Transcriptional repressor ZEB2 promotes terminal differentiation of CD8+ effector and memory T cell populations during infection

Restriction of innate Tγδ17 cell plasticity by an AP-1 regulatory axis

IL-17-producing γδ T (Tγδ17) cells are innate-like mediators of intestinal barrier immunity. While Th17 cell and ILC3 plasticity have been extensively studied, the mechanisms governing Tγδ17 cell effector flexibility remain undefined. Here, we combined type 3 fate-mapping with single cell ATAC/RNA-seq multiome profiling to define the cellular features and regulatory networks underlying Tγδ17 cell plasticity. During homeostasis, Tγδ17 cell effector identity was stable across tissues, including for intestinal T-bet+ Tγδ17 cells that restrained IFNγ production. However, S. typhimurium infection induced intestinal Vγ6+ Tγδ17 cell conversion into type 1 effectors, with loss of IL-17A production and partial RORγt downregulation. Multiome analysis revealed a trajectory along Vγ6+ Tγδ17 effector conversion, with TIM-3 marking ex-Tγδ17 cells with enhanced type 1 functionality. Lastly, we characterized and validated a critical AP-1 regulatory axis centered around JunB and Fosl2 that controls Vγ6+ Tγδ17 cell plasticity by stabilizing type 3 identity and restricting type 1 effector conversion.

DNA methylation profiling identifies TBKBP1 as potent amplifier of cytotoxic activity in CMV-specific human CD8+ T cells

Epigenetic mechanisms stabilize gene expression patterns during CD8+ T cell differentiation. Although adoptive transfer of virus-specific T cells is clinically applied to reduce the risk of virus infection or reactivation in immunocompromised individuals, the DNA methylation pattern of virus-specific CD8+ T cells is largely unknown. Hence, we here performed whole-genome bisulfite sequencing of cytomegalovirus-specific human CD8+ T cells and found that they display a unique DNA methylation pattern consisting of 79 differentially methylated regions (DMRs) when compared to memory CD8+ T cells. Among the top demethylated DMRs in cytomegalovirus-specific CD8+ T cells was TBKBP1, coding for TBK-binding protein 1 that can interact with TANK-binding kinase 1 (TBK1) and mediate pro-inflammatory responses in innate immune cells downstream of intracellular virus sensing. Since TBKBP1 has not yet been reported in T cells, we aimed to unravel its role in virus-specific CD8+ T cells. TBKBP1 demethylation in terminal effector CD8+ T cells correlated with higher TBKBP1 expression at both mRNA and protein level, independent of alternative splicing of TBKBP1 transcripts. Notably, the distinct DNA methylation patterns in CD8+ T cell subsets was stable upon long-term in vitro culture. TBKBP1 overexpression resulted in enhanced TBK1 phosphorylation upon stimulation of CD8+ T cells and significantly improved their virus neutralization capacity. Collectively, our data demonstrate that TBKBP1 modulates virus-specific CD8+ T cell responses and could be exploited as therapeutic target to improve adoptive T cell therapies.

Attenuated effector T cells are linked to control of chronic HBV infection

Hepatitis B virus (HBV)-specific CD8+ T cells play a dominant role during acute-resolving HBV infection but are functionally impaired during chronic HBV infection in humans. These functional deficits have been linked with metabolic and phenotypic heterogeneity, but it has remained unclear to what extent different subsets of HBV-specific CD8+ T cells still suppress viral replication. We addressed this issue by deep profiling, functional testing and perturbation of HBV-specific CD8+ T cells during different phases of chronic HBV infection. Our data revealed a mechanism of effector CD8+ T cell attenuation that emerges alongside classical CD8+ T cell exhaustion. Attenuated HBV-specific CD8+ T cells were characterized by cytotoxic properties and a dampened effector differentiation program, determined by antigen recognition and TGFβ signaling, and were associated with viral control during chronic HBV infection. These observations identify a distinct subset of CD8+ T cells linked with immune efficacy in the context of a chronic human viral infection with immunotherapeutic potential.

