NKT cells: what's in a name?

Combination of pentoxifylline and α-galactosylceramide with radiotherapy promotes necro-apoptosis and leukocyte infiltration and reduces the mitosis rate in murine melanoma

Despite the success for the treatment of melanoma such as targeted molecular therapy, the use of such treatments are expensive For this reason, this study was carried out to explore the anti-cancer properties of available drugs that are able to modify the melanoma prognosis. The study was conducted in two phases: Evaluation of pharmacological effects of pentoxifylline (PTX) administered above (60 mg/kg) which is the therapeutic dose that is aimed at reducing the side-effect of radiotherapy, and of α- galactosylceramide (GalCer) administered at 100 μg/kg, as well as their combination using a murine model (BDF1 mice) of melanoma cell line (B16-F1, ATCC). For the radiotherapy phase, 9 Gy was applied in the tumor area, before (3 days), during (30 min) and after (3 days) the PTX + GalCer treatment. In both study phases, the mitosis rate, leukocyte infiltration and necro-apoptosis were assessed using histological and immunohistochemical approach and tumor volume evaluation as biomarkers. All treatments showed good prognosis results estimated as reduction of mitosis rate (PTX + GalCer after radiotherapy and GalCer), increased leukocyte infiltrate (PTX + GalCer after radiotherapy and GalCer) and necro-apoptosis augmentation (PTX + GalCer after radiotherapy and radiotherapy control). Nevertheless, a lower development of tumor volume was found in GalCer treatment. In this way, it is possible to suggest that the integrated treatment with immuno-stimulators such as GalCer, plus drug used for peripheral vascular disease (PTX) after radiotherapy is probably an alternative for controlling aggressive melanoma in murine model.

The role of the gut microbiome in chronic liver disease: the clinical evidence revised

Recent research has suggested a role for the intestinal microbiota in the pathogenesis and potential treatment of a wide range of liver diseases. The intestinal microbiota and bacterial products may contribute to the development of liver diseases through multiple mechanisms including increased intestinal permeability, chronic systemic inflammation, production of short-chain fatty acids and changes in metabolism. This suggests a potential role for pre-, pro- and synbiotic products in the prevention or treatment of some liver diseases. In addition, there is emerging evidence on the effects of faecal microbial transplant. Herein, we discuss the relationship between the intestinal microbiota and liver diseases, as well as reviewing intestinal microbiota-based treatment options that are currently being investigated.

CD160 serves as a negative regulator of NKT cells in acute hepatic injury

CD160 and BTLA both bind to herpes virus entry mediator. Although a negative regulatory function of BTLA in natural killer T (NKT) cell activation has been reported, whether CD160 is also involved is unclear. By analyzing CD160^-/- mice and mixed bone marrow chimeras, we show that CD160 is not essential for NKT cell development. However, CD160^-/- mice exhibit severe liver injury after in vivo challenge with α-galactosylceramide (α-GalCer). Moreover, CD160^-/- mice are more susceptible to Concanavalin A challenge, and display elevated serum AST and ALT levels, hyperactivation of NKT cells, and enhanced IFN-γ, TNF, and IL-4 production. Lastly, inhibition of BTLA by anti-BTLA mAb aggravates α-GalCer-induced hepatic injury in CD160^-/- mice, suggesting that both CD160 and BTLA serve as non-overlapping negative regulators of NKT cells. Our data thus implicate CD160 as a co-inhibitory receptor that delivers antigen-dependent signals in NKT cells to dampen cytokine production during early innate immune activation.

Mouse CD8+NKT-like cells exert dual cytotoxicity against mouse tumor cells and myeloid-derived suppressor cells

Our previous work has demonstrated the high efficiency of CD8⁺ natural killer T (NKT)-like cells in killing antigen-bearing dendritic cells. To evaluate their role in the tumor microenvironment, we performed in vitro and in vivo antitumor experiments to investigate whether CD8⁺NKT-like cells could kill Yac-1 and B16 cells like NK cells and kill EL4-OVA8 cells in an antigen-specific manner like cytotoxic T lymphocytes (CTLs). Unlike NK1.1⁻CTLs, CD8⁺NKT-like cells also exhibit the capability to kill myeloid-derived suppressor cells (MDSCs) in an antigen-specific manner, indicative of their potential role in clearing tumor antigen-bearing MDSCs to improve the antitumor microenvironment. In vitro blocking experiments showed that granzyme B inhibitor efficiently suppressed the cytotoxicity of CD8⁺NKT-like cells against tumor cells and MDSCs, while Fas ligand (FasL) or tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) inhibition failed to produce similar effects. Transcriptomic and phenotypic analyses of CD8⁺NKT-like cells, NK cells, and NK1.1⁻CTLs indicated that CD8⁺NKT-like cells expressed both T-cell activation markers and NK cell markers, thus bearing features of both the activated T cells and NK cells. Taken together, CD8⁺NKT-like cells could exert NK- and CTL-like antitumor effects through the elimination of both tumor cells and MDSCs in a granzyme B-dependent manner.

Defining a novel subset of CD1d-dependent type II natural killer T cells using natural killer cell-associated markers

Natural killer T (NKT) cells are αβ T cell receptor (TCR) expressing innate‐like T cells that display natural killer (NK) cell markers. Based on TCR characteristics, they are divided into two groups restricted to the MHC class I‐like molecule CD1d. Type I NKT cells, most extensively studied, are identified by a semi‐invariant Vα14‐Jα18 (mouse, Vα24‐Jα18 in humans) TCR reactive to the prototypic ligand α‐galactosylceramide presented on CD1d. In contrast, type II NKT cells display diverse TCR reacting to different CD1d‐presented ligands. There are no reagents that identify all type II NKT cells, limiting their exploration. Here, we searched for novel type II NKT cells by comparing Jα18^−/−MHCII^−/− mice that harbour type II but not type I NKT cells, and CD1d^−/−MHCII^−/− mice, lacking all NKT cells. We identified significantly larger populations of CD4⁺ and CD4⁻CD8⁻ (double negative, DN) TCRβ⁺ cells expressing NKG2D or NKG2A/C/E in Jα18^−/−MHCII^−/− mice compared with CD1d^−/−MHCII^−/− mice, suggesting that 30%‐50% of these cells were type II NKT cells. They expressed CD122, NK1.1, CXCR3 and intermediate/low levels of CD45RB. Further, the CD4⁺ subset was CD69⁺, while the DN cells were CD49b⁺ and CD62L⁺. Both subsets expressed the NKT cell‐associated promyelocytic leukaemia zinc finger (PLZF) transcription factor and Tbet, while fewer cells expressed RORγt. NKG2D⁺ CD4⁺ and DN populations were producers of IFN‐γ, but rarely IL‐4 and IL‐17. Taken together, we identify a novel subset of primary CD4⁺ and DN type II NKT cells that expresses NKG2 receptors have typical NKT cell phenotypes and a TH1‐like cytokine production.

Hyperactivated peripheral invariant natural killer T cells correlate with the progression of HBV-relative liver cirrhosis

Invariant NKT (iNKT) cells express markers of both T and NK cells and may produce various cytokines to regulate liver immunity. However, the role of iNKT cells in the progression of HBV-relative liver cirrhosis (HBV-LC) is incompletely understood. Here, we investigated the impact of peripheral iNKT cells on a cohort of patients with HBV-LC. The frequency, number, activation status, apoptosis and proliferation ability of peripheral iNKT cells were detected with flow cytometry. The impact of peripheral iNKT cells on the proliferation of hepatocyte cell line (MIHA) and activation of hepatic stellate cell line (LX-2) was detected with flow cytometry and PCR. In HBV-LC patients, the frequency and absolute number of peripheral iNKT cells significantly reduced, but the expression levels of CD25, interleukin (IL)-4, IL-13 and interferon (IFN)-γ increased. No difference was observed in the proliferation and apoptosis of circulating iNKT cells between patients and healthy controls (HCs). CXCR6 (CD186), known to be closely associated with iNKT cells migration from the periphery to the liver, was highly expressed on peripheral iNKT cells in HBV-LC patients. Furthermore, peripheral iNKT cells had a profound impact on MIHA cell proliferation and LX-2 cell activation through IL-4 or IL-13. Our data suggest that in HBV-LC patients, highly activated peripheral iNKT cells may migrate to the liver and affect hepatocyte cell line (MIHA) proliferation and hepatic stellate cell line (LX-2) activation through the expression of type 2 cytokines, which may result in excessive healing and contributing to the progression of fibrosis toward cirrhosis in liver.

The Important Role of Dendritic Cell (DC) in iNKT-Mediated Modulation of NK Cell Function in Chlamydia pneumoniae Lung Infection

Chlamydia pneumoniae (Cpn) infection causes multiple acute and chronic human diseases. The role of DCs in host defense against Cpn infection has been well documented. The same is true for invariant natural killer T (iNKT) cells and NK cells, but the interaction among cells is largely unknown. In this study, we investigated the influence and mechanism of iNKT cell on the differentiation and function of NK cell in Cpn lung infection and the role played by DCs in this process. We found that expansion of IFN-γ-producing NK cells quickly happened after the infection, but this response was altered in iNKT knockout (KO) mice. The expression of activation markers and the production of IFN-γ by different NK subsets were significantly lower in KO mice than wild-type (WT) mice. Using in vitro DC-NK coculture and in vivo adoptive transfer approaches, we further examined the role of DCs in iNKT-mediated modulation of NK cell function. We found that NK cells expressed lower levels of activation markers and produced less IFN-γ when they were cocultured with DCs from KO mice than WT mice. More importantly, we found that the adoptive transfer of DCs from the KO mice induced less NK cell activation and IFN-γ production. The results provided evidence on the modulating effect of iNKT cell on NK cell function, particularly the critical role of DCs in this modulation process. The finding suggests the complexity of cellular interactions in Cpn lung infection, which should be considered in designing preventive and therapeutic approaches for diseases and infections.

Ageing characteristics of bone indicated by transcriptomic and exosomal proteomic analysis of cortical bone cells

BACKGROUND

Degenerative changes in the skeleton play an important role in ageing. As the foremost sensors and orchestrators of bone remodelling, osteocytes contribute significantly to the health of the skeleton. Embedded in a mineralized bone matrix, the osteocyte network and the surrounding lacunar canaliculae work together as a functional syncytium-the osteocytic lacunar-canalicular system (OLCS). However, changes in the OLCS during ageing and related mechanisms cannot be fully understood by using traditional histological analysis.

METHODS

To link the phenotypes of aged osteocytes and their functional changes during ageing, we analysed the changes in the gene expression profiles of bone cells and the proteomic profiles of OLCS exosomes derived from aged and young cortical bone.

RESULTS

Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of differentially expressed genes (DEGs) suggested that a decline in cell energy metabolism and an increased level of the proinflammatory state are major characteristics of bone ageing. Moreover, some DEGs were key regulators of bone mechanical sensation and bone remodelling, which are indicative of reduced bone-specific function with age. Further, the identified proteins in OLCS exosomes showed potential changes in the secretory function bone. Compared with young controls, the decreased functional proteins in aged OLCS exosomes were enriched mainly in GO terms that included regulating bone development and remodelling, cell-matrix adhesion, and cell clearance and homeostasis. Notably, several functions of exosomal proteins of the aged group revealed potential new roles, such as regulating innate and adaptive immunity, wound healing, and angiogenesis and eliminating oxidative stress.

CONCLUSION

The information obtained from bone cells and OLCS exosomes will help us discover new features of bone ageing.

Improved Th17 Selectivity of α-Galactosylceramide via Noncovalent Interactions with Diether Moiety

α-Galactosylceramide (α-GalCer) is a typical antigen for invariant natural killer T cells that are a subset of T cells and play critical roles in regulating immune responses. To selectively induce the secretion of certain cytokines via introducing hydrogen-bonding interaction with polar amino acid residues in the binding pocket of CD1d, a series of α-GalCer analogues with diether moiety in the acyl chain were designed and synthesized. The subsequent in vitro biological evaluation of these analogues revealed the structure-activity relationship for the selective IL-17 secretion. Analogues 5 and 6 induced the significantly increased IL-17 secretion over other cytokines, suggesting protective effects against pathogens. In contrast, analogue 7 showed the highly reduced IL-17 secretion, which may indicate potential anti-inflammatory effects.

Characterization of circulating T-, NK-, and NKT cell subsets in patients with colorectal cancer: the peripheral blood immune cell profile

Objective

As the development and progression of colorectal cancer (CRC) are known to be affected by the immune system, cell subsets such as T cells, natural killer (NK) cells, and natural killer T (NKT) cells are considered interesting targets for immunotherapy and clinical biomarker research. Until now, the role of systemic immune profiles in tumor progression remains unclear. In this study, we aimed to characterize the immunophenotype of circulating T cells, NK cells, and NKT-like cells in patients with CRC, and to subsequently correlate these immunophenotypes to clinical follow-up data.

Methods

Using multiparameter flow cytometry, the subset distribution and immunophenotype of T cells (CD3⁺CD56⁻), CD56^dim NK cells (CD3⁻CD56^dim), CD56^bright NK cells (CD3⁻CD56^bright), and NKT-like (CD3⁺CD56⁺) cells were investigated in peripheral blood mononuclear cell (PBMC) samples from 71 CRC patients and 19 healthy donors.

Results

CRC patients showed profound differences in immune cell subset distribution and their immunophenotype compared to healthy donors, as characterized by increased percentage of regulatory T cells, and reduced expression level of the natural cytotoxicity receptors NKp44 and NKp46 on both CD56^dim NK cells and NKT-like cells. Finally, we showed in a multivariate analysis that above-median percentage of CD16⁺ NKT-like cells was independently associated with shorter disease-free survival in CRC patients.

Conclusion

The altered phenotype of circulating immune cell subsets in CRC and its association with clinical outcome highlight the potential use of PBMC subsets as prognostic biomarkers in CRC, thereby contributing to better insight into the role of systemic immune profiles in tumor progression.

Electronic supplementary material

The online version of this article (10.1007/s00262-019-02343-7) contains supplementary material, which is available to authorized users.

Single-cell transcriptomic landscape of nucleated cells in umbilical cord blood

BACKGROUND

For both pediatric and adult patients, umbilical cord blood (UCB) transplant is a therapeutic option for a variety of hematologic diseases, such as blood cancers, myeloproliferative disorders, genetic diseases, and metabolic disorders. However, the level of cellular heterogeneity and diversity of nucleated cells in UCB has not yet been assessed in an unbiased and systemic fashion. In the present study, nucleated cells from UCB were subjected to single-cell RNA sequencing to simultaneously profile the gene expression signatures of thousands of cells, generating a rich resource for further functional studies. Here, we report the transcriptomes of 17,637 UCB cells, covering 12 major cell types, many of which can be further divided into distinct subpopulations.

RESULTS

Pseudotemporal ordering of nucleated red blood cells identifies wave-like activation and suppression of transcription regulators, leading to a polarized cellular state, which may reflect nucleated red blood cell maturation. Progenitor cells in UCB also comprise 2 subpopulations with activation of divergent transcription programs, leading to specific cell fate commitment. Detailed profiling of cytotoxic cell populations unveiled granzymes B and K signatures in natural killer and natural killer T-cell types in UCB.

CONCLUSIONS

Taken together, our data form a comprehensive single-cell transcriptomic landscape that reveals previously unrecognized cell types, pathways, and mechanisms of gene expression regulation. These data may contribute to the efficacy and outcome of UCB transplant, broadening the scope of research and clinical innovations.

