T Cell Receptor Expression Timing and Signal Strength in the Functional Differentiation of Invariant Natural Killer T Cells

Understanding cervical cancer at single-cell resolution

Cervical cancer is now the fourth most prevalent malignancy in women worldwide, representing a tremendous burden of cancer. The heterogeneity of complex tumor ecosystem impacts tumorigenesis, malignant progression, and response to treatment; thus, a thorough understanding of the tumor ecosystem is vital for enhancing the prognosis of patients with cervical cancer. The rapid development and widespread use of single-cell sequencing have generated a new paradigm of cancer research, providing a comprehensive and in-depth understanding of cancers. In this review, we give an overview of the recent advances made by leveraging single-cell sequencing studies in the dissection of cervical cancer ecosystem heterogeneity. We highlight the evolution of the cervical cancer ecosystem during tumor initiation, progression, and treatment. High-resolution dissection of cervical cancer at the single-cell level has the potential to drive the development of targeted therapies and enable the realization of personalized medicine.

Ru(bpy)3 2+ -Enabled Cell-Surface Photocatalytic Proximity Labeling toward More Efficient Capture of Physically Interacting Cells

Intercellular proximity labeling has emerged as a promising approach to enable the study of cell-cell interactions (CCIs), but the efficiency of current platforms is limited. Here, we use Ru(bpy)3 2+ to construct an efficient photocatalytic proximity labeling (PPL) system on the cell surface that allows the highly discriminative CCI detection with spatiotemporal resolution. Through the mechanism study and quantitative characterization on living cells, we demonstrate that the singlet-oxygen (1 O2 ) mechanism is more efficient and specific than the single electron transfer (SET) mechanism in Ru-mediated PPL. Ru(bpy)3 2+ catalysts with different cell-anchoring moieties are prepared to facilitate the catalyst loading on primary cells. Finally, based on this system, we develop a "live" T cell receptor (TCR) multimer with TCR-T cells that could sensitively identify and discriminate cells presenting antigens of different affinity, providing a powerful tool to better understand the heterogeneity of antigen presenting cells.

The RAG1 Ubiquitin Ligase Domain Stimulates Recombination of TCRβ and TCRα Genes and Influences Development of αβ T Cell Lineages

RAG1/RAG2 (RAG) endonuclease-mediated assembly of diverse lymphocyte Ag receptor genes by V(D)J recombination is critical for the development and immune function of T and B cells. The RAG1 protein contains a ubiquitin ligase domain that stabilizes RAG1 and stimulates RAG endonuclease activity in vitro. We report in this study that mice with a mutation that inactivates the Rag1 ubiquitin ligase in vitro exhibit decreased rearrangements and altered repertoires of TCRβ and TCRα genes in thymocytes and impaired thymocyte developmental transitions that require the assembly and selection of functional TCRβ and/or TCRα genes. These Rag1 mutant mice present diminished positive selection and superantigen-mediated negative selection of conventional αβ T cells, decreased genesis of invariant NK T lineage αβ T cells, and mature CD4+ αβ T cells with elevated autoimmune potential. Our findings reveal that the Rag1 ubiquitin ligase domain functions in vivo to stimulate TCRβ and TCRα gene recombination and influence differentiation of αβ T lineage cells, thereby establishing replete diversity of αβ TCRs and populations of αβ T cells while restraining generation of potentially autoreactive conventional αβ T cells.

Alteration of circulating unconventional T cells in cerebral ischemia: an observational study

Immune reactions provoked by cerebral ischemia play crucial roles in the pathogenesis of brain damage and contribute to tissue regeneration processes. While functions of many immune cell types in post-ischemic inflammation have been well studied in experimental stroke, the exact roles played by unconventional T cells in pathogenesis of the clinical stroke remain to be precisely determined. In the present study, we investigated the frequencies and absolute cell numbers of peripheral blood T lymphocyte subpopulations including those of invariant natural killer T (iNKT) cells, CD3⁺CD56⁺ NKT-like (NKTL) cells, and γδ T cells from patients with acute cerebral infarction (ACI), chronic cerebrovascular disease (CCD) or chronic cerebral circulation insufficiency (CCI) by flow cytometry, and analyzed their association with the disease severity and the clinical outcome. We observed significantly reduced cell numbers of circulating iNKT cells, NKTL cells and γδ T cells in cerebral ischemia patients as compared with the healthy controls. Of note, we also demonstrated that numbers of peripheral blood iNKT and γδ T cells are significantly reduced in patients with ACI when compared among different cerebral ischemia patient groups. Moreover, the reduced number of iNKT cells is significantly associated with the disease severity and recovery in cerebral ischemia patients. Our results demonstrate for the first time the reduction of peripheral blood NKTL, iNKT and γδ T cells in patients with the cerebral ischemia, and particularly reduced iNKT and γδ T cells in the acute phase. The reduction of iNKT cells seems to be significantly associated with the disease severity and recovery. We hope that our findings might lead to the identification of predictive and prognostic values of human peripheral unconventional T cell subsets in the cerebral ischemia.

Type 2 and Type 17 Invariant Natural Killer T Cells Contribute to Local Eosinophilic and Neutrophilic Inflammation and Their Function Is Regulated by Mucosal Microenvironment in Nasal Polyps

Chronic rhinosinusitis with nasal polyps (CRSwNP) is characterized by heterogeneous inflammatory endotypes of unknown etiology. Invariant natural killer T (iNKT) cells are multifunctional innate T cells that exhibit Th1-, Th2-, and Th17-like characteristics. We investigated functional relationships between iNKT cells and inflammatory subtypes of CRSwNP. Eighty patients with CRSwNP and thirty-two control subjects were recruited in this study. Flow cytometry was used to analyze the frequencies and functions of iNKT cells and their subsets in peripheral blood mononuclear cells (PBMCs) and tissues. Polyp tissue homogenates were used to study the multifunctionality of iNKT cells. iNKT cells were significantly increased in polyps (0.41%) than in control mucosa (0.12%). iNKT cells were determined in the paucigranunlocytic (n=20), eosinophilic (n=22), neutrophilic (n=23), and mixed granulocytic (n=13) phenotypes of CRSwNP. The percentages of iNKT cells and HLA-DR⁺PD-1⁺ subsets were lower in eosinophilic or mixed granulocytic polyps than those of other phenotypes. iNKT cells and subsets were enriched in polyp tissues than in matched PBMCs. The evaluation of surface markers, transcription factors, and signature cytokines indicated that the frequencies of iNKT2 and iNKT17 subsets were significantly increased in eosinophilic and neutrophilic polyps, respectively, than in the paucigranulocytic group. Moreover, the production of type 2 (partially dependent on IL-7) and type 17 (partially dependent on IL-23) iNKT cells could be stimulated by eosinophilic and neutrophilic homogenates, respectively. Our study revealed that type 2 and type 17 iNKT cells were involved in eosinophilic and neutrophilic inflammation, respectively, in CRSwNP, while different inflammatory microenvironments could modulate the functions of iNKT cells, suggesting a role of iNKT cells in feedback mechanisms and local inflammation.

Protein abundance of the cytokine receptor γc controls the thymic generation of innate-like T cells

Innate-like T (iT) cells comprise a population of immunoregulatory T cells whose effector function is imposed during their development in the thymus to provide protective immunity prior to antigen encounter. The molecular mechanism that drives the generation of iT cells remains unclear. Here, we report that the cytokine receptor γc plays a previously unappreciated role for thymic iT cells by controlling their cellular abundance, lineage commitment, and subset differentiation. As such, γc overexpression on thymocytes dramatically altered iT cell generation in the thymus, as it skewed the subset composition of invariant NKT (iNKT) cells and promoted the generation of IFNγ-producing innate CD8 T cells. Mechanistically, we found that the γc-STAT6 axis drives the differentiation of IL-4-producing iNKT cells, which in turn induced the generation of innate CD8 T cells. Collectively, these results reveal a cytokine-driven circuity of thymic iT cell differentiation that is controlled by the abundance of γc proteins.

Brief homogeneous TCR signals instruct common iNKT progenitors whose effector diversification is characterized by subsequent cytokine signaling

Innate-like T cell populations expressing conserved TCRs play critical roles in immunity through diverse developmentally acquired effector functions. Focusing on the prototypical lineage of invariant natural killer T (iNKT) cells, we sought to dissect the mechanisms and timing of fate decisions and functional effector differentiation. Utilizing induced expression of the semi-invariant NKT cell TCR on double positive thymocytes, an initially highly synchronous wave of iNKT cell development was triggered by brief homogeneous TCR signaling. After reaching a uniform progenitor state characterized by IL-4 production potential and proliferation, effector subsets emerged simultaneously, but then diverged toward different fates. While NKT17 specification was quickly completed, NKT1 cells slowly differentiated and expanded. NKT2 cells resembled maturing progenitors, which gradually diminished in numbers. Thus, iNKT subset diversification occurs in dividing progenitor cells without acute TCR input but utilizes multiple active cytokine signaling pathways. These data imply a two-step model of iNKT effector differentiation.

The Mechanism of Stimulating and Mobilizing the Immune System Enhancing the Anti-Tumor Immunity

Cancer immunotherapy is a kind of therapy that can control and eliminate tumors by restarting and maintaining the tumor-immune cycle and restoring the body's normal anti-tumor immune response. Although immunotherapy has great potential, it is currently only applicable to patients with certain types of tumors, such as melanoma, lung cancer, and cancer with high mutation load and microsatellite instability, and even in these types of tumors, immunotherapy is not effective for all patients. In order to enhance the effectiveness of tumor immunotherapy, this article reviews the research progress of tumor microenvironment immunotherapy, and studies the mechanism of stimulating and mobilizing immune system to enhance anti-tumor immunity. In this review, we focused on immunotherapy against tumor microenvironment (TME) and discussed the important research progress. TME is the environment for the survival and development of tumor cells, which is composed of cell components and non-cell components; immunotherapy for TME by stimulating or mobilizing the immune system of the body, enhancing the anti-tumor immunity. The checkpoint inhibitors can effectively block the inhibitory immunoregulation, indirectly strengthen the anti-tumor immune response and improve the effect of immunotherapy. We also found the checkpoint inhibitors have brought great changes to the treatment model of advanced tumors, but the clinical treatment results show great individual differences. Based on the close attention to the future development trend of immunotherapy, this study summarized the latest progress of immunotherapy and pointed out a new direction. To study the mechanism of stimulating and mobilizing the immune system to enhance anti-tumor immunity can provide new opportunities for cancer treatment, expand the clinical application scope and effective population of cancer immunotherapy, and improve the survival rate of cancer patients.

The Timing and Abundance of IL-2Rβ (CD122) Expression Control Thymic iNKT Cell Generation and NKT1 Subset Differentiation

Invariant NKT (iNKT) cells are thymus-generated innate-like T cells, comprised of three distinct subsets with divergent effector functions. The molecular mechanism that drives the lineage trifurcation of immature iNKT cells into the NKT1, NKT2, and NKT17 subsets remains a controversial issue that remains to be resolved. Because cytokine receptor signaling is necessary for iNKT cell generation, cytokines are proposed to contribute to iNKT subset differentiation also. However, the precise roles and requirements of cytokines in these processes are not fully understood. Here, we show that IL-2Rβ, a nonredundant component of the IL-15 receptor complex, plays a critical role in both the development and differentiation of thymic iNKT cells. While the induction of IL-2Rβ expression on postselection thymocytes is necessary to drive the generation of iNKT cells, surprisingly, premature IL-2Rβ expression on immature iNKT cells was detrimental to their development. Moreover, while IL-2Rβ is necessary for NKT1 generation, paradoxically, we found that the increased abundance of IL-2Rβ suppressed NKT1 generation without affecting NKT2 and NKT17 cell differentiation. Thus, the timing and abundance of IL-2Rβ expression control iNKT lineage fate and development, thereby establishing cytokine receptor expression as a critical regulator of thymic iNKT cell differentiation.

Classical MHC expression by DP thymocytes impairs the selection of non-classical MHC restricted innate-like T cells

Conventional T cells are selected by peptide-MHC expressed by cortical epithelial cells in the thymus, and not by cortical thymocytes themselves that do not express MHC I or MHC II. Instead, cortical thymocytes express non-peptide presenting MHC molecules like CD1d and MR1, and promote the selection of PLZF⁺ iNKT and MAIT cells, respectively. Here, we report an inducible class-I transactivator mouse that enables the expression of peptide presenting MHC I molecules in different cell types. We show that MHC I expression in DP thymocytes leads to expansion of peptide specific PLZF⁺ innate-like (PIL) T cells. Akin to iNKT cells, PIL T cells differentiate into three functional effector subsets in the thymus, and are dependent on SAP signaling. We demonstrate that PIL and NKT cells compete for a narrow niche, suggesting that the absence of peptide-MHC on DP thymocytes facilitates selection of non-peptide specific lymphocytes.

Serpinb1a Is Dispensable for the Development and Cytokine Response of Invariant Natural Killer T Cell Subsets

Invariant natural killer T (iNKT) cells are innate-like T lymphocytes. They quickly respond to antigenic stimulation by producing copious amounts of cytokines and chemokines. iNKT precursors differentiate into three subsets iNKT1, iNKT2, and iNKT17 with specific cytokine production signatures. While key transcription factors drive subset differentiation, factors that regulate iNKT subset homeostasis remain incompletely defined. Transcriptomic analyses of thymic iNKT subsets indicate that Serpinb1a is one of the most specific transcripts for iNKT17 cells suggesting that iNKT cell maintenance and function may be regulated by Serpinb1a. Serpinb1a is a major survival factor in neutrophils and prevents cell death in a cell-autonomous manner. It also controls inflammation in models of bacterial and viral infection as well as in LPS-driven inflammation. Here, we examined the iNKT subsets in neutropenic Serpinb1a^−/− mice as well as in Serpinb1a^−/− mice with normal neutrophil counts due to transgenic re-expression of SERPINB1 in neutrophils. In steady state, we found no significant effect of Serpinb1a-deficiency on the proliferation and numbers of iNKT subsets in thymus, lymph nodes, lung, liver and spleen. Following systemic activation with α-galactosylceramide, the prototypic glycolipid agonist of iNKT cells, we observed similar serum levels of IFN-γ and IL-4 between genotypes. Moreover, splenic dendritic cells showed normal upregulation of maturation markers following iNKT cell activation with α-galactosylceramide. Finally, lung instillation of α-galactosylceramide induced a similar recruitment of neutrophils and production of iNKT-derived cytokines IL-17, IFN-γ, and IL-4 in wild-type and Serpinb1a^−/− mice. Taken together, our results indicate that Serpinb1a, while dominantly expressed in iNKT17 cells, is not essential for iNKT cell homeostasis, subset differentiation and cytokine release.

Invariant Natural Killer T cells resilience to paradoxical sleep deprivation-associated stress

Although several studies demonstrate that stressful situations, such as sleep disturbances, negatively impact the innate and adaptive arms of the immune system, their influence on invariant Natural Killer T (iNKT) cells remains unclear. iNKT cells are CD1d-restricted innate T cells that recognize glycolipid antigens and rapidly produce polarizing cytokines being key players in several immune responses, and a potential target for immunotherapy. iNKT cells differ in several aspects from conventional T lymphocytes, including a unique dependence on CD1d-expressing double-positive (DP) thymocytes for intrathymic maturation. As a consequence of stress, DP thymocytes undergo glucocorticoid-induced apoptosis, which might compromise iNKT developmental pathway. Therefore, we used a paradoxical sleep deprivation (SD) model to determine the impact of sleep disturbance on iNKT cell biology. After 72 h of SD, C57Bl/6 mice exhibited a significant increase in systemic glucocorticoid levels and thymus atrophy. Despite marked decrease in the number of DP thymocytes, the ratio CD1d⁺/CD1d^- was higher in SD mice, and the number of thymic iNKT cells remained unaltered, suggesting that SD did not compromise the iNKT developmental pathway. In contrast, SD reduced hepatic IFN-γ, but not, IL-4-producing iNKT cells, without further effect in the spleen. Despite this fact, SD did not affect stimulation of IFN-γ production by iNKT cells, or cytokine release, in response to α-galactosylceramide, a specific antigen. Furthermore, although SD impaired splenic NK cells activity against tumor cells, it did not affect iNKT cell-specific cytotoxicity. Thus, our study shows that SD-induced stress did not impair the iNKT cells' responses to a cognate antigen.

EZH2 function in immune cell development

The polycomb repressive complex 2 (PRC2) consists of three core components EZH2, SUZ12 and EED. EZH2 catalyzes the methylation of lysine 27 of histone H3, a modification associated with gene silencing. Through gene duplication higher vertebrate genomes also encode a second partially redundant methyltransferase, EZH1. Within the mammalian immune system most research has concentrated on EZH2 which is expressed predominantly in proliferating cells. EZH2 and other PRC2 components are required for hematopoietic stem cell function and lymphocyte development, at least in part by repressing cell cycle inhibitors. At later stages of immune cell differentiation, EZH2 plays essential roles in humoral and cell-mediated adaptive immunity, as well as the maintenance of immune homeostasis. EZH2 is often overactive in cancers, through both gain-of-function mutations and over-expression, an observation that has led to the development and clinical testing of specific EZH2 inhibitors. Such inhibitors may also be of use in inflammatory and autoimmune settings, as EZH2 inhibition dampens the immune response. Here, we will review the current state of understanding of the roles for EZH2, and PRC2 more generally, in the development and function of the immune system.

Nur77 controls tolerance induction, terminal differentiation, and effector functions in semi-invariant natural killer T cells

Semi-invariant natural killer T (iNKT) cells are self-reactive lymphocytes, yet how this lineage attains self-tolerance remains unknown. iNKT cells constitutively express high levels of Nr4a1-encoded Nur77, a transcription factor that integrates signal strength downstream of the T cell receptor (TCR) within activated thymocytes and peripheral T cells. The function of Nur77 in iNKT cells is unknown. Here we report that sustained Nur77 overexpression (Nur77tg) in mouse thymocytes abrogates iNKT cell development. Introgression of a rearranged Vα14-Jα18 TCR-α chain gene into the Nur77tg (Nur77tg;Vα14tg) mouse rescued iNKT cell development up to the early precursor stage, stage 0. iNKT cells in bone marrow chimeras that reconstituted thymic cellularity developed beyond stage 0 precursors and yielded IL-4-producing NKT2 cell subset but not IFN-γ-producing NKT1 cell subset. Nonetheless, the developing thymic iNKT cells that emerged in these chimeras expressed the exhaustion marker PD1 and responded poorly to a strong glycolipid agonist. Thus, Nur77 integrates signals emanating from the TCR to control thymic iNKT cell tolerance induction, terminal differentiation, and effector functions.

Reduction of Peripheral Blood iNKT and γδT Cells in Patients With Parkinson's Disease: An Observational Study

Objective: To investigate the frequencies and numbers of invariant natural killer T (iNKT) cells and γδT cells in the peripheral blood of patients with the Parkinson's disease (PD), and to examine their association with the PD severity.

Methods: Peripheral blood samples from 47 PD patients (PD group) and 47 age-matched healthy control subjects (HC group) were collected. The frequencies and the absolute cell numbers were analyzed by flow cytometry. Mann-Whitney U-test was used to test the difference between two groups, where P < 0.05 was considered as significant. An ordered probit regression method was used to examine the association of the iNKT and γδT cells with severity of PD.

Results: Patients in the PD group showed significantly lower frequencies (0.039 vs. 0.139%; P = 0) and cell counts (308/mL vs. 1,371/mL; P = 0) of iNKT cells compared to the HC group. Moreover, the percentages and absolute numbers of γδT cells were significantly decreased in the PD group compared to the HC group (3.69 vs. 7.95% and 30/μL vs. 66/μL; P = 0). The iNKT cells were significantly reduced in PD patients with higher Unified Parkinson's Disease Rating Scale (UPDRS) scores or cognitive decline.

Conclusions: Cell frequencies and absolute numbers of iNKT cells and γδT cells are significantly reduced in the peripheral blood samples of PD patients. Patients with high UPDRS scores or cognitive decline also showed significant reduction of iNKT cells. Our results suggest that iNKT cells and γδT cells may contribute to the development of PD.

Recent advances in iNKT cell development

Recent studies suggest that murine invariant natural killer T (iNKT) cell development culminates in three terminally differentiated iNKT cell subsets denoted as NKT1, 2, and 17 cells. Although these studies corroborate the significance of the subset division model, less is known about the factors driving subset commitment in iNKT cell progenitors. In this review, we discuss the latest findings in iNKT cell development, focusing in particular on how T-cell receptor signal strength steers iNKT cell progenitors toward specific subsets and how early progenitor cells can be identified. In addition, we will discuss the essential factors for their sustenance and functionality. A picture is emerging wherein the majority of thymic iNKT cells are mature effector cells retained in the organ rather than developing precursors.

Przewalcyrones A–F, epoxychromene-containing polycyclic polyprenylated acylphloroglucinols with immunosuppressive activity from Hypericum przewalskii Maxim

Chemical investigation of Hypericum przewalskii Maxim. resulted in the identification of six new epoxychromene-containing polycyclic polyprenylated acylphloroglucinols with potential immunosuppressive activity.