The Role of Epithelial-to-Mesenchymal Transition Transcription Factors (EMT-TFs) in Acute Myeloid Leukemia Progression

Acute myeloid leukemia (AML) is a diverse malignancy originating from myeloid progenitor cells, with significant genetic and clinical variability. Modern classification systems like those from the World Health Organization (WHO) and European LeukemiaNet use immunophenotyping, molecular genetics, and clinical features to categorize AML subtypes. This classification highlights crucial genetic markers such as FLT3, NPM1 mutations, and MLL-AF9 fusion, which are essential for prognosis and directing targeted therapies. The MLL-AF9 fusion protein is often linked with therapy-resistant AML, highlighting the risk of relapse due to standard chemotherapeutic regimes. In this sense, factors like the ZEB, SNAI, and TWIST gene families, known for their roles in epithelial-mesenchymal transition (EMT) and cancer metastasis, also regulate hematopoiesis and may serve as effective therapeutic targets in AML. These genes contribute to cell proliferation, differentiation, and extramedullary hematopoiesis, suggesting new possibilities for treatment. Advancing our understanding of the molecular mechanisms that promote AML, especially how the bone marrow microenvironment affects invasion and drug resistance, is crucial. This comprehensive insight into the molecular and environmental interactions in AML emphasizes the need for ongoing research and more effective treatments.

Quantized multi-task learning for context-specific representations of gene network dynamics

While often represented as static entities, gene networks are highly context-dependent. Here, we developed a multi-task learning strategy to yield context-specific representations of gene network dynamics. We assembled a corpus comprising ~103 million human single-cell transcriptomes from a broad range of tissues and diseases and performed a two stage pretraining, first with non-malignant cells to generate a foundational model and then with continual learning on cancer cells to tune the model to the cancer domain. We performed multi-task learning with the foundational model to learn context-specific representations of a broad range of cell types, tissues, developmental stages, and diseases. We then leveraged the cancer-tuned model to jointly learn cell states and predict tumor-restricting factors within the colorectal tumor microenvironment. Model quantization allowed resource-efficient fine-tuning and inference while preserving biological knowledge. Overall, multi-task learning enables context-specific disease modeling that can yield contextual predictions of candidate therapeutic targets for human disease.

Aging trajectories of memory CD8 + T cells differ by their antigen specificity

Memory T cells are a highly dynamic and heterogeneous population that is maintained by cytokine-driven homeostatic proliferation interspersed with episodes of antigen-mediated expansion and contraction which affect their functional state and their durability. This heterogeneity complicates studies on the impact of aging on global human memory cells, specifically, it is unclear how aging drives memory T cell dysfunction. Here, we used chronic infection with Epstein-Barr virus (EBV) to assess the influence of age on memory states at the level of antigen-specific CD8 + T cells. We find that in young adults (<40 years), EBV-specific CD8 + T cells assume preferred differentiation states depending on their peptide specificity. By age >65-years, different T cell specificities had undergone largely distinct aging trajectories, which had in common a loss in adaptive and a gain in innate immunity signatures. No evidence was seen for cellular senescence or exhaustion. While naïve/stem-like EBV-specific T cells disappeared with age, T cell diversity of EBV-specific memory cells did not change or even increased. In summary, by controlling for antigen specificity we uncover age-associated shifts in gene expression and TCR diversity that have implications for optimizing vaccination strategies and adoptive T cell therapy.

BRD7 as key factor in PBAF complex assembly and CD8+ T cell differentiation

Upon infection, naive CD8+ T cells differentiate into cytotoxic effector cells to eliminate the pathogen-infected cells. Although many mechanisms underlying this process have been demonstrated, the regulatory role of chromatin remodeling system in this process remains largely unknown. Here we show that BRD7, a component of the polybromo-associated BAF complex (PBAF), was required for naive CD8+ T cells to differentiate into functional short-lived effector cells (SLECs) in response to acute infections caused by influenza virus or lymphocytic choriomeningitis virus (LCMV). BRD7 deficiency in CD8+ T cells resulted in profound defects in effector population and functions, thereby impairing viral clearance and host recovery. Further mechanical studies indicate that the expression of BRD7 significantly turned to high from naive CD8+ T cells to effector cells, which bridged BRG1 and PBRM1 to the core module of PBAF complex, consequently facilitating the assembly of PBAF complex rather than BAF complex in the effector cells. The PBAF complex changed the chromatin accessibility at the loci of Tbx21 gene and upregulated its expression, leading to the maturation of effector T cells. Our research demonstrates that BRD7 and the PBAF complex are key in CD8+ T cell development and present a significant target for advancing immune therapies.

