Distinct and overlapping effector functions of expanded human CD4+, CD8α+ and CD4-CD8α- invariant natural killer T cells

Thymic development of human natural killer T cells: recent advances and implications for immunotherapy

Invariant natural killer T (iNKT) cells are a subset of lipid-reactive, unconventional T cells that have anti-tumor properties that make them a promising target for cancer immunotherapy. Recent studies have deciphered the developmental pathway of human MAIT and Vγ9Vδ2 γδ-T cells as well as murine iNKT cells, yet our understanding of human NKT cell development is limited. Here, we provide an update in our understanding of how NKT cells develop in the human body and how knowledge regarding their development could enhance human treatments by targeting these cells.

Protective effects of Ganoderma lucidum spores on estradiol benzoate-induced TEC apoptosis and compromised double-positive thymocyte development

Backgroud: Thymic atrophy marks the onset of immune aging, precipitating developmental anomalies in T cells. Numerous clinical and preclinical investigations have underscored the regulatory role of Ganoderma lucidum spores (GLS) in T cell development. However, the precise mechanisms underlying this regulation remain elusive. Methods: In this study, a mice model of estradiol benzoate (EB)-induced thymic atrophy was constructed, and the improvement effect of GLS on thymic atrophy was evaluated. Then, we employs multi-omics techniques to elucidate how GLS modulates T cell development amidst EB-induced thymic atrophy in mice. Results: GLS effectively mitigates EB-induced thymic damage by attenuating apoptotic thymic epithelial cells (TECs) and enhancing the output of CD4+ T cells into peripheral blood. During thymic T cell development, sporoderm-removed GLS (RGLS) promotes T cell receptor (TCR) α rearrangement by augmenting V-J fragment rearrangement frequency and efficiency. Notably, biased Vα14-Jα18 rearrangement fosters double-positive (DP) to invariant natural killer T (iNKT) cell differentiation, partially contingent on RGLS-mediated restriction of peptide-major histocompatibility complex I (pMHCⅠ)-CD8 interaction and augmented CD1d expression in DP thymocytes, thereby promoting DP to CD4+ iNKT cell development. Furthermore, RGLS amplifies interaction between a DP subpopulation, termed DPsel-7, and plasmacytoid dendritic cells (pDCs), likely facilitating the subsequent development of double-negative iNKT1 cells. Lastly, RGLS suppresses EB-induced upregulation of Abpob and Apoa4, curbing the clearance of CD4+Abpob+ and CD4+Apoa4+ T cells by mTECs, resulting in enhanced CD4+ T cell output. Discussion: These findings indicate that the RGLS effectively mitigates EB-induced TEC apoptosis and compromised double-positive thymocyte development. These insights into RGLS's immunoregulatory role pave the way for its potential as a T-cell regeneration inducer.

Traversing the bench to bedside journey for iNKT cell therapies

Invariant natural killer T (iNKT) cells are immune cells that harness properties of both the innate and adaptive immune system and exert multiple functions critical for the control of various diseases. Prevention of graft-versus-host disease (GVHD) by iNKT cells has been demonstrated in mouse models and in correlative human studies in which high iNKT cell content in the donor graft is associated with reduced GVHD in the setting of allogeneic hematopoietic stem cell transplants. This suggests that approaches to increase the number of iNKT cells in the setting of an allogeneic transplant may reduce GVHD. iNKT cells can also induce cytolysis of tumor cells, and murine experiments demonstrate that activating iNKT cells in vivo or treating mice with ex vivo expanded iNKT cells can reduce tumor burden. More recently, research has focused on testing anti-tumor efficacy of iNKT cells genetically modified to express a chimeric antigen receptor (CAR) protein (CAR-iNKT) cells to enhance iNKT cell tumor killing. Further, several of these approaches are now being tested in clinical trials, with strong safety signals demonstrated, though efficacy remains to be established following these early phase clinical trials. Here we review the progress in the field relating to role of iNKT cells in GVHD prevention and anti- cancer efficacy. Although the iNKT field is progressing at an exciting rate, there is much to learn regarding iNKT cell subset immunophenotype and functional relationships, optimal ex vivo expansion approaches, ideal treatment protocols, need for cytokine support, and rejection risk of iNKT cells in the allogeneic setting.

Aseptic meningitis in Fabry disease due to a novel GLA variant: an expanded phenotype?

BACKGROUND

F abry disease (FD) is an X-linked lysosomal storage disorder with accumulation of globotriosylceramide, causing neurologic involvement mainly as acroparesthesias and cerebrovascular disease. Aseptic meningitis has been reported in 11 patients with FD, but no prior study has correlated alpha-galactosidase (GLA) specific variants with meningitis. We present in this manuscript a family in which a novel GLA pathogenic variant was associated with aseptic meningitis in 2 of 5 family members.

METHODS

This study began with identifying the proband, then screening family members for FD symptoms and evaluating symptomatic individuals for genetic and biochemical status. All patients underwent magnetic resonance imaging, and those with headache underwent cerebrospinal fluid (CSF) analysis.

RESULTS

Five patients (3 females) from a single family were included in this study. Mean age at diagnosis was 20.6 years. Two patients (40%) had aseptic meningitis; one of them also had cerebrovascular events. C-reactive protein and erythrocyte sedimentation rate were elevated during aseptic meningitis episodes. Both patients responded to intravenous methylprednisolone with resolution of fever, headache, and vomiting. One of them recurred and needed chronic immunosuppression with azathioprine.

CONCLUSION

We described aseptic meningitis in a family with a novel GLA variant. Meningitis might be a common phenomenon in FD and not a particularity of this variant. Understanding the mechanisms underlying meningitis and its association with cerebrovascular events may lead to a new paradigm of treatment for stroke in these patients. Further prospective studies with CSF collection in patients with FD and recurrent headache could help to elucidate this question.

T-cell responses in asthma exacerbations

OBJECTIVE

Asthma is a chronic lung disease comprising multiple endotypes and characterized by periodic exacerbations. A diverse array of T cells has been found to contribute to all endotypes of asthma in pathogenic and regulatory roles. Here, we review the contributions of CD4+, CD8+, and unconventional T cells in allergic and nonallergic asthma.

DATA SOURCES

Review of published literature pertaining to conventional and unconventional T-cell types in asthma.

STUDY SELECTIONS

Recent peer-reviewed articles pertaining to T cells in asthma, with additional peer-reviewed studies for context.

RESULTS

Much research in asthma has focused on the roles of CD4+ TH cells. Roles for TH2 cells in promoting allergic asthma pathogenesis have been well-described, and the recent description of pathogenic TH2A cells provides additional insight into these responses. Other TH types, notably TH1 and TH17, have been linked to neutrophilic and steroid-resistant asthma phenotypes. Beyond CD4+ T cells, CD8+ Tc2 cells are also strongly associated with allergic asthma. An emerging area for study is unconventional T-cell types, including γδT, invariant natural killer T, and mucosal-associated invariant T cells. Although data in asthma remain limited for these cells, their ability to bridge innate and adaptive responses likely makes them key players in asthma. A number of asthma therapies target T-cell responses, and, although data are limited, they seem to modulate T-cell populations.

CONCLUSION

Given the diversity and heterogeneity of asthma and T-cell responses, there remain many rich avenues for research to better understand the pathogenesis of asthma. Despite the breadth of T cells in asthma, approved therapeutics remain limited to TH2 networks.

Invariant Natural Killer T-cells and their subtypes may play a role in the pathogenesis of endometriosis

OBJECTIVE

To evaluate the frequencies of iNKT cells and their subsets in patients with deep endometriosis.

