Roles of γδ T cells in the pathogenesis of autoimmune diseases

Synthetic BSA-conjugated disaccharide related to the Streptococcus pneumoniae serotype 3 capsular polysaccharide increases IL-17A Levels, γδ T cells, and B1 cells in mice

The disaccharide (β-D-glucopyranosyluronic acid)-(1→4)-β-D-glucopyranoside represents a repeating unit of the capsular polysaccharide of Streptococcus pneumoniae serotype 3. A conjugate of the disaccharide with BSA (di-BSA conjugate) adjuvanted with aluminum hydroxide induced - in contrast to the non-adjuvanted conjugate - IgG1 antibody production and protected mice against S. pneumoniae serotype 3 infection after intraperitoneal prime-boost immunization. Adjuvanted and non-adjuvanted conjugates induced production of Th1 (IFNγ, TNFα); Th2 (IL-5, IL-13); Th17 (IL-17A), Th1/Th17 (IL-22), and Th2/Th17 cytokines (IL-21) after immunization. The concentration of cytokines in mice sera was higher in response to the adjuvanted conjugate, with the highest level of IL-17A production after the prime and boost immunizations. In contrast, the non-adjuvanted conjugate elicited only weak production of IL-17A, which gradually decreased after the second immunization. After boost immunization of mice with the adjuvanted di-BSA conjugate, there was a significant increase in the number of CD45+/CD19+ B cells, TCR+ γδ T cell, CD5+ В1 cells, and activated cells with MHC II+ expression in the spleens of the mice. IL-17A, TCR+ γδ T cells, and CD5+ В1 cells play a crucial role in preventing pneumococcal infection, but can also contribute to autoimmune diseases. Immunization with the adjuvanted and non-adjuvanted di-BSA conjugate did not elicit autoantibodies against double-stranded DNA targeting cell nuclei in mice. Thus, the molecular and cellular markers associated with antibody production and protective activity in response to immunization with the di-BSA conjugate adjuvanted with aluminum hydroxide are IL-17A, TCR+ γδ T cells, and CD5+ В1 cells against the background of increasing MHC II+ expression.

Identification of distinct immune signatures in inclusion body myositis by peripheral blood immunophenotyping using machine learning models

Objective

Inclusion body myositis (IBM) is a progressive late-onset muscle disease characterised by preferential weakness of quadriceps femoris and finger flexors, with elusive causes involving immune, degenerative, genetic and age-related factors. Overlapping with normal muscle ageing makes diagnosis and prognosis problematic.

Methods

We characterised peripheral blood leucocytes in 81 IBM patients and 45 healthy controls using flow cytometry. Using a random forest classifier, we identified immune changes in IBM compared to HC. K-means clustering and the random forest one-versus-rest model classified patients into three immunophenotypic clusters. Functional outcome measures including mTUG, 2MWT, IBM-FRS, EAT-10, knee extension and grip strength were assessed across clusters.

Results

The random forest model achieved a 94% AUC ROC with 82.76% specificity and 100% sensitivity. Significant differences were found in IBM patients, including increased CD8+ T-bet+ cells, CD4+ T cells skewed towards a Th1 phenotype and altered γδ T cell repertoire with a reduced proportion of Vγ9+Vδ2+ cells. IBM patients formed three clusters: (i) activated and inflammatory CD8+ and CD4+ T-cell profile and the highest proportion of anti-cN1A-positive patients in cluster 1; (ii) limited inflammation in cluster 2; (iii) highly differentiated, pro-inflammatory T-cell profile in cluster 3. Additionally, no significant differences in patients' age and gender were detected between immunophenotype clusters; however, worsening trends were detected with several functional outcomes.

Conclusion

These findings unveil distinct immune profiles in IBM, shedding light on underlying pathological mechanisms for potential immunoregulatory therapeutic development.

Cell-Mediated Cytotoxicity in Lyme Arthritis

OBJECTIVE

Obliterative microvascular lesions are found in the synovial tissue of ~50% of patients with post-antibiotic Lyme arthritis (LA) and correlate with autoantibodies to certain vascular antigens. In this study, we identified lymphocytes with cytotoxic potential that may also mediate this feature of synovial pathology.

METHODS

The cytotoxic potential of lymphocytes and their T cell receptor (TCR) Vβ gene usage were determined using samples of peripheral blood mononuclear cells (PBMCs) and synovial fluid mononuclear cells (SFMCs) from patients with antibiotic-responsive or post-antibiotic LA. Cell phenotypes were analyzed using flow cytometry and intracellular cytokine staining. Immunohistochemistry was performed on post-antibiotic synovial tissue samples.

RESULTS

In SFMC and PBMC samples, the percentages of CD8+ T cells and double-negative T cells (primarily γδ T cells) were greater among 22 patients with post-antibiotic LA than in 14 patients with antibiotic-responsive LA. Moreover, CD8+ T cells and γδ T cells often expressed cytotoxic mediators, granzyme A/granzyme B, and perforin. The same 3 TCR Vβ segments were over-represented in both CD4+ T cells and CD8+ T cells in SFMC samples from post-antibiotic LA patients. In synovial tissue samples from 3 patients with post-antibiotic LA, CD8+ T cells intermixed with CD4+ T cells were seen around blood vessels, and 2 patients with microvascular damage had autoantibodies to vascular-associated antigens. One of these 2 patients, the one in whom cytotoxicity appeared to be active, had complement (C5b-9) deposition on obliterated vessels. Very few natural killer cells or γδ T cells were seen.

CONCLUSION

We propose that CD8+ T cell-mediated cytotoxicity, CD4+ T cell help, autoantibodies to vascular antigens, and complement deposition may each have a role in microvasculature damage in post-antibiotic LA.

Adenosine 2A receptor contributes to the facilitation of post-infectious irritable bowel syndrome by γδ T cells via the PKA/CREB/NF-κB signaling pathway

BACKGROUND

Immunological dysfunction-induced low-grade inflammation is regarded as one of the predominant pathogenetic mechanisms in post-infectious irritable bowel syndrome (PI-IBS). γδ T cells play a crucial role in innate and adaptive immunity. Adenosine receptors expressed on the surface of γδ T cells participate in intestinal inflammation and immunity regulation.