Eomesodermin spatiotemporally orchestrates the early and late stages of NK cell development by targeting KLF2 and T-bet, respectively

Eomesodermin (Eomes) is a critical factor in the development of natural killer (NK) cells, but its precise role in temporal and spatial coordination during this process remains unclear. Our study revealed that Eomes plays distinct roles during the early and late stages of NK cell development. Specifically, the early deletion of Eomes via the CD122-Cre transgene resulted in significant blockade at the progenitor stage due to the downregulation of KLF2, another important transcription factor. ChIP-seq revealed direct binding of Eomes to the conserved noncoding sequence (CNS) of Klf2. Utilizing the CHimeric IMmune Editing (CHIME) technique, we found that deletion of the CNS region of Klf2 via CRISPRi led to a reduction in the NK cell population and developmental arrest. Moreover, constitutive activation of this specific CNS region through CRISPRa significantly reversed the severe defects in NK cell development caused by Eomes deficiency. Conversely, Ncr1-Cre-mediated terminal deletion of Eomes expedited the transition of NK cell subsets from the CD27+CD11b+ phenotype to the CD27-CD11b+ phenotype. Late-stage deficiency of Eomes led to a significant increase in T-bet expression, which subsequently increased the expression of the transcription factor Zeb2. Genetic deletion of one allele of Tbx21, encoding T-bet, effectively reversed the aberrant differentiation of Eomes-deficient NK cells. In summary, we utilized two innovative genetic models to elucidate the intricate mechanisms underlying Eomes-mediated NK cell commitment and differentiation.

Single-cell transcriptomic and T cell antigen receptor analysis of human cytomegalovirus (hCMV)-specific memory T cells reveals effectors and pre-effectors of CD8+- and CD4+-cytotoxic T cells

Latent human cytomegalovirus (hCMV) infection can pose a serious threat of reactivation and disease occurrence in immune-compromised individuals. Although T cells are at the core of the protective immune response to hCMV infection, a detailed characterization of different T cell subsets involved in hCMV immunity is lacking. Here, in an unbiased manner, we characterized over 8000 hCMV-reactive peripheral memory T cells isolated from seropositive human donors, at a single-cell resolution by analysing their single-cell transcriptomes paired with the T cell antigen receptor (TCR) repertoires. The hCMV-reactive T cells were highly heterogeneous and consisted of different developmental and functional memory T cell subsets such as, long-term memory precursors and effectors, T helper-17, T regulatory cells (TREGs) and cytotoxic T lymphocytes (CTLs) of both CD4 and CD8 origin. The hCMV-specific TREGs, in addition to being enriched for molecules known for their suppressive functions, showed enrichment for the interferon response signature gene sets. The hCMV-specific CTLs were of two types, the pre-effector- and effector-like. The co-clustering of hCMV-specific CD4-CTLs and CD8-CTLs in both pre-effector as well as effector clusters suggest shared transcriptomic signatures between them. The huge TCR clonal expansion of cytotoxic clusters suggests a dominant role in the protective immune response to CMV. The study uncovers the heterogeneity in the hCMV-specific memory T cells revealing many functional subsets with potential implications in better understanding of hCMV-specific T cell immunity. The data presented can serve as a knowledge base for designing vaccines and therapeutics.