METHODS

A case-control study was conducted between 2013 and 2015, with 73 patients distributed into two groups: 47 women with a histological diagnosis of endometriosis and 26 controls. Peripheral blood, endometriosis lesions, and healthy peritoneal samples were collected on the day of surgery to determine the frequencies of iNKT cells and subtypes via flow cytometry analysis.

RESULTS

The authors observed a lower number of iNKT (p = 0.01) and Double-Negative (DN) iNKT cells (p = 0.02) in the blood of patients with endometriosis than in the control group. The number of DN iNKT IL-17+ cells in the secretory phase was lower in the endometriosis group (p = 0.049). There was an increase in the secretion of IL-17 by CD4+ iNKT cells in the blood of patients with endometriosis and severe dysmenorrhea (p = 0.038), and severe acyclic pelvic pain (p = 0.048). Patients with severe dysmenorrhea also had a decreased number of CD4+ CCR7+ cells (p = 0.022).

CONCLUSION

The decreased number of total iNKT and DN iNKT cells in patients with endometriosis suggests that iNKT cells play a role in the pathogenesis of endometriosis and can be used to develop new diagnostic and therapeutic agents.

iNKT: A new avenue for CAR-based cancer immunotherapy

Chimeric antigen receptor (CAR) T cell is a T lymphocyte-based immunotherapy, which achieves great successes in treating blood malignancies and provides new hope to cue advanced cancer patients. Invariant natural killer T (iNKT) cells are a kind of special T lymphocytes characterized by expressing invariant TCR of Vα24Vβ11 to recognize CD1d-presented glycolipid antigens, which bridge innate and adaptive immune responses. iNKT cells themselves show strong anti-tumor effect in tumor models via CD1d-mediated killing of CD1d-positive tumor cells and immunosuppressive TAMs and MDSCs, and are closely related to the prognosis of cancer patients. iNKT cells are not restricted to polymorphic human leukocyte antigen (HLA) and can prevent Graft versus Host Disease (GvHD), which makes it to be an ideal CAR vector for allogeneic therapy. Although CAR-iNKT was developed and verified by several different teams and attracts more and more attentions, many obstacles are still needed to be resolved before obtaining CAR-iNKT therapeutics. In this review, we summarized the current status of clinical application of iNKT cells and the latest achievements of CAR-iNKT cells, which provides new insight in CAR-iNKT development and usages.

The evolving role of immune cells in prostate cancer

Prostate cancer is the most commonly diagnosed cancer and the second leading cause of cancer-related death among men in western countries. Androgen deprivation therapy (ADT) is considered the standard therapy for recurrent prostate cancer; however, this therapy may lead to ADT resistance and tumor progression, which seems to be regulated by epithelial-mesenchymal transition (EMT) and/or neuroendocrine differentiation (NED). In addition, recent data suggested the involvement of either adaptive or innate infiltrated immune cells in the initiation, progression, metastasis, and treatment of prostate cancer. In this review, we outlined the characteristics and roles of these immune cells in the initiation, progression, metastasis, and treatments of prostate cancer. We also summarized the current therapeutic strategies in targeting immune cells of the prostate tumor microenvironment.

CD4 and CD8 co-receptors modulate functional avidity of CD1b-restricted T cells

T cells recognize mycobacterial glycolipid (mycolipid) antigens presented by CD1b molecules, but the role of CD4 and CD8 co-receptors in mycolipid recognition is unknown. Here we show CD1b-mycolipid tetramers reveal a hierarchy in which circulating T cells expressing CD4 or CD8 co-receptor stain with a higher tetramer mean fluorescence intensity than CD4-CD8- T cells. CD4+ primary T cells transduced with mycolipid-specific T cell receptors bind CD1b-mycolipid tetramer with a higher fluorescence intensity than CD8+ primary T cells. The presence of either CD4 or CD8 also decreases the threshold for interferon-γ secretion. Co-receptor expression increases surface expression of CD3ε, suggesting a mechanism for increased tetramer binding and activation. Targeted transcriptional profiling of mycolipid-specific T cells from individuals with active tuberculosis reveals canonical markers associated with cytotoxicity among CD8+ compared to CD4+ T cells. Thus, expression of co-receptors modulates T cell receptor avidity for mycobacterial lipids, leading to in vivo functional diversity during tuberculosis disease.

Harnessing invariant natural killer T cells to control pathological inflammation

Invariant natural killer T (iNKT) cells are innate T cells that are recognized for their potent immune modulatory functions. Over the last three decades, research in murine models and human observational studies have revealed that iNKT cells can act to limit inflammatory pathology in a variety of settings. Since iNKT cells are multi-functional and can promote inflammation in some contexts, understanding the mechanistic basis for their anti-inflammatory effects is critical for effectively harnessing them for clinical use. Two contrasting mechanisms have emerged to explain the anti-inflammatory activity of iNKT cells: that they drive suppressive pathways mediated by other regulatory cells, and that they may cytolytically eliminate antigen presenting cells that promote excessive inflammatory responses. How these activities are controlled and separated from their pro-inflammatory functions remains a central question. Murine iNKT cells can be divided into four functional lineages that have either pro-inflammatory (NKT1, NKT17) or anti-inflammatory (NKT2, NKT10) cytokine profiles. However, in humans these subsets are not clearly evident, and instead most iNKT cells that are CD4⁺ appear oriented towards polyfunctional (T_H0) cytokine production, while CD4^- iNKT cells appear more predisposed towards cytolytic activity. Additionally, structurally distinct antigens have been shown to induce T_H1- or T_H2-biased responses by iNKT cells in murine models, but human iNKT cells may respond to differing levels of TCR stimulation in a way that does not neatly separate T_H1 and T_H2 cytokine production. We discuss the implications of these differences for translational efforts focused on the anti-inflammatory activity of iNKT cells.

Peripheral blood iNKT cell activation correlates with liver damage during acute hepatitis C

Invariant NK T (iNKT) cells are implicated in viral clearance; however, their role in hepatitis C virus (HCV) infection remains controversial. Here, iNKT cells were studied during different stages of HCV infection. iNKT cells from patients with acute HCV infection and people who inject drugs (PWID) with chronic or spontaneously resolved HCV infection were characterized by flow cytometry. In a longitudinal analysis during acute HCV infection, frequencies of activated CD38⁺ iNKT cells reproducibly declined in spontaneously resolving patients, whereas they were persistently elevated in patients progressing to chronic infection. During the first year of infection, the frequency of activated CD38⁺ or CD69⁺ iNKT cells strongly correlated with alanine transaminase levels with particularly pronounced correlations in spontaneously resolving patients. Increased frequencies of activated iNKT cells in chronic HCV infection were confirmed in cross-sectional analyses of PWID with chronic or spontaneously resolved HCV infection; however, no apparent functional differences were observed with various stimulation protocols. Our data suggest that iNKT cells are activated during acute hepatitis C and that activation is sustained in chronic infection. The correlation between the frequency of activated iNKT cells and alanine transaminase may point toward a role of iNKT cells in liver damage.