AIM

To investigate the role of γδ T cell regulated by adenosine 2A receptor (A2AR) in PI-IBS.

METHODS

The PI-IBS mouse model has been established with Trichinella spiralis (T. spiralis) infection. The intestinal A2AR and A2AR in γδ T cells were detected by immunohistochemistry, and the inflammatory cytokines were measured by western blot. The role of A2AR on the isolated γδ T cells, including proliferation, apoptosis, and cytokine production, were evaluated in vitro. Their A2AR expression was measured by western blot and reverse transcription polymerase chain reaction (RT-PCR). The animals were administered with A2AR agonist, or A2AR antagonist. Besides, γδ T cells were also injected back into the animals, and the parameters described above were examined, as well as the clinical features. Furthermore, the A2AR-associated signaling pathway molecules were assessed by western blot and RT-PCR.

RESULTS

PI-IBS mice exhibited elevated ATP content and A2AR expression (P < 0.05), and suppression of A2AR enhanced PI-IBS clinical characteristics, indicated by the abdominal withdrawal reflex and colon transportation test. PI-IBS was associated with an increase in intestinal T cells, and cytokine levels of interleukin-1 (IL-1), IL-6, IL-17A, and interferon-α (IFN-α). Also, γδ T cells expressed A2AR in vitro and generated IL-1, IL-6, IL-17A, and IFN-α, which can be controlled by A2AR agonist and antagonist. Mechanistic studies demonstrated that the A2AR antagonist improved the function of γδ T cells through the PKA/CREB/NF-κB signaling pathway.

CONCLUSION

Our results revealed that A2AR contributes to the facilitation of PI-IBS by regulating the function of γδ T cells via the PKA/CREB/NF-κB signaling pathway.

The function of γδ T cells in humoral immune responses

PURPOSE

The purpose of this review is to discuss the role of γδ T cells played in humoral immune responses.

BACKGROUND

The γδ T cell receptor (γδ TCR) recognizes antigens, including haptens and proteins, in an MHC-independent manner. The recognition of these antigens by γδ TCRs crosses antigen recognition by the B cell receptors (BCRs), suggesting that γδ T cells may be involved in the process of antigen recognition and activation of B cells. However, the role of γδ T cells in humoral immune responses is still less clear.

METHODS

The kinds of literature about the γδ T cell-B cell interaction were searched on PubMed with search terms, such as γδ T cells, antibody, B cell responses, antigen recognition, and infection.

RESULTS

Accumulating evidence indicates that γδ T cells, independent of αβ T cells, participate in multiple steps of humoral immunity, including B cell maturation, activation and differentiation, antibody production and class switching. Mechanically, γδ T cells affect B cell function by directly interacting with B cells, secreting cytokines, or modulating αβ T cells.

CONCLUSION

In this review, we summarize current knowledge on how γδ T cells take part in the humoral immune response, which may assist future vaccine design.

γδ T Lymphocytes as a Double-Edged Sword-State of the Art in Gynecological Diseases

Human gamma-delta (γδ) T cells are a heterogeneous cell population that bridges the gap between innate and acquired immunity. They are involved in a variety of immunological processes, including tumor escape mechanisms. However, by being prolific cytokine producers, these lymphocytes also participate in antitumor cytotoxicity. Which one of the two possibilities takes place depends on the tumor microenvironment (TME) and the subpopulation of γδ T lymphocytes. The aim of this paper is to summarize existing knowledge about the phenotype and dual role of γδ T cells in cancers, including ovarian cancer (OC). OC is the third most common gynecological cancer and the most lethal gynecological malignancy. Anticancer immunity in OC is modulated by the TME, including by immunosuppressive cells, cytokines, and soluble factors. Immune cells are exposed in the TME to many signals that determine their immunophenotype and can manipulate their functions. The significance of γδ T cells in the pathophysiology of OC is enigmatic and remains to be investigated.

Recent advances in cutaneous lupus

Cutaneous lupus erythematosus (CLE) is an inflammatory and autoimmune skin condition that affects patients with systemic lupus erythematosus (SLE) and exists as an isolated entity without associated SLE. Flares of CLE, often triggered by exposure to ultraviolet (UV) light result in lost productivity and poor quality of life for patients and can be associated with trigger of systemic inflammation. In the past 10 years, the knowledge of CLE etiopathogenesis has grown, leading to promising targets for better therapies. Development of lesions likely begins in a pro-inflammatory epidermis, conditioned by excess type I interferon (IFN) production to undergo increased cell death and inflammatory cytokine production after UV light exposure. The reasons for this inflammatory predisposition are not well-understood, but may be an early event, as ANA + patients without criteria for autoimmune disease exhibit similar (although less robust) findings. Non-lesional skin of SLE patients also exhibits increased innate immune cell infiltration, conditioned by excess IFNs to release pro-inflammatory cytokines, and potentially increase activation of the adaptive immune system. Plasmacytoid dendritic cells are also found in non-lesional skin and may contribute to type I IFN production, although this finding is now being questioned by new data. Once the inflammatory cycle begins, lesional infiltration by numerous other cell populations ensues, including IFN-educated T cells. The heterogeneity amongst lesional CLE subtypes isn't fully understood, but B cells appear to discriminate discoid lupus erythematosus from other subtypes. Continued discovery will provide novel targets for additional therapeutic pursuits. This review will comprehensively discuss the contributions of tissue-specific and immune cell populations to the initiation and propagation of disease.

Associations of lymphocyte subpopulations with clinical phenotypes and long-term outcomes in juvenile-onset systemic lupus erythematosus

OBJECTIVE

Juvenile-onset systemic lupus erythematosus (JSLE) is a complex and heterogeneous immune-mediated disease. Cellular components have crucial roles in disease phenotypes and outcomes. We aimed to determine the associations of lymphocyte subsets with clinical manifestations and long-term outcomes in JSLE patients.

METHODS

A cohort of 60 JSLE patients provided blood samples during active disease, of whom 34 provided further samples during inactive disease. In a longitudinal study, blood samples were obtained from 49 of the JSLE patients at 0, 3, and 6 months. The healthy control (HC) group consisted of 42 age-matched children. Lymphocyte subsets were analyzed by flow cytometry.

RESULTS

The percentages of CD4+ T, γδ T, and NK cells were significantly decreased in JSLE patients compared with HC, while the percentages of CD8+ T, NKT, and CD19+ B cells were significantly increased. The percentage of regulatory T cells (Tregs) was significantly lower in JSLE patients with lupus nephritis (LN) than in non-LN JSLE patients and HC. The patients were stratified into high and low groups by the median frequency of each lymphocyte subset. The γδ T cells high group and NK cells high group were significantly related to mucosal ulcer. The CD4+ T cells high group was significantly associated with arthritis, and the NKT cells high group was substantially linked with autoimmune hemolytic anemia. The CD8+ T cells low group was mainly related to vasculitis, and the Tregs low group was significantly associated with LN. The percentage of Tregs was significantly increased at 6 months of follow-up, and the LN JSLE group had a lower Treg percentage than the non-LN JSLE group. Predictors of remission on therapy were high Tregs, high absolute lymphocyte count, direct Coombs test positivity, and LN absence at enrollment.

CONCLUSION

JSLE patients exhibited altered lymphocyte subsets, which were strongly associated with clinical phenotypes and long-term outcomes.

The Diverse Roles of γδ T Cells in Cancer: From Rapid Immunity to Aggressive Lymphoma

γδ T cells are unique players in shaping immune responses, lying at the intersection between innate and adaptive immunity. Unlike conventional αβ T cells, γδ T cells largely populate non-lymphoid peripheral tissues, demonstrating tissue specificity, and they respond to ligands in an MHC-independent manner. γδ T cells display rapid activation and effector functions, with a capacity for cytotoxic anti-tumour responses and production of inflammatory cytokines such as IFN-γ or IL-17. Their rapid cytotoxic nature makes them attractive cells for use in anti-cancer immunotherapies. However, upon transformation, γδ T cells can give rise to highly aggressive lymphomas. These rare malignancies often display poor patient survival, and no curative therapies exist. In this review, we discuss the diverse roles of γδ T cells in immune surveillance and response, with a particular focus on cancer immunity. We summarise the intriguing dichotomy between pro- and anti-tumour functions of γδ T cells in solid and haematological cancers, highlighting the key subsets involved. Finally, we discuss potential drivers of γδ T-cell transformation, summarising the main γδ T-cell lymphoma/leukaemia entities, their clinical features, recent advances in mapping their molecular and genomic landscapes, current treatment strategies and potential future targeting options.

Resident human dermal γδT-cells operate as stress-sentinels: Lessons from the hair follicle

Murine γδT-cells have stress-surveillance functions and are implicated in autoimmunity. Yet, whether human γδT-cells are also stress sentinels and directly promote autoimmune responses in the skin is unknown. Using a novel (mini-)organ assay, we tested if human dermis resident γδT-cells can recognize stressed human scalp hair follicles (HFs) to promote an alopecia areata (AA)-like autoimmune response. Accordingly, we show that γδT-cells from healthy human scalp skin are activated (CD69⁺), up-regulate the expression of NKG2D and IFN-γ, and become cytotoxic when co-cultured with autologous stressed HFs ex vivo. These autologous γδT-cells induce HF immune privilege collapse, dystrophy, and premature catagen, i.e. three hallmarks of the human autoimmune HF disorder, AA. This is mediated by CXCL12, MICA, and in part by IFN-γ and CD1d. In conclusion, human dermal γδT-cells exert physiological stress-sentinel functions in human skin, where their excessive activity can promote autoimmunity towards stressed HFs that overexpress CD1d, CXCL12, and/or MICA.

The innate immune perspective of autoimmune and autoinflammatory conditions

Innate immunity is one of two immune defence system arms. It is present at birth and does not require ‘learning’ through exposure to foreign organisms. It activates various mechanisms collectively to eliminate pathogens and hold an infection until the adaptive response are mounted. The innate immune system consists of four elements: the epithelial barrier, cells (e.g. macrophages, NK cells), plasma proteins (e.g. complement) and cytokines. These components act in concert to induce complex processes, as well as recruitment, activation and differentiation of adaptive responses. The innate response is more than just the ‘first line of defence’, as it essentially withholds the vast majority of any intruder, has a complex interplay with the adaptive arm and is crucial for survival of the host. Finally, yet importantly, a myriad of diseases has been linked with innate immune dysregulation. In this mini-review we will shed some light on these conditions, particularly regarding autoinflammatory ones.

Human Peripheral Blood Gamma Delta T Cells: Report on a Series of Healthy Caucasian Portuguese Adults and Comprehensive Review of the Literature

Gamma delta T cells (Tc) are divided according to the type of Vδ and Vγ chains they express, with two major γδ Tc subsets being recognized in humans: Vδ2Vγ9 and Vδ1. Despite many studies in pathological conditions, only a few have quantified the γδ Tc subsets in healthy adults, and a comprehensive review of the factors influencing its representation in the blood is missing. Here we quantified the total γδ Tc and the Vδ2/Vγ9 and Vδ1 Tc subsets in the blood from 30 healthy, Caucasian, Portuguese adults, we characterized their immunophenotype by 8-color flow cytometry, focusing in a few relevant Tc markers (CD3/TCR-γδ, CD5, CD8), and costimulatory (CD28), cytotoxic (CD16) and adhesion (CD56) molecules, and we examined the impacts of age and gender. Additionally, we reviewed the literature on the influences of race/ethnicity, age, gender, special periods of life, past infections, diet, medications and concomitant diseases on γδ Tc and their subsets. Given the multitude of factors influencing the γδ Tc repertoire and immunophenotype and the high variation observed, caution should be taken in interpreting “abnormal” γδ Tc values and repertoire deviations, and the clinical significance of small populations of “phenotypically abnormal” γδ Tc in the blood.

The prostaglandin E2 increases the production of IL-17 and the expression of costimulatory molecules on γδ T cells in rheumatoid arthritis

γδ T cells play important roles in the development of rheumatoid arthritis (RA) through their antigen-presenting capacity, release of pro-inflammatory cytokines, immunomodulatory properties, interaction with CD4⁺ CD25⁺ Tregs and promotion of antibody production by helping B cells. Although prostaglandin E2 (PGE2) was proved to have the ability to enhance the antigen-presenting function of dendritic cells and IL-17 production of CD4⁺ αβ T cells in RA, the role of PGE2 in γδ T cells from RA disease has not yet been clarified. The goal of this study was to determine the role of PGE2 in γδ T cells in RA. We first demonstrated that the population of γδT17 cells increased in patients with RA compared to healthy controls. Then, IL-17A level in patients with RA was shown to increase compared to healthy controls. After adding PGE2 to γδ T cells from patients with RA, the IL-17A level increased accordingly, and the expression of the costimulatory molecules, CD80 and CD86, on these cells also increased. These results suggest that PEG2 can increase the production of IL-17A and the expression of CD80 and CD86 on γδ T cells in patients with RA. These findings will benefit to explore new therapeutic targets for RA disease.

γδ T cells in rheumatic diseases: from fundamental mechanisms to autoimmunity

The innate and adaptive arms of the immune system tightly regulate immune responses in order to maintain homeostasis and host defense. The interaction between those two systems is critical in the activation and suppression of immune responses which if unchecked may lead to chronic inflammation and autoimmunity. γδ T cells are non-conventional lymphocytes, which express T cell receptor (TCR) γδ chains on their surface and straddle between innate and adaptive immunity. Recent advances in of γδ T cell biology have allowed us to expand our understanding of γδ T cell in the dysregulation of immune responses and the development of autoimmune diseases. In this review, we summarize current knowledge on γδ T cells and their roles in skin and joint inflammation as commonly observed in rheumatic diseases.

Vascular Leaking, a Pivotal and Early Pathogenetic Event in Systemic Sclerosis: Should the Door Be Closed?

The early phase of systemic sclerosis (SSc) presents edema as one of the main features: this is clinically evident in the digital swelling (puffy fingers) as well as in the edematous skin infiltration of the early active diffuse subset. Other organs could be affected by this same disease process, such as the lung (with the appearance of ground glass opacities) and the heart (with edematous changes on cardiac magnetic resonance imaging). The genesis of tissue edema is tightly linked to pathological changes in the endothelium: various reports demonstrated the effect of transforming growth factor β, vascular endothelial growth factor and hypoxia-reperfusion damage with reactive oxygen species generation in altering vascular permeability and extravasation, in particular in SSc. This condition has an alteration in the glycocalyx thickness, reducing the protection of the vessel wall and causing non-fibrotic interstitial edema, a marker of vascular leak. Moreover, changes in the junctional adhesion molecule family and other adhesion molecules, such as ICAM and VCAM, are associated with an increased myeloid cells' extravasation in the skin and increased myofibroblasts transformation with further vascular leak and cellular migration. This mini-review examines current knowledge on determinants of vascular leak in SSc, shedding light on the role of vascular protection. This could enhance further studies in the light of drug development for early treatment, suggesting that the control of vascular leakage should be considered in the same way that vasodilation and inflammation reduction, as potential therapeutic targets.

IFNγ Regulates Activated Vδ2+ T Cells through a Feedback Mechanism Mediated by Mesenchymal Stem Cells

γδ T cells play a role in a wide range of diseases such as autoimmunity and cancer. The majority of circulating human γδ T lymphocytes express a Vγ9Vδ2+ (Vδ2+) T cell receptor (TCR) and following activation release pro-inflammatory cytokines. In this study, we show that IFNγ, produced by Vδ2+ cells, activates mesenchymal stem cell (MSC)-mediated immunosupression, which in turn exerts a negative feedback mechanism on γδ T cell function ranging from cytokine production to proliferation. Importantly, this modulatory effect is limited to a short period of time (<24 hours) post-T cell activation, after which MSCs can no longer exert their immunoregulatory capacity. Using genetically modified MSCs with the IFNγ receptor 1 constitutively silenced, we demonstrate that IFNγ is essential to this process. Activated γδ T cells induce expression of several factors by MSCs that participate in the depletion of amino acids. In particular, we show that indolamine 2,3-dioxygenase (IDO), an enzyme involved in L-tryptophan degradation, is responsible for MSC-mediated immunosuppression of Vδ2+ T cells. Thus, our data demonstrate that γδ T cell responses can be immuno-modulated by different signals derived from MSC.

Chaperonin-containing T-complex Protein 1 Subunit ζ Serves as an Autoantigen Recognized by Human Vδ2 γδ T Cells in Autoimmune Diseases

Human γδ T cells recognize conserved endogenous and stress-induced antigens typically associated with autoimmune diseases. However, the role of γδ T cells in autoimmune diseases is not clear. Few autoimmune disease-related antigens recognized by T cell receptor (TCR) γδ have been defined. In this study, we compared Vδ2 TCR complementarity-determining region 3 (CDR3) between systemic lupus erythematosus (SLE) patients and healthy donors. Results show that CDR3 length distribution differed significantly and displayed oligoclonal characteristics in SLE patients when compared with healthy donors. We found no difference in the frequency of Jδ gene fragment usage between these two groups. According to the dominant CDR3δ sequences in SLE patients, synthesized SL2 peptides specifically bound to human renal proximal tubular epithelial cell line HK-2; SL2-Vm, a mutant V sequence of SL2, did not bind. We identified the putative protein ligand chaperonin-containing T-complex protein 1 subunit ζ (CCT6A) using SL2 as a probe in HK-2 cell protein extracts by affinity chromatography and liquid chromatography-electrospray ionization-tandem mass spectrometry analysis. We found CCT6A expression on the surface of HK-2 cells. Cytotoxicity of only Vδ2 γδ T cells to HK-2 cells was blocked by anti-CCT6A antibody. Finally, we note that CCT6A concentration was significantly increased in plasma of SLE and rheumatoid arthritis patients. These data suggest that CCT6A is a novel autoantigen recognized by Vδ2 γδ T cells, which deepens our understanding of mechanisms in autoimmune diseases.

Dose-Dependent Suppression of Cytokine production from T cells by a Novel Phosphoinositide 3-Kinase Delta Inhibitor

There remains a significant need for development of effective small molecules that can inhibit cytokine-mediated inflammation. Phosphoinositide 3 kinase (PI3K) is a direct upstream activator of AKT, and plays a critical role in multiple cell signaling pathways, cell cycle progression, and cell growth, and PI3K inhibitors have been approved or are in clinical development. We examined novel PI3Kdelta inhibitors, which are highly selective for the p110delta isoform of in CD3/CD28 stimulated T-cell cytokine production. In vitro generated CD4+ T effector cells stimulated in the presence of a PI3Kdelta inhibitor demonstrated a dose-dependent suppression of cytokines produced by Th1, Th2, and Th17 cells. This effect was T-cell intrinsic, and we observed similar effects on human PBMCs. Th17 cells expressing a constitutively activated form of AKT were resistant to PI3Kdelta inhibition, suggesting that the inhibitor is acting through AKT signaling pathways. Additionally, PI3Kdelta inhibition decreased IL-17 production in vivo and decreased neutrophil recruitment to the lung in a murine model of acute pulmonary inflammation. These experiments show that targeting PI3Kdelta activity can modulate T-cell cytokine production and reduce inflammation in vivo, suggesting that PI3Kdelta inhibition could have therapeutic potential in treating inflammatory diseases.

Association of γδ T Cell Compartment Size to Disease Activity and Response to Therapy in SLE

OBJECTIVE

Although γδT cells are widely recognized as pivotal elements in immune-mediated diseases, their role in the pathogenesis of SLE and therapeutic outcome remains under explored. The current study aims to characterize the γδT cell compartment in SLE and correlate its status to disease severity and response to therapy.

METHODS

Human peripheral blood-derived γδ T cells were isolated from 14 healthy volunteers and 22 SLE patients (before and after 4 and 12 weeks following the onset of glucocorticoids (GC), mycophenolatemofetil (MMF) orhydroxychloroquine (HCQ) treatment). The γδ T cells were characterized using flow cytometry. In addition, serum concentration of IFN-γ, TNF-α, IL-2, IL-4, IL-6, IL-10 and IL-17A was determined by cytometric bead array (CBA).

RESULTS

The SLEDAI scores dropped significantly following therapy in a subset of patients (responders-R) but not in some (non- responders-NR). Peripheral blood γδ T cells in general, and γ9+δ T cells and TNF-α/IL-17-secreting CD4-CD8-γδ T cell subsets in particular, were decreased in SLE compared to healthy controls. The numbers of the γδ T cell subsets reached levels similar to those of healthy controls following therapy in R but not in NR. Serum IL-6, IL-10 and IL-17 but not IFN-γ and TNF-α were significantly increased in SLE compared to the healthy controls and exhibited differential changes following therapy. In addition, inverse correlation was observed between SLEDAI scores and γδ T cell compartments, especially with TNF-α+γδT cells, TNF-α+γ9+δT cells and IL17+CD4-CD8-γδT cells subsets. Differential correlation patterns were also observed between serum cytokine levels and various γδ T cell compartments.

CONCLUSIONS

A strong association exists between γδ T cell compartments and SLE pathogenesis, disease severity and response to therapy.

The Role of γδ T Cells in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that is characterized by the overproduction of autoantibodies against an array of nuclear and cytoplasmic antigens and affects multiple organs, such as the skin, joints, kidneys, and neuronal tissues. T cells have been recognized as important players in the development of SLE due to their functions in cytokine secretion, antigen presentation, and supporting B cells for antibody production. γδ T cells are a minor population of T cells that play important roles in infection and tumor-associated disease. In recent years, the role of γδ T cells in autoimmune diseases has been investigated. In this review, we discussed the role of γδ T cells in the pathogenesis of SLE.

γδ Τ cells enhance B cells for antibody production in Hashimoto's thyroiditis, and retinoic acid induces apoptosis of the γδ Τ cell

TCR γδ(+) Τ cells are important in the pathogenesis of inflammatory and autoimmune conditions. This study investigated the effect of γδ T cells on autoantibody production in patients with Hashimoto's thyroiditis (HT). A total of 148 subjects were enrolled, including 99 patients with HT, 5 with simple goiters, and 44 healthy controls. Peripheral blood and thyroid mononuclear cells were subjected to flow cytometric analysis. Thyroid tissues underwent immunofluorescent staining and immunohistochemistry for γδ T cells and anti-thyroid antibody detection. Antibody production was measured by ELISA and automated chemiluminescent immunoassays. And activation and apoptosis of peripheral blood γδT cells and B cells were measured by flow cytometric analysis. The percentage of γδ T cells were greater in thyroid tissue from HT patients than that of goiter patients (n = 5, 5.33 ± 1.20 vs. 2.07 ± 0.44 %; P < 0.05), with the Vδ1(+) γδ T cell subset especially dominant. Frequencies of CD69 (8.42 ± 1.08 vs. 1.60 ± 0.38 %, P < 0.001), HLA-DR (58.12 ± 6.36 vs. 37.82 ± 3.70 %, P < 0.05), CD40L (1.58 ± 0.35 vs. 0.15 ± 0.05 %, P < 0.01), and ICOS (2.78 ± 0.66 vs. 0.28 ± 0.13 %, P < 0.01) expressed on γδ T cells from HT patients (n = 19) were significantly increased compared with those of healthy controls (n = 15). More importantly, γδ T cells from HT patients enhanced B cells for antibody production, and all-trans retinoic acid (ATRA) treatment inhibited the effect by inducing apoptosis of γδ Τ cells. γδ Τ cells appear to play an important role in the pathogenesis of HT, and ATRA might be an effective regulator for HT patients.

Bi-Allelic TCRα or β Recombination Enhances T Cell Development but Is Dispensable for Antigen Responses and Experimental Autoimmune Encephalomyelitis

Dual TCRα-expressing T cells outnumber dual TCRβ-expressing cells by ~10:1. As a result, efforts to understand how dual TCR T cells impact immunity have focused on dual TCRα expression; dual TCRβ expression remains understudied. We recently demonstrated, however, that dual TCRβ expression accelerated disease in a TCR transgenic model of autoimmune arthritis through enhanced positive selection efficiency, indicating that dual TCRβ expression, though rare, can impact thymic selection. Here we generated mice hemizygous for TCRα, TCRβ, or both on the C57BL/6 background to investigate the impact bi-allelic TCR chain recombination has on T cell development, repertoire diversity, and autoimmunity. Lack of bi-allelic TCRα or TCRβ recombination reduced αβ thymocyte development efficiency, and the absence of bi-allelic TCRβ recombination promoted γδ T cell development. However, we observed no differences in the numbers of naïve and expanded antigen-specific T cells between TCRα^+/-β^+/- and wildtype mice, and TCR repertoire analysis revealed only subtle differences in Vβ gene usage. Finally, the absence of dual TCR T cells did not impact induced experimental autoimmune encephalomyelitis pathogenesis. Thus, despite more stringent allelic exclusion of TCRβ relative to TCRα, bi-allelic TCRβ expression can measurably impact thymocyte development and is necessary for maintaining normal αβ/γδ T cell proportions.

Disturbed T Cell Signaling and Altered Th17 and Regulatory T Cell Subsets in the Pathogenesis of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the presence of autoantibodies against nuclear components. Circulating immune complexes of chromatin and autoantibodies deposit in various tissues leading to inflammation and tissue damage. It has been well documented that autoimmunity in SLE depends on autoreactive T cells. In this review, we summarize the literature that addresses the roles of T cell signaling, and Th17 and regulatory T cells (Tregs) in the development of SLE. T cell receptor (TCR) signaling appears to be aberrant in T cells of patients with SLE. In particular, defects in the TCRζ chain, Syk kinase, and calcium signaling molecules have been associated with SLE, which leads to hyperresponsive autoreactive T cells. Furthermore, in patients with SLE increased numbers of autoreactive Th17 cells have been documented, and Th17 cells appear to be responsible for tissue inflammation and damage. In addition, reduced numbers of Tregs as well as Tregs with an impaired regulatory function have been associated with SLE. The altered balance between the number of Tregs and Th17 cells in SLE may result from changes in the cytokine milieu that favors the development of Th17 cells over Tregs.

γδ T cells support gut Ag-reactive colitogenic effector T-cell generation by enhancing Ag presentation by CD11b(+) DCs in the mesenteric LN

T cells expressing the γδ TCR are dominant T-cell subsets in the intestinal immune system. We previously demonstrated that γδ T cells play important roles in augmenting Th17-type colitogenic immune responses in a T-cell-induced colitic inflammation model. However, its underlying mechanism remains poorly understood. In this study, an in vitro coculture system using effector T cells enriched in gut Ag-reactive cells was employed as a readout tool to search for gut Ag presenting APCs. We found that the presence of γδ T cells dramatically enhances gut Ag presentation within the mLN in mice. Gut Ag presentation by CD11b(+) DC subsets was particularly controlled by γδ T cells. Interestingly, γδ T-cell entry to the lymph nodes was essential to improve the Ag presentation. Therefore, our results highlight that γδ T cells play a previously unrecognized role to support colitogenic immunity by regulating gut Ag presentation in the draining LN.

Gamma Delta (γδ) T Cells and Their Involvement in Behçet's Disease

Behçet's disease (BD) is a multisystem inflammatory disorder characterized by orogenital ulcerations, ocular manifestations, arthritis, and vasculitis. The disease follows a relapsing-remitting course and its pathogenesis is unknown. Genetic predisposition and immune-dysregulation involving gamma delta (γδ) T cells are reported to have a role. γδ T cells are atypical T cells, which represent a small proportion of total lymphocytes. They have features of both innate and adaptive immunity and express characteristics of conventional T cells, natural killer cells, and myeloid antigen presenting cells. These unconventional T cells are found in the inflammatory BD lesions and have been suggested to be responsible for inducing and/or maintaining the proinflammatory environment characteristic of the disease. Over the last 20 years there has been much interest in the role of γδ T cells in BD. We review the literature and discuss the roles that γδ T cells may play in BD pathogenesis.

Hyperactivation and in situ recruitment of inflammatory Vδ2 T cells contributes to disease pathogenesis in systemic lupus erythematosus

In this study, we measured the proportion of peripheral Vδ2 T cells as well as the status and chemokine receptor expression profiles in SLE patients and healthy control (HC). In addition, Vδ2 T cell infiltration in the kidneys of patients with lupus nephritis was examined. The results showed that the percentage of peripheral Vδ2 T cells in new-onset SLE was decreased, and negatively correlated with the SLE Disease Activity Index score and the severity of proteinuria. These cells had a decreased apoptosis but an increased proliferation, and they showed increased accumulation in SLE kidneys. Moreover, IL-21 production and CD40L, CCR4, CCR7, CCR8, CXCR1 and CX3CR1 expression in Vδ2 T cells from SLE patients was significantly higher than from HC (p < 0.05), and these factors were downregulated in association with the repopulation of peripheral Vδ2 T cells in patients who were in remission (p < 0.05). In addition, anti-TCR Vδ2 antibodies activation significantly upregulated these chemokine receptors on Vδ2 T cells from HC, and this effect was blocked by inhibitors of PLC-γ1, MAPK/Erk, and PI3K signaling pathways. Our findings demonstrate that the distribution and function status of Vδ2 T cells from SLE patients are abnormal, and these aberrations may contribute to disease pathogenesis.