Human γδ T cells in diverse tissues exhibit site-specific maturation dynamics across the life span

During ontogeny, γδ T cells emerge from the thymus and directly seed peripheral tissues for in situ immunity. However, their functional role in humans has largely been defined from blood. Here, we analyzed the phenotype, transcriptome, function, and repertoire of human γδ T cells in blood and mucosal and lymphoid tissues from 176 donors across the life span, revealing distinct profiles in children compared with adults. In early life, clonally diverse Vδ1 subsets predominate across blood and tissues, comprising naïve and differentiated effector and tissue repair functions, whereas cytolytic Vδ2 subsets populate blood, spleen, and lungs. With age, Vδ1 and Vδ2 subsets exhibit clonal expansions and elevated cytolytic signatures, which are disseminated across sites. In adults, Vδ2 cells predominate in blood, whereas Vδ1 cells are enriched across tissues and express residency profiles. Thus, antigenic exposures over childhood drive the functional evolution and tissue compartmentalization of γδ T cells, leading to age-dependent roles in immunity.

Corneal injury repair and the potential involvement of ZEB1

The cornea, consisting of three cellular and two non-cellular layers, is the outermost part of the eyeball and frequently injured by external physical, chemical, and microbial insults. The epithelial-to-mesenchymal transition (EMT) plays a crucial role in the repair of corneal injuries. Zinc finger E-box binding homeobox 1 (ZEB1), an important transcription factor involved in EMT, is expressed in the corneal tissues. It regulates cell activities like migration, transformation, and proliferation, and thereby affects tissue inflammation, fibrosis, tumor metastasis, and necrosis by mediating various major signaling pathways, including transforming growth factor (TGF)-β. Dysfunction of ZEB1 would impair corneal tissue repair leading to epithelial healing delay, interstitial fibrosis, neovascularization, and squamous cell metaplasia. Understanding the mechanism underlying ZEB1 regulation of corneal injury repair will help us to formulate a therapeutic approach to enhance corneal injury repair.

1-L Transcription of SARS-CoV-2 Spike Protein S1 Subunit

The COVID-19 pandemic prompted rapid research on SARS-CoV-2 pathogenicity. Consequently, new data can be used to advance the molecular understanding of SARS-CoV-2 infection. The present bioinformatics study discusses the "spikeopathy" at the molecular level and focuses on the possible post-transcriptional regulation of the SARS-CoV-2 spike protein S1 subunit in the host cell/tissue. A theoretical protein-RNA recognition code was used to check the compatibility of the SARS-CoV-2 spike protein S1 subunit with mRNAs in the human transcriptome (1-L transcription). The principle for this method is elucidated on the defined RNA binding protein GEMIN5 (gem nuclear organelle-associated protein 5) and RNU2-1 (U2 spliceosomal RNA). Using the method described here, it was shown that 45% of the genes/proteins identified by 1-L transcription of the SARS-CoV-2 spike protein S1 subunit are directly linked to COVID-19, 39% are indirectly linked to COVID-19, and 16% cannot currently be associated with COVID-19. The identified genes/proteins are associated with stroke, diabetes, and cardiac injury.

Multimodal stimulation screens reveal unique and shared genes limiting T cell fitness

Genes limiting T cell antitumor activity may serve as therapeutic targets. It has not been systematically studied whether there are regulators that uniquely or broadly contribute to T cell fitness. We perform genome-scale CRISPR-Cas9 knockout screens in primary CD8 T cells to uncover genes negatively impacting fitness upon three modes of stimulation: (1) intense, triggering activation-induced cell death (AICD); (2) acute, triggering expansion; (3) chronic, causing dysfunction. Besides established regulators, we uncover genes controlling T cell fitness either specifically or commonly upon differential stimulation. Dap5 ablation, ranking highly in all three screens, increases translation while enhancing tumor killing. Loss of Icam1-mediated homotypic T cell clustering amplifies cell expansion and effector functions after both acute and intense stimulation. Lastly, Ctbp1 inactivation induces functional T cell persistence exclusively upon chronic stimulation. Our results functionally annotate fitness regulators based on their unique or shared contribution to traits limiting T cell antitumor activity.