IL-7 During Antigenic Stimulation Using Allogeneic Dendritic Cells Promotes Expansion of CD45RA-CD62L+CD4+ Invariant NKT Cells With Th-2 Biased Cytokine Production Profile

Invariant natural killer T (iNKT) cells are innate-like T lymphocytes cells that recognize glycolipid antigens associated with CD1d, non-classical antigen presenting proteins. They can drive either pro-inflammatory (Th-1) or anti-inflammatory (Th-2) immune microenvironment through the production of both Th-1 and Th-2 type cytokines upon activation, thus play a vital role in cancer, infection, and autoimmune diseases. Adoptive cell therapy using ex vivo expanded iNKT cells is a promising approach to enhance anti-tumor immunity or immunosuppression. However, overcoming phenotypic and functional heterogeneity and promoting in vivo persistency of iNKT cells remains to be a challenge. Here, we compared various methods for ex vivo expansion of human iNKT cells and assessed the quality of expansion, phenotype, and cytokine production profile of expanded iNKT cells. While a direct stimulation of iNKT cells in peripheral blood mononuclear cells with agonist glycolipid led to the expansion of iNKT cells in varying degrees, stimulation of enriched iNKT cells by irradiated autologous peripheral blood mononuclear cells or allogeneic dendritic cells resulted in consistent expansion of highly pure iNKT cells. Interestingly, the mode of antigenic stimulation influenced the dominant subtype of expanded iNKT cells. Further, we evaluated whether additional IL-7 or IL-15 during antigenic stimulation with allogeneic dendritic cells can improve the phenotypic heterogeneity and modify cytokine production profile of iNKT cells expanded from 18 consecutive donors. The presence of IL-7 or IL-15 during antigenic stimulation did not affect the fold of expansion or purity of expanded iNKT cells. However, IL-7, but not IL-15, led to a better expansion of CD4⁺ iNKT cells, enhanced Th-2 type cytokine production of CD4⁺ iNKT cells, and maintained the expansion of central memory (CD45RA^-CD62L⁺) CD4⁺ iNKT cells. Our results suggest the addition of IL-7 during antigenic stimulation with allogeneic dendritic cells can promote the expansion of CD62L⁺Th-2⁺CD4⁺ human iNKT cells that can be used as novel immunotherapeutic to control excessive inflammation to treat various autoimmune diseases.

Expansion and CD2/CD3/CD28 stimulation enhance Th2 cytokine secretion of human invariant NKT cells with retained anti-tumor cytotoxicity

BACKGROUND AIMS

Key obstacles in human iNKT cell translational research and immunotherapy include the lack of robust protocols for dependable expansion of human iNKT cells and the paucity of data on phenotypes in post-expanded cells.

METHODS

We delineate expansion methods using interleukin (IL)-2, IL-7 and allogeneic feeder cells and anti-CD2/CD3/CD28 stimulation by which to dependably augment Th2 polarization and direct cytotoxicity of human peripheral blood CD3⁺Vα24⁺Vβ11⁺ iNKT cells.

RESULTS

Gene and protein expression profiling demonstrated augmented Th2 cytokine secretion (IL-4, IL-5, IL-13) in expanded iNKT cells stimulated with anti-CD2/CD3/CD28 antibodies. Cytotoxic effector molecules including granzyme B were increased in expanded iNKT cells after CD2/CD3/CD28 stimulation. Direct cytotoxicity assays using unstimulated expanded iNKT cell effectors revealed α-galactosyl ceramide (α-GalCer)-dependent killing of the T-ALL cell line Jurkat. Moreover, CD2/CD3/CD28 stimulation of expanded iNKT cells augmented their (α-GalCer-independent) killing of Jurkat cells. Co-culture of expanded iNKT cells with stimulated responder cells confirmed contact-dependent inhibition of activated CD4⁺ and CD8⁺ responder T cells.

DISCUSSION

These data establish a robust protocol to expand and novel pathways to enhance Th2 cytokine secretion and direct cytotoxicity in human iNKT cells, findings with direct implications for autoimmunity, vaccine augmentation and anti-infective immunity, cancer immunotherapy and transplantation.

Selective effects of radiotherapy on viability and function of invariant natural killer T cells in vitro

BACKGROUND AND PURPOSE

Immunotherapies involving the adoptive transfer of ex vivo expanded autologous invariant natural killer (iNKT) cells are a potential option for cancer patients and are under investigation in clinical trials. Most cancer patients receive radiotherapy at some point during their treatment. We investigated the effects of therapeutic doses of radiation on the viability and function of human primary cultures of iNKT cells in vitro.

MATERIALS AND METHODS

iNKT cell lines generated from 6 healthy donors were subjected to therapeutically-relevant doses of radiation. Cell cycle arrest and cell death were assessed by flow cytometry. Double strand DNA breaks were analysed by measuring phosphorylated histone H2AX expression by fluorescence microscopy. Cytolytic degranulation, cytokine production and cytotoxicity by antigen-stimulated iNKT cells were assessed by flow cytometry.

RESULTS

Radiation inhibited viability of iNKT cells in a dose-dependent manner. Radiation caused double strand DNA breaks, which were rapidly repaired, and affected the cell cycle at high doses. Moderate doses of radiation did not inhibit degranulation or cytotoxicity by iNKT cells, but induced perforin expression and inhibited proliferation and interferon-γ production by surviving iNKT cells.

DISCUSSION

Exposure of iNKT cell to radiation can negatively affect their viability and function.

Survey of cellular immune responses to human cytomegalovirus infection in the microenvironment of the uterine-placental interface

Congenital human cytomegalovirus (HCMV) infection is a leading cause of birth defects, yet there are no established treatments for preventing maternal-fetal transmission. During first trimester, HCMV replicates in basal decidua that functions as a reservoir for virus and source of transmission to the attached placenta and fetal hemiallograft but also contains immune cells, including natural killer cells, macrophages, and T cell subsets, that respond to pathogens, protecting the placenta and fetus. However, the specific cellular and cytokine responses to infection are unknown, nor are the immune correlates of protection that guide development of therapeutic strategies. Here we survey immune cell phenotypes in intact explants of basal decidua infected with a clinical pathogenic HCMV strain ex vivo and identify specific changes occurring in response to infection in the tissue environment. Using 4-color immunofluorescence microscopy, we found that at 3 days postinfection, virus replicates in decidual stromal cells and epithelial cells of endometrial glands. Infected cells and effector memory CD8+ T cells (TEM) in contact with them make IFN-γ. CD8+ TEM cells produce granulysin and cluster at sites of infection in decidua and the epithelium of endometrial glands. Quantification indicated expansion of two immune cell subtypes-CD8+ TEM cells and, to a lesser extent, iNKT cells. Approximately 20% of immune cells were found in pairs in both control and infected decidua, suggesting frequent cross-talk in the microenvironment of decidua. Our findings indicate a complex immune microenvironment in basal decidua and suggest CD8+ TEM cells play a role in early responses to decidual infection in seropositive women.

The peripheral differentiation of human natural killer T cells

The peripheral maturation of human CD1d‐restricted natural killer T (NKT) cells has not been well described. In this study, we identified four major subsets of NKT cells in adults, distinguished by the expression of CD4, CD8 and CCR5. Phenotypic analysis suggested a hierarchical pattern of differentiation, whereby immature CD4⁺CD8⁻CCR5⁻ cells progressed to an intermediate CD4⁺CD8⁻CCR5⁺ stage, which remained less differentiated than the CD4⁻CD8⁻ and CD4⁻CD8⁺ subsets, both of which expressed CCR5. This interpretation was supported by functional data, including clonogenic potential and cytokine secretion profiles, as well as T‐cell receptor (TCR) excision circle analysis. Moreover, conventional and high‐throughput sequencing of the corresponding TCR repertoires demonstrated significant clonotypic overlap within individuals, especially between the more differentiated CD4⁻CD8⁻ and CD4⁻CD8⁺ subsets. Collectively, these results mapped a linear differentiation pathway across the post‐thymic landscape of human CD1d‐restricted NKT cells.

