transferring Vγ4 γδ T cells may provide a novel therapeutic approach for this devastating liver disease.

Background: Melanoma is an immunogenic tumour but, despite the wide range of immunotherapies tested, only few promising results have been reported to date. Both in vitro and in xenograft models, γδ lymphocyte-mediated cytotoxicity against melanoma cells has been reported. IL-2/zoledronate treatment can expand γδ cells in vitro and in animal models. This could represent an immunotherapeutic strategy against melanoma. To evaluate the feasibility of this approach, we studied γδ lymphocyte phenotype from patients with melanoma, their ability to be expanded by IL-2/zoledronate and their cytotoxic activity against SK-MEL-30 cell line., Materials and Methods: Peripheral blood samples were collected from 30 patients with melanoma and 10 healthy donors. Percentage of γδ lymphocytes and CD45RO+CD27+, CD45RA+CD27-, CD57+, Vγ9Vδ2 subpopulations were evaluated by flow cytometry. IL-2/zoledronate γδ cell expansion rate and their cytotoxicity against SK-MEL-30 cell line were studied., Results: A percentage decrease in circulating Vγ9Vδ2 and an increase in CD45RA+CD27- and CD57+ γδ lymphocytes were observed in melanoma. IL-2/zoledronate expansion rate did not differ between controls and patients with melanoma but cytotoxicity against SK-MEL-30 appeared reduced., Conclusions: Our results show that γδ cell function is impaired in patients with advanced melanoma and suggest a possible role in tumour progression., (© 2011 The Authors. European Journal of Clinical Investigation © 2011 Stichting European Society for Clinical Investigation Journal Foundation.)

A small subset of T cells (gamma-delta T cells) is able to recognize phosphoantigens that are overexpressed in some cancer cells and may selectively target and kill cancer cells with high levels of phosphoantigen. Moreover, nitrogen-containing bisphosphonates, such as zoledronic acid, are able to induce accumulation of specific phosphoantigens in some cancer cells. A recent preclinical study showed that gamma-delta T cells effectively targeted and killed zoledronic acid-treated estrogen-receptor-positive breast cancer cells. These new data provide growing insight into a potential mechanism of action for some of the anticancer activity demonstrated by zoledronic acid in breast cancer clinical trials.

Little is known regarding the function of γδ T cells, although they accumulate at sites of inflammation in infections and autoimmune disorders. We previously observed that γδ T cells in vitro are activated by Borrelia burgdorferi in a TLR2-dependent manner. We now observe that the activated γδ T cells can in turn stimulate dendritic cells in vitro to produce cytokines and chemokines that are important for the adaptive immune response. This suggested that in vivo γδ T cells may assist in activating the adaptive immune response. We examined this possibility in vivo and observed that γδ T cells are activated and expand in number during Borrelia infection, and this was reduced in the absence of TLR2. Furthermore, in the absence of γδ T cells, there was a significantly blunted response of adaptive immunity, as reflected in reduced expansion of T and B cells and reduced serum levels of anti-Borrelia antibodies, cytokines, and chemokines. This paralleled a greater Borrelia burden in γδ-deficient mice as well as more cardiac inflammation. These findings are consistent with a model of γδ T cells functioning to promote the adaptive immune response during infection.

Semliki Forest Virus (SFV) encephalomyelitis has been used to study the pathogenesis of virus-induced demyelination and serves as a model for multiple sclerosis. SFV-infection of mice invariably leads to clinical weakness accompanied by CNS inflammation, viral clearance and primary demyelination by day 21 postinfection (pi), followed by recovery and remyelination by day 35 pi. We have applied this model to the examination of the effects of γδ T cells in antibody production and the pathogenesis of demyelinating lesions. SFV-infection of γδ T cell KO mice resulted in more severe clinical signs than in wild type (WT) B6 mice. SFV-infected WT and γδ KO mice both cleared virus by day 10 pi and inflammation was comparable. Demyelination also appeared to be similar in both groups except that KO mice did not exhibit extensive remyelination which was seen in WT mice by day 21. SFV-infected WT mice showed widespread remyelination by day 35 pi, whereas KO mice still displayed some demyelination through day 42 pi. Both WT and KO mice developed serum antibodies to SFV. However, the reactivity of WT sera with the SFV epitope, E2 T(h) peptide₂, was significantly higher than in KO sera. Immunization with E2 T(h) peptide₂ resulted in elevated antibody production to this peptide (p<0.05) and earlier remyelination (day 28 pi) in KO mice. Thus, our study has shown for the first time that immunization of SFV-infected γδ T cell KO mice with a viral peptide, E2 T(h) peptide₂ led to enhanced recovery and repair of the CNS., (Copyright © 2011 Elsevier B.V. All rights reserved.)