Modular chimeric cytokine receptors with leucine zippers enhance the antitumour activity of CAR T cells via JAK/STAT signalling

The limited availability of cytokines in solid tumours hinders maintenance of the antitumour activity of chimeric antigen receptor (CAR) T cells. Cytokine receptor signalling pathways in CAR T cells can be activated by transgenic expression or injection of cytokines in the tumour, or by engineering the activation of cognate cytokine receptors. However, these strategies are constrained by toxicity arising from the activation of bystander cells, by the suboptimal biodistribution of the cytokines and by downregulation of the cognate receptor. Here we show that replacement of the extracellular domains of heterodimeric cytokine receptors in T cells with two leucine zipper motifs provides optimal Janus kinase/signal transducer and activator of transcription signalling. Such chimeric cytokine receptors, which can be generated for common γ-chain receptors, interleukin-10 and -12 receptors, enabled T cells to survive cytokine starvation without induction of autonomous cell growth, and augmented the effector function of CAR T cells in vitro in the setting of chronic antigen exposure and in human tumour xenografts in mice. As a modular design, leucine zippers can be used to generate constitutively active cytokine receptors in effector immune cells.

Zeb2 drives the formation of CD11c+ atypical B cells to sustain germinal centers that control persistent infection

CD11c+ atypical B cells (ABCs) are an alternative memory B cell lineage associated with immunization, infection, and autoimmunity. However, the factors that drive the transcriptional program of ABCs have not been identified, and the function of this population remains incompletely understood. Here, we identified candidate transcription factors associated with the ABC population based on a human tonsillar B cell single-cell dataset. We identified CD11c+ B cells in mice with a similar transcriptomic signature to human ABCs, and using an optimized CRISPR-Cas9 knockdown screen, we observed that loss of zinc finger E-box binding homeobox 2 (Zeb2) impaired ABC formation. Furthermore, ZEB2 haplo-insufficient Mowat-Wilson syndrome (MWS) patients have decreased circulating ABCs in the blood. In Cd23Cre/+Zeb2fl/fl mice with impaired ABC formation, ABCs were dispensable for efficient humoral responses after Plasmodium sporozoite immunization but were required to control recrudescent blood-stage malaria. Immune phenotyping revealed that ABCs drive optimal T follicular helper (TFH) cell formation and germinal center (GC) responses and they reside at the red/white pulp border, likely permitting better access to pathogen antigens for presentation. Collectively, our study shows that ABC formation is dependent on Zeb2, and these cells can limit recrudescent infection by sustaining GC reactions.

Hierarchal single-cell lineage tracing reveals differential fate commitment of CD8 T-cell clones in response to acute infection

Generating balanced populations of CD8 effector and memory T cells is necessary for immediate and durable immunity to infections and cancer. Yet, a definitive understanding of CD8 differentiation remains unclear. We used CARLIN, a processive lineage recording mouse model with single-cell RNA-seq and TCR-seq to track endogenous antigen-specific CD8 T cells during acute viral infection. We identified a diverse repertoire of expanded T-cell clones represented by seven transcriptional states. TCR enrichment analysis revealed differential memory- or effector-fate biases within clonal populations. Shared Vb segments and amino acid motifs were found within biased categories despite high TCR diversity. Using single-cell CARLIN barcode-seq we tracked multi-generational clones and found that unlike unbiased or memory-biased clones, which stably retain their fate profiles, effector-biased clones could adopt memory- or effector-bias within subclones. Collectively, our study demonstrates that a heterogenous T-cell repertoire specific for a shared antigen is composed of clones with distinct TCR-intrinsic fate-biases.