Novel thioglycoside analogs of α-galactosylceramide stimulate cytotoxicity and preferential Th1 cytokine production by human invariant natural killer T cells

Invariant natural killer T (iNKT) cells recognize glycolipid antigens bound to CD1d molecules on antigen-presenting cells. Therapeutic activation of iNKT cells with the xenogeneic glycolipid α-galactosylceramide (α-GalCer) can prevent and reverse tumor growth in murine models, but clinical trials using α-GalCer-stimulated human iNKT cells have shown limited efficacy. We synthesized a series of thioglycoside analogs of α-GalCer with different substituents to the galactose residue and found that two of these compounds, XZ7 and XZ11, bound to CD1d-transfected HeLa cells and activated lines of expanded human iNKT cells. Both compounds stimulated cytolytic degranulation by iNKT cells and while XZ7 preferentially stimulated the production of the antitumor cytokine interferon-γ (IFN-γ), XZ11 preferentially stimulated interleukin-4 (IL-4) production. This biased T helper type 1 effector profile of XZ7 was also evident when iNKT were stimulated with dendritic cells presenting this glycolipid. Separate analysis of the responses of CD4+, CD8α+ and CD4-CD8- iNKT cells indicated that XZ7 preferentially activated CD8α+ iNKT cells, and to a lesser degree, CD4-CD8- iNKT cells. The partial agonist effect of glycolipid XZ7, inducing cytotoxicity and IFN-γ production but not IL-4 production, indicates that specific protumour activities of iNKT cells can be abolished, while preserving their antitumor activities, by introducing structural modifications to α-GalCer. Since XZ7 was much less potent than α-GalCer as an iNKT cell agonist, it is unlikely to be superior to α-GalCer as a therapeutic agent for cancer, but may serve as a parent compound for developing more potent structural analogs.

The CD4-CD8- MAIT cell subpopulation is a functionally distinct subset developmentally related to the main CD8+ MAIT cell pool

Mucosa-associated invariant T (MAIT) cells are unconventional innate-like T cells recognizing microbial riboflavin metabolites presented by the monomorphic MR1 molecule. Here, we show that the CD8⁺CD4⁻ and CD8⁻CD4⁻ subpopulations of human MAIT cells represent transcriptionally and phenotypically discrete subsets with distinct functional profiles. Furthermore, T cell receptor repertoire analysis, as well as MAIT cell data based on human fetal tissues, umbilical cord blood, and culture systems indicate that the CD8⁻CD4⁻ subset may derive from the main CD8⁺CD4⁻ MAIT cell pool. Thus, MAIT cells, a major antimicrobial effector T cell population in humans, segregate into two functionally distinct but developmentally related subsets separated by the expression of CD8. This functional difference may have significant implications in infectious and inflammatory diseases.

Mucosa-associated invariant T (MAIT) cells are unconventional innate-like T cells that recognize microbial riboflavin metabolites presented by the MHC class I-like protein MR1. Human MAIT cells predominantly express the CD8α coreceptor (CD8⁺), with a smaller subset lacking both CD4 and CD8 (double-negative, DN). However, it is unclear if these two MAIT cell subpopulations distinguished by CD8α represent functionally distinct subsets. Here, we show that the two MAIT cell subsets express divergent transcriptional programs and distinct patterns of classic T cell transcription factors. Furthermore, CD8⁺ MAIT cells have higher levels of receptors for IL-12 and IL-18, as well as of the activating receptors CD2, CD9, and NKG2D, and display superior functionality following stimulation with riboflavin-autotrophic as well as riboflavin-auxotrophic bacterial strains. DN MAIT cells display higher RORγt/T-bet ratio, and express less IFN-γ and more IL-17. Furthermore, the DN subset displays enrichment of an apoptosis gene signature and higher propensity for activation-induced apoptosis. During development in human fetal tissues, DN MAIT cells are more mature and accumulate over gestational time with reciprocal contraction of the CD8⁺ subset. Analysis of the T cell receptor repertoire reveals higher diversity in CD8⁺ MAIT cells than in DN MAIT cells. Finally, chronic T cell receptor stimulation of CD8⁺ MAIT cells in an in vitro culture system supports the accumulation and maintenance of the DN subpopulation. These findings define human CD8⁺ and DN MAIT cells as functionally distinct subsets and indicate a derivative developmental relationship.

Rapid ex vivo expansion of highly enriched human invariant natural killer T cells via single antigenic stimulation for cell therapy to prevent graft-versus-host disease

BACKGROUND AIMS

CD1d-restricted invariant natural killer (iNK) T cells are rare regulatory T cells that may contribute to the immune-regulation in allogeneic stem cell transplantation (ASCT). Here, we sought to develop an effective strategy to expand human iNK T cells for use in cell therapy to prevent graft-versus-host disease (GVHD) in ASCT.

METHODS

Human iNK T cells were first enriched from peripheral blood mononuclear cells (PBMCs) using magnetic-activated cell sorting separation, then co-cultured with dendritic cells in the presence of agonist glycolipids, alpha-galactosylceramide, for 2 weeks.

RESULTS

The single antigenic stimulation reliably expanded iNK T cells to an average of 2.8 × 10⁷ per 5 × 10⁸ PBMCs in an average purity of 98.8% in 2 weeks (N = 24). The expanded iNK T cells contained a significantly higher level of CD4⁺ and central memory phenotype (CD45RA^-CD62L⁺) compared with freshly isolated iNK T cells, and maintained their ability to produce both Th-1 (interferon [IFN]γ and tumor necrosis factor [TNF]α) and Th-2 type cytokines (interleukin [IL]-4, IL-5 and IL-13) upon antigenic stimulation or stimulation with Phorbol 12-myristate 13-acetate/ionomycin. Interestingly, expanded iNK T cells were highly autoreactive and produced a Th-2 polarized cytokine production profile after being co-cultured with dendritic cells alone without exogenous agonist glycolipid antigen. Lastly, expanded iNK T cells suppressed conventional T-cell proliferation and ameliorated xenograft GVHD (hazard ratio, 0.1266; P < 0.0001).

CONCLUSION

We have demonstrated a feasible approach for obtaining ex vivo expanded, highly enriched human iNK T cells for use in adoptive cell therapy to prevent GVHD in ASCT.

Insights Into Mucosal-Associated Invariant T Cell Biology From Studies of Invariant Natural Killer T Cells

Mucosal-associated invariant T (MAIT) cells and invariant natural killer T (iNKT) cells are innate-like T cells that function at the interface between innate and adaptive immunity. They express semi-invariant T cell receptors (TCRs) and recognize unconventional non-peptide ligands bound to the MHC Class I-like molecules MR1 and CD1d, respectively. MAIT cells and iNKT cells exhibit an effector-memory phenotype and are enriched within the liver and at mucosal sites. In humans, MAIT cell frequencies dwarf those of iNKT cells, while in laboratory mouse strains the opposite is true. Upon activation via TCR- or cytokine-dependent pathways, MAIT cells and iNKT cells rapidly produce cytokines and show direct cytotoxic activity. Consequently, they are essential for effective immunity, and alterations in their frequency and function are associated with numerous infectious, inflammatory, and malignant diseases. Due to their abundance in mice and the earlier development of reagents, iNKT cells have been more extensively studied than MAIT cells. This has led to the routine use of iNKT cells as a reference population for the study of MAIT cells, and such an approach has proven very fruitful. However, MAIT cells and iNKT cells show important phenotypic, functional, and developmental differences that are often overlooked. With the recent availability of new tools, most importantly MR1 tetramers, it is now possible to directly study MAIT cells to understand their biology. Therefore, it is timely to compare the phenotype, development, and function of MAIT cells and iNKT cells. In this review, we highlight key areas where MAIT cells show similarity or difference to iNKT cells. In addition, we discuss important avenues for future research within the MAIT cell field, especially where comparison to iNKT cells has proven less informative.

The Role of Invariant NKT in Autoimmune Liver Disease: Can Vitamin D Act as an Immunomodulator?