The mammalian gastrointestinal tract harbors thousands of bacterial species that include symbionts as well as potential pathogens. The immune responses that limit access of these bacteria to underlying tissue remain poorly defined. Here we show that γδ intraepithelial lymphocytes (γδ IEL) of the small intestine produce innate antimicrobial factors in response to resident bacterial "pathobionts" that penetrate the intestinal epithelium. γδ IEL activation was dependent on epithelial cell-intrinsic MyD88, suggesting that epithelial cells supply microbe-dependent cues to γδ IEL. Finally, γδ T cells protect against invasion of intestinal tissues by resident bacteria specifically during the first few hours after bacterial encounter, indicating that γδ IEL occupy a unique temporal niche among intestinal immune defenses. Thus, γδ IEL detect the presence of invading bacteria through cross-talk with neighboring epithelial cells and are an essential component of the hierarchy of immune defenses that maintain homeostasis with the intestinal microbiota.

Purpose: To determine the function of γδ T cells in early- and late-phase responses in allergic conjunctivitis., Methods: Wild-type (WT) C57BL/6 and γδ T cell-deficient (TCR-δ(-/-)) mice were immunized intraperitoneally and challenged topically for 7 consecutive days with short ragweed pollen. Natural killer T (NKT) and γδ T cell-double-deficient mice were generated by treating TCR-δ(-/-) mice with anti-CD1d antibody. Allergic conjunctivitis was evaluated clinically, and the late-phase response was assessed by histopathology. Cytokine profiles were evaluated by ELISA. The afferent and efferent arms of allergic conjunctivitis were assessed by adoptive transfer of CD4(+) T cells from WT or TCR-δ(-/-) mice into naive TCR-δ(-/-) or WT mice., Results: TCR-δ(-/-) mice had decreased clinical manifestations of allergic conjunctivitis compared with WT mice. TCR-δ(-/-) mice had decreased eosinophilic infiltration compared with WT mice. TCR-δ(-/-) mice produced less Th2-associated cytokines interleukin (IL)-4, -5, and -13 compared with WT mice. Clinical manifestations of allergic conjunctivitis were lowest in NKT cell-depleted TCR-δ(-/-) mice. However, late-phase allergic conjunctivitis in NKT cell-depleted, TCR-δ(-/-) mice was the same as TCR-δ(-/-) mice. Adoptive transfer of CD4(+) T cells revealed that γδ T cells are needed for the afferent and efferent arms of allergic conjunctivitis., Conclusions: γδ T cells are needed for full expression of both the clinical manifestations and the late phase of allergic conjunctivitis. Thus, γδ T cells have an important impact in the expression of allergic conjunctivitis and are a potential therapeutic target in the management of allergic diseases of the ocular surface.

By triggering immunogenic cell death, some anticancer compounds, including anthracyclines and oxaliplatin, elicit tumor-specific, interferon-γ-producing CD8(+) αβ T lymphocytes (Tc1 CTLs) that are pivotal for an optimal therapeutic outcome. Here, we demonstrate that chemotherapy induces a rapid and prominent invasion of interleukin (IL)-17-producing γδ (Vγ4(+) and Vγ6(+)) T lymphocytes (γδ T17 cells) that precedes the accumulation of Tc1 CTLs within the tumor bed. In T cell receptor δ(-/-) or Vγ4/6(-/-) mice, the therapeutic efficacy of chemotherapy was compromised, no IL-17 was produced by tumor-infiltrating T cells, and Tc1 CTLs failed to invade the tumor after treatment. Although γδ T17 cells could produce both IL-17A and IL-22, the absence of a functional IL-17A-IL-17R pathway significantly reduced tumor-specific T cell responses elicited by tumor cell death, and the efficacy of chemotherapy in four independent transplantable tumor models. Adoptive transfer of γδ T cells restored the efficacy of chemotherapy in IL-17A(-/-) hosts. The anticancer effect of infused γδ T cells was lost when they lacked either IL-1R1 or IL-17A. Conventional helper CD4(+) αβ T cells failed to produce IL-17 after chemotherapy. We conclude that γδ T17 cells play a decisive role in chemotherapy-induced anticancer immune responses.

The first TCR-dependent checkpoint in the thymus determines αβ versus γδ T lineage fate and sets the stage for later T cell differentiation decisions. We had previously shown that early T cells in NOD mice that are unable to rearrange a TCR exhibit a defect in checkpoint enforcement at this stage. To determine if T cell progenitors from wild-type NOD mice also exhibit cell-autonomous defects in development, we investigated their differentiation in the Notch-ligand-presenting OP9-DL1 coculture system, as well as by analysis of T cell development in vivo. Cultured CD4 and CD8 double-negative cells from NOD mice exhibited major defects in the generation of CD4 and CD8 double-positive αβ T cells, whereas γδ T cell development from bipotent precursors was enhanced. Limiting dilution and single-cell experiments show that the divergent effects on αβ and γδ T cell development did not spring from biased lineage choice but from increased proliferation of γδ T cells and impaired accumulation of αβ T lineage double-positive cells. In vivo, NOD early T cell subsets in the thymus also show characteristics indicative of defective β-selection, and peripheral αβ T cells are poorly established in mixed bone marrow chimeras, contrasting with strong γδ T as well as B cell repopulation. Thus, NOD T cell precursors reveal divergent, lineage-specific differentiation abnormalities in vitro and in vivo from the first TCR-dependent developmental choice point, which may have consequences for subsequent lineage decisions and effector functions.

We have previously demonstrated that PAS-1, a 200 kDa protein from Ascaris suum, has a potent immunomodulatory effect on humoral and cell-mediated responses induced by APAS-3 (an allergenic protein from A. suum) or unrelated antigens. In this study, we investigated the mechanisms by which PAS-1 is able to induce this effect on an allergic airway inflammation induced by OVA in mice. C57BL/6 mice were adoptively transferred on day 0 with seven different PAS-1-primed cell populations: PAS-1-primed CD19(+) or B220(+) or CD3(+) or CD4(+) or CD8(+) or CD4(+) CD25⁻ or CD4(+) CD25(+) lymphocytes. These mice were immunized twice with OVA and alum by intraperitoneal route (days 0 and 7) and challenged twice by intranasal route (days 14 and 21). Two days after the last challenge, the airway inflammation was evaluated by antibody levels, cellular migration, eosinophil peroxidase levels, cytokine and eotaxin production, and pulmonary mechanical parameters. Among the adoptively transferred primed lymphocytes, only CD4(+) CD25(+) , CD8(+) or the combination of both T cells impaired the production of total IgE and OVA-specific IgE and IgG1 antibodies, eosinophilic airway inflammation, Th2-type cytokines (IL-4, IL-5 and IL-13), eotaxin release and airway hyperreactivity. Moreover, airway recruited cells from CD4(+) CD25(+) and CD8(+) T-cell recipient secreted more IL-10/TGF-β and IFN-γ, respectively. Moreover, we found that PAS-1 expands significantly the number of CD4(+) CD25(+) FoxP3(+) and CD8(+) γδTCR(+) cells. In conclusion, these findings demonstrate that the immunomodulatory effect of PAS-1 is mediated by these T-cell subsets., (© 2010 The Authors. Scandinavian Journal of Immunology © 2010 Blackwell Publishing Ltd.)

γδ T lymphocytes are commonly viewed as embracing properties of both adaptive and innate immunity. Contributing to this is their responsiveness to pathogen products, either with or without the involvement of the TCR and its coreceptors. This study clarifies this paradoxical behavior by showing that these two modes of responsiveness are the properties of two discrete sets of murine lymphoid γδ T cells. Thus, MyD88 deficiency severely impaired the response to malaria infection of CD27((-)), IL-17A-producing γδ T cells, but not of IFN-γ-producing γδ cells. Instead, the latter compartment was severely contracted by ablating CD27, which synergizes with TCRγδ in the induction of antiapoptotic mediators and cell cycle-promoting genes in CD27((+)), IFN-γ-secreting γδ T cells. Hence, innate versus adaptive receptors differentially control the peripheral pool sizes of discrete proinflammatory γδ T cell subsets during immune responses to infection.

Mice that lack interleukin-23 (IL-23) are resistant to T cell-mediated autoimmunity. Although IL-23 is a maturation factor for T helper 17 (Th17) cells, a subset of γδ T cells expresses the IL-23 receptor (IL-23R) constitutively. Using IL-23R reporter mice, we showed that γδ T cells were the first cells to respond to IL-23 during experimental autoimmune encephalomyelitis (EAE). Although γδ T cells produced Th17 cell-associated cytokines in response to IL-23, their major function was to prevent the development of regulatory T (Treg) cell responses. IL-23-activated γδ T cells rendered αβ effector T cells refractory to the suppressive activity of Treg cells and also prevented the conversion of conventional T cells into Foxp3(+) Treg cells in vivo. Thus, IL-23, which by itself has no direct effect on Treg cells, is able to disarm Treg cell responses and promote antigen-specific effector T cell responses via activating γδ T cells., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Natural killer (NK) and unconventional gammadelta T cells, by their ability to sense ligands induced by oncogenic stress on cell surface and to kill tumor cells without a need for clonal expansion, show a great therapeutic interest. They use numerous activating and inhibitory receptors which can function with some independence to trigger or inhibit destruction of target cells. Previous reports demonstrated that PGE(2) is able to suppress the destruction of some tumor cell lines by NK and gammadelta T cells but it remained uncertain if PGE(2) interferes with the different activating receptors governing the cytolytic responses of NK and gammadelta T cells. In this report, using the model of specific redirected lysis of the mouse FcgammaR(+) cell line P815, we clearly demonstrate that the major NK receptors (NKR): NKG2D, CD16 and natural cytotoxicity receptors (NCR: NKp30, NKp44, NKp46) and gammadelta T cell receptors TCR Vgamma9Vdelta2, NKG2D and CD16 are all inhibited by PGE(2). As is the case with gammadelta T cells, we show that PGE(2) binds on E-prostanoid 2 (EP2) and EP4 receptors on NK cells. Finally, we delineate that the signaling of the blockade by PGE(2) is mediated through a cAMP-dependent activation of PKA type I which inhibits early signaling protein of cytotoxic cells. In the discussion, we focused on how these data should impact particular approaches in the treatment of cancer., (Copyright 2010 Elsevier Inc. All rights reserved.)

We previously demonstrated that gammadelta T cells played an important role in tumor immune surveillance by providing an early source of IFN-gamma. The precise role of different subsets of gammadelta T cells in the antitumor immune response, however, is unknown. Vgamma1 and Vgamma4 gammadelta T cells are the principal subsets of peripheral lymphoid gammadelta T cells and they might play distinct roles in tumor immunity. In support of this, we observed that reconstitution of TCRdelta(-/-) mice with Vgamma4, but not Vgamma1, gammadelta T cells restored the antitumor response. We also found that these effects were exerted by the activated (CD44(high)) portion of Vgamma4 gammadelta T cells. We further determined that IFN-gamma and perforin are critical elements in the Vgamma4-mediated antitumor immune response. Indeed, CD44(high) Vgamma4 gammadelta T cells produced significantly more IFN-gamma and perforin on activation, and showed greater cytolytic activity than did CD44(high) Vgamma1 gammadelta T cells, apparently due to the high level of eomesodermin (Eomes) in these activated Vgamma4 gammadelta T cells. Consistently, transfection of dominant-negative Eomes in Vgamma4 gammadelta T cells diminished the level of IFN-gamma secretion, indicating a critical role of Eomes in the effector function of these gammadelta T cells. Our results thus reveal distinct functions of Vgamma4 and Vgamma1 gammadelta T cells in antitumor immune response, and identify a protective role of activated Vgamma4 gammadelta T cells, with possible implications for tumor immune therapy.

The role individual skin dendritic cell (DC) subsets play in the immune response to HSV remains unclear. We investigated the effect of HSV on DC virus uptake, viability, and migration after cutaneous infection in vitro and in vivo. HSV increased the emigration of skin DCs from whole skin explants over 3 d postinfection (p.i.) compared with mock controls, but the kinetics of emigration was influenced by the skin DC subset. Uninfected (bystander) Langerhans cells (LCs) were the major emigrant DC subset at 24 h p.i., but thereafter, large increases in infected CD103(+)langerin(+) dermal DC (dDC) and uninfected langerin(-) dDC emigration were also observed. LC infection was confirmed by the presence of HSV glycoprotein D (gD) and was associated with impaired migration from cultured skin. Langerin(+) dDC also expressed HSV gD, but infection did not impede migration. We then followed the virus in live MacGreen mice in which LCs express GFP using a fluorescent HSV-1 strain by time-lapse confocal microscopy. We observed a sequential infection of epidermal cells, first in keratinocytes and epidermal gammadelta T cells at 6 h p.i., followed by the occurrence of HSVgD(+) LCs at 24 h p.i. HSV induced CCR7 upregulation on all langerin(+) DC, including infected LCs, and increased production of skin TNF-alpha and IL-1beta. However, a large proportion of infected LCs that remained within the skin was apoptotic and failed to downregulate E-cadherin compared with bystander LCs or mock controls. Thus, HSV infection of LCs is preceded by infection of gammadelta T cells and delays migration.

Human Vgamma9Vdelta2 T cells, a major innate-like peripheral T cell subset, are thought to play in vivo an important role in innate and adaptive immune responses to infection agents and tumors. However, the mechanisms regulating their broad effector functions, such as cytotoxicity and cytokine responses, remain poorly understood. In this study, we used single-cell calcium video imaging to analyze the early intracellular events associated with TCR-induced Vgamma9Vdelta2 T cell functional responses. When compared with other human T cell subsets, including NKT and Vdelta2(neg) gammadelta T cells, TCR/CD3-activated Vgamma9Vdelta2 T cells displayed an unusually delayed and sustained intracellular calcium mobilization, which was dramatically quickened and shortened on costimulation by NKG2D, a main activating NKR regulating gammadelta T cell tumor cytolysis. Importantly, the protein kinase C transduction pathway was identified as a main regulator of the NKG2D-mediated costimulation of antitumor Vgamma9Vdelta2 cytolytic responses. Therefore, this study identifies a new mechanism regulating Vgamma9Vdelta2 T cell functional plasticity through fine-tuning of early signal transduction events.

T cells contribute to the pathophysiology of ischemic stroke by yet unknown mechanisms. Mice with transgenic T-cell receptors (TCRs) and mutations in costimulatory molecules were used to define the minimal immunologic requirements for T cell-mediated ischemic brain damage. Stroke was induced in recombination activating gene 1-deficient (RAG1(-/-)) mice devoid of T and B cells, RAG1(-/-) mice reconstituted with B cells or T cells, TCR-transgenic mice bearing 1 single CD8(+) (2C/RAG2, OTI/RAG1 mice) or CD4(+) (OTII/RAG1, 2D2/RAG1 mice) TCR, mice lacking accessory molecules of TCR stimulation (CD28(-/-), PD1(-/-), B7-H1(-/-) mice), or mice deficient in nonclassical T cells (natural killer T [NKT] and gammadelta T cells) by transient middle cerebral artery occlusion (tMCAO). Stroke outcome was assessed at day 1. RAG1(-/-) mice and RAG1(-/-) mice reconstituted with B cells developed significantly smaller brain infarctions compared with controls, but thrombus formation after FeCl(3)-induced vessel injury was unimpaired. In contrast, TCR-transgenic mice and mice lacking costimulatory TCR signals were fully susceptible to tMCAO similar to mice lacking NKT and gammadelta T cells. These findings were corroborated by adoptive transfer experiments. Our data demonstrate that T cells critically contribute to cerebral ischemia, but their detrimental effect neither depends on antigen recognition nor TCR costimulation or thrombus formation.

Mouse models of disease and injury have been invaluable in investigations of the functional role of gammadelta T cells. They show that gammadelta T cells engage in immune responses both early and late, that they can function both polyclonally and as peripherally selected clones, and that they can be effector cells and immune regulators. They also suggest that functional development of gammadelta T cells occurs stepwise in thymus and periphery, and that it is governed by gammadelta TCR-signaling and other signals. Finally, they indicate that gammadelta T cell functions often segregate with TCR-defined subsets, in contrast to conventional T cells. From the functional studies in mice and other animal models, gammadelta T cells emerge as a distinct lymphocyte population with a unique and broad functional repertoire, and with important roles in Ab responses, inflammation and tissue repair. They also are revealed as a potentially useful target for immune intervention.