Pregnancy Associated with Systemic Lupus Erythematosus: Immune Tolerance in Pregnancy and Its Deficiency in Systemic Lupus Erythematosus--An Immunological Dilemma

Pregnancy is a physiological condition that requires immune tolerance to the product of conception. Systemic lupus erythematosus (SLE) is a disease with well-represented immune mechanisms that disturb immune tolerance. The association of pregnancy with systemic lupus erythematosus creates a particular immune environment in which the immune tolerance specific of pregnancy is required to coexist with alterations of the immune system caused by SLE. The main role is played by T regulatory (Treg) cells, which attempt to regulate and adapt the immune system of the mother to the new conditions of pregnancy. Other components of the immune system also participate to maintain maternal-fetal immune tolerance. If the immune system of pregnant women with SLE is not able to maintain maternal immune tolerance to the fetus, pregnancy complications (miscarriage, fetal hypotrophy, and preterm birth) or maternal complications (preeclampsia or activation of SLE, especially in conditions of lupus nephritis) may occur. In certain situations this can be responsible for neonatal lupus. At the same time, it must be noted that during pregnancy, the immune system is able to achieve immune tolerance while maintaining the anti-infectious immune capacity of the mother. Immunological monitoring of pregnancy during SLE, as well as of the mother's disease, is required. It is important to understand immune tolerance to grafts in transplant pathology.

γδ T Cell-Mediated Immune Responses in Disease and Therapy

The role of γδ T cells in immunotherapy has gained specific importance in the recent years because of their prominent function involving directly or indirectly in the rehabilitation of the diseases. γδ T cells represent a minor population of T cells that express a distinct T cell receptor (TCR) composed of γδ chains instead of αβ chains. Unlike αβ T cells, γδ T cells display a restricted TCR repertoire and recognize mostly unknown non-peptide antigens. γδ T cells act as a link between innate and adaptive immunity, because they lack precise major histocompatibility complex (MHC) restriction and seize the ability to recognize ligands that are generated during affliction. Skin epidermal γδ T cells recognize antigen expressed by damaged or stressed keratinocytes and play an indispensable role in tissue homeostasis and repair through secretion of distinct growth factors. γδ T cell based immunotherapy strategies possess great prominence in the treatment because of the property of their MHC-independent cytotoxicity, copious amount of cytokine release, and a immediate response in infections. Understanding the role of γδ T cells in pathogenic infections, wound healing, autoimmune diseases, and cancer might provide knowledge for the successful treatment of these diseases using γδ T cell based immunotherapy. Enhancing the human Vγ9Vδ2 T cells functions by administration of aminobisphosphonates like zoledronate, pamidronate, and bromohydrin pyrophosphate along with cytokines and monoclonal antibodies shows a hopeful approach for treatment of tumors and infections. The current review summarizes the role of γδ T cells in various human diseases and immunotherapeutic approaches using γδ T cells.

Role of non-conventional T lymphocytes in respiratory infections: the case of the pneumococcus

Non-conventional T lymphocytes constitute a special arm of the immune system and act as sentinels against pathogens at mucosal surfaces. These non-conventional T cells (including mucosal-associated invariant T [MAIT] cells, gamma delta [γδ] T cells, and natural killer T [NKT] cells) display several innate cell-like features and are rapidly activated by the recognition of conserved, stress-induced, self, and microbial ligands. Here, we review the role of non-conventional T cells during respiratory infections, with a particular focus on the encapsulated extracellular pathogen Streptococcus pneumoniae, the leading cause of bacterial pneumonia worldwide. We consider whether MAIT cells, γδ T cells, and NKT cells might offer opportunities for preventing and/or treating human pneumococcus infections.

The parasitic worm product ES-62 up-regulates IL-22 production by γδ T cells in the murine model of Collagen-Induced Arthritis

ES-62 is a phosphorylcholine (PC)-containing glycoprotein secreted by the filarial nematode Acanthocheilonema viteae that acts to modulate the host immune response to promote the establishment of chronic helminth infection. Reflecting its anti-inflammatory actions, we have previously reported that ES-62 protects mice from developing Collagen-Induced Arthritis (CIA): thus, as this helminth-derived product may exhibit therapeutic potential in Rheumatoid Arthritis (RA), it is important to understand the protective immunoregulatory mechanisms triggered by ES-62 in this model in vivo. We have established to date that ES-62 acts by downregulating pathogenic Th17/IL-17-mediated responses and upregulating the regulatory cytokine IL-10. In addition, our studies have identified that IL-22, another member of the IL-10 family of cytokines, exerts dual pathogenic and protective roles in this model of RA with ES-62 harnessing the cytokine's inflammation-resolving and tissue repair properties in the joint during the established phase of disease. Here, we discuss the counter-regulatory roles of IL-22 in the murine model of CIA and present additional novel data showing that ES-62 selectively induces γδ T cells with the capacity to induce IL-22 production and that γδ T cells with the capacity to produce IL-22, but not IL-17, induced during CIA can be identified by their expression of TLR4. Moreover, we also show that treatment of mice undergoing CIA with the active PC moiety of ES-62, in the form of PC conjugated to BSA, is not only sufficient to mimic the ES-62-dependent suppression of pathogenic IL-17 responses shown previously but also that of the IL-22 and IL-10 up-regulation observed with the parasitic worm product during CIA. These findings not only reinforce the potential of IL-22, firstly described as a Th17-related pro-inflammatory cytokine, as a protective factor in arthritis but also suggest that drugs based on the PC moiety found in ES-62 may be able to harness the joint-protecting activities of IL-22 therapeutically.

Regulatory effect of astragalus polysaccharides on intestinal intraepithelial γδT cells of tumor bearing mice

Astragalus polysaccharides (APS) possess multiple immunomodulatory activities. Due to its high molecular weight, orally administration of APS is not easily absorbed into the blood stream, and how APS exerts its capacity in vivo is still not well elucidated. We assume that enteric mucosal immune response might trigger the immune regulation of APS, and our previous studies demonstrated that APS had regulatory activity on intraepithelial lymphocytes (IELs). Therefore, this study aimed to investigate the functions of APS on intestinal intraepithelial γδT cells, a major subset in IELs and an essential component of maintaining homeostasis and immune regulation in enteric mucosa. Results showed that APS could promote proliferation and function of intestinal intraepithelial γδT cells in vitro, the IFN-γ, FasL and GrB mRNA levels in γδT cells were all significantly increased. Moreover, APS also improved the activity of intestinal intraepithelial γδT cells in vivo, as cytokines production and cytotoxicity of γδT cells were all remarkably improved in tumor-bearing mice treated with APS. In addition, the levels of TNF-α and IFN-γ were significantly increased, whereas the levels of IL-10 and TGF-β were significantly decreased in tumor-bearing mice treated with APS. In conclusion, this study demonstrated that APS could improve proliferation and function of intestinal intraepithelial γδT cells, which might an important pathway for immunomodulation of APS in cancer therapy.

Neonatal thymectomy favors Helicobacter pylori-promoted gastric mucosa-associated lymphoid tissue lymphoma lesions in BALB/c mice

Neonatal thymectomy in BALB/c mice has been described as a model of gastric mucosa-associated lymphoid tissue (MALT) lymphoma (GML). By using this experimental system, we screened, for the first time to our knowledge, Helicobacter pylori GML-associated strains for their capacity to promote disease. A cohort of BALB/c mice underwent thymectomy at day 3 after birth (d3Tx). Successful thymic ablation was evaluated by the degree of lymphopenia in blood samples collected at 4 weeks of age. d3Tx and non-thymectomized controls were infected with either GML strains (B38 or B47) or control strains (SS1 or TN2GF4). Gastric samples collected at 6, 12, and 18 months after infection were studied for bacteria content, and submitted to histological, immunochemical, molecular, and immunological analyses. Severe gastric inflammation was only observed in d3Tx mice. In these animals, the gastric lamina propria was infiltrated with lymphoid cells organized in follicles composed of B cells with few infiltrating T cells. PCR of D/J IgH gene segments proved the monoclonality of infiltrating B cells, which strongly correlated with the presence of lymphoepithelial lesions. B-cell infiltrates were particularly prominent in mice infected with the B47-GML strain. No pathological changes were detected in noninfected d3Tx mice. We identified new H. pylori isolates adapted to the mouse stomach with high potential of GML development, which is only revealed in hosts rendered lymphopenic by neonatal thymic ablation.

γδ T cells and their potential for immunotherapy

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.

Innate and Adaptive Responses to Heat Shock Proteins in Behcet's Disease

Behcet's disease (BD) is a systemic, chronic inflammatory disorder with both innate and adaptive immune responses. Heat shock proteins (HSP) are highly conserved molecules in different species with scavenger activity and involved in correct folding of newly synthesized proteins. T and B cell responses against HSPs are observed in BD patients in both αβ and γδ T-cell populations. 60-kD HSP (HSP60) is also shown to be recognized by pattern recognition receptors such as toll-like receptors (TLR) and is suggested to be an endogenous "danger" signal to the immune system with rapid inflammatory cytokine releases and enhancement of adaptive Th1-type responses. Elucidating the exact role of HSPs in BD pathogenesis might pave the way to less toxic therapeutic approaches to BD, such as antibacterial therapies and immunomodulation.

Role of adaptive and innate immune cells in chronic fatigue syndrome/myalgic encephalomyelitis

Perturbations in immune processes are a hallmark of a number of autoimmune and inflammatory disorders. Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is an inflammatory disorder with possible autoimmune correlates, characterized by reduced NK cell activity, elevations in regulatory T cells (Tregs) and dysregulation in cytokine levels. The purpose of this article is to examine innate and adaptive immune cell phenotypes and functional characteristics that have not been previously examined in CFS/ME patients. Thirty patients with CFS/ME and 25 non-fatigued controls were recruited for this study. Whole blood samples were collected from all participants for the assessment of cell phenotypes, functional properties, receptors, adhesion molecules, antigens and intracellular proteins using flow cytometric protocols. The cells investigated included NK cells, dendritic cells, neutrophils, B cells, T cells, γδT cells and Tregs. Significant changes were observed in B-cell subsets, Tregs, CD4(+)CD73(+)CD39(+) T cells, cytotoxic activity, granzyme B, neutrophil antigens, TNF-α and IFN-γ in the CFS/ME patients in comparison with the non-fatigued controls. Alterations in B cells, Tregs, NK cells and neutrophils suggest significant impairments in immune regulation in CFS/ME and these may have similarities to a number of autoimmune disorders.

Elevated apoptosis and impaired proliferation contribute to downregulated peripheral γ δ T cells in patients with systemic lupus erythematosus

OBJECTIVE

To investigate the frequency of peripheral γ δ T cells in patients with systemic lupus erythematosus (SLE) and its correlation with disease activity and to analyze the apoptotic status, proliferation ability, and intracellular cytokine profile of these cells.

METHODS

Flow cytometry was performed to detect the percentage and intracellular cytokine expression of peripheral γ δ T cells from SLE patients. Annexin-V/PI double staining was applied to determine the proportion of apoptotic γ δ and CD3(+) T cells. γ δ T cell proliferation was analyzed by CFSE labeling technique.

RESULTS

The percentage and absolute number of γ δ T cells were remarkably decreased in active SLE patients compared to those in inactive patients and healthy controls, with γ δ T cell count negatively correlated with disease activity. Compared with healthy controls, peripheral γ δ T cells from active SLE patients exhibited higher apoptotic rate and lower proliferation ability, as well as elevated expression of intracellular IFN-γ , IL-4, IL-10, and TGF- β , but not IL-17 or Foxp3.

CONCLUSION

Decreased γ δ T cells in the peripheral blood of SLE patients might be caused by upregulated apoptosis and downregulated cell proliferation. These γ δ T cells may secret both pro- and anti-inflammatory cytokines to perform their functions in SLE.