Natural killer T (NKT) cells are a distinct lineage of T cells which express both the T cell receptor (TCR) and natural killer (NK) cell markers. Invariant NKT (iNKT) cells bear an invariant TCR and recognize a small variety of glycolipid antigens presented by CD1d (nonclassical MHC-I). CD1d-restricted iNKT cells are regulators of immune responses and produce cytokines that may be proinflammatory (such as interferon-gamma (IFN-γ)) or anti-inflammatory (such as IL-4). iNKT cells also appear to play a role in B cell regulation and antibody production. Alpha-galactosylceramide (α-GalCer), a derivative of the marine sponge, is a potent stimulator of iNKT cells and has been proposed as a therapeutic iNKT cell activator. Invariant NKT cells have been implicated in the development and perpetuation of several autoimmune diseases such as multiple sclerosis and systemic lupus erythematosus (SLE). Animal models of SLE have shown abnormalities in iNKT cells numbers and function, and an inverse correlation between the frequency of NKT cells and IgG levels has also been observed. The role of iNKT cells in autoimmune liver disease (AiLD) has not been extensively studied. This review discusses the current data with regard to iNKT cells function in AiLD, in addition to providing an overview of iNKT cells function in other autoimmune conditions and animal models. We also discuss data regarding the immunomodulatory effects of vitamin D on iNKT cells, which may serve as a potential therapeutic target, given that deficiencies in vitamin D have been reported in various autoimmune disorders.

Activation and Regulation of B Cell Responses by Invariant Natural Killer T Cells

CD1d-restricted invariant natural killer T (iNKT) cells play central roles in the activation and regulation of innate and adaptive immunity. Cytokine-mediated and CD1d-dependent interactions between iNKT cells and myeloid and lymphoid cells enable iNKT cells to contribute to the activation of multiple cell types, with important impacts on host immunity to infection and tumors and on the prevention of autoimmunity. Here, we review the mechanisms by which iNKT cells contribute to B cell maturation, antibody and cytokine production, and antigen presentation. Cognate interactions with B cells contribute to the rapid production of antibodies directed against conserved non-protein antigens resulting in rapid but short-lived innate humoral immunity. iNKT cells can also provide non-cognate help for the generation of antibodies directed against protein antigens, by promoting the activation of follicular helper T cells, resulting in long-lasting adaptive humoral immunity and B cell memory. iNKT cells can also regulate humoral immunity by promoting the development of autoreactive B cells into regulatory B cells. Depletions and functional impairments of iNKT cells are found in patients with infectious, autoimmune and malignant diseases associated with altered B cell function and in murine models of these conditions. The adjuvant and regulatory activities that iNKT cells have for B cells makes them attractive therapeutic targets for these diseases.

Epigenetic induction of CD1d expression primes lung cancer cells for killing by invariant natural killer T cells

Immunotherapies that target CD1d-restricted invariant NKT (iNKT) cells can prevent tumor growth in murine models but trials in humans have shown limited clinical efficacy. Here, we show that iNKT cells are depleted from blood and bronchial lavage samples from patients with non-small cell lung cancer (NSCLC) suggesting a role for these cells in immunity against NSCLC. We interrogated the Lung Cancer Explorer and Kaplan-Meier Plotter databases of NSCLC patients and found that pulmonary CD1d expression is reduced in patients with NSCLC and that low expression of CD1d mRNA is significantly associated with poor patient survival. We hypothesized that CD1d expression in NSCLC is epigenetically regulated and can be modulated using epigenetic targeting therapies. Treatment of the CD1d-negative NSCLC cell lines, A549 and SK-MES-1, with DNA methyltransferase inhibitors and histone deacetylase inhibitors resulted in a dose-dependent induction of CD1d mRNA and protein expression. Chromatin immunoprecipitation analysis indicated that this induction of CD1d expression directly involved chromatin remodelling. Induction of CD1d expression by A549 and SK-MES-1 cells using therapeutic low doses of DNA methyltransferase inhibitors and histone deacetylase inhibitors made them targets for iNKT cell-mediated cytolytic degranulation. Thus, epigenetic manipulation of CD1d expression may augment the efficacy of iNKT cell-based immunotherapies for NSCLC.

Skewed Invariant Natural Killer T (iNKT) Cells, Impaired iNKT:B Cell Help and Decreased SAP Expression in Blood Lymphocytes from Patients with Common Variable Immunodeficiency

Common variable immunodeficiency (CVID) is a syndrome with predominantly defective B cell function. However, abnormalities in the number and function of other lymphocyte subpopulations in peripheral blood (PB) have been described in most patients. We have analysed the distribution of iNKT cell subpopulations in the PB of CVID patients and the ability of these cells to provide in vitro cognate B cell help. The total of iNKT cells was reduced in the PB of CVID patients, especially CD4+, CD4-/CD8- and CCR5+/CXCR3+. These findings were associated with an enrichment of memory-like and a tendency towards a reduction in TNF-α-expressing effector iNKT cells in the peripheral blood mononuclear cells (PBMC) of CVID patients. Moreover, an accumulation of follicular helper iNKT cells in the PB of CVID patients was demonstrated. CVID αGalCer-pulsed iNKT cells are not able to induce autologous B cell proliferation although they do induce proliferation to healthy donor B cells. Interestingly, autologous and heterologous co-cultures did not differ in the amount of immunoglobulin secreted by B cells in vitro. Finally, reduced intracellular SAP expression in iNKT cells and other lymphocytes in the blood from CVID patients was observed. These results provide further insights into the immunological mechanisms underlying the iNKT cell defects and the potential targets to improve B cell help in CVID.

Innate immune cells for immunotherapy of autoimmune and cancer disorders

Modulation of the immune system has been widely targeted for the treatment of several immune-related diseases, such as autoimmune disorders and cancer, due to its crucial role in these pathologies. Current available therapies focus mainly on symptomatic treatment and are often associated with undesirable secondary effects. For several years, remission of disease and subsequently recovery of immune homeostasis has been a major goal for immunotherapy. Most current immunotherapeutic strategies are aimed to inhibit or potentiate directly the adaptive immune response by modulating antibody production and B cell memory, as well as the effector potential and memory of T cells. Although these immunomodulatory approaches have shown some success in the clinic with promising therapeutic potential, they have some limitations related to their effectiveness in disease models and clinical trials, as well as elevated costs. In the recent years, a renewed interest has emerged on targeting innate immune cells for immunotherapy, due to their high plasticity and ability to exert a potent and extremely rapid response, which can influence the outcome of the adaptive immune response. In this review, we discuss the immunomodulatory potential of several innate immune cells, as well as they use for immunotherapy, especially in autoimmunity and cancer.

Retinoic acid induction of CD1d expression primes chronic lymphocytic leukemia B cells for killing by CD8+ invariant natural killer T cells

Invariant natural killer T (iNKT) cells are cytotoxic T cells that respond to glycolipid antigens presented by CD1d. Therapeutic activation of iNKT cells with α-galactosylceramide (α-GalCer) can prevent and reverse tumor growth in mice and clinical trials involving α-GalCer-stimulated iNKT cells are ongoing in humans. B cells express CD1d, however, we show that CD1d expression is reduced on B cells from patients with chronic lymphocytic leukemia (CLL). B cells from CLL patients pulsed with α-GalCer failed to stimulate cytolytic degranulation by iNKT cell lines, but could present the more potent glycolipid analogue, 7DW8-5. Retinoic acid receptor-α (RAR-α) agonists induced CD1d expression by CLL B cells, restoring their ability to present α-GalCer to CD8α⁺ iNKT cells, resulting in cytolytic degranulation. Thus, RAR-α agonists can augment the anti-tumor activities of iNKT cells against CLL cells in vitro. Their inclusion in iNKT cell-based therapies may benefit patients with CLL.

Invariant Natural Killer T Cells As Suppressors of Graft-versus-Host Disease in Allogeneic Hematopoietic Stem Cell Transplantation

Invariant natural killer T (iNKT) cells serve as a bridge between innate and adaptive immunity and have been shown to play an important role in immune regulation, defense against pathogens, and cancer immunity. Recent data also suggest that this compartment of the immune system plays a significant role in reducing graft-versus-host disease (GVHD) in the setting of allogeneic hematopoietic stem cell transplantation. Murine studies have shown that boosting iNKT numbers through certain conditioning regimens or adoptive transfer leads to suppression of acute or chronic GVHD. Preclinical work reveals that iNKT cells exert their suppressive function by expanding regulatory T cells in vivo, though the exact mechanism by which this occurs has yet to be fully elucidated. Human studies have demonstrated that a higher number of iNKT cells in the graft or in the peripheral blood of the recipient post-transplantation are associated with a reduction in GVHD risk, importantly without a loss of graft-versus-tumor effect. In two separate analyses of many immune cell subsets in allogeneic grafts, iNKT cell dose was the only parameter associated with a significant improvement in GVHD or in GVHD-free progression-free survival. Failure to reconstitute iNKT cells following allogeneic transplantation has also been associated with an increased risk of relapse. These data demonstrate that iNKT cells hold promise for future clinical application in the prevention of GVHD in allogeneic stem cell transplantation and warrant further study of the immunoregulatory functions of iNKT cells in this setting.

Differential intratumoral distributions of CD8 and CD163 immune cells as prognostic biomarkers in breast cancer

Background

Tumor immune cell infiltrates are essential in hindering cancer progression and may complement the TNM classification. CD8+ and CD163+ cells have prognostic impact in breast cancer but their spatial heterogeneity has not been extensively explored in this type of cancer. Here, their potential as prognostic biomarkers was evaluated, depending on their combined densities in the tumor center (TC) and the tumor invasive margin (IM).

Methods

CD8+ and CD163+ cells were quantified by immunohistochemistry of formalin-fixed, paraffin-embedded (FFPE) tumor tissue samples from a cohort totaling 162 patients with histologically-confirmed primary invasive non-metastatic ductal breast cancer diagnosed between 2000 and 2015. Clinical follow-up (median 6.9 years) was available for 97 of these patients.

Results

Differential densities of CD8+ and CD163+ cells in the combined TC and IM compartments (i.e., high(H)/low(L), respectively for CD8+ cells and the reverse L/H combination for CD163+ cells) were found to have significant prognostic value for survival, and allowed better patient stratification than TNM stage, tumor size, lymph node invasion and histological grade. The combined evaluation of CD8+ and CD163+ cell densities jointly in TC and IM further improves prediction of clinical outcomes based on disease-free and overall survival. Patients having the favorable immune signatures had favorable clinical outcomes despite poor clinicopathological parameters.

Conclusions

Given the important roles of CD8+ and CD163+ cells in regulating opposing immune circuits, adding an assessment of their differential densities to the prognostic biomarker armamentarium in breast cancer would be valuable. Larger validation studies are necessary to confirm these findings.

Trial registrations

Study code: IRB-ID 6079/448/10-6-13

Date of approval: 10/06/2013

Retrospective study (2000–2010)

First patient prospectively enrolled 14/2/2014

Electronic supplementary material

The online version of this article (doi:10.1186/s40425-017-0240-7) contains supplementary material, which is available to authorized users.

Invariant NKT Cell Activation Is Potentiated by Homotypic trans-Ly108 Interactions

Invariant NKT (iNKT) cells are innate lymphocytes that respond to glycolipids presented by the MHC class Ib molecule CD1d and are rapidly activated to produce large quantities of cytokines and chemokines. iNKT cell development uniquely depends on interactions between double-positive thymocytes that provide key homotypic interactions between signaling lymphocyte activation molecule (SLAM) family members. However, the role of SLAM receptors in the differentiation of iNKT cell effector subsets and activation has not been explored. In this article, we show that C57BL/6 mice containing the New Zealand Black Slam locus have profound alterations in Ly108, CD150, and Ly9 expression that is associated with iNKT cell hyporesponsiveness. This loss of function was only apparent when dendritic cells and iNKT cells had a loss of SLAM receptor expression. Using small interfering RNA knockdowns and peptide-blocking strategies, we demonstrated that trans-Ly108 interactions between dendritic cells and iNKT cells are critical for robust activation. LY108 costimulation similarly increased human iNKT cell activation. Thus, in addition to its established role in iNKT cell ontogeny, Ly108 regulates iNKT cell function in mice and humans.

From Lysosomal Storage Diseases to NKT Cell Activation and Back

Lysosomal storage diseases (LSDs) are inherited metabolic disorders characterized by the accumulation of different types of substrates in the lysosome. With a multisystemic involvement, LSDs often present a very broad clinical spectrum. In many LSDs, alterations of the immune system were described. Special emphasis was given to Natural Killer T (NKT) cells, a population of lipid-specific T cells that is activated by lipid antigens bound to CD1d (cluster of differentiation 1 d) molecules at the surface of antigen-presenting cells. These cells have important functions in cancer, infection, and autoimmunity and were altered in a variety of LSDs’ mouse models. In some cases, the observed decrease was attributed to defects in either lipid antigen availability, trafficking, processing, or loading in CD1d. Here, we review the current knowledge about NKT cells in the context of LSDs, including the alterations detected, the proposed mechanisms to explain these defects, and the relevance of these findings for disease pathology. Furthermore, the effect of enzyme replacement therapy on NKT cells is also discussed.

Invariant natural killer T cells and mucosal-associated invariant T cells in multiple sclerosis

Multiple sclerosis (MS) is a chronic progressive inflammatory demyelinating disorder of the central nervous system, and in several countries is a leading cause of permanent neurological disability in young adults, particularly women. MS is considered an autoimmune disease, caused by an aberrant immune response to environmental triggers in genetically susceptible subjects. However, the contribution of the innate or of the adaptive immune system to the development and progression of the disease has not yet been fully elucidated. Innate-like T lymphocytes are unconventional T cells that bridge the innate and adaptive arms of the immune system, because they use a T cell receptor to sense external ligands, but behave like innate cells when they rapidly respond to stimuli. These cells could play an important role in the pathogenesis of MS. Here, we focus on invariant natural killer T (iNKT) cells and mucosal-associated invariant T (MAIT) cells, and we review the current knowledge on their biology and possible involvement in MS. Although several studies have evaluated the frequency and functions of iNKT and MAIT cells both in MS patients and in experimental mouse models, contradictory observations have been reported, and it is not clear whether they exert a protective or a pro-inflammatory and harmful role. A better understanding of how immune cells are involved in MS, and of their interactions could be of great interest for the development of new therapeutic strategies.

CD1-Restricted T Cells at the Crossroad of Innate and Adaptive Immunity

Lipid-specific T cells comprise a group of T cells that recognize lipids bound to the MHC class I-like CD1 molecules. There are four isoforms of CD1 that are expressed at the surface of antigen presenting cells and therefore capable of presenting lipid antigens: CD1a, CD1b, CD1c, and CD1d. Each one of these isoforms has distinct structural features and cellular localizations, which promotes binding to a broad range of different types of lipids. Lipid antigens originate from either self-tissues or foreign sources, such as bacteria, fungus, or plants and their recognition by CD1-restricted T cells has important implications in infection but also in cancer and autoimmunity. In this review, we describe the characteristics of CD1 molecules and CD1-restricted lipid-specific T cells, highlighting the innate-like and adaptive-like features of different CD1-restricted T cell subtypes.

Cross-talk between iNKT cells and monocytes triggers an atheroprotective immune response in SLE patients with asymptomatic plaque

Accelerated atherosclerosis is a complication of the autoimmune rheumatic disease systemic lupus erythematosus (SLE). We questioned the role played by invariant natural killer T (iNKT) cells in this process because they not only are defective in autoimmunity but also promote atherosclerosis in response to CD1d-mediated lipid antigen presentation. iNKT cells from SLE patients with asymptomatic plaque (SLE-P) had increased proliferation and interleukin-4 production compared with those from SLE patients with no plaque. The anti-inflammatory iNKT cell phenotype was associated with dyslipidemia and was driven by altered monocyte phospholipid expression and CD1d-mediated cross-talk between iNKT cells and monocytes but not B cells. Healthy iNKT cells differentiated in the presence of healthy monocytes and SLE-P serum polarized macrophages toward an anti-inflammatory M2 phenotype. Conversely, patients with clinical cardiovascular disease had unresponsive iNKT cells and increased proinflammatory monocytes. iNKT cell function could link immune responses, lipids, and cardiovascular disease in SLE patients and, together with serum lipid taxonomy, help predict preclinical atherosclerosis in SLE patients.

iNKT Cells in Secondary Progressive Multiple Sclerosis Patients Display Pro-inflammatory Profiles

BACKGROUND

Multiple sclerosis (MS), an autoimmune disease with neurodegeneration and inflammation is characterized by several alterations of different T cell subsets. However, few data exist on the role of iNKT lymphocytes.

OBJECTIVE

To identify possible changes in the phenotype of iNKT cells in patients with different clinical forms of MS and find alterations in their polyfunctionality [i.e., ability to produce simultaneously up to four cytokines such as IL-17, tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and IL-4].

METHODS

We studied a total of 165 patients, 91 with a relapsing-remitting form [RR; 31 were treated with interferon (IFN)1a-β, 25 with natalizumab (NAT), 29 with glatiramer acetate; 17 were newly diagnosed RR without treatment, 19 not-active RR without treatment]. Forty-four patients had a progressive MS: 20 primary progressive (PP) and 24 secondary progressive (SP). A total of 55 age- and sex-matched subjects represented healthy controls (CTR). Among fresh peripheral blood mononuclear cells, iNKT cells were identified by flow cytometry. Moreover, the capability of iNKT cells to produce different cytokines (IL-17, TNF-α, IFN-γ, and IL-4) after in vitro stimulation were evaluated in 18 RR (11 treated with NAT and 7 with IFN), 4 PP, 6 SP, and 16 CTR.

RESULTS

No main differences were found in iNKT cell phenotype among MS patients with different MS forms or during different treatments. However, the polyfunctional response of iNKT cells showed Th1 and Th17 profiles. This was well evident in patients with SP form, who are characterized by high levels of inflammation and neurodegeneration, and exhibited a sustained increase in the production of Th17 cytokines. Patients treated with NAT displayed lower levels of iNKT cells producing IL-17, TNF-α, and IFN-γ.

CONCLUSION

Our data suggest that the progressive phase of the disease is characterized by permanent iNKT activation and a skewing towards an inflammatory phenotype. Compared to other treatments, NAT was able to modulate iNKT cell function.

iNKT and memory B-cell alterations in HHV-8 multicentric Castleman disease

Human herpesvirus 8 (HHV-8) is the causative agent of Kaposi sarcoma (KS) and multicentric Castleman disease (MCD), a life-threatening, virally induced B-cell lymphoproliferative disorder. HHV-8 is a B-lymphotropic γ-herpesvirus closely related to the Epstein-Barr virus (EBV). Invariant natural killer T (iNKT) cells are innate-like T cells that play a role in antiviral immunity, specifically in controlling viral replication in EBV-infected B cells. Decline of iNKT cells is associated with age or HIV infection, both situations associated with HHV-8-related diseases. We analyzed iNKT cells in both blood (n = 26) and spleen (n = 9) samples from 32 patients with HHV-8 MCD and compared them with patients with KS (n = 24) and healthy donors (n = 29). We determined that both circulating and splenic iNKT cell frequencies were markedly decreased in patients with HHV-8 MCD and were undetectable in 6 of them. Moreover, iNKT cells from patients with HHV-8 MCD displayed a proliferative defect after stimulation with α-galactosylceramide. These iNKT cell alterations were associated with an imbalance in B-cell subsets, including a significant decrease in memory B cells, particularly of marginal zone (MZ) B cells. Coculture experiments revealed that the decrease in iNKT cells contributed to the alterations in the B-cell subset distribution. These observations contribute to a better understanding of the complex interactions between HHV-8 and immune cells that cause HHV-8-related MCD.

Cytotoxic cell involvement in human cutaneous leishmaniasis: assessments in active disease, under therapy and after clinical cure

Cutaneous leishmaniasis (CL) is an important public health issue worldwide. The control of Leishmania infection depends on cellular immune mechanisms, and the inflammatory response may contribute to pathogenesis. A beneficial role of CD8(+) T lymphocytes has been proposed; nevertheless, other studies suggest a cytotoxic role of CD8(+) T lymphocytes involved in tissue damage, showing controversial role of these cells. The goal of the current study was to understand the immunopathology of CL and determine the profile of cytotoxic cells--such as CD4(+) T, natural killer and natural killer T cells--that might be involved in triggering immunological mechanisms, and may lead to cure or disease progression. The frequencies of cytotoxic cell populations in peripheral blood, obtained from patients with active disease, during treatment and after clinical healing, were assessed by flow cytometry. Cytotoxicity could not be related to a deleterious role in Leishmania braziliensis infection, as patients with active CL showed similar percentages of degranulation to healthy individuals (HI). Cured patients exhibited a lower percentage of degranulating cells, which may be due to a downregulation of the immune response. The understanding of the immunopathological mechanisms involved in CL and the commitment of cytotoxic cells enables improvements in therapeutic strategies.

Expansion of highly activated invariant natural killer T cells with altered phenotype in acute dengue infection

Invariant natural killer T (iNKT) cells are capable of rapid activation and production of cytokines upon recognition of antigenic lipids presented by CD1d molecules. They have been shown to play a significant role in many viral infections and were observed to be highly activated in patients with acute dengue infection. In order to characterize further their role in dengue infection, we investigated the proportion of iNKT cells and their phenotype in adult patients with acute dengue infection. The functionality of iNKT cells in patients was investigated by both interferon (IFN)-γ and interleukin (IL)-4 ex-vivo enzyme-linked immunospot (ELISPOT) assays following stimulation with alpha-galactosyl-ceramide (αGalCer). We found that circulating iNKT cell proportions were significantly higher (P = 0·03) in patients with acute dengue when compared to healthy individuals and were predominantly of the CD4(+) subset. iNKT cells of patients with acute dengue had reduced proportions expressing CD8α and CD161 when compared to healthy individuals. The iNKT cells of patients were highly activated and iNKT activation correlated significantly with dengue virus-specific immunoglobulin (Ig)G antibody levels. iNKT cells expressing Bcl-6 (P = 0·0003) and both Bcl-6 and inducible T cell co-stimulator (ICOS) (P = 0·006) were increased significantly in patients when compared to healthy individuals. Therefore, our data suggest that in acute dengue infection there is an expansion of highly activated CD4(+) iNKT cells, with reduced expression of CD161 markers.