Multimodal profiling reveals site-specific adaptation and tissue residency hallmarks of γδ T cells across organs in mice

γδ T cells perform heterogeneous functions in homeostasis and disease across tissues. However, it is unclear whether these roles correspond to distinct γδ subsets or to a homogeneous population of cells exerting context-dependent functions. Here, by cross-organ multimodal single-cell profiling, we reveal that various mouse tissues harbor unique site-adapted γδ subsets. Epidermal and intestinal intraepithelial γδ T cells are transcriptionally homogeneous and exhibit epigenetic hallmarks of functional diversity. Through parabiosis experiments, we uncovered cellular states associated with cytotoxicity, innate-like rapid interferon-γ production and tissue repair functions displaying tissue residency hallmarks. Notably, our observations add nuance to the link between interleukin-17-producing γδ T cells and tissue residency. Moreover, transcriptional programs associated with tissue-resident γδ T cells are analogous to those of CD8+ tissue-resident memory T cells. Altogether, this study provides a multimodal landscape of tissue-adapted γδ T cells, revealing heterogeneity, lineage relationships and their tissue residency program.

Interplay of Zeb2a, Id2a and Batf3 regulates microglia and dendritic cell development in the zebrafish brain

In vertebrates, the central nervous system (CNS) harbours various immune cells, including parenchymal microglia, perivascular macrophages and dendritic cells, which act in coordination to establish an immune network to regulate neurogenesis and neural function, and to maintain the homeostasis of the CNS. Recent single cell transcriptomic profiling has revealed that the adult zebrafish CNS contains microglia, plasmacytoid dendritic cells (pDCs) and two conventional dendritic cells (cDCs), ccl35+ cDCs and cnn3a+cDCs. However, how these distinct myeloid cells are established in the adult zebrafish CNS remains incompletely defined. Here, we show that the Inhibitor of DNA binding 2a (Id2a) is essential for the development of pDCs and cDCs but is dispensable for the formation of microglia, whereas the Basic leucine zipper transcription factor ATF-like 3 (Batf3) acts downstream of id2a and is required exclusively for the formation of the cnn3a+ cDC subset. In contrast, the Zinc finger E-box-binding homeobox 2a (Zeb2a) promotes the expansion of microglia and inhibits the DC specification, possibly through repressing id2a expression. Our study unravels the genetic networks that govern the development of microglia and brain-associated DCs in the zebrafish CNS.

FOXP1 and KLF2 reciprocally regulate checkpoints of stem-like to effector transition in CAR T cells

In cancer and infections, self-renewing stem-like CD8+ T cells mediate the response of immunotherapies and replenish terminally exhausted T cells and effector-like T cells. However, the programs governing the lineage choice in chimeric antigen receptor (CAR) T cells are unclear. Here, by simultaneously profiling single-cell chromatin accessibility and transcriptome in the same CAR T cells, we identified heterogeneous chromatin states within CD8+ T cell subsets that foreshadowed transcriptional changes and were primed for regulation by distinct transcription factors. Transcription factors that controlled each CD8+ T cell subset were regulated by high numbers of enhancers and positioned as hubs of gene networks. FOXP1, a hub in the stem-like network, promoted expansion and stemness of CAR T cells and limited excessive effector differentiation. In the effector network, KLF2 enhanced effector CD8+ T cell differentiation and prevented terminal exhaustion. Thus, we identified gene networks and hub transcription factors that controlled the differentiation of stem-like CD8+ CAR T cells into effector or exhausted CD8+ CAR T cells.

Genetic Association and Differential RNA Expression of Histone (De)Acetylation-Related Genes in Pemphigus Foliaceus-A Possible Epigenetic Effect in the Autoimmune Response

Pemphigus foliaceus (PF) is an autoimmune skin blistering disease characterized by antidesmoglein-1 IgG production, with an endemic form (EPF) in Brazil. Genetic and epigenetic factors have been associated with EPF, but its etiology is still not fully understood. To evaluate the genetic association of histone (de)acetylation-related genes with EPF susceptibility, we evaluated 785 polymorphisms from 144 genes, for 227 EPF patients and 194 controls. Carriers of HDAC4_rs4852054*A were more susceptible (OR = 1.79, p = 0.0038), whereas those with GSE1_rs13339618*A (OR = 0.57, p = 0.0011) and homozygotes for PHF21A_rs4756055*A (OR = 0.39, p = 0.0006) were less susceptible to EPF. These variants were not associated with sporadic PF (SPF) in German samples of 75 SPF patients and 150 controls, possibly reflecting differences in SPF and EPF pathