Thymocytes Research Articles

T-Switch: A specificity-based engineering platform for developing safe and effective Tcell therapeutics.

Many promising targets for adoptive Tcell therapy (ACT) are self-antigens, but self-reactive Tcells are generally eliminated during thymic selection or diverted to regulatory phenotypes. To bypass Tcell tolerance and obtain potent and safe Tcell therapeutics, we developed T-Switch, an invitro Tcell receptor (TCR) engineering platform for the creation, modification, and comprehensive profiling of TCRs that can target self-antigens. T-Switch first expands Tcells that recognize a "foreign" peptide closely related to a self-antigen. The fine specificity of the TCR is then modified by directed evolution of the peptide binding region to switch its specificity to the self-antigen of interest. We applied T-Switch to engineer synthetic TCRs reactive to a tumor-associated self-antigen, validated the safety and efficacy of this approach, and detected no off-target recognition as measured against the human proteome. Thus, T-Switch represents a resource for the creation of collections of highly sensitive synthetic TCRs for Tcell-based immunotherapies.

A spatial human thymus cell atlas mapped to a continuous tissue axis

T cells develop from circulating precursor cells, which enter the thymus and migrate through specialized subcompartments that support their maturation and selection1. In humans, this process starts in early fetal development and is highly active until thymic involution in adolescence. To map the microanatomical underpinnings of this process in pre- and early postnatal stages, we established a quantitative morphological framework for the thymus—the Cortico-Medullary Axis—and used it to perform a spatially resolved analysis. Here, by applying this framework to a curated multimodal single-cell atlas, spatial transcriptomics and high-resolution multiplex imaging data, we demonstrate establishment of the lobular cytokine network, canonical thymocyte trajectories and thymic epithelial cell distributions by the beginning of the the second trimester of fetal development. We pinpoint tissue niches of thymic epithelial cell progenitors and distinct subtypes associated with Hassall’s corpuscles and identify divergence in the timing of medullary entry between CD4 and CD8 T cell lineages. These findings provide a basis for a detailed understanding of T lymphocyte development and are complemented with a holistic toolkit for cross-platform imaging data analysis, annotation and OrganAxis construction (TissueTag), which can be applied to any tissue.

Neural Crest-Derived Mesenchymal Cells Support Thymic Reconstitution After Lethal Irradiation.

Reconstitution of the thymus is essential for assessing thymic function following injury. However, the currently employed cytoreductive regimes unvaryingly affect the thymic microenvironment, thereby impeding the recovery of T lymphopoiesis. The thymic stroma is composed of epithelial and mesenchymal cells. Thymic mesenchymal cells originate from the Neural crest (NC) and mesoderm and contribute to thymus organogenesis, yet their role in thymic regeneration is unclear. In this study, using transgenic mice expressing NC-specific Cre and Cre-driven DT receptors, we investigated the role of NC-derived mesenchymal cells in thymic regeneration following total body irradiation. We revealed that NC-derived mesenchymal cells have reduced susceptibility to irradiation and induce the upregulation of hematopoietic factors that promote thymus regeneration after irradiation. Additionally, using adult thymic organ culture and renal capsule transplantation, depletion of NC-derived mesenchymal cells resulted in a reduction of DN1-like early T-cell progenitors (ETP) and impaired thymic regeneration. Furthermore, among the numerous factors upregulated by NC-derived mesenchymal cells, Periostin and Flt3L were markedly increased after irradiation and promoted abundance of DN1-like ETPs during thymic reconstitution. Collectively, these findings highlight the importance of NC-derived mesenchymal cells in thymic regeneration.

Early-life thymectomy leads to an increase of granzyme-producing γδ T cells in children with congenital heart disease

Congenital heart disease (CHD) is the most common birth defect in newborns, often requiring cardiac surgery with concomitant thymectomy that is known to increase disease susceptibility later in life. Studies of γδ T cells, which are one of the dominant T cells in the early fetal human thymus, are rare. Here, we provide a comprehensive analysis of the γδ T cell compartment via flow cytometry and next-generation sequencing in children and infants with CHD, who underwent cardiac surgery shortly after birth. A perturbation of the γδ T cell repertoire is evident, and Vδ1 T cell numbers are reduced. However, those cells that are present, do retain cytotoxicity. In contrast, GZMA+CD28+CD161hi innate effector Vγ9Vδ2 T cells are found in higher proportions. TCR-seq identifies an increase in TRDJ3+ γδ T cell clones in children with CHD, but not in a confirmatory group of neonates prior to CHD surgery, which overall points to a persistence of fetal-derived effector γδ T cells in children with CHD.

Molecular mimicry as a mechanism of viral immune evasion and autoimmunity

Mimicry of host protein structures, or ‘molecular mimicry’, is a common mechanism employed by viruses to evade the host’s immune system. Short linear amino acid (AA) molecular mimics can elicit cross-reactive antibodies and T cells from the host, but the prevalence of such mimics throughout the human virome has not been fully explored. Here we evaluate 134 human-infecting viruses and find significant usage of linear mimicry across the virome, particularly those in the Herpesviridae and Poxviridae families. Furthermore, host proteins related to cellular replication and inflammation, autosomes, the X chromosome, and thymic cells are enriched as viral mimicry targets. Finally, we find that short linear mimicry from Epstein-Barr virus (EBV) is higher in auto-antibodies found in patients with multiple sclerosis than previously appreciated. Our results thus hint that human-infecting viruses leverage mimicry in the course of their infection, and that such mimicry may contribute to autoimmunity, thereby prompting potential targets for therapies.

The kisspeptin effects on the thymic regulatory cell compositions (Th17, Treg, iNKT) <i>in vitro</i>

The peptide hormone kisspeptin, produced by neurons of the hypothalamus anterior zone, is a key regulator of the gonadostat formation and reproductive function, and has immunoregulatory activity. During pregnancy, kisspeptin is produced by the placenta, presents in the peripheral blood and affects on immune cells that express specific receptors for the hormone, including thymus cells. However, the kisspeptin effects on thymopoiesis during pregnancy have not been studied. The purpose of the work was to study the kisspeptin effect on the thymic regulatory cell composition in vitro. Thymocytes were cultured for 72 hours with kisspeptin at a concentration (9.6 pM) characterizing its maximum level in the peripheral blood during pregnancy, in the presence of CD3/CD28-activating particles and further assessed the regulatory cell composition and Ki-67 and Bcl-2 expression by flow cytometry. The percentage of T regulatory lymphocytes (Treg) was assessed as the percentage of CD4+CD25+FoxP3+ cells; T helper cells producing interleukin17 (Th17), as a percentage of CD4+IL-17A+RORγt+ cells; invariant T lymphocytes with natural killer functions(iNKT), as a percentage of CD3hiVa24Ja18+ cells in thymocyte culture. Dexamethasone (10-6M) was added to induce apoptosis. The effect of kisspeptin-primed thymic plasmacytoid dendritic cells (pDCs) on the regulatory cell composition (Th17, Treg, iNKT) in thymocyte culture was assessed. Thymic pDCs isolated by immunomagnetic separation were cultured for 24 hours with kisspeptin, and then intact autologous thymocytes were added in a ratio of 1:10 and cultured for another 72 hours. The thymocyte incubation of with kisspeptin did not affect the Tregs, iNKT and Th17 percentage in vitro, as well as the expression of Ki-67 and Bcl-2 in these cells. Under dexamethasone influence, the Bcl-2+Th17 percentage in thymocyte cultures with kisspeptin was increased. The Th17 percentage was increased in cultures of kisspeptin-primed pDCs with thymocytes, while the Treg and iNKT number did not change. It can be concluded that kisspeptin has regulatory effects on the Th17 percentage in thymocyte culture in vitro, mediating its effects by influencing thymic pDCs. And kisspeptin acted directly on thymocytes, increases the resistance of thymic Th17 to dexamethasone-induced apoptosis. The obtained results expand our understanding of the hormonal regulation of regulatory cell balance during pregnancy.

Developmental trajectory of unconventional T cells of the cynomolgus macaque thymus

As nonhuman primates are immunologically the closest model to humans, a comprehensive understanding of T-cell development in these species is crucial. However, the differentiation pathways in which thymocytes participate, along with their heterogeneity, remain poorly characterized. Using single-cell RNA sequencing, we thoroughly profiled the development of various T-cell lineages in the juvenile cynomolgus monkey thymus, identifying and characterizing 12 distinct thymic cell states or types. Interestingly, we identified two unexpected cell types, an agonist-selected and a memory-like cell population. The agonist-selected cell population expressed genes associated with strong TCR signaling, such as PDCD1, CD5, NFKBID, NFATC1, BCL2L11, and NR4A1 but exhibiting significantly higher PDCD1 expression compared with cells following the conventional developmental pathway. Additionally, we identified a substantial number of memory-like cell populations characterized by high CXCR3 and EOMES expression. Notably, this population also highly expressed the effector-associated markers, GZMK, NKG7, and GNLY, as well as the innate cell-associated markers, ZBTB16, TYROBP, KLRB1, KLRC1, and NCR3. The EOMES + memory-like cell population expressed highly PDCD1, indicating the presence of an agonist-selection footprint. Our findings provide insights into the agonist-selection pathway that allows self-reactive thymocytes to survive thymic selections and differentiate into various unconventional T-cell lineages.

Comparison of the cytotoxic impact of samsum ant venom (Brachyponera sennaarensis) administration routes on quantitative histological analysis of thymus

Samsum (Brachyponera sennaarensis) ant venom contains several peptides that have an aggressive impact on the architecture of the internal organs including the thymus. The objective of this study was to evaluate the effectiveness of venom with various doses as a toxin insult by examining the histological alterations and measurable biochemical parameters in the thymus. Forty Wistar albino rats separated into seven groups were used.Data demonstrated statistically significant hyperplasia in the cellular density, shrinkage in cortical thickness, and medullary area in the venom- intraperitoneally treated group compared to the − orally treated group. Additionally, there was a prominent increase in apoptotic cells TGB, the density of lesions, and hemorrhagic cysts effects of the venom on thymic cells. There was a notable higher intensity of pathological features in the thymus.Results validated the role of SAV in the general thymic atrophy in the histological structure of thymus tissues and acted as a carcinogenic agent. The structural analysis of the thymus revealed that a larger dosage of SAV produced a thymoma in the histoarchitecture. The differences between the low dose of SAV-treated groups orally and (IP) were not statistically significant in some analyses. In terms of the thymus tissue’s structure, the administration of a high dose of (450 µl) intraperitoneally had the worst impact on the health of the thymus.

The partitioning of TCR repertoires by thymic selection.

αβ T cells are critical components of the adaptive immune system; they maintain tissue and immune homeostasis during health, provide sterilizing immunity after pathogen infection, and are capable of eliminating transformed tumor cells. Fundamental to these distinct functions is the ligand specificity of the unique antigen receptor expressed on each mature T cell (TCR), which endows lymphocytes with the ability to behave in a cell-autonomous, disease context-specific manner. Clone-specific behavioral properties are initially established during T cell development when thymocytes use TCR recognition of major histocompatibility complex (MHC) and MHC-like ligands to instruct survival versus death and to differentiate into a plethora of inflammatory and regulatory T cell lineages. Here, we review the ligand specificity of the preselection thymocyte repertoire and argue that developmental stage-specific alterations in TCR signaling control cross-reactivity and foreign versus self-specificity of T cell sublineages.

Thymic Mimetic Cells: Ontogeny as Immunology.

Medullary thymic epithelial cells (mTECs) generate immunological self-tolerance by ectopically expressing peripheral-tissue antigens (PTAs) within the thymus to preview the peripheral self to maturing Tcells. Recent work, drawing inspiration from old histological observations, has shown that subtypes of mTECs, collectively termed mimetic cells, co-opt developmental programs from throughout the organism to express biologically coherent groups of PTAs. Here, we review key aspects of mimetic cells, especially as they relate to the larger contexts of molecular, cellular, developmental, and evolutionary biology. We highlight lineage-defining transcription factors as key regulators of mimetic cells and speculate as to what other factors, including Aire and the chromatin potential of mTECs, permit mimetic cell differentiation and function. Last, we consider what mimetic cells can teach us about not only the thymus but also other tissues.

Internal regulation between constitutively expressed T cell co-inhibitory receptors BTLA and CD5 and tolerance in recent thymic emigrants.

Immunologic self-tolerance involves signals from co-inhibitory receptors. Several T cell co-inhibitors, including PD-1, are expressed upon activation, whereas CD5 and BTLA are expressed constitutively. The relationship between constitutively expressed co-inhibitors and when they are needed is unknown. Deletion of Btla demonstrated BTLA regulates CD5 expression. Loss of BTLA signals, but not signalling by its ligand, HVEM, leads to increased CD5 expression. Higher CD5 expression set during thymic selection is associated with increased self-recognition, suggesting that BTLA might be needed early to establish self-tolerance. We found that BTLA and PD-1 were needed post-thymic selection in recent thymic emigrants (RTE). RTE lacking BTLA caused a CD4 T cell and MHC class II dependent multi-organ autoimmune disease. Together, our findings identify a negative regulatory pathway between two constitutively expressed co-inhibitors, calibrating their expression. Expression of constitutive and induced co-inhibitory receptors is needed early to establish tolerance in the periphery for RTE.

EP.14B.06 A Retrospective Multicenter Study Evaluating Experience of Perioperative Treatment for Thymic Squamous Cell Carcinoma

EP.14B.06 A Retrospective Multicenter Study Evaluating Experience of Perioperative Treatment for Thymic Squamous Cell Carcinoma

Analysis of CD3, CD68, CD163 and CK-19 expression in thymuses of neonatal children during infectious diseases

Objective: to identify the features of expression of immunohistochemical markers CD3, CD68, CD163 and CK-19 in thymus cells of neonatal children with enlarged thymus who died from infectious diseases. Material and methods. Autopsy material of children of early and late neonatal period (n=33) who died in the hospitals of Saratov city served as the material of the study. The causes of death of children were pneumonia (n=17), sepsis (n=16). Morphologic material was divided into 2 groups: Group 1 (comparison) — children whose thymus gland mass corresponded to the age norm (n=19); Group 2 (study group) — children whose thymus mass exceeded the age norm (n=14). The expression of the following markers was evaluated in the study: CD3, CD68, CD163 and CK-19. Results. As a result of the study, it was found that with increasing thymus mass in its cortical substance the proportion of CD3+ cells increase 2.7 times (p=0.009), the proportion of CD68+ cells increase almost threefold (p=0.009) CD163+ cells decreases by 10% (p=0.005), and CK-19 positive cells do not form a network. Conclusion. Increased thymus mass in children of early neonatal period with infectious diseases is accompanied by disturbances in the processes of migration and differentiation of lymphocytes.

An extremely rare case of thymic squamous cell carcinoma complicated with B3 thymoma and myasthenia gravis: a case report

BackgroundThymomas complicated with myasthenia gravis are conventionally treated during thoracic surgery. Particularly, invasive thymomas are resected alongside the surrounding organs. Here, we present a case where surgical and perioperative management was performed under the presumption of thymoma with myasthenia gravis. However, definitive pathology revealed the co-occurrence of B3 thymoma and thymic squamous cell carcinoma. This case highlights the unique presentation and exceptional rarity of thymomas that are complicated by myasthenia gravis and thymic carcinoma. Case presentationA 65-year-old female presented with eyelid ptosis at our hospital. Following a comprehensive examination, the patient was diagnosed with myasthenia gravis. Her computed tomography (CT) scan revealed an anterior mediastinal tumor suggestive of a thymoma, prompting a referral to the Department of Thoracic Surgery. Moreover, preoperative assessment could not definitively exclude pericardial invasion. She subsequently underwent an extended thymectomy via a longitudinal sternal incision. The tumor exhibited partial invasion of the pericardium, necessitating resection and reconstruction. Definitive pathological examination confirmed the co-occurrence of B3 thymoma and thymic squamous cell carcinoma. Positive lymph node metastasis classified the patient as stage IVa according to the Union for International Cancer Control (UICC) TNM Classification of Malignant Tumors, 8th Edition, and she was started on adjuvant radiotherapy postoperatively. Currently, the patient remains under observation, with follow-up CT scans showing no signs of recurrence.ConclusionsThis report describes an extremely rare case of thymoma complicated with myasthenia gravis and thymic squamous cell carcinoma.

S1PR1 mediates Th17 cell migration from the thymus to the skin in health and disease.

Th17 cells play crucial roles in host defense and the pathogenesis of autoimmune diseases in the skin. While their differentiation mechanisms have been extensively studied, the origin of skin Th17 cells remains unclear. In this study, we analyzed single-cell RNA-sequencing data and identify the presence of Th17 cells in the human thymus. Thymic Th17 cells were characterized by high expression levels of Sphingosine-1-Phosphate Receptor 1 (S1PR1), a receptor crucial for T cell egress from lymphoid tissues. In mice, Th17 cell-specific knockout of S1pr1 resulted in the accumulation of Th17 cells in the thymus and a corresponding decrease in their numbers in the skin. Th17 cells that accumulated in the thymus exhibited a lower IL-17A production capacity compared to those in the skin, indicating that the local environment in the skin is important for maintaining the Th17 cell phenotype. Additionally, using a murine psoriasis model, we demonstrated that Th17 cell-specific knockout of S1pr1 reduced their migration to the inflamed skin, thereby ameliorating disease progression. Collectively, our data suggest that S1PR1 mediates Th17 cell migration from the thymus to the skin, thereby modulating their functional engagement in both homeostatic and inflammatory conditions.

Antigen presentation for central tolerance induction.

The extent of central T cell tolerance is determined by the diversity of self-antigens that developing thymocytes 'see' on thymic antigen-presenting cells (APCs). Here, focusing on insights from the past decade, we review the functional adaptations of medullary thymic epithelial cells, thymic dendritic cells and thymic B cells for the purpose of tolerance induction. Their distinct cellular characteristics range from unconventional phenomena, such as promiscuous gene expression or mimicry of peripheral cell types, to strategic positioning in distinct microenvironments and divergent propensities to preferentially access endogenous or exogenous antigen pools. We also discuss how 'tonic' inflammatory signals in the thymic microenvironment may extend the intrathymically visible 'self' to include autoantigens that are otherwise associated with highly immunogenic peripheral environments.

TMPRSS2::ETS translocation in nonprostatic malignancies: an unexpected finding in thymic carcinoma and pulmonary adenocarcinoma.

TMPRSS2::ETS fusions occur in about half of the prostate adenocarcinomas and are generally considered characteristic and even diagnostic of this tumour. Despite this fact, the frequency of this fusion is not well established in other tumour types. Incidental identification of a TMPRSS2::ETV1 fusion in a thymic squamous cell carcinoma prompted us to assess 1758 solid tumours by next-generation sequencing panel for TMPRSS2::ETS fusions, including 1690 non-prostatic malignancies. In addition to 28 of the 68 prostatic adenocarcinomas, we identified TMPRRS2::ETS fusion in two non-prostatic tumours, where a prostatic adenocarcinoma could be confidently excluded. Besides the TMPRSS2::ETV1 fusion identified in the thymic carcinoma, we also observed TMPRSS2::ERG fusion in pulmonary adenocarcinoma. Both patients were male, which would support an androgen-driven background. Our findings suggest that although at a low frequency, TMPRSS2::ETS fusion may occur in non-prostatic tumours, and sole reliance on its identification can potentially result in erroneous diagnostic conclusions.

Streptococcus suis Induces Macrophage M1 Polarization and Pyroptosis.

Streptococcus suis is an important bacterial pathogen that affects the global pig industry. The immunosuppressive nature of S. suis infection is recognized, and our previous research has confirmed thymus atrophy with a large number of necrotic cells. In this current work, we aimed to uncover the role of pyroptosis in cellular necrosis in thymic cells of S. suis-infected mice. Confocal microscopy revealed that S. suis activated the M1 phenotype and primed pyroptosis in the macrophages of atrophied thymus. Live cell imaging further confirmed that S. suis could induce porcine alveolar macrophage (PAM) pyroptosis in vitro, displaying cell swelling and forming large bubbles on the plasma membrane. Meanwhile, the levels of p-p38, p-extracellular signal-regulated kinase (ERK) and protein kinase B (AKT) were increased, which indicated the mitogen-activated protein kinase (MAPK) and AKT pathways were also involved in the inflammation of S. suis-infected PAMs. Furthermore, RT-PCR revealed significant mRNA expression of pro-inflammatory mediators, including interleukin (IL)-1β, IL-6, IL-18, tumor necrosis factor (TNF)-α and chemokine CXCL8. The data indicated that the inflammation induced by S. suis was in parallel with pro-inflammatory activities of M1 macrophages, pyroptosis and MAPK and AKT pathways. Pyroptosis contributes to necrotic cells and thymocyte reduction in the atrophied thymus of mice.

Abnormal Cellular Populations Shape Thymic Epithelial Tumor Heterogeneity and Anti-Tumor by Blocking Metabolic Interactions in Organoids.

A variety of abnormal epithelial cells and immature and mature immune cells in thymic epithelial tumors (TETs) affect histopathological features, the degree of malignancy, and the response to treatment. Here, gene expression, trajectory inference, and T cell antigen receptor (TCR)-based lineage tracking are profiled in TETs at single-cell resolution. An original subpopulation of KRT14+ progenitor cells with a spindle cell phenotype is shown. An abnormal infiltration of immature T cells with a TCR hyper-rearrangement state is revealed, due to the lack of CCL21+ medullary epithelial cells. For thymic carcinoma, the novel biomarkers of MSLN, CCL20, and SLC1A5 are identified and observed an elevated expression of LAG3 and HAVCR2 in malignant tumorn-infiltrating mature T cells. These common features based on the single-cell populations may inform pathological reclassification of TETs. Meanwhile, it is found that macrophages (MACs) attract thymic tumor cells through the LGALS9-SLC1A5 axis, providing them with glutamine to elicit metabolic reprogramming. This MAC-based metabolic pattern can promote malignancy progression. Additionally, an interactive immune environment in TETs is identified that correlates with the infiltration of abnormal FOXI1+ CFTR- ionocytes. Collectively, the data broaden the knowledge of TET cellular ecosystems, providing a basis for tackling histopathological diagnosis and related treatment.

Non-coding RNA and its network in the pathogenesis of Myasthenia Gravis.

Myasthenia Gravis (MG) is a chronic autoimmune disease that primarily affects the neuromuscular junction, leading to muscle weakness in patients with this condition. Previous studies have identified several dysfunctions in thymus and peripheral blood mononuclear cells (PBMCs), such as the formation of ectopic germinal centers in the thymus and an imbalance of peripheral T helper cells and regulatory T cells, that contribute to the initiation and development of MG. Recent evidences suggest that noncoding RNA, including miRNA, lncRNA and circRNA may play a significant role in MG progression. Additionally, the network between these noncoding RNAs, such as the competing endogenous RNA regulatory network, has been found to be involved in MG progression. In this review, we summarized the roles of miRNA, lncRNA, and circRNA, highlighted their potential application as biomarkers in diagnosing MG, and discussed their potential regulatory networks in the abnormal thymus and PBMCs during MG development.