Human Natural Killer cell expression of ULBP2 is associated with a mature functional phenotype

NKG2D is an important activating receptor expressed on NK cells. Ligands (termed NKG2DL) for this receptor include ULBP1-6, MICA and MICB in humans; they are upregulated in stressed, cancerous or infected cells where they engage NKG2D to induce NK cell cytotoxicity and cytokine production. Expression of NKG2DL on effector cells has been described in mice and more recently in human cells. We confirm that NK cell lines and IL-2 stimulated primary human NK cells also express the NKG2DL, ULBP2. However, expression of ULBP2 was not a result of transfer from a non-NK cell to an NK cell and in contrast to recent reports we saw no evidence that ULBP2 expression targeted these NK cells for fratricide or for cytotoxicity by NKG2D-expressing, non-NK effector cells. ULBP2 expression was however linked to expression of mature CD57(+) NK cells. In particular, expression of ULBP2 was strongest on those NK cells that had evidence of recent activation and proliferation. We suggest that ULBP2 could be used to identify recently activated "mature" NK cells. Defining this phenotype would be useful for understanding the ontogeny on human NK cells.

The cytokine profile of human NKT cells and PBMCs is dependent on donor sex and stimulus

Sex-related variations in natural killer T (NKT) cells may influence immunoregulation and outcome of infectious and autoimmune diseases. We analyzed sex-specific differences in peripheral blood NKTs and peripheral blood mononuclear cells (PBMCs) from men and women and determined the frequencies of NKT cells and their subpopulations [CD4(+); CD8(+); double negative (DN)] and the levels of cytokine production following stimulation with the NKT cell ligands α-Galactosylceramide (αGalCer) and Entamoeba histolytica lipopeptidephosphoglycan (Lotter et al. in PLoS Pathog 5(5):e1000434, 2009). Total and DN NKT cells were more abundant in women than in men. In women, αGalCer induced higher production of intracellular IFNγ, IL-4, IL-17 and TNF by CD4(+) and DN(+)NKT cells. Both ligands induced expression of multiple cytokines in PBMCs and influenced the ratio of NKT cell subpopulations during long-term culture. Although the sex-specific differences in frequencies of NKT cells and their subpopulations were marginal, the significant sex-specific differences in cytokine production might influence disease outcomes.

Human Invariant Natural Killer T cells possess immune-modulating functions during Aspergillus infection

Aspergillus fumigatus is the most common cause for invasive fungal infections, a disease associated with high mortality in immune-compromised patients. CD1d-restricted invariant natural killer T (iNKT) cells compose a small subset of T cells known to impact the immune response toward various infectious pathogens. To investigate the role of human iNKT cells during A. fumigatus infection, we studied their activation as determined by CD69 expression and cytokine production in response to distinct fungal morphotypes in the presence of different CD1d(+) antigen presenting cells using flow cytometry and multiplex enzyme-linked immunosorbent assay (ELISA). Among CD1d(+) subpopulations, CD1d(+)CD1c(+) mDCs showed the highest potential to activate iNKT cells on a per cell basis. The presence of A. fumigatus decreased this effect of CD1d(+)CD1c(+) mDCs on iNKT cells and led to reduced secretion of TNF-α, G-CSF and RANTES. Production of other Th1 and Th2 cytokines was not affected by the fungus, suggesting an immune-modulating function for human iNKT cells during A. fumigatus infection.

Immunity, tolerance and autoimmunity in the liver: A comprehensive review

The hepatic immune system is constantly exposed to a massive load of harmless dietary and commensal antigens, to which it must remain tolerant. Immune tolerance in the liver is mediated by a number of specialized antigen-presenting cells, including dendritic cells, Kupffer cells, liver sinusoidal endothelial cells and hepatic stellate cells. These cells are capable of presenting antigens to T cells leading to T cell apoptosis, anergy, or differentiation into regulatory T cells. However, the hepatic immune system must also be able to respond to pathogens and tumours and therefore must be equipped with mechanisms to override immune tolerance. The liver is a site of accumulation of a number of innate lymphocyte populations, including natural killer cells, CD56(+) T cells, natural killer T cells, γδ T cells, and mucosal-associated invariant T cells. Innate lymphocytes recognize conserved metabolites derived from microorganisms and host cells and respond by killing target cells or promoting the differentiation and/or activation of other cells of the immune system. Innate lymphocytes can promote the maturation of antigen-presenting cells from their precursors and thereby contribute to the generation of immunogenic T cell responses. These cells may be responsible for overriding hepatic immune tolerance to autoantigens, resulting in the induction and maintenance of autoreactive T cells that mediate liver injury causing autoimmune liver disease. Some innate lymphocyte populations can also directly mediate liver injury by killing hepatocytes or bile duct cells in murine models of hepatitis, whilst other populations may protect against liver disease. It is likely that innate lymphocyte populations can promote or protect against autoimmune liver disease in humans and that these cells can be targeted therapeutically. Here I review the cellular mechanisms by which hepatic antigen-presenting cells and innate lymphocytes control the balance between immunity, tolerance and autoimmunity in the liver.

Adipose-Derived Mesenchymal Stem Cell Exosomes Suppress Hepatocellular Carcinoma Growth in a Rat Model: Apparent Diffusion Coefficient, Natural Killer T-Cell Responses, and Histopathological Features

We sought to evaluate the effects of adipose-derived mesenchymal stem cells (ADMSCs) exosomes on hepatocellular carcinoma (HCC) in rats using apparent diffusion coefficient (ADC), natural killer T-cell (NKT-cell) responses, and histopathological features. ADMSC-derived exosomes appeared as nanoparticles (30–90 nm) on electron microscopy and were positive for CD63, tumor susceptibility gene-101, and β-catenin on western blotting. The control (n = 8) and exosome-treated (n = 8) rats with N1S1-induced HCC underwent baseline and posttreatment day 10 and day 20 magnetic resonance imaging and measurement of ADC. Magnetic resonance imaging showed rapidly enlarged HCCs with low ADCs in the controls. The exosome-treated rats showed partial but nonsignificant tumor reduction, and significant ADC and ADC ratio increases on day 10. On day 20, the exosome-treated rats harbored significantly smaller tumors and volume ratios, higher ADC and ADC ratios, more circulating and intratumoral NKT-cells, and low-grade HCC (P < 0.05 for all comparisons) compared to the controls. The ADC and volume ratios exhibited significant inverse correlations (P < 0.001, R² = 0.679). ADMSC-derived exosomes promoted NKT-cell antitumor responses in rats, thereby facilitating HCC suppression, early ADC increase, and low-grade tumor differentiation. ADC may be an early biomarker of treatment response.

Characterization of the immune cell repertoire in the normal fallopian tube

Recent studies implicating the fallopian tube as the site of putative precursors of ovarian serous carcinoma, and the hypothesis that injury, inflammation, and repair of the ovarian surface epithelium at the time of ovulation, may be contributing factors to ovarian carcinogenesis, prompted us to undertake a comprehensive analysis of the immune cells in the normal fallopian tube. Accordingly, the aim of this study was to provide a baseline for future studies exploring the relationship of inflammation with the early events of ovarian carcinogenesis by characterizing the immune cell repertoire in 13 normal human fallopian tubes, combining digital microscopy of immunostained slides and flow cytometry of fresh single-cell suspensions, with a panel of markers that identify the most important adaptive and innate immune cells. We found that CD45(+) leukocytes are regularly observed in the fallopian tube and are mainly composed of CD163(+) macrophages, CD11c dendritic cells, and CD8(+) T cells. In addition, there are minor populations of CD56(+) NK cells, CD4(+) T cells, CD20(+) B cells, TCRγδ(+) T cells, and, among dendritic cells, CD207(Langerin)(+) Langerhans cells. The cellular mapping that we performed indicates that the local immune system in the human fallopian tube is composed of a mixture of innate and adaptive immune cells, many of which are recognized as playing a role in cancer immune surveillance. This local immune system could provide a first line of defense against early precancerous lesions and could potentially be exploited for immune-based therapies.