Adipocytes harbor a glucosylceramide biosynthesis pathway involved in iNKT cell activation

BACKGROUND

Natural killer T (NKT) cells in adipose tissue (AT) contribute to whole body energy homeostasis.

RESULTS

Inhibition of the glucosylceramide synthesis in adipocytes impairs iNKT cell activity.

CONCLUSION

Glucosylceramide biosynthesis pathway is important for endogenous lipid antigen activation of iNKT cells in adipocytes.

SIGNIFICANCE

Unraveling adipocyte-iNKT cell communication may help to fight obesity-induced AT dysfunction. Overproduction and/or accumulation of ceramide and ceramide metabolites, including glucosylceramides, can lead to insulin resistance. However, glucosylceramides also fulfill important physiological functions. They are presented by antigen presenting cells (APC) as endogenous lipid antigens via CD1d to activate a unique lymphocyte subspecies, the CD1d-restricted invariant (i) natural killer T (NKT) cells. Recently, adipocytes have emerged as lipid APC that can activate adipose tissue-resident iNKT cells and thereby contribute to whole body energy homeostasis. Here we investigate the role of the glucosylceramide biosynthesis pathway in the activation of iNKT cells by adipocytes. UDP-glucose ceramide glucosyltransferase (Ugcg), the first rate limiting step in the glucosylceramide biosynthesis pathway, was inhibited via chemical compounds and shRNA knockdown in vivo and in vitro. β-1,4-Galactosyltransferase (B4Galt) 5 and 6, enzymes that convert glucosylceramides into potentially inactive lactosylceramides, were subjected to shRNA knock down. Subsequently, (pre)adipocyte cell lines were tested in co-culture experiments with iNKT cells (IFNγ and IL4 secretion). Inhibition of Ugcg activity shows that it regulates presentation of a considerable fraction of lipid self-antigens in adipocytes. Furthermore, reduced expression levels of either B4Galt5 or -6, indicate that B4Galt5 is dominant in the production of cellular lactosylceramides, but that inhibition of either enzyme results in increased iNKT cell activation. Additionally, in vivo inhibition of Ugcg by the aminosugar AMP-DNM results in decreased iNKT cell effector function in adipose tissue. Inhibition of endogenous glucosylceramide production results in decreased iNKT cells activity and cytokine production, underscoring the role of this biosynthetic pathway in lipid self-antigen presentation by adipocytes.

Select sequencing of clonally expanded CD8+ T cells reveals limits to clonal expansion

T cells are a central component of our immune system. They express a T cell receptor (TCR) on their surface, which detects pathogens and stimulates the T cell to initiate an immune response. Upon exposure to a specific pathogen, some T cells are activated and clonally expand. These pathogen-specific clonally expanded T cells, however, are generally rare and difficult to isolate. We have developed a technology (SELECT-seq) to isolate this rare population and to analyze their transcriptome and TCR composition. Therefore, our work may be the key to achieving a better understanding of pathogen-specific T cell clonality and function.

To permit the recognition of antigens, T cells generate a vast diversity of T cell receptor (TCR) sequences. Upon binding of the TCR to an antigen–MHC complex, T cells clonally expand to establish an immune response. To study antigen-specific T cell clonality, we have developed a method that allows selection of rare cells, based on RNA expression, before in-depth scRNA-seq (named SELECT-seq). We applied SELECT-seq to collect both TCR sequences and then transcriptomes from single cells of peripheral blood lymphocytes activated by a Mycobacterium tuberculosis (Mtb) lysate. TCR sequence analysis allowed us to preferentially select expanded conventional CD8⁺ T cells as well as invariant natural killer T (iNKT) cells and mucosal-associated invariant T (MAIT) cells. The iNKT and MAIT cells have a highly similar transcriptional pattern, indicating that they carry out similar immunological functions and differ considerably from conventional CD8⁺ T cells. While there is no relationship between expression profiles and clonal expansion in iNKT or MAIT cells, highly expanded conventional CD8⁺ T cells down-regulate the interleukin 2 (IL-2) receptor alpha (IL2RA, or CD25) protein and show signs of senescence. This suggests inherent limits to clonal expansion that act to diversify the T cell response repertoire.

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.

Circulating NK cell subsets and NKT‑like cells in renal transplant recipients with acute T‑cell‑mediated renal allograft rejection

Emerging evidence indicates that natural killer (NK) cells and NKT-like cells may affect allograft outcomes following solid organ transplantation. However, the roles of these cells in allograft acceptance and dysfunction are controversial. To assess the changes in NK cell and CD3⁺CD56⁺ NKT-like cell frequency and phenotype in renal allograft recipients and to explore their associations with acute T-cell-mediated renal allograft rejection (ACR), longitudinal changes in NK and NKT-like cell frequency and phenotype were characterized using flow cytometry and immunohistochemistry in the peripheral blood and kidney allograft tissues in 142 recipients undergoing kidney transplantation. The serum concentrations of NK cell-associated cytokines were also detected by cytokine multiplex immunoassay. In contrast to the healthy controls, recipients with stable graft function exhibited increased proportions of CD56^brightCD16^dim subsets and decreased proportions of NKT-like cells in their peripheral blood mononuclear cells (PBMCs). Patients with ACR demonstrated increased proportions of NK cells, which were associated with increased CD3⁻CD56^bright subsets and decreased CD3⁻CD56^dim subsets, an increase in the CD56^bright/CD56^dim ratio in PBMCs and increased CD56⁺ NK cell infiltration in the kidney allograft, compared with the stable controls. In addition, there was a decreased proportion of NKT-like cells in patients with ACR, and an increased ratio of CD56^bright/NKT-like cells compared with the stable controls. These differences appeared to be consistent with the increase in the serum concentrations of C-C motif chemokine 19 and the decrease in the serum concentrations of interleukin-15. These data indicate that CD56^bright NK cells may promote the development of ACR, and that NKT-like cells may have immunoregulatory function. The results also imply that the CD56^bright/CD56^dim ratio may affect the ACR signatures.

Cytotoxic Function and Cytokine Production of Natural Killer Cells and Natural Killer T-Like Cells in Systemic Lupus Erythematosis Regulation with Interleukin-15

Natural killer cells and NKT-like cells are the first line immune defense against tumor and virus infection. Deficient NK and NKT-like cell effector function may contribute to increased susceptibility to infection in SLE patients. We sought to examine the perforin and granzyme B expression, interferon-gamma (IFN-γ), and tumor-necrosis factor-alpha (TNF-α) production and CD107a degranulation of NK and NKT-like cells from SLE patients and their regulation by IL-15. We established that (1) perforin expression on SLE NK cells was decreased but unrelated to disease activity; (2) the MFI of granzyme B was increased in NK cells from SLE patients with active disease, associated with increased percentages of granzyme B⁺ CD56^bright NK cells; (3) NK cells from active SLE patients, both CD56^dim and CD56^bright NK subsets, produced higher IFN-γ compared to controls; (4) CD56^dim, but not CD56^bright NK cells from active SLE patients, produced lower TNF-α, compared to inactive SLE patients and controls; (5) CD107a degranulation of SLE NK cells was comparable to controls; (6) IL-15 enhanced perforin/granzyme B expression, IFN-γ/TNF-α production, and CD107a degranulation of NK cells from SLE patients; and (7) similar observations were found for CD56⁺CD3⁺ NKT-like cells. Taken together, we demonstrated the differential expression of the heightened granzyme B and decreased TNF-α in NK and NKT-like cells in SLE patients. Higher granzyme B expression of NK and NKT-like cells in active SLE patients, further enhanced by circulating IL-15, may contribute to the maintenance of inflammation in SLE.

Immune Cell Profiling of the Cerebrospinal Fluid Provides Pathogenetic Insights Into Inflammatory Neuropathies

Objective: Utilize immune cell profiles in the cerebrospinal fluid (CSF) to advance the understanding and potentially support the diagnosis of inflammatory neuropathies.

Methods: We analyzed CSF cell flow cytometry data of patients with definite Guillain-Barré syndrome (GBS, n = 26) and chronic inflammatory demyelinating polyneuropathy (CIDP, n = 32) based on established diagnostic criteria in comparison to controls with relapsing-remitting multiple sclerosis (RRMS, n = 49) and idiopathic intracranial hypertension (IIH, n = 63).

Results: Flow cytometry revealed disease-specific changes of CSF cell composition with a significant increase of NKT cells and CD8+ T cells in CIDP, NK cells in GBS, and B cells and plasma cells in MS in comparison to IIH controls. Principal component analysis demonstrated distinct CSF immune cells pattern in inflammatory neuropathies vs. RRMS. Systematic receiver operator curve (ROC) analysis identified NKT cells as the best parameter to distinguish GBS from CIDP. Composite scores combing several of the CSF parameters differentiated inflammatory neuropathies from IIH and GBS from CIDP with high confidence. Applying a novel dimension reduction technique, we observed an intra-disease heterogeneity of inflammatory neuropathies.

Conclusion: Inflammatory neuropathies display disease- and subtype-specific alterations of CSF cell composition. The increase of NKT cells and CD8+ T cells in CIDP and NK cells in GBS, suggests a central role of cytotoxic cell types in inflammatory neuropathies varying between acute and chronic subtypes. Composite scores constructed from multi-dimensional CSF parameters establish potential novel diagnostic tools. Intra-disease heterogeneity suggests distinct disease mechanisms in subgroups of inflammatory neuropathies.

Immunometabolism regulates TCR recycling and iNKT cell functions

Invariant natural killer T (iNKT) cells are innate-like T lymphocytes that express an invariant T cell receptor (TCR), which recognizes glycolipid antigens presented on CD1d molecules. These cells are phenotypically and functionally distinct from conventional T cells. When we characterized the metabolic activity of iNKT cells, consistent with their activated phenotype, we found that they had much less mitochondrial respiratory capacity but increased glycolytic activity in comparison to naïve conventional CD4⁺ T cells. After TCR engagement, iNKT cells further increased aerobic glycolysis, which was important for the expression of interferon-γ (IFN-γ). Glycolytic metabolism promoted the translocation of hexokinase-II to mitochondria and the activation of mammalian target of rapamycin complex 2 (mTORC2). Inhibiting glycolysis reduced the activity of Akt and PKCθ, which inhibited TCR recycling and accumulation within the immune synapse. Diminished TCR accumulation in the immune synapse reduced the activation of proximal and distal TCR signaling pathways and IFN-γ production in activated iNKT cells. Our studies demonstrate that glycolytic metabolism augments TCR signaling duration and IFN-γ production in iNKT cells by increasing TCR recycling.

Analyzing Antigen Recognition by Natural Killer T Cells

Natural killer T (NKT) cells are a subset of T lymphocytes that recognize a wide variety of lipid antigens presented by the atypical MHC class I molecule CD1d. NKT cells exhibit rapid activation after recognition of cognate antigens, secrete abundant amounts of T helper (Th) 1, Th2, and Th17 cytokines within hours of activation and shape the immune response through subsequent activation of dendritic, NK, T, and B cells. NKT cells therefore play central roles in antimicrobial and anticancer immunity and in the modulation of various autoimmune disorders. Consequently, recent research has focused on the discovery of microbial and self-antigens involved in NKT cell activation. In this chapter, we will discuss different strategies for studying antigen recognition by NKT cells including CD1d tetramer-based approaches and in vitro assays characterizing NKT cell activation in response to lipid antigen presentation. While Toll-like receptor (TLR) agonists and cytokines such as IL-12 are critical for NKT cell activation in vivo, particularly in the context of microbial infection, methods for detection of TLR- and cytokine-dependent NKT cell activation will not be discussed in this section.

A Novel Liposome Formulation Carrying Both an Insulin Peptide and a Ligand for Invariant Natural Killer T Cells Induces Accumulation of Regulatory T Cells to Islets in Nonobese Diabetic Mice

Type 1 diabetes (T1D) is an autoimmune disease caused by the destruction of pancreatic β cells by autoantigen-reactive diabetogenic cells. Antigen-specific therapies using islet autoantigens for restoring immune tolerance have emerged as promising approaches for the treatment of T1D but have been unsuccessful in humans. Herein, we report that RGI-3100-iB, a novel liposomal formulation carrying both α-galactosylceramide (α-GalCer), which is a representative ligand for invariant natural killer T (iNKT) cells, and insulin B chain 9-23 peptide, which is an epitope for CD4⁺ T cells, could induce the accumulation of regulatory T cells (Tregs) in islets in a peptide-dependent manner, followed by the remarkable prevention of diabetes onset in nonobese diabetic (NOD) mice. While multiple administrations of a monotherapy using either α-GalCer or insulin B peptide in a liposomal formulation was confirmed to delay/prevent T1D in NOD mice, RGI-3100-iB synergistically enhanced the prevention effect of each monotherapy and alleviated insulitis in NOD mice. Immunopathological analysis showed that Foxp3⁺ Tregs accumulated in the islets in RGI-3100-iB-treated mice. Cotransfer of diabetogenic T cells and splenocytes of NOD mice treated with RGI-3100-iB, but not liposomal α-GalCer encapsulating an unrelated peptide, to NOD-SCID mice resulted in the prevention of diabetes and elevation of Foxp3 mRNA expression in the islets. These data indicate that the migration of insulin B-peptide-specific Tregs to islet of NOD mice that are involved in the suppression of pathogenic T cells related to diabetes onset and progression could be enhanced by the administration of liposomes containing α-GalCer and insulin B peptide.

Cytotoxic lymphocytes in COPD airways: increased NK cells associated with disease, iNKT and NKT-like cells with current smoking

BACKGROUND

Cytotoxic lymphocytes are increased in the airways of COPD patients. Whether this increase is driven primarily by the disease or by smoking is not clear, nor whether it correlates with the rate of decline in lung function.

METHODS

Bronchoscopy with BAL was performed in 52 subjects recruited from the longitudinal OLIN COPD study according to pre-determined criteria; 12 with COPD and a rapid decline in lung function (loss of FEV₁ ≥ 60 ml/year), 10 with COPD and a non-rapid decline in lung function (loss of FEV₁ ≤ 30 ml/year), 15 current and ex-smokers and 15 non-smokers with normal lung function. BAL lymphocyte subsets were determined using flow cytometry.

RESULTS

In BAL fluid, the proportions of NK, iNKT and NKT-like cells all increased with pack-years. Within the COPD group, NK cells - but not iNKT or NKT-like cells - were significantly elevated also in subjects that had quit smoking. In contrast, current smoking was associated with a marked increase in iNKT and NKT-like cells but not in NK cells. Rate of lung function decline did not significantly affect any of the results.

CONCLUSIONS

In summary, increased proportions of NK cells in BAL fluid were associated with COPD; iNKT and NKT-like cells with current smoking but not with COPD. Interestingly, NK cell percentages did not normalize in COPD subjects that had quit smoking, indicating that these cells might play a role in the continued disease progression seen in COPD even after smoking cessation.

TRIAL REGISTRATION

Clinicaltrials.gov identifier NCT02729220 .

Innate and adaptive stimulation of murine diverse NKT cells result in distinct cellular responses

Natural killer T (NKT) cells recognize glycolipids presented on CD1d. They share features of adaptive T lymphocytes and innate NK cells, and mediate immunoregulatory functions via rapid production of cytokines. Invariant (iNKT) and diverse (dNKT) NKT cell subsets are defined by their TCR. The immunological role of dNKT cells, that do not express the invariant TCRα‐chain used by iNKT cells, is less well explored than that of iNKT cells. Here, we investigated signals driving Toll‐like receptor (TLR) ligand activation of TCR‐transgenic murine dNKT cells. IFN‐γ production by dNKT cells required dendritic cells (DC), cell‐to‐cell contact and presence of TLR ligands. TLR‐stimulated DC activated dNKT cells to secrete IFN‐γ in a CD1d‐, CD80/86‐ and type I IFN‐independent manner. In contrast, a requirement for IL‐12p40, and a TLR ligand‐selective dependence on IL‐18 or IL‐15 was observed. TLR ligand/DC stimulation provoked early secretion of pro‐inflammatory cytokines by both CD62L⁺ and CD62L⁻ dNKT cells. However, proliferation was limited. In contrast, TCR/co‐receptor‐mediated activation resulted in proliferation and delayed production of a broader cytokine spectrum preferentially in CD62L⁻ dNKT cells. Thus, innate (TLR ligand/DC) and adaptive (TCR/co‐receptor) stimulation of dNKT cells resulted in distinct cellular responses that may contribute differently to the formation of immune memory.

Unconventional T Cell Targets for Cancer Immunotherapy

Most studies on the immunotherapeutic potential of T cells have focused on CD8 and CD4 T cells that recognize peptide antigens (Ag) presented by polymorphic major histocompatibility complex (MHC) class I and MHC class II molecules, respectively. However, unconventional T cells, which interact with MHC class Ib and MHC-I like molecules, are also implicated in tumor immunity, although their role therein is unclear. These include unconventional T cells targeting MHC class Ib molecules such as HLA-E and its murine ortholog Qa-1b, natural killer T (NKT) cells, mucosal associated invariant T (MAIT) cells, and γδ T cells. Here, we review the current understanding of the roles of these unconventional T cells in tumor immunity and discuss why further studies into the immunotherapeutic potential of these cells is warranted.

Sulfatides ameliorate experimental autoimmune neuritis by suppressing Th1/Th17 cells

Sulfatides have immunomodulatory functions, and play protective roles in multiple autoimmune diseases. In the present study, we showed that sulfatides ameliorated experimental autoimmune neuritis in Lewis rats induced with bovine peripheral myelin, which was associated with decreased proportions of Th1 and Th17 cells. Furthermore, compared control group, cells from sulfatide-treated rats exhibited lower potential in proliferation and IL-17 secretion in the presence of BPM or ConA in vitro. Moreover, sulfatides also reduced the proportions of NK and NKT cells. In summary, our study indicated that sulfatides might become a new therapeutic agent in Guillain-Barré syndrome in the future.

The Role of CD1d and MR1 Restricted T Cells in the Liver

The liver is one of the most important immunological organs that remains tolerogenic in homeostasis yet promotes rapid responses to pathogens in the presence of a systemic infection. The composition of leucocytes in the liver is highly distinct from that of the blood and other lymphoid organs, particularly with respect to enrichment of innate T cells, i.e., invariant NKT cells (iNKT cells) and Mucosal-Associated Invariant T cells (MAIT cells). In recent years, studies have revealed insights into their biology and potential roles in maintaining the immune-environment in the liver. As the primary liver-resident immune cells, they are emerging as significant players in the human immune system and are associated with an increasing number of clinical diseases. As such, innate T cells are promising targets for modifying host defense and inflammation of various liver diseases, including viral, autoimmune, and those of tumor origin. In this review, we emphasize and discuss some of the recent discoveries and advances in the biology of innate T cells, their recruitment and diversity in the liver, and their role in various liver diseases, postulating on their potential application in immunotherapy.

T Cells in Adipose Tissue: Critical Players in Immunometabolism

Adipose tissue performs immunoregulatory functions in addition to fat storage. Various T cells in different fat depots either help maintain metabolic homeostasis under healthy conditions or contribute to metabolic disorders in pathological conditions such as obesity, diabetes, cardiovascular diseases, or even cancer. These T cells play critical roles in immunometabolism, which refers to the intersection of immunity and metabolism. Numerous studies have examined the presence and changes of different T cell subsets, including helper T cells, regulatory T cells, cytotoxic T cells, and natural killer T cells, in adipose depots in health and diseases. In this review, we will discuss the adipose tissue niches that influence the patterns and functions of T cell subsets and in turn the impact of these T cells on cell- or body-based immunometabolism accounting for health and obesity.

NK1.1 Expression Defines a Population of CD4+ Effector T Cells Displaying Th1 and Tfh Cell Properties That Support Early Antibody Production During Plasmodium yoelii Infection

Early plasmablast induction is a hallmark of Plasmodium infection and is thought to contribute to the control of acute parasite burden. Although long understood to be a T-cell dependent phenomenon, regulation of early plasmablast differentiation, however, is poorly understood. Here, we identify a population of CD4⁺ T cells that express the innate NK cell marker NK1.1 as an important source of T cell help for early plasmablast and parasite-specific Ab production. Interestingly, NK1.1⁺ CD4⁺ T cells arise from conventional, naive NK1.1⁻ CD4⁺ T cells, and their generation is independent of CD1d but critically reliant on MHC-II. CD4⁺ T cells that express NK1.1 early after activation produce IFN-γ and IL-21, and express the follicular helper T (Tfh) cell markers ICOS, PD-1 and CXCR5 more frequently than NK1.1⁻ CD4⁺ T cells. Further analysis of this population revealed that NK1.1⁺ Tfh-like cells were more regularly complexed with plasmablasts than NK1.1⁻ Tfh-like cells. Ultimately, depletion of NK1.1⁺ cells impaired class-switched parasite-specific antibody production during early Plasmodium yoelii infection. Together, these data suggest that expression of NK1.1 defines a population of rapidly expanding effector CD4⁺ T cells that specifically promote plasmablast induction during Plasmodium infection and represent a subset of T cells whose modulation could promote effective vaccine design.

The Pathophysiological Relevance of the iNKT Cell/Mononuclear Phagocyte Crosstalk in Tissues

CD1d-restricted Natural Killer T (NKT) cells are regarded as sentinels of tissue integrity by sensing local cell stress and damage. This occurs via recognition of CD1d-restricted lipid antigens, generated by stress-related metabolic changes, and stimulation by inflammatory cytokines, such as IL-12 and IL-18. Increasing evidence suggest that this occurs mainly upon NKT cell interaction with CD1d-expressing cells of the Mononuclear Phagocytic System, i.e., monocytes, macrophages and DCs, which patrol parenchymatous organs and mucosae to maintain tissue homeostasis and immune surveillance. In this review, we discuss critical examples of this crosstalk, presenting the known underlying mechanisms and their effects on both cell types and the environment, and suggest that the interaction with CD1d-expressing mononuclear phagocytes in tissues is the fundamental job of NKT cells.

Innate T Cells Govern Adipose Tissue Biology

During the past 25 y, the immune system has appeared as a key regulator of adipose tissue biology and metabolic homeostasis. In lean animals, adipose-resident leukocytes maintain an anti-inflammatory microenvironment that preserves the proper functioning of the tissue. In this review, we describe two populations of innate T cells enriched in adipose tissue, invariant NKT and γδ T cells, and how they serve overlapping and nonredundant roles in controlling adipose tissue functions. These cells interact with and expand anti-inflammatory regulatory T cells and M2 macrophages, thereby driving a metabolically beneficial tissue milieu. Surprisingly, we have found that adipose invariant NKT and γδ T cells also promote weight loss and heat production in a process called "nonshivering thermogenesis." The data surrounding these two cell types highlight their powerful ability to regulate not only other leukocytes, but also tissue-wide processes that affect an entire organism.

Murine DX5+NKT Cells Display Their Cytotoxic and Proapoptotic Potentials against Colitis-Inducing CD4+CD62Lhigh T Cells through Fas Ligand

Introduction

It has been previously shown that immunoregulatory DX5⁺NKT cells are able to prevent colitis induced by CD4⁺CD62L^high T lymphocytes in a SCID mouse model. The aim of this study was to further investigate the underlying mechanism in vitro.

Methods

CD4⁺CD62L^high and DX5⁺NKT cells from the spleen of Balb/c mice were isolated first by MACS, followed by FACS sorting and cocultured for up to 96 h. After polyclonal stimulation with anti-CD3, anti-CD28, and IL-2, proliferation of CD4⁺CD62L^high cells was assessed using a CFSE assay and activity of proapoptotic caspase-3 was determined by intracellular staining and flow cytometry. Extrinsic apoptotic pathway was blocked using an unconjugated antibody against FasL, and activation of caspase-3 was measured.

Results

As previously shown in vivo, DX5⁺NKT cells inhibit proliferation of CD4⁺CD62L^high cells in vitro after 96 h coculture compared to a CD4⁺CD62L^high monoculture (proliferation index: 1.39 ± 0.07 vs. 1.76 ± 0.12; P = 0.0079). The antiproliferative effect of DX5⁺NKT cells was likely due to an induction of apoptosis in CD4⁺CD62L^high cells as evidenced by increased activation of the proapoptotic caspase-3 after 48 h (38 ± 3% vs. 28 ± 3%; P = 0.0451). Furthermore, DX5⁺NKT cells after polyclonal stimulation showed an upregulation of FasL on their cell surface (15 ± 2% vs. 2 ± 1%; P = 0.0286). Finally, FasL was blocked on DX5⁺NKT cells, and therefore, the extrinsic apoptotic pathway abrogated the activation of caspase-3 in CD4⁺CD62L^high cells.

Conclusion

Collectively, these data confirmed that DX5⁺NKT cells inhibit proliferation of colitis-inducing CD4⁺CD62L^high cells by induction of apoptosis. Furthermore, DX5⁺NKT cells likely mediate their cytotoxic and proapoptotic potentials via FasL, confirming recent reports about iNKT cells. Further studies will be necessary to evaluate the therapeutical potential of these immunoregulatory cells in patients with colitis.

Detection of Autoreactive Type II NKT Cells: A Pilot Study of Comparison Between Healthy Individuals and Patients with Vasculitis

NKT cells are defined as T cells that recognize hydrophobic antigens presented by class I MHC-like molecules, including CD1d. Among CD1d-restricted NKT cells, type I and type II subsets have been noted. CD1d-restricted type I NKT cells are regarded as pro-inflammatory cells in general. On the contrary, accumulated evidence has demonstrated an anti-inflammatory property of CD1d-restricted type II NKT cells. In our earlier study using a rat model with vasculitis, we demonstrated the pro-inflammatory function of CD1d-restricted type II NKT cells and identified that one such cell recognized P_518-532 of rat sterol carrier protein 2 (rSCP2_518-532 ), which appeared on vascular endothelial cells presented by CD1d. Based on this evidence, we attempted to detect human CD1d-restricted type II NKT cells in peripheral blood using hSCP2_518-532 , the human counterpart of rSCP2_518-532, together with a CD1d tetramer in flow cytometry. First, we determined the binding of hSCP2_518-532 to CD1d. Next, we detected CD3-positive hSCP2_518-532 -loaded CD1d (hSCP2_518-532 /CD1d) tetramer-binding cells in peripheral blood of healthy donors. The abundance of TGF-β-producing cells rather than TNF-α-producing cells in CD3-positive hSCP2_518-532 /CD1d tetramer-binding cells suggests the anti-inflammatory property of SCP2-loaded CD1d (SCP2/CD1d) tetramer-binding type II NKT cells in healthy individuals. Furthermore, we compared cytokine profile between healthy individuals and patients with vasculitis in a pilot study. Interestingly, the percentage of TGF-β-producing cells in SCP2/CD1d tetramer-binding type II NKT cells in vasculitic patients was significantly lower than that in healthy controls despite the greater number of these cells. Although further studies to clarify the mechanism and significance of this phenomenon are needed, SCP2/CD1d tetramer-binding type II NKT cells in peripheral blood should be examined in more detail to understand the pathophysiology of vasculitides in humans. © 2018 International Society for Advancement of Cytometry.

Clinical Application of iNKT Cell-mediated Anti-tumor Activity Against Lung Cancer and Head and Neck Cancer

Invariant natural killer T (iNKT) cells produce copious amounts of cytokines in response to T-cell receptor (TCR) stimulation by recognizing antigens such as α-galactosylceramide (α-GalCer) presented on CD1d; thus, orchestrating other immune cells to fight against pathogen infection and tumors. Because of their ability to induce strong anti-tumor responses and the convenience of their invariant TCR activated by a synthetic ligand, α-GalCer, iNKT cells have been intensively studied for application in immunotherapeutic approaches to treat cancer patients in the clinic. Here, we summarize the clinical trials of iNKT cell based immunotherapy for non-small cell lung cancer, and head and neck cancer. Although solid tumors are thought to be refractory to immunotherapeutic approaches, our clinical trials showed that the intravenous injection of α-GalCer-pulsed antigen presenting cells (APCs) activated endogenous iNKT cells and iNKT cell dependent responses. Moreover, an increase in the number of IFN-γ producing cells in PBMCs was associated with prolonged survival. The marked infiltration of iNKT cells and the accumulation of conventional T cells in the tumor microenvironment were also observed after the administration of α-GalCer-pulsed APCs and/or ex vivo activated iNKT cells. In cases of advanced head and neck squamous cell carcinoma, the increased accumulation of iNKT cells in the tumor microenvironment was correlated with objective clinical responses. We will also discuss potential combination therapies of iNKT cell based immunotherapy to achieve enhanced anti-tumor activity and provide better treatment options for these patients.

Type II NKT Cells: An Elusive Population With Immunoregulatory Properties

Natural killer T (NKT) cells are unique unconventional T cells that are reactive to lipid antigens presented on the non-polymorphic major histocompatibility class (MHC) I-like molecule CD1d. They have characteristics of both innate and adaptive immune cells, and have potent immunoregulatory roles in tumor immunity, autoimmunity, and infectious diseases. Based on their T cell receptor (TCR) expression, NKT cells are divided into two subsets, type I NKT cells with an invariant TCRα-chain (Vα24 in humans, Vα14 in mice) and type II NKT cells with diverse TCRs. While type I NKT cells are well-studied, knowledge about type II NKT cells is still limited, and it is to date only possible to identify subsets of this population. However, recent advances have shown that both type I and type II NKT cells play important roles in many inflammatory situations, and can sometimes regulate the functions of each other. Type II NKT cells can be both protective and pathogenic. Here, we review current knowledge on type II NKT cells and their functions in different disease settings and how these cells can influence immunological outcomes.

Natural killer T cells and ulcerative colitis

Ulcerative colitis (UC) is one of the two major forms of inflammatory bowel disease (IBD). Both innate immunity and adaptive immunity are aberrant in IBD. The pathogenesis of UC includes abnormal inflammation and immune responses of the digestive tract. Natural killer T (NKT) cells participate in the innate and adaptive immune responses, together with a vast array of cytokines. Recent studies suggested that IL-13, IL5 and IL-4 are involved in the occurrence and the development of UC. Manipulating NKT cells may be a potential strategy to reconstruct the abnormal immune responses in UC. In this review, we explore the roles of NKT cells and cytokines in UC. Additionally, neutralizing antibodies and inhibitors of cytokines produced by NKT cells or their receptors are also discussed as novel therapeutic choices for UC.

Tissue-Specific Roles of NKT Cells in Tumor Immunity

NKT cells are an unusual population of T cells recognizing lipids presented by CD1d, a non-classical class-I-like molecule, rather than peptides presented by conventional MHC molecules. Type I NKT cells use a semi-invariant T cell receptor and almost all recognize a common prototype lipid, α-galactosylceramide (α-GalCer). Type II NKT cells are any lipid-specific CD1d-restricted T cells that use other receptors and generally don't recognize α-GalCer. They play important regulatory roles in immunity, including tumor immunity. In contrast to type I NKT cells that most have found to promote antitumor immunity, type II NKT cells suppress tumor immunity and the two subsets cross-regulate each other, forming an immunoregulatory axis. They also can promote other regulatory cells including regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs), and can induce MDSCs to secrete TGF-β, one of the most immunosuppressive cytokines known. In some tumors, both Tregs and type II NKT cells can suppress immunosurveillance, and the balance between these is determined by a type I NKT cell. We have also seen that regulation of tumor immunity can depend on the tissue microenvironment, so the same tumor in the same animal in different tissues may be regulated by different cells, such as type II NKT cells in the lung vs Tregs in the skin. Also, the effector T cells that protect those sites when Tregs are removed do not always act between tissues even in the same animal. Thus, metastases may require different immunotherapy from primary tumors. Newly improved sulfatide-CD1d tetramers are starting to allow better characterization of the elusive type II NKT cells to better understand their function and control it to overcome immunosuppression.

Intranuclear delivery of synthetic nuclear factor-kappa B p65 reduces inflammasomes after surgery

Patients undergoing surgery can suffer from various complications, including post-operative bleeding, local or systematic infection, and neurologic disorders. Major surgery can initiate innate immune responses and trigger overproduction of inflammatory mediators, which can contribute to organ dysfunction. Inflammasomes are innate immune complexes, which are connected to the pathogenesis of various diseases, including atherosclerosis, hemorrhagic brain injury, and Alzheimer's disease. In the present study, we hypothesized that nucleotide-binding oligomerization domain-containing-like receptor protein (NLRP) inflammasomes may have a role in the pathological effects of surgery. Therefore, we designed a protein inhibitor of nuclear factor kappa B (NF-κB) p65 transcripts, called nt-p65-TMD (nuclear transducible (nt) transcription modulated domain (TMD) of RelA (p65)), that can penetrate the nucleus, and evaluated its therapeutic efficacy for dampening surgery-induced inflammasome activation. It was found that the nt-p65-TMD significantly reduced the NLRP1 inflammasome complex components (NLRP1, ASC, and Caspase-1) and interleukin (IL)-1β and IL-18 productions in the spleen after surgery. In the spleen, specific cell population and selective mediators were altered after surgery with/without nt-p65-TMD treatment. Also, we found that treatment of nt-p65-TMD decreased cell death in the spleen after surgery. Therefore, nt-p65-TMD is a potential novel strategy for reducing surgery-induced NLRP1 inflammasome and complications.

New Genetically Manipulated Mice Provide Insights Into the Development and Physiological Functions of Invariant Natural Killer T Cells

Invariant natural killer T (iNKT) cells are a unique T cell subset that exhibits characteristics of both innate immune cells and T cells. They express Vα14-Jα18 (Trav11-Traj18) as an invariant chain of the T cell receptor (TCR) and are restricted to the MHC class I-like monomorphic antigen presenting molecule CD1d. iNKT cells are known as immune regulators that bridge the innate and acquired immune systems by rapid and massive production of a wide range of cytokines, which could enable them to participate in immune responses during various disease states. Thus, Traj18-deficient mice, Cd1d-deficient mice, or iNKT cell-overexpressing mice such as iNKT TCRα transgenic mice and iNKT cell cloned mice which contain a Vα14-Jα18 rearrangement in the TCRα locus are useful experimental models for the analysis of iNKT cells in vivo and in vitro. In this review, we describe the pros and cons of the various available genetically manipulated mice and summarize the insights gained from their study, including the possible roles of iNKT cells in obesity and diabetes.

Regulatory Roles of Invariant Natural Killer T Cells in Adipose Tissue Inflammation: Defenders Against Obesity-Induced Metabolic Complications

Adipose tissue is a metabolic organ that plays a central role in controlling systemic energy homeostasis. Compelling evidence indicates that immune system is closely linked to healthy physiologic functions and pathologic dysfunction of adipose tissue. In obesity, the accumulation of pro-inflammatory responses in adipose tissue subsequently leads to dysfunction of adipose tissue as well as whole body energy homeostasis. Simultaneously, adipose tissue also activates anti-inflammatory responses in an effort to reduce the unfavorable effects of pro-inflammation. Notably, the interplay between adipocytes and resident invariant natural killer T (iNKT) cells is a major component of defensive mechanisms of adipose tissue. iNKT cells are leukocytes that recognize lipids loaded on CD1d as antigens, whereas most other immune cells are activated by peptide antigens. In adipose tissue, adipocytes directly interact with iNKT cells by presenting lipid antigens and stimulate iNKT cell activation to alleviate pro-inflammation. In this review, we provide an overview of the molecular and cellular determinants of obesity-induced adipose tissue inflammation. Specifically, we focus on the roles of iNKT cell-adipocyte interaction in maintaining adipose tissue homeostasis as well as the consequent modulation in systemic energy metabolism. We also briefly discuss future research directions regarding the interplay between adipocytes and adipose iNKT cells in adipose tissue inflammation.

Mechanism of Premature Apoptosis in CD1d-Restricted Natural Killier T Cells From Human Peripheral Blood During the Induction of Proliferation In Vitro

OBJECTIVE

A preliminary investigation on the proliferation and cultivation process of natural killer T cells (NKT) was carried out. We provide reference data for future NKT-related research and development.

METHODS

Peripheral blood mononuclear cells (PBMCs) were isolated from healthy people and were induced by α-galactosylceramide (α-GalCer). The phenotypic changes of the cells and the activation and apoptosis of Caspase-3 were recorded for 3-4 weeks.

RESULTS

The proliferation of the NKT cells continued for approximately 3 weeks, and then apoptosis started to occur. The activity of Caspase-3 was maintained at a high level from the second week. The responses of individual human NKT cells to α-GalCer stimulation differed significantly.

CONCLUSION

The proliferation of the NKT cells continued for approximately 3 weeks, and then apoptosis Semiconstitutively started to occur. The activity of Caspase-3 was maintained at a high level from the second week. The responses of individual human NKT cells to α-GalCer stimulation differed significantly.

Molecular recognition of microbial lipid-based antigens by T cells

The immune system has evolved to protect hosts from pathogens. T cells represent a critical component of the immune system by their engagement in host defence mechanisms against microbial infections. Our knowledge of the molecular recognition by T cells of pathogen-derived peptidic antigens that are presented by the major histocompatibility complex glycoproteins is now well established. However, lipids represent an additional, distinct chemical class of molecules that when presented by the family of CD1 antigen-presenting molecules can serve as antigens, and be recognized by specialized subsets of T cells leading to antigen-specific activation. Over the past decades, numerous CD1-presented self- and bacterial lipid-based antigens have been isolated and characterized. However, our understanding at the molecular level of T cell immunity to CD1 molecules presenting microbial lipid-based antigens is still largely unexplored. Here, we review the insights and the molecular basis underpinning the recognition of microbial lipid-based antigens by T cells.

Varicella zoster virus productively infects human natural killer cells and manipulates phenotype

Varicella zoster virus (VZV) is a ubiquitous human alphaherpesvirus, responsible for varicella upon primary infection and herpes zoster following reactivation from latency. To establish lifelong infection, VZV employs strategies to evade and manipulate the immune system to its advantage in disseminating virus. As innate lymphocytes, natural killer (NK) cells are part of the early immune response to infection, and have been implicated in controlling VZV infection in patients. Understanding of how VZV directly interacts with NK cells, however, has not been investigated in detail. In this study, we provide the first evidence that VZV is capable of infecting human NK cells from peripheral blood in vitro. VZV infection of NK cells is productive, supporting the full kinetic cascade of viral gene expression and producing new infectious virus which was transmitted to epithelial cells in culture. We determined by flow cytometry that NK cell infection with VZV was not only preferential for the mature CD56^dim NK cell subset, but also drove acquisition of the terminally-differentiated maturity marker CD57. Interpretation of high dimensional flow cytometry data with tSNE analysis revealed that culture of NK cells with VZV also induced a potent loss of expression of the low-affinity IgG Fc receptor CD16 on the cell surface. Notably, VZV infection of NK cells upregulated surface expression of chemokine receptors associated with trafficking to the skin –a crucial site in VZV disease where highly infectious lesions develop. We demonstrate that VZV actively manipulates the NK cell phenotype through productive infection, and propose a potential role for NK cells in VZV pathogenesis.

Varicella zoster virus (VZV) is a pervasive pathogen, causing chickenpox during primary infection and shingles when the virus reactivates from latency. VZV is therefore a lifelong infection for humans, warranting investigation of how this virus interacts with the immune system. One of the first immune cells to respond to viral infection are natural killer (NK) cells, yet little is known about how VZV interacts with NK cells. We demonstrate for the first time that VZV infects human blood NK cells and can use them to pass on infection to other cells in culture. Furthermore, VZV displays a predilection for infecting mature NK cells, and amplifies expression of receptors that would promote trafficking to the skin– the site of highly infectious lesions during chickenpox and shingles. Our findings suggest a role for NK cells in VZV disease and enhances our understanding of how lifelong infections interact with the human immune system.

Emerging Concepts of Adaptive Immunity in Leprosy

Leprosy is a chronic intracellular infection caused by the acid-fast bacillus, Mycobacterium leprae. The disease chiefly affects the skin, peripheral nerves, mucosa of the upper respiratory tract, and the eyes. The damage to peripheral nerves results in sensory and motor impairment with characteristic deformities and disability. Presently, the disease remains concentrated in resource-poor countries in tropical and warm temperate regions with the largest number of cases reported from India. Even though innate immunity influences the clinical manifestation of the disease, it is the components of adaptive immune system which seem to tightly correlate with the characteristic spectrum of leprosy. M. leprae-specific T cell anergy with bacillary dissemination is the defining feature of lepromatous leprosy (LL) patients in contrast to tuberculoid leprosy (TT) patients, which is characterized by strong Th1-type cell response with localized lesions. Generation of Th1/Th2-like effector cells, however, cannot wholly explain the polarized state of immunity in leprosy. A comprehensive understanding of the role of various regulatory T cells, such as Treg and natural killer T cells, in deciding the polarized state of T cell immunity is crucial. Interaction of these T cell subsets with effector T cells like Th1 (IFN-γ dominant), Th2 (interluekin-4 dominant), and Th17 (IL-17+) cells through various regulatory cytokines and molecules (programmed death-1/programmed death ligand-1) may constitute key events in dictating the state of immune polarization, thus controlling the clinical manifestation. Studying these important components of the adaptive immune system in leprosy patients is essential for better understanding of immune function, correlate(s) the immunity and mechanism(s) of its containment.

Diminished Frequency of Menstrual and Peripheral Blood NKT-Like Cells in Patients With Unexplained Recurrent Spontaneous Abortion and Infertile Women

Systemic monitoring of immune system may not precisely outline the local immune status in the uterus. This survey is a continuation of our previous studies on potential usefulness of menstrual blood (MB) immunophenotyping as a tool for investigation of immunological disturbances in pregnancy-related disorders. Peripheral blood (PB) and MB from healthy fertile (n = 15), unexplained recurrent spontaneous abortion (URSA; n = 15), and unexplained infertile women (n = 8) were collected simultaneously in the second day of their menstrual cycle and frequency of natural killer T (NKT)-like cell subpopulations were assessed by flow cytometry. Menstrual blood of all experimental groups contained higher percentage of TCRαβ⁺, CD45RO⁺, and CD16^- NKT-like cells compared to corresponding PB. Frequency of MB NKT-like cells in unexplained infertile participants was lower than fertile and URSA groups. Compared to normal participants, patients with URSA had lower frequency of PB TCRαβ⁺ and higher CD16⁺, while in infertile woman frequencies of PB CD45RO⁺, CD45RO^-, CD16^-, IL17⁺, and MB CD45RO⁺ NKT-like cells were lower. Although, PB and MB seemingly have the same histological nature, our results showed that MB contained different composition of NKT-like subsets with different cytokine profiles and could be viewed as one potential biological sample for evaluation of patients with infertility and URSA.

Human blood MAIT cell subsets defined using MR1 tetramers

Mucosal‐associated invariant T (MAIT) cells represent up to 10% of circulating human T cells. They are usually defined using combinations of non‐lineage‐specific (surrogate) markers such as anti‐TRAV1‐2, CD161, IL‐18Rα and CD26. The development of MR1‐Ag tetramers now permits the specific identification of MAIT cells based on T‐cell receptor specificity. Here, we compare these approaches for identifying MAIT cells and show that surrogate markers are not always accurate in identifying these cells, particularly the CD4⁺ fraction. Moreover, while all MAIT cell subsets produced comparable levels of IFNγ, TNF and IL‐17A, the CD4⁺ population produced more IL‐2 than the other subsets. In a human ontogeny study, we show that the frequencies of most MR1 tetramer⁺ MAIT cells, with the exception of CD4⁺ MAIT cells, increased from birth to about 25 years of age and declined thereafter. We also demonstrate a positive association between the frequency of MAIT cells and other unconventional T cells including Natural Killer T (NKT) cells and Vδ2⁺ γδ T cells. Accordingly, this study demonstrates that MAIT cells are phenotypically and functionally diverse, that surrogate markers may not reliably identify all of these cells, and that their numbers are regulated in an age‐dependent manner and correlate with NKT and Vδ2⁺ γδ T cells.

CD1d-Restricted Type II NKT Cells Reactive With Endogenous Hydrophobic Peptides

NKT cells belong to a distinct subset of T cells that recognize hydrophobic antigens presented by major histocompatibility complex class I-like molecules, such as CD1d. Because NKT cells stimulated by antigens can activate or suppress other immunocompetent cells through an immediate production of a large amount of cytokines, they are regarded as immunological modulators. CD1d-restricted NKT cells are classified into two subsets, namely, type I and type II. CD1d-restricted type I NKT cells express invariant T cell receptors (TCRs) and react with lipid antigens, including the marine sponge-derived glycolipid α-galactosylceramide. On the contrary, CD1d-restricted type II NKT cells recognize a wide variety of antigens, including glycolipids, phospholipids, and hydrophobic peptides, by their diverse TCRs. In this review, we focus particularly on CD1d-restricted type II NKT cells that recognize endogenous hydrophobic peptides presented by CD1d. Previous studies have demonstrated that CD1d-restricted type I NKT cells usually act as pro-inflammatory cells but sometimes behave as anti-inflammatory cells. It has been also demonstrated that CD1d-restricted type II NKT cells play opposite roles to CD1d-restricted type I NKT cells; thus, they function as anti-inflammatory or pro-inflammatory cells depending on the situation. In line with this, CD1d-restricted type II NKT cells that recognize type II collagen peptide have been demonstrated to act as anti-inflammatory cells in diverse inflammation-induction models in mice, whereas pro-inflammatory CD1d-restricted type II NKT cells reactive with sterol carrier protein 2 peptide have been demonstrated to be involved in the development of small vessel vasculitis in rats.