γδ-T cells: an unpolished sword in human anti-infection immunity

The role of innate immune cells in modulating vascular dynamics in skin malignancies

A developing tumor relies heavily on blood vessels to supply oxygen and nutrients. As a result, angiogenesis, the formation of new blood vessels, supports tumor growth and progression. Similarly, lymphangiogenesis, the formation of new lymphatic vessels, plays a critical role in metastatic dissemination by providing pathways for malignant cells to spread. The tumor microenvironment is crucial for establishing and maintaining these vascular networks, with innate immune cells playing a key regulatory role. Notably, immune cells are specifically enriched in barrier tissues, such as the skin, emphasizing their importance in skin malignancies. Therefore, understanding their role in regulating angiogenesis and lymphangiogenesis is essential for developing novel therapeutic strategies. This review article explores how innate immune cells influence tumor vasculature and highlights the therapeutic potential that may arise from this knowledge.

Diverse Subsets of γδT Cells and Their Specific Functions Across Liver Diseases

γδT cells, a distinct group of T lymphocytes, serve as a link between innate and adaptive immune responses. They are pivotal in the pathogenesis of various liver disorders, such as viral hepatitis, nonalcoholic fatty liver disease (NAFLD), alcoholic liver disease (ALD), liver fibrosis, autoimmune liver diseases, and hepatocellular carcinoma (HCC). Despite their importance, the functional diversity and regulatory mechanisms of γδT cells remain incompletely understood. Recent advances in high-throughput single-cell sequencing and spatial transcriptomics have revealed significant heterogeneity among γδT cell subsets, particularly Vδ1+ and Vδ2+, which exhibit distinct immunological roles. Vδ1+ T cells are mainly tissue-resident and contribute to tumor immunity and chronic inflammation, while Vδ2+ T cells, predominantly found in peripheral blood, play roles in systemic immune surveillance but may undergo dysfunction in chronic liver diseases. Additionally, γδT17 cells exacerbate inflammation in NAFLD and ALD, whereas IFN-γ-secreting γδT cells contribute to antiviral and antifibrotic responses. These discoveries have laid the foundation for the creation of innovative solutions. γδT cell-based immunotherapeutic approaches, such as adoptive cell transfer, immune checkpoint inhibition, and strategies targeting metabolic pathways. Future research should focus on harnessing γδT cells' therapeutic potential through targeted interventions, offering promising prospects for precision immunotherapy in liver diseases.

TANK-Binding Kinase 1 in the Pathogenesis and Treatment of Inflammation-Related Diseases

TANK-binding kinase 1 (TBK1) is a key signaling kinase involved in innate immune and inflammatory responses. TBK1 drives immune cells to participate in the inflammatory response by activating the NF-κB and interferon regulatory factor signaling pathways in immune cells, promoting the expression of pro-inflammatory genes, and regulating immune cell function. Thus, it plays a crucial role in initiating a signaling cascade that establishes an inflammatory environment. In inflammation-related diseases, TBK1 acts as a bridge linking inflammation to immunity, metabolism, or tumorigenesis, playing an important role in the pathogenesis of immune-mediated inflammatory diseases, metabolic, inflammatory syndromes, and inflammation-associated cancers by regulating the activation of inflammatory pathways and the production of inflammatory cytokines in cells. In this review, we focused on the mechanisms of TBK1 in immune cells and inflammatory-related diseases, providing new insights for further studies targeting TBK1 as a potential treatment for inflammation-related diseases. Thus, optimizing and investigating highly selective cell-specific TBK1 inhibitors is important for their application in these diseases.

Photosensitive Hybrid γδ-T Exosomes for Targeted Cancer Photoimmunotherapy

Melanoma is the most aggressive type of skin cancers. Traditional chemotherapy and radiotherapy have limited effectiveness and can lead to systemic side effects. Photodynamic therapy (PDT) is a photoresponsive cancer therapy based on photosensitizers to generate reactive oxygen species (ROS) to eradicate tumor cells. Our previous study showed that exosomes derived from human γδ-T cells (γδ-T exosomes) could control Epstein-Barr virus-associated tumors. Here, we combined γδ-T exosomes and PDT for targeted photoimmunotherapy by membrane fusion of γδ-T exosomes and Chlorin e6 (Ce6)-loaded liposomes. The functional surface proteins, such as CCR5 and PD-1, on the hybrid exosomes mediated the specific binding of hybrid exosomes toward melanoma tissues. The cytolytic molecules, such as granzyme A, granzyme B, perforin, and granulysin from γδ-T exosomes, induced specific apoptosis of cancer cells without harming normal cells. In response to light irradiation, ROS generation inside melanoma cells synergized with cytolytic molecules to induce apoptosis and promote immunogenic cancer cell death (ICD). The subsequently released damage-associated molecular patterns (DAMPs) could stimulate human dendritic cell maturation and induce melanoma antigen-specific CD4+ and CD8+ T-cell responses, thereby enhancing antitumor immunity. This study provides a promising strategy by combining γδ-T exosomes and PDT for photoimmunotherapy, thereby expanding the clinical applications of γδ-T exosome therapy for cancer patients.

Ligands for Intestinal Intraepithelial T Lymphocytes in Health and Disease

The intestinal tract is constantly exposed to a diverse mixture of luminal antigens, such as those derived from commensals, dietary substances, and potential pathogens. It also serves as a primary route of entry for pathogens. At the forefront of this intestinal defense is a single layer of epithelial cells that forms a critical barrier between the gastrointestinal (GI) lumen and the underlying host tissue. The intestinal intraepithelial T lymphocytes (T-IELs), one of the most abundant lymphocyte populations in the body, play a crucial role in actively surveilling and maintaining the integrity of this barrier by tolerating non-harmful factors such as commensal microbiota and dietary components, promoting epithelial turnover and renewal while also defending against pathogens. This immune balance is maintained through interactions between ligands in the GI microenvironment and receptors on T-IELs. This review provides a detailed examination of the ligands present in the intestinal epithelia and the corresponding receptors expressed on T-IELs, including T cell receptors (TCRs) and non-TCRs, as well as how these ligand-receptor interactions influence T-IEL functions under both steady-state and pathological conditions. By understanding these engagements, we aim to shed light on the mechanisms that govern T-IEL activities within the GI microenvironment. This knowledge may help in developing strategies to target GI ligands and modulate T-IEL receptor expression, offering precise approaches for treating intestinal disorders.

γδ T cells in hematological malignancies: mechanisms and therapeutic strategies

γδ T cells are a unique subset of lymphocytes with both innate and adaptive features. They recognize and eradicate various hematological malignancies through different mechanisms, employing factors including γδ TCR, NKR, NKG2D, TRAIL, and perforin/granzyme. They also modulate other immune cells to enhance their antitumor activity. Moreover, γδ T cells have potent antiviral functions after hematopoietic stem cell transplantation (HSCT), which may improve the outcome of patients with hematological malignancies. In this review, we summarize the current knowledge on γδ T cell biology and function in hematological malignancies and HSCT complications. We also discuss the challenges and limitations of the clinical application of γδ T cells, such as their low frequency in peripheral blood and heterogeneity among different subsets. We then highlight some promising strategies for γδ T cell-based therapy, such as using agonist antibodies, cell engagers, or genetic modification technology. Furthermore, we review the recent clinical trials evaluating the safety and efficacy of γδ T-cell therapy in different hematological malignancies. In conclusion, γδ T cells represent a promising immunotherapeutic tool for hematological malignancies that deserves further exploration.

Mucosal immunization with the lung Lactobacillus-derived amphiphilic exopolysaccharide adjuvanted recombinant vaccine improved protection against P. aeruginosa infection

Respiratory infections caused by Pseudomonas aeruginosa are a major health problem globally. Current treatment for P. aeruginosa infections relies solely on antibiotics, but the rise of antibiotic-resistant strains necessitates an urgent need for a protective vaccine. Traditional parenteral vaccines, despite employing potent adjuvants aimed at serotype-dependent immunity, often fail to elicit the desired mucosal immune response. Thus, developing vaccines that target both localized mucosal and systemic immune responses represents a promising direction for future research on P. aeruginosa vaccination. In this study, we explored EPS301, the exopolysaccharide derived from the lung microbiota strain Lactobacillus plantarum WXD301, which exhibits excellent self-assembly properties, enabling the formation of homogeneous nanoparticles when encapsulating recombinant PcrV of P. aeruginosa, designated as EPS301@rPcrV. Notably, the EPS301 vector effectively enhanced antigen adhesion to the nasal and pulmonary mucosal tissues and prolonged antigen retention. Moreover, EPS301@rPcrV provided effective and sustained protection against P. aeruginosa pneumonia, surpassing the durability achieved with the "gold standard" cholera toxin adjuvant. The EPS301-adjuvanted vaccine formulation elicited robust mucosal IgA and Th17/γδ17 T cell responses, which exceeded those induced by the CTB-adjuvanted vaccination and were sustained for over 112 days. Additionally, Th 17 and γδ 17 resident memory T cells induced by EPS301@rPcrV were crucial for protection against P. aeruginosa challenge. Intriguingly, IL-17A knockout mice exhibited lower survival rates, impaired bacterial clearance ability, and exacerbated lung tissue damage upon EPS301 adjuvanted vaccination against P. aeruginosa-induced pneumonia, indicating an IL-17A-dependent protective mechanism. In conclusion, our findings provided direct evidence that EPS301@rPcrV mucosal vaccine is a promising candidate for future clinical application against P. aeruginosa-induced pulmonary infection.

Investigation of the relationship of tissue-resident γδ T cells and IL-17 gene expression with the pathogenesis of autoimmune hepatitis

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease. Elevated serum immunoglobulin G (IgG) levels, autoantibodies, and histopathological interface hepatitis are the hallmarks of AIH. Autoantibodies and pathological findings, clinical and biochemical features, typical immunoglobulin levels, and exclusion of other diseases are used to diagnose the condition. Gamma-delta (γδ) T cells are a unique population of unconventional T cells with γ and δ glycoprotein chains. γδ T cells have been shown to play a crucial role in autoimmune diseases by producing interleukin (IL)-17. However, its role in AIH remains to be further elucidated. In this study, we aimed to examine the role of γδ T cells and IL-17 in the pathogenesis of AIH, by working on biopsy samples. Paraffin blocks of 18 patients with type 1 AIH and 18 control liver tissues were analyzed. qRT-PCR assessed IL-17 gene expression. Immunofluorescence double staining of CD3+TCRγδ+ was performed to reveal tissue-resident γδ T cells' role in AIH. When comparing AIH to the control, there was a substantial increase in the ratio of CD3+TCRγδ+ cells in total inflammatory cells (p = 0.01). IL-17 gene expression was lowered in AIH when compared to the control (p = 0.01). This study provides evidence for the involvement of γδ T cells and IL-17 in the pathogenesis of AIH. The ratio of γδ T cells and IL-17 gene expression showed a significant difference in AIH suggesting a potential role for γδ T cells in driving liver inflammation in A fIH.

The complex landscape of immune dysregulation in multisystem inflammatory syndrome in children with COVID-19

The immune responses following SARS-CoV-2 infection in children are still under investigation. While coronavirus disease 2019 (COVID-19) is usually mild in the paediatric population, some children develop severe clinical manifestations or multisystem inflammatory syndrome in children (MIS-C) after infection. MIS-C, typically emerging 2-6 weeks after SARS-CoV-2 exposure, is characterized by a hyperinflammatory response affecting multiple organs. This review aims to explore the complex landscape of immune dysregulation in MIS-C, focusing on innate, T cell-, and B cell-mediated immunity, and discusses the role of SARS-CoV-2 spike protein as a superantigen in MIS-C pathophysiology. Understanding these mechanisms is crucial for improving the management and outcomes for affected children.

γδT Cells Induce the Inflammatory Response of Human Fibroblast-Like Synoviocytes Directly or by Stimulating B Cells to Activate IL-17/STAT3 Signaling Pathway

INTRODUCTION

Rheumatoid arthritis (RA) combined with hashimoto thyroiditis (HT) is an important cause of various fatal comorbidities of RA. There is no precise conclusion about the cause of this disease.

METHODS

Peripheral blood and synovial tissue were collected from healthy participants, patients with RA, and patients with both RA and HT. Immunofluorescence staining and Pearson correlation analysis were used to detect the levels of γδTCR and the correlation between IL-17 and p-STAT3, respectively. ELISA, chemiluminescence assays, qRT-PCR and Western blot were performed to detect the levels of IgG, IgM, IFN-γ, IL-1β, TNF-α, Tg-Ab, Tpo-Ab, IL-17, IL-2, p-SATA3, and STAT3, respectively.

RESULTS

There was increased proportion of γδT cells, IL-17, and p-STAT3 levels in RA and HT patients. IL-17 was positively correlated with p-STAT3. γδT cells significantly promoted the expression of IgG, Tg-Ab, Tpo-Ab, and IL-17. When γδT and human fibroblast-like synoviocytes (FLSs) were co-cultured, the levels of IL-2, IFN-γ, IL-1β, TNF-α, and IL-17 were increased, and the IL-17/STAT3 signaling pathway was activated. When IL-17-silenced γδT cells and STAT3-silenced FLSs were co-cultured, the levels of IL-1β and TNF-α in FLSs were significantly decreased. Furthermore, when STAT3-silenced FLSs were added to the co-culture medium of B cells and γδT cells, the levels of IL-1β and TNF-α were also decreased significantly.

CONCLUSION

γδT cells induced RA directly or by stimulating B cells to activate STAT3 through IL-17.

Trained Immunity Generated by the Recombinant Zoster Vaccine

Trained immunity may play a role in vaccine-induced protection against infections. We showed that the highly efficacious recombinant VZV-gE zoster vaccine (RZV) generated trained immunity in monocytes, natural killer (NK) cells, and dendritic cells (DCs) and that the less efficacious live zoster vaccine did not. RZV stimulated ex vivo gE-specific monocyte, DC and NK cell responses that did not correlate with CD4 + T-cell responses. These responses were also elicited in purified monocyte and NK cell cocultures stimulated with VZV-gE and persisted above prevaccination levels for ≥ 4 years post-RZV administration. RZV administration also increased ex vivo heterologous monocyte and NK cell responses to herpes simplex and cytomegalovirus antigens. ATAC-seq analysis and ex vivo TGFβ1 supplementation and inhibition experiments demonstrated that decreased tgfβ1 transcription resulting from RZV-induced chromatin modifications may explain the development of monocyte trained immunity. The role of RZV-trained immunity in protection against herpes zoster and other infections should be further studied.

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.

From Host Defense to Metabolic Signatures: Unveiling the Role of γδ T Cells in Bacterial Infections

The growth of antibiotic-resistant bacterial infections necessitates focusing on host-derived immunotherapies. γδ T cells are an unconventional T cell subset, making up a relatively small portion of healthy circulating lymphocytes but a substantially increased proportion in mucosal and epithelial tissues. γδ T cells are activated and expanded in response to bacterial infection, having the capability to produce proinflammatory cytokines to recruit neutrophils and clear infection. They also play a significant role in dampening immune response to control inflammation and protecting the host against secondary challenge, making them promising targets when developing immunotherapy. Importantly, γδ T cells have differential metabolic states influencing their cytokine profile and subsequent inflammatory capacity. Though these differential metabolic states have not been well studied or reviewed in the context of bacterial infection, they are critical in understanding the mechanistic underpinnings of the host's innate immune response. Therefore, this review will focus on the context-specific host defense conferred by γδ T cells during infection with Staphylococcus aureus, Streptococcus pneumoniae, Listeria monocytogenes, and Mycobacterium tuberculosis.

Hyperactivation and enhanced cytotoxicity of reduced CD8+ gamma delta T cells in the intestine of patients with Crohn's disease correlates with disease activity

BACKGROUND AND AIMS

We aimed to investigate the immune characteristics of intestinal CD8+ gamma delta T (CD8+ γδ T) cells in Crohn's disease (CD) and their correlation with disease activity.

METHODS

The study cohorts included 21 CD patients and 21 healthy individuals. CD8+ γδ T cells were isolated from human ileal mucosa for detection by flow cytometry. The activation or inhibition status of cells was detected by detecting the expression of activation marker HLA-DR and the immunosuppressive molecule PD-1 on cells. The cytotoxicity of cells was assessed by detecting the expression of cytotoxic molecules (Perforin, Granzyme B, and TRAIL) in cells. Ratios of investigated cells were calculated as prediction factors by receiver operating characteristic curve (ROC) analysis.

RESULTS

The study revealed a reduction in intestinal CD8+ γδT cells among active CD patients, with a more pronounced reduction observed in moderately active patients compared to mildly active patients. Moreover, active CD patients exhibited heightened activation levels in their intestinal CD8+ γδT cells, whereas the activation was comparatively weakened in moderately active patients compared with mildly active patients. Additionally, the cytotoxicity of intestinal CD8+ γδT cells was enhanced solely in mildly active patients, while it was impaired in moderately active patients compared with mildly active patients. Furthermore, HLA-DR+ CD8+ γδT cell ratio, CD8+ γδT ratio, and CD8+ γδT count were identified as indicators in the diagnosis of active CD. Meanwhile, the ratios of Granzyme B+ CD8+ γδT cell and Perforin+ CD8+ γδT cell were identified as indicators that distinguish mildly moderately active CD cases.

CONCLUSIONS

Intestinal CD8+ γδT was reduced in active CD patients, but their activation and cytotoxicity were enhanced. However, with increased disease activity, intestinal CD8+ γδ T cells became dysfunctional. CD-specific perturbations observed in various phenotypic markers in CD8+ γδ T cells can be used as indicators to assist in diagnosing CD patients.

The Changes in the Quantity of Lymphocyte Subpopulations during the Process of Sepsis

Sepsis remains a global challenge, especially in low- and middle-income countries, where there is an urgent need for easily accessible and cost-effective biomarkers to predict the occurrence and prognosis of sepsis. Lymphocyte counts are easy to measure clinically, and a large body of animal and clinical research has shown that lymphocyte counts are closely related to the incidence and prognosis of sepsis. This review extensively collected experimental articles related to lymphocyte counts since the unification of the definition of sepsis. The article categorizes and discusses the relationship between absolute lymphocyte counts, intrinsic lymphocyte subsets, effector T-lymphocytes, B-lymphocytes, dendritic cells, and the incidence and prognosis of sepsis. The results indicate that comparisons of absolute lymphocyte counts alone are meaningless. However, in addition to absolute lymphocyte counts, innate lymphocyte subsets, effector T-cells, B-lymphocytes, and dendritic cells have shown certain research value in related studies.

Innate and Adaptive Cell-Mediated Immune Responses to a COVID-19 mRNA Vaccine in Young Children

Background

There is little information on cell-mediated immunity (CMI) to COVID-19 mRNA vaccines in children. We studied adaptive and innate CMI in vaccinated children aged 6 to 60 months.

Methods

Blood obtained from participants in a randomized placebo-controlled trial of an mRNA vaccine before and 1 month after the first dose was used for antibody measurements and CMI (flow cytometry).

Results

We enrolled 29 children with a mean age of 28.5 months (SD, 15.7). Antibody studies revealed that 10 participants were infected with SARS-CoV-2 prevaccination. Ex vivo stimulation of peripheral blood mononuclear cells with SARS-CoV-2 spike peptides showed significant increases pre- to postimmunization of activated conventional CD4+ and γδ T cells, natural killer cells, monocytes, and conventional dendritic cells but not mucosa-associated innate T cells. Conventional T-cell, monocyte, and conventional dendritic cell responses in children were higher immediately after vaccination than after SARS-CoV-2 infection. The fold increase in CMI pre- to postvaccination did not differ between children previously infected with SARS-CoV-2 and those uninfected.

Conclusions

Children aged 6 to 60 months who were vaccinated with a COVID-19 mRNA vaccine developed robust CMI responses, including adaptive and innate immunity.

C5a enhances Vδ1 T cells recruitment via the CCL2-CCR2 axis in IgA nephropathy

BACKGROUND

Mucosal immune-associated γδ T cells have been implicated in IgA nephropathy (IgAN). However, the involvement of Vδ1 T cells, the major γδ T cells subtype, in renal damage and the mechanism underlying their migration from peripheral blood to kidney in IgAN remain unclear.

METHODS

Clinical data from IgAN patients and healthy controls (HC) were analyzed. Phenotypes and chemokine receptors of γδ T cell were compared between IgAN patients and HC. Immunohistochemistry and immunofluorescence were performed to assess the infiltration of γδ T cell subsets and the expression of chemokine in renal tissues. In vitro, C5a was used to stimulate the human glomerular mesangial cells (HMCs) and chemotaxis experiment was used to examine Vδ1 T cells migration. Correlation between Vδ1 T cells and related clinical indicators were analyzed.

RESULTS

IgAN patients exhibited decreased Vδ1 T cell in blood but increased levels in kidneys compared to HC. Increased CCR2-expressing Vδ1 T cells and serum level of CCL2 were observed in IgAN patients. CCL2 co-localized with CCR2 in HMCs of IgAN. In vitro, C5a enhanced Vδ1 T cells recruitment by HMCs through CCL2-CCR2 axis. Importantly, circulating Vδ1 T cell levels showed a negatively correlated with both the urinary protein creatinine ratio (UACR) and 24-hour urine protein (UP). Moreover, kidney infiltration of Vδ1 cells positively correlated with UACR, UP, mesangial hyperplasia and renal tubule atrophy/interstitial fibrosis in IgAN.

CONCLUSIONS

C5a-induced production of CCL2 by HMCs facilitates Vδ1 T cells recruitment via the CCL2-CCR2 axis, contributing to renal damage in IgAN.

Comparative immune responses to Mycobacterium tuberculosis in people with latent infection or sterilizing protection

There is great need for vaccines against tuberculosis (TB) more efficacious than the licensed BCG. Our goal was to identify new vaccine benchmarks by identifying immune responses that distinguish individuals able to eradicate the infection (TB-resisters) from individuals with latent infection (LTBI-participants). TB-resisters had higher frequencies of circulating CD8+ glucose monomycolate (GMM)+ Granzyme-B+ T cells than LTBI-participants and higher proportions of polyfunctional conventional and nonconventional T cells expressing Granzyme-B and/or PD-1 after ex vivo M. tuberculosis stimulation of blood mononuclear cells. LTBI-participants had higher expression of activation markers and cytokines, including IL10, and IFNγ. An exploratory analysis of BCG-recipients with minimal exposure to TB showed absence of CD8+GMM+Granzyme-B+ T cells, lower or equal proportions of Granzyme-B+PD-1+ polyfunctional T cells than TB-resisters and higher or equal than LTBI-participants. In conclusion, high Granzyme-B+PD-1+ T cell responses to M. tuberculosis and, possibly, of CD8+GMM+Granzyme-B+ T cells may be desirable for new TB vaccines.

Distinct, age-dependent TLR7/8 signaling responses in porcine gamma-delta T cells

Gamma-Delta T cells are a prominent subset of T cells in pigs. However, developmental changes, antigen recognition, cell migration, and their contributions to pathogen clearance remain largely unknown. We have recently shown that porcine γδ T cells express Toll-like receptors (TLRs), and that TLR7/8 stimulation can function as a co-stimulatory signal that complements cytokine-induced signals to enhance INFγ production. Nonetheless, the signaling pathways behind this increased cytokine responsiveness remained unclear. Here, we analyzed the signaling pathways by measuring cellular kinase activity and selective inhibition, confirming that the TLR7/8 expression by γδ T cells is indeed functional. Moreover, TLR downstream signaling responses showed a distinct age-dependency, emphasizing the importance of age in immune function. While the TLR7/8 co-stimulation depended on activation of IRAK1/4, p38 and JNK in adult-derived γδ T cells, γδ T cells from young pigs utilized only p38, indicating the existence of an alternative signaling pathway in young pigs. Overall, this data suggests that porcine γδ T cells could be able to recognize viral RNA through TLR7/8 and subsequently support the survival and activation of the adaptive immune response by cytokine production.

Delayed-onset adenosine deaminase deficiency with a novel synonymous mutation and a case series from China

BACKGROUND

Adenosine deaminase (ADA) is a key enzyme in the purine salvage pathway. Genetic defects of the ADA gene can cause a subtype of severe combined immunodeficiency. To date, few Chinese cases have been reported.

METHODS

We retrospectively reviewed the medical records of patients diagnosed with ADA deficiency in Beijing Children's Hospital and summarized the previously published ADA deficiency cases from China in the literature.

RESULTS

Nine patients were identified with two novel mutations (W272X and Q202 =). Early-onset infection, thymic abnormalities and failure to thrive were the most common manifestations of Chinese ADA-deficient patients. The ADA genotype has a major effect on the clinical phenotype. Notably, a novel synonymous mutation (c.606G>A, p.Q202=) was identified in a delayed-onset patient, which affected pre-mRNA splicing leading to a frameshift and premature truncation of the protein. Furthermore, the patient showed γδT cells expansion with an increased effect or phenotype, which may be associated with the delayed onset of disease. In addition, we reported cerebral aneurysm and intracranial artery stenosis for the first time in ADA deficiency. Five patients died with a median age of four months, while two patients received stem cell transplantation and are alive.

CONCLUSIONS

This study described the first case series of Chinese ADA-deficient patients. Early-onset infection, thymic abnormalities and failure to thrive were the most common manifestations in our patients. We identified a synonymous mutation that affected pre-mRNA splicing in the ADA gene, which had never been reported in ADA deficiency. Furthermore, we reported cerebral aneurysm in a delayed-onset patient for the first time. Further study is warranted to investigate the underlying mechanisms.

OMIP-91: A 27-color flow cytometry panel to evaluate the phenotype and function of human conventional and unconventional T-cells

This 27-color panel was developed to simultaneously measure different T-cell populations (CD4, CD8, γδ T-cells, and MAIT cells) and their subsets (Memory, Th1, Th2, Th17, Tfh, and Treg) along with functional markers associated with their activation status, cytokine production and cytotoxicity. This panel will be useful for both in vivo and in vitro studies evaluating T-cells in the context of human health and disease. This panel is valuable in settings where samples are limited as a large amount of data will be generated using small volumes of blood.

Immunotherapeutic potential of blinatumomab-secreting γ9δ2 T Cells

Previous studies have explored the use of engineered blinatumomab-secreting autologous αβ T cells for CD19-targeted cancer therapy. To create a more flexible allogeneic delivery system, we utilized γ9δ2 T cells rather than αβ T cells in a similar application. First, we showed that γ9δ2 T cells could serve as effector cells for blinatumomab, and these effector memory cells could survive for at least 7 days after infusion. The genetically modified blinatumomab-secreting γ9δ2 T cells induced significant cytotoxicity in CD19⁺ tumor cell lines and primary cells from chronic lymphocytic leukemia patients. Of note, blinatumomab-secreting γ9δ2 T cells might also exhibit dual-targeting of CD19 and isopentenyl pyrophosphate, a universal tumor-associated antigen. Furthermore, blinatumomab-secreting γ9δ2 T cells killed CD19-transfected adherent cells, suggesting that the γ9δ2 T cells might be effective for treating solid tumors with appropriate cancer antigens. Together, these results demonstrate the promise of blinatumomab-secreting γ9δ2 T cells as a cancer therapy.

Co-stimulation by TLR7/8 ligand R848 modulates IFN-γ production of porcine γδ T cells in a microenvironment-dependent manner

Gamma-Delta (γδ) T cells represent a prominent lymphocyte subset in pigs. Their role and function, however, remains largely unknown. Toll-like receptors (TLR) are key receptors for the recognition of pathogens, but so far, it is unknown if porcine γδ T cells express TLRs and therefore have the innate ability to recognize pathogens through pattern recognition receptors. In this study, we compared γδ T cells in different age groups of pigs and investigated the functional relevance of TLR7/8 expression. We found that the major γδ T cell phenotype shifts from CD2^-CD8α^-/dimCD27⁺ in young pigs to CD2⁺CD8α^highCD27^- in 3-year-old pigs impacting their ability to produce IFN-γ upon cytokine and TLR stimulation. Furthermore, we report that stimulation with TLR7/8 ligand R848 increased IFN-γ production in purified γδ T cells upon co-stimulation with IL-2 and IL-12. However, the effect of R848 as a co-activator of γδ T cells was abrogated by the addition of monocytes or within PBMCs, suggesting that γδ T cells respond to multiple direct and indirect stimulations. Thus, our results indicate that γδ T cells express TLRs, are modulated by TLR7/8 ligand R848 and have subset-specific responses.

The deciphering of the immune cells and marker signature in COVID-19 pathogenesis: An update

The precise interaction between the immune system and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is critical in deciphering the pathogenesis of coronavirus disease 2019 (COVID-19) and is also vital for developing novel therapeutic tools, including monoclonal antibodies, antivirals drugs, and vaccines. Viral infections need innate and adaptive immune reactions since the various immune components, such as neutrophils, macrophages, CD4+ T, CD8+ T, and B lymphocytes, play different roles in various infections. Consequently, the characterization of innate and adaptive immune reactions toward SARS-CoV-2 is crucial for defining the pathogenicity of COVID-19. In this study, we explain what is currently understood concerning the conventional immune reactions to SARS-CoV-2 infection to shed light on the protective and pathogenic role of immune response in this case. Also, in particular, we investigate the in-depth roles of other immune mediators, including neutrophil elastase, serum amyloid A, and syndecan, in the immunopathogenesis of COVID-19.

Gamma delta T-cell reconstitution after allogeneic HCT: A platform for cell therapy

Allogeneic Hematopoietic stem cell transplantation (allo-HCT) is a curative platform for several hematological diseases. Despite its therapeutic benefits, the profound immunodeficiency associated with the transplant procedure remains a major challenge that renders patients vulnerable to several complications. Today, It is well established that a rapid and efficient immune reconstitution, particularly of the T cell compartment is pivotal to both a short-term and a long-term favorable outcome. T cells expressing a TCR heterodimer comprised of gamma (γ) and delta (δ) chains have received particular attention in allo-HCT setting, as a large body of evidence has indicated that γδ T cells can exert favorable potent anti-tumor effects without inducing severe graft versus host disease (GVHD). However, despite their potential role in allo-HCT, studies investigating their detailed reconstitution in patients after allo-HCT are scarce. In this review we aim to shed lights on the current literature and understanding of γδ T cell reconstitution kinetics as well as the different transplant-related factors that may influence γδ reconstitution in allo-HCT. Furthermore, we will present data from available reports supporting a role of γδ cells and their subsets in patient outcome. Finally, we discuss the current and future strategies to develop γδ cell-based therapies to exploit the full immunotherapeutic potential of γδ cells in HCT setting.

Neuroendocrine regulations in tissue-specific immunity: From mechanism to applications in tumor

Immune responses in nonlymphoid tissues play a vital role in the maintenance of homeostasis. Lots of evidence supports that tissue-specific immune cells provide defense against tumor through the localization in different tissue throughout the body, and can be regulated by diverse factors. Accordingly, the distribution of nervous tissue is also tissue-specific which is essential in the growth of corresponding organs, and the occurrence and development of tumor. Although there have been many mature perspectives on the neuroendocrine regulation in tumor microenvironment, the neuroendocrine regulation of tissue-specific immune cells has not yet been summarized. In this review, we focus on how tissue immune responses are influenced by autonomic nervous system, sensory nerves, and various neuroendocrine factors and reversely how tissue-specific immune cells communicate with neuroendocrine system through releasing different factors. Furthermore, we pay attention to the potential mechanisms of neuroendocrine-tissue specific immunity axis involved in tumors. This may provide new insights for the immunotherapy of tumors in the future.

Glucose metabolism controls human γδ T-cell-mediated tumor immunosurveillance in diabetes

Patients with type 2 diabetes mellitus (T2DM) have an increased risk of cancer. The effect of glucose metabolism on γδ T cells and their impact on tumor surveillance remain unknown. Here, we showed that high glucose induced Warburg effect type of bioenergetic profile in Vγ9Vδ2 T cells, leading to excessive lactate accumulation, which further inhibited lytic granule secretion by impairing the trafficking of cytolytic machinery to the Vγ9Vδ2 T-cell-tumor synapse by suppressing AMPK activation and resulted in the loss of antitumor activity in vitro, in vivo and in patients. Strikingly, activating the AMPK pathway through glucose control or metformin treatment reversed the metabolic abnormalities and restored the antitumor activity of Vγ9Vδ2 T cells. These results suggest that the impaired antitumor activity of Vγ9Vδ2 T cells induced by dysregulated glucose metabolism may contribute to the increased cancer risk in T2DM patients and that metabolic reprogramming by targeting the AMPK pathway with metformin may improve tumor immunosurveillance.

Impact of Anti-T-lymphocyte globulin dosing on GVHD and Immune reconstitution in matched unrelated myeloablative peripheral blood stem cell transplantation

Data on the influence of different Anti-lymphocyte globulin (ATLG) doses on graft versus host disease (GVHD) incidence and immune reconstitution in matched unrelated (MUD) allogeneic Stem cell transplantation (allo-SCT) is limited. This retrospective study conducted at the University Medical-Center Hamburg compares GVHD and Immune reconstitution after myeloablative MUD (HLA 10/10) PBSC allogeneic stem cell transplant between 30 mg/Kg (n = 73) and 60 mg/Kg (n = 216) ATLG. Detailed phenotypes of T, B natural killer (NK), natural killer T (NKT) cells were analyzed by multicolor flow at day 30, 100, and 180 posttransplant. Neutrophil and platelet engraftments were significantly delayed in the 60 mg/kg group with a higher Cumulative incidence of Infections (67% vs 75% p = 0.049) and EBV (21% vs 41% p = 0.049) reactivation at day 100 in this group. In the 30 mg/kg group, we observed a faster reconstitution of naïve-B cells (p < 0.0001) and γδ T cells (p = 0.045) at day+30 and a faster naïve helper T-cell (p = 0.046), NK-cells (p = 0.035), and naïve B-cell reconstitution (p = 0.009) at day+180. There were no significant differences in aGVHD, cGVHD, NRM, RI, PFS, and OS between the groups. The choice of ATLG dose has significant impact on IR but not on GVHD after MUD-allo-SCT. Higher doses are associated with delayed engraftment and increased infections.

Clinical Characteristics of Posttransplant Lymphoproliferative Disorder After Cord Blood Transplantation Without Antithymocyte Globulin

BACKGROUND

CBT with ATG use is a well-known PTLD risk factor. However, little is known regarding the clinical features of PTLD after ATG-free CBT.

PATIENTS AND METHODS

We analyzed the incidence, risk factors and prognosis of PTLD in 183 adults undergoing ATG-free CBT.

RESULTS

Fifteen patients (diffuse large B-cell lymphoma, n = 9, mucosa-associated lymphoid tissue lymphoma, n = 2 nondestructive PTLD, n = 1, T-cell lymphoma, n = 3) developed PTLD. The 2-year CuI of PTLD was 8.0% (95% CI: 4.6-12.7). Pathologically, all 12 B-cell PTLD patients had Epstein-Barr virus (EBV), compared with 1 of 3 T-cell PTLD patients. All patients, excluding one with nondestructive PTLD, showed extranodal involvement. In the univariate analysis, the 2-year CuI of PTLD was significantly higher in patients who received mycophenolate mofetil to prevent graft-versus-host disease than in nonrecipients (11.2%/2.9%, P = .0457). However, multivariate analysis revealed no independent PTLD risk factors. All 11 PTLD patients who received specific therapy achieved complete remission. The 1-year overall survival of PTLD patients was 70.9%.

CONCLUSION

Although we found a higher CuI of PTLD than previously reported, the prognosis was generally good. In CBT recipients, many factors, including MMF use, may be associated with the clinical features of PTLD.

Interleukin-17A and interleukin-22 production by conventional and non-conventional lymphocytes in three different end-stage lung diseases

Objectives

The contribution of adaptive vs. innate lymphocytes to IL-17A and IL-22 secretion at the end stage of chronic lung diseases remains largely unexplored. In order to uncover tissue- and disease-specific secretion patterns, we compared production patterns of IL-17A and IL-22 in three different human end-stage lung disease entities.

Methods

Production of IL-17A, IL-22 and associated cytokines was assessed in supernatants of re-stimulated lymphocytes by multiplex assays and multicolour flow cytometry of conventional T cells, iNKT cells, γδ T cells and innate lymphoid cells in bronchial lymph node and lung tissue from patients with emphysema (n = 19), idiopathic pulmonary fibrosis (n = 14) and cystic fibrosis (n = 23), as well as lung donors (n = 17).

Results

We detected secretion of IL-17A and IL-22 by CD4⁺ T cells, CD8⁺ T cells, innate lymphoid cells, γδ T cells and iNKT cells in all end-stage lung disease entities. Our analyses revealed disease-specific contributions of individual lymphocyte subpopulations to cytokine secretion patterns. We furthermore found the high levels of microbial detection in CF samples to associate with a more pronounced IL-17A signature upon antigen-specific and unspecific re-stimulation compared to other disease entities and lung donors.

Conclusion

Our results show that both adaptive and innate lymphocyte populations contribute to IL-17A-dependent pathologies in different end-stage lung disease entities, where they establish an IL-17A-rich microenvironment. Microbial colonisation patterns and cytokine secretion upon microbial re-stimulation suggest that pathogens drive IL-17A secretion patterns in end-stage lung disease.

CD137 Costimulation Enhances the Antitumor Activity of Vγ9Vδ2-T Cells in IL-10-Mediated Immunosuppressive Tumor Microenvironment

Although γδ-T cell-based tumor immunotherapy using phosphoantigens to boost γδ-T cell immunity has shown success in some cancer patients, the clinical application is limited due to the rapid exhaustion of Vγ9Vδ2-T cells caused by repetitive stimulation from phosphoantigens and the profoundly immunosuppressive tumor microenvironment (TME). In this study, using a cell culture medium containing human and viral interleukin-10 (hIL-10 and vIL-10) secreted from EBV-transformed lymphoblastoid B cell lines (EBV-LCL) to mimic the immunosuppressive TEM, we found that the antitumor activity of Vγ9Vδ2-T cells was highly suppressed by endogenous hIL-10 and vIL-10 within the TME. CD137 costimulation could provide an anti-exhaustion signal to mitigate the suppressive effects of IL-10 in TME by suppressing IL-10R1 expression on Vγ9Vδ2-T cells. CD137 costimulation also improved the compromised antitumor activity of Vγ9Vδ2-T cells in TME with high levels of IL-10 in Rag2^-/- γc^-/- mice. In humanized mice, CD137 costimulation boosted the therapeutic effects of aminobisphosphonate pamidronate against EBV-induced lymphoma. Our study offers a novel approach to overcoming the obstacle of the hIL-10 and vIL-10-mediated immunosuppressive microenvironment by costimulating CD137 and enhancing the efficacy of γδ-T cell-based tumor therapy.

Emerging role of γδ T cells in protozoan infection and their potential clinical application

γδ T cells are thymus derived heterogeneous and unconventional T- lymphocyte expressing TCR γ (V γ9) and TCRδ (Vδ2) chain and play an important role in connecting innate and adaptive armaments of immune response. These cells can recognize wide ranges of antigens even without involvement of major histocompatibility complex and exert their biological functions by cytotoxicity or activating various types of immune cells. In recent past, γδ T cells have emerged as an important player during protozoa infection and rapidly expand after exposure with them. They have also been widely studied in vaccine induced immune response against many bacterial and protozoan infections with improved clinical outcome. In this review, we will discuss the various roles of γδ T cells in immunity against malaria and leishmaniasis, the two important protozoan diseases causing significant mortality and morbidity throughout the world.

CD161 expression defines new human γδ T cell subsets

γδ T cells are a highly versatile immune lineage involved in host defense and homeostasis, but questions remain around their heterogeneity, precise function and role during health and disease. We used multi−parametric flow cytometry, dimensionality reduction, unsupervised clustering, and self-organizing maps (SOM) to identify novel γδ T cell naïve/memory subsets chiefly defined by CD161 expression levels, a surface membrane receptor that can be activating or suppressive. We used middle-to-old age individuals given immune blockade is commonly used in this population. Whilst most Vδ1+subset cells exhibited a terminal differentiation phenotype, Vδ1− subset cells showed an early memory phenotype. Dimensionality reduction revealed eight γδ T cell clusters chiefly diverging through CD161 expression with CD4 and CD8 expression limited to specific subpopulations. Comparison of matched healthy elderly individuals to bronchiectasis patients revealed elevated Vδ1+ terminally differentiated effector memory cells in patients potentially linking this population with chronic proinflammatory disease.

Exosomes derived from γδ-T cells synergize with radiotherapy and preserve antitumor activities against nasopharyngeal carcinoma in immunosuppressive microenvironment

Background

Radiotherapy is the first-line treatment for patients nasopharyngeal carcinoma (NPC), but its therapeutic efficacy is poor in some patients due to radioresistance. Adoptive T cell-based immunotherapy has also shown promise to control NPC; however, its antitumor efficacy may be attenuated by an immunosuppressive tumor microenvironment. Exosomes derived from γδ-T cells (γδ-T-Exos) have potent antitumor potentials. However, it remains unknown whether γδ-T-Exos have synergistic effect with radiotherapy and preserve their antitumor activities against NPC in an immunosuppressive tumor microenvironment.

Methods

γδ-T-Exos were stained with fluorescent membrane dye, and their interactions with NPC were determined both in vitro and in vivo. NPC cell deaths were detected after treatment with γδ-T-Exos and/or irradiation. Moreover, effects of γδ-T-Exos on radioresistant cancer stem-like cells (CSCs) were determined. The therapeutic efficacy of combination therapy using γδ-T-Exos and irradiation on NPC tumor progression was also monitored in vivo. Finally, the tumor-killing and T cell-promoting activities of γδ-T-Exos were determined under the culture in immunosuppressive NPC supernatant.

Results

γδ-T-Exos effectively interacted with NPC tumor cells in vitro and in vivo. γδ-T-Exos not only killed NPC cells in vitro, which was mainly mediated by Fas/Fas ligand (FasL) and death receptor 5 (DR5)/tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) pathways, but also controlled NPC tumor growth and prolonged tumor-bearing mice survival in vivo. Furthermore, γδ-T-Exos selectively targeted the radioresistant CD44^+/high CSCs and induced profound cell apoptosis. The combination of γδ-T-Exos with radiotherapy overcame the radioresistance of CD44^+/high NPC cells and significantly improved its therapeutic efficacy against NPC in vitro and in vivo. In addition, γδ-T-Exos promoted T-cell migration into NPC tumors by upregulating CCR5 on T cells that were chemoattracted by CCR5 ligands in the NPC tumor microenvironment. Although NPC tumor cells secreted abundant tumor growth factor beta to suppress T-cell responses, γδ-T-Exos preserved their direct antitumor activities and overcame the immunosuppressive NPC microenvironment to amplify T-cell antitumor immunity.

Conclusions

γδ-T-Exos synergized with radiotherapy to control NPC by overcoming the radioresistance of NPC CSCs. Moreover, γδ-T-Exos preserved their tumor-killing and T cell-promoting activities in the immunosuppressive NPC microenvironment. This study provides a proof of concept for a novel and potent strategy by combining γδ-T-Exos with radiotherapy in the control of NPC.

Impairment of antigen-presenting function of peripheral γδ T cells in patients with sepsis

Impairment of antigen-presenting functions is a key mechanism contributing to sepsis-induced immunosuppression. Recently, γδ T cells have been demonstrated as professional antigen-presenting cells (APCs); however, their role in sepsis remains unknown. In this in vitro study, the APC function of human peripheral γδ T cells was assessed using samples collected from 42 patients with sepsis and 27 age-matched healthy controls. The APC-related markers HLA-DR, CD27, CD80, and CCR7 on fresh γδT cells were significantly higher in patients with sepsis compared with matched controls; however, they responded poorly to 4-hydroxy-3-methyl-2-butenyl pyrophosphate (HMBPP) stimulation, characterized by the deactivation of these APC markers and impaired proliferation. Furthermore, the adhesion function of γδ T cells, essential for antigen presentation, was greatly reduced in patients with sepsis; for instance, in co-cultures with green fluorescent protein-expressing Escherichia coli, HMBPP-activated γδT cells from healthy individuals adhered to E. coli efficiently, whereas no such phenomenon was observed with respect to γδT cells from patients with sepsis. In line with these results, in co-cultures with isolated CD4⁺ αβ T cells, HMBPP-activated γδT cells of healthy individuals promoted the efficient proliferation of CD4⁺ αβ T cells, whereas γδT cells from patients with sepsis did not do so. In conclusion, our findings show that the antigen-presenting function of γδT cells is severely impaired in patients with sepsis and the mechanisms behind need further study.

Allogeneic gamma delta T cells as adoptive cellular therapy for hematologic malignancies

Cancer immunotherapy, especially T-cell driven targeting, has significantly evolved and improved over the past decade, paving the way to treat previously refractory cancers. Hematologic malignancies, given their direct tumor accessibility and less immunosuppressive microenvironment compared to solid tumors, are better suited to be targeted by cellular immunotherapies. Gamma delta (γδ) T cells, with their unique attributes spanning the entirety of the immune system, make a tantalizing therapeutic platform for cancer immunotherapy. Their inherent anti-tumor properties, ability to act like antigen-presenting cells, and the advantage of having no major histocompatibility complex (MHC) restrictions, allow for greater flexibility in their utility to target tumors, compared to their αβ T cell counterpart. Their MHC-independent anti-tumor activity, coupled with their ability to be easily expanded from peripheral blood, enhance their potential to be used as an allogeneic product. In this review, the potential of utilizing γδ T cells to target hematologic malignancies is described, with a specific focus on their applicability as an allogeneic adoptive cellular therapy product.

Recognition of the antigen-presenting molecule MR1 by a Vδ3+ γδ T cell receptor

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.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

Bone Marrow-Resident Vδ1 T Cells Co-express TIGIT With PD-1, TIM-3 or CD39 in AML and Myeloma

Background: γδ T cells represent a unique T cell subpopulation due to their ability to recognize cancer cells in a T cell receptor- (TCR) dependent manner, but also in a non-major histocompatibility complex- (MHC) restricted way via natural killer receptors (NKRs). Endowed with these features, they represent attractive effectors for immuno-therapeutic strategies with a better safety profile and a more favorable anti-tumor efficacy in comparison to conventional αβ T cells. Also, remarkable progress has been achieved re-activating exhausted T lymphocytes with inhibitors of co-regulatory receptors e.g., programmed cell death protein 1 (PD-1), T cell immunoreceptor with Ig and ITIM domains (TIGIT) and of the adenosine pathway (CD39, CD73). Regarding γδ T cells, little evidence is available. This study aimed to immunophenotypically characterize γδ T cells from patients with diagnosed acute myeloid leukemia (AML) in comparison to patients with multiple myeloma (MM) and healthy donors (HD).

Methods: The frequency, differentiation, activation, and exhaustion status of bone marrow- (BM) derived γδ T cells from patients with AML (n = 10) and MM (n = 11) were assessed in comparison to corresponding CD4⁺ and CD8⁺ T cells and peripheral blood- (PB) derived γδ T cells from HDs (n = 16) using multiparameter flow cytometry.

Results: BM-infiltrating Vδ1 T cells showed an increased terminally differentiated cell population (TEMRAs) in AML and MM in comparison to HDs with an aberrant subpopulation of CD27⁻CD45RA⁺⁺ cells. TIGIT, PD-1, TIM-3, and CD39 were more frequently expressed by γδ T cells in comparison to the corresponding CD4⁺ T cell population, with expression levels that were similar to that on CD8⁺ effector cells in both hematologic malignancies. In comparison to Vδ2 T cells, the increased frequency of PD-1⁺-, TIGIT⁺-, TIM-3⁺, and CD39⁺ cells was specifically observed on Vδ1 T cells and related to the TEMRA Vδ1 population with a significant co-expression of PD-1 and TIM-3 together with TIGIT.

Conclusion: Our results revealed that BM-resident γδ T cells in AML and MM express TIGIT, PD-1, TIM-3 and CD39. As effector population for autologous and allogeneic strategies, inhibition of co-inhibitory receptors on especially Vδ1 γδ T cells may lead to re-invigoration that could further increase their cytotoxic potential.

Our evolving understanding of the role of the γδ T cell receptor in γδ T cell mediated immunity

The γδ T cell immune cell lineage has remained relatively enigmatic and under-characterised since their identification. Conversely, the insights we have, highlight their central importance in diverse immunological roles and homeostasis. Thus, γδ T cells are considered as potentially a new translational tool in the design of new therapeutics for cancer and infectious disease. Here we review our current understanding of γδ T cell biology viewed through a structural lens centred on the how the γδ T cell receptor mediates ligand recognition. We discuss the limited knowledge of antigens, the structural basis of such reactivities and discuss the emerging trends of γδ T cell reactivity and implications for γδ T cell biology.

Characterization of Adaptive-like γδ T Cells in Ugandan Infants during Primary Cytomegalovirus Infection

Gamma-delta (γδ) T cells are unconventional T cells that help control cytomegalovirus (CMV) infection in adults. γδ T cells develop early in gestation, and a fetal public γδ T cell receptor (TCR) clonotype is detected in congenital CMV infections. However, age-dependent γδ T cell responses to primary CMV infection are not well-understood. Flow cytometry and TCR sequencing was used to comprehensively characterize γδ T cell responses to CMV infection in a cohort of 32 infants followed prospectively from birth. Peripheral blood γδ T cell frequencies increased during infancy, and were higher among CMV-infected infants relative to uninfected. Clustering analyses revealed associations between CMV infection and activation marker expression on adaptive-like Vδ1 and Vδ3, but not innate-like Vγ9Vδ2 γδ T cell subsets. Frequencies of NKG2C⁺CD57⁺ γδ T cells were temporally associated with the quantity of CMV shed in saliva by infants with primary infection. The public γδ TCR clonotype was only detected in CMV-infected infants <120 days old and at lower frequencies than previously described in fetal infections. Our findings support the notion that CMV infection drives age-dependent expansions of specific γδ T cell populations, and provide insight for novel strategies to prevent CMV transmission and disease.

IL-15 Is Overexpressed in γδ T Cells and Correlates with Disease Severity in Relapsing-Remitting Multiple Sclerosis

Interleukin 15 (IL-15) is known to be involved in the pathogenesis of multiple sclerosis (MS). An animal study revealed a distinct subset of IL-15-producing γδ T cells that correlate with disease severity. The aim of the current study was to test whether such a subset is also present in humans and its importance for the pathogenesis of MS. The peripheral blood from 29 patients with relapsing-remitting MS (including 6 relapses) and 22 controls was stained with monoclonal antibodies and analyzed with flow cytometry. The existence of IL-15+ γδ T cells was confirmed. Moreover, the percentage of IL-15+ γδ T is significantly increased in MS patients and correlates with disease severity. Nevertheless, additional functional studies are needed to fully understand the importance of those cells in multiple sclerosis pathogenesis.

Immunosuppressant indulges EBV reactivation and related lymphoproliferative disease by inhibiting Vδ2+ T cells activities after hematopoietic transplantation for blood malignancies

Background

Following the extensive use of immunosuppressive drugs in the clinic, immunosuppression-associated side effects have received increasing attention. Epstein-Barr virus (EBV) reactivation and related lymphoproliferative diseases (LPD) are the lethal complications observed after allogeneic hematopoietic cell transplantation (alloHCT). While studies generally suggest an association between immunosuppressants and EBV reactivation, the effects of specific immunosuppressive drugs and which T-cell subsets mediate these correlations are unclear. Vδ2⁺ T cells are correlated with EBV reactivation after alloHCT. Researchers have not determined whether Vδ2⁺ T-cell activities are affected by immunosuppressants and thereby facilitate EBV reactivation and related LPD.

Methods

A clinical cohort study of 170 patients with hematopoietic malignancies who received haploidentical hematopoietic cell transplantation (haploHCT) was performed to investigate whether the early cessation of mycophenolate mofetil (MMF) decreases EBV reactivation and related LPD and to determine whether this change is associated with the recovery of Vδ2 ⁺ T cells after transplantation. The effects of MMF on the expansion and anti-EBV capacity of Vδ2⁺ T cells were detected in vitro and in an immunodeficient mouse model.

Results

A reduction in the course of MMF significantly improved the recovery of Vδ2⁺ T cells from 30 to 90 days after haploHCT (p=0.002, p=0.042 and p=0.035, respectively), accompanied by a significant decrease in EBV reactivation (from 26% to 13%, p=0.033) and EBV-LPD (from 10.6% to 2.4%, p=0.029). The day-30 Vδ2⁺ T level remained an independent factor for EBV reactivation in patients with different MMF durations (p=0.007). In the in-vitro experiments, MMF inhibited Vδ2⁺ T-cell expansion and its cytotoxicity on EBV-transformed malignant cells. Furthermore, the therapeutic and prophylactic effects of adoptively transferred human Vδ2⁺ T cells were attenuated by the MMF treatment in immunodeficient mice with EBV-LPD.

Conclusions

These results elucidated a negative effect of immunosuppressants on the anti-EBV capacity of Vδ2⁺ T cells. Strategies that appropriately relieve the immunosuppression may improve anti-EBV immunity by increasing the activity of Vδ2⁺ T cells after alloHCT.

γδ T Cells May Aggravate Acute Graft-Versus-Host Disease Through CXCR4 Signaling After Allogeneic Hematopoietic Transplantation

Graft-versus-host disease (GVHD) is a pathology in which chemokines and their receptors play essential roles in directing the migration of alloreactive donor T cells into GVHD organs, thereby leading to further target tissue damage. Currently, acute GVHD (aGVHD) remains a major cause of high morbidity and mortality in patients who underwent allogeneic hematopoietic cell transplantation (alloHCT). The identification of immune cells that correlate with aGVHD is important and intriguing. To date, the involvement of innate-like γδ T cells in the pathogenesis of aGVHD is unclear. Herein, we found that primary human γδ T cells did not directly trigger allogeneic reactions. Instead, we revealed that γδ T cells facilitated the migration of CD4 T cells via the SDF-1-CXCR4 axis. These results indicate indirect regulation of γδ T cells in the development of aGVHD rather than a direct mechanism. Furthermore, we showed that the expression of CXCR4 was significantly elevated in γδ T cells and CD4 and CD8 T cells in recipients who experienced grades II-IV aGVHD after alloHCT. Consistently, CXCR4-expressing γδ T cells and CD4 T cells were induced in the target organs of mice suffering aGVHD. The depletion of γδ T cells in transplant grafts and treatment with AMD3100, an inhibitor of CXCR4 signaling, delayed the onset of aGVHD and prolonged survival in mice. Taken together, these findings suggest a role for γδ T cells in recruiting alloreactive CD4 T cells to target tissues through the expression of CXCR4. Our findings may help in understanding the mechanism of aGVHD and provide novel therapeutic targets.

Revisiting the Role of γδ T Cells in Anti-CMV Immune Response after Transplantation

Gamma delta (γδ) T cells form an unconventional subset of T lymphocytes that express a T cell receptor (TCR) consisting of γ and δ chains. Unlike conventional αβ T cells, γδ T cells share the immune signature of both the innate and the adaptive immunity. These features allow γδ T cells to act in front-line defense against infections and tumors, rendering them an attractive target for immunotherapy. The role of γδ T cells in the immune response to cytomegalovirus (CMV) has been the focus of intense research for several years, particularly in the context of transplantation, as CMV reactivation remains a major cause of transplant-related morbidity and mortality. Therefore, a better understanding of the mechanisms that underlie CMV immune responses could enable the design of novel γδ T cell-based therapeutic approaches. In this regard, the advent of next-generation sequencing (NGS) and single-cell TCR sequencing have allowed in-depth characterization of CMV-induced TCR repertoire changes. In this review, we try to shed light on recent findings addressing the adaptive role of γδ T cells in CMV immunosurveillance and revisit CMV-induced TCR reshaping in the era of NGS. Finally, we will demonstrate the favorable and unfavorable effects of CMV reactive γδ T cells post-transplantation.

Infection and Immune Memory: Variables in Robust Protection by Vaccines Against SARS-CoV-2

SARS-CoV-2 is the cause of a recent pandemic that has led to more than 3 million deaths worldwide. Most individuals are asymptomatic or display mild symptoms, which raises an inherent question as to how does the immune response differs from patients manifesting severe disease? During the initial phase of infection, dysregulated effector immune cells such as neutrophils, macrophages, monocytes, megakaryocytes, basophils, eosinophils, erythroid progenitor cells, and Th17 cells can alter the trajectory of an infected patient to severe disease. On the other hand, properly functioning CD4+, CD8+ cells, NK cells, and DCs reduce the disease severity. Detailed understanding of the immune response of convalescent individuals transitioning from the effector phase to the immunogenic memory phase can provide vital clues to understanding essential variables to assess vaccine-induced protection. Although neutralizing antibodies can wane over time, long-lasting B and T memory cells can persist in recovered individuals. The natural immunological memory captures the diverse repertoire of SARS-CoV-2 epitopes after natural infection whereas, currently approved vaccines are based on a single epitope, spike protein. It is essential to understand the nature of the immune response to natural infection to better identify 'correlates of protection' against this disease. This article discusses recent findings regarding immune response against natural infection to SARS-CoV-2 and the nature of immunogenic memory. More precise knowledge of the acute phase of immune response and its transition to immunological memory will contribute to the future design of vaccines and the identification of variables essential to maintain immune protection across diverse populations.

Host immune response against leishmaniasis and parasite persistence strategies: A review and assessment of recent research

Leishmaniasis, a neglected parasitic disease caused by a unicellular protozoan of the genus Leishmania, is transmitted through the bite of a female sandfly. The disease remains a major public health problem and is linked to tropical and subtropical regions, with an endemic picture in several regions, including East Africa, the Mediterranean basin and South America. The different causative species display a diversity of clinical presentations; therefore, the immunological data on leishmaniasis are both scarce and controversial for the different forms and infecting species of the parasite. The present review highlights the main immune parameters associated with leishmaniasis that might contribute to a better understanding of the pathogenicity of the parasite and the clinical outcomes of the disease. Our aim was to provide a concise overview of the immunobiology of the disease and the factors that influence it, as this knowledge may be helpful in developing novel chemotherapeutic and vaccine strategies.

Neuronal-Activated ILC2s Promote IL-17A Production in Lung γδ T Cells During Sepsis

Background

Studies have revealed important roles for IL-17A in the development of acute lung injury (ALI) following sepsis. However, the mechanism underlying the regulation of lung IL-17A remains to be fully addressed. Recent studies suggested the effect of neuromedin U (NMU) on immune cell activation and the role of group 2 innate lymphoid cells (ILC2s) in the modulation of IL-17A production. We aimed to gain in-depth insight into the mechanism underlying sepsis-induced lung IL-17A production, particularly, the role of NMU in mediating neuronal regulation of ILC2s and IL-17A-producing γδ T cells activation in sepsis.

Methods

Wild type mice were subjected to cecal ligation and puncture (CLP) to induce sepsis with or without intraperitoneal injection of NMU. The levels of ILC2s, γδ T cells, IL-17A, NMU and NMU receptor 1 (NMUR1) in the lung were then measured. In order to determine the role of NMU signaling in ILC2 activation and the role of ILC2-released IL-9 in ILC2-γδ T cell interaction, ILC2s were sorted, and the genes of nmur1 and il9 in the ILC2s were knocked down using CRISPR/Cas9. The genetically manipulated ILC2s were then co-cultured with lung γδ T cells, and the levels of IL-17A from co-culture systems were measured.

Results

In septic mice, the levels of NMU, IL-17A, ILC2s, and IL-17A-producing γδ T cells in the lung are significantly increased, and the expression of NMUR1 in ILC2s is increased as well. Exogenous NMU further augments these increases. The main source of IL-17A in response to CLP is γδ T cells, and lung nmur1 is specifically expressed in ILC2s. In vitro co-culture of ILC2s and γδ T cells leads to increased number of γδ T cells and higher production of IL-17A from γδ T cells, and these alterations are further augmented by septic treatment and exogenous NMU. Genetic knockdown of nmur1 or il9 in ILC2s attenuated the upregulation of γδ T cells and IL-17A production.

Conclusion

In sepsis, NMU acting through NMUR1 in lung ILC2s initiates the ILC2 activation, which, in turn, promote IL-17A-producing γδ T cell expansion and secretion of IL-17A. ILC2-derived IL-9 plays an important role in mediating γδ T cell expansion and IL-17A production. This study explores a new mechanism underlying neuronal regulation of innate immunity in sepsis.

Immunophenotypic characterization of TCR γδ T cells and MAIT cells in HIV-infected individuals developing Hodgkin's lymphoma

Background

Despite successful combined antiretroviral therapy (cART), the risk of non-AIDS defining cancers (NADCs) remains higher for HIV-infected individuals than the general population. The reason for this increase is highly disputed. Here, we hypothesized that T-cell receptor (TCR) γδ cells and/or mucosal-associated invariant T (MAIT) cells might be associated with the increased risk of NADCs. γδ T cells and MAIT cells both serve as a link between the adaptive and the innate immune system, and also to exert direct anti-viral and anti-tumor activity.

Methods

We performed a longitudinal phenotypic characterization of TCR γδ cells and MAIT cells in HIV-infected individuals developing Hodgkin’s lymphoma (HL), the most common type of NADCs. Cryopreserved PBMCs of HIV-infected individuals developing HL, matched HIV-infected controls without (w/o) HL and healthy controls were used for immunophenotyping by polychromatic flow cytometry, including markers for activation, exhaustion and chemokine receptors.

Results

We identified significant differences in the CD4⁺ T cell count between HIV-infected individuals developing HL and HIV-infected matched controls within 1 year before cancer diagnosis. We observed substantial differences in the cellular phenotype mainly between healthy controls and HIV infection irrespective of HL. A number of markers tended to be different in Vδ1 and MAIT cells in HIV⁺HL⁺ patients vs. HIV⁺ w/o HL patients; notably, we observed significant differences for the expression of CCR5, CCR6 and CD16 between these two groups of HIV⁺ patients.

Conclusion

TCR Vδ1 and MAIT cells in HIV-infected individuals developing HL show subtle phenotypical differences as compared to the ones in HIV-infected controls, which may go along with functional impairment and thereby may be less efficient in detecting and eliminating malignant cells. Further, our results support the potential of longitudinal CD4⁺ T cell count analysis for the identification of patients at higher risk to develop HL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13027-021-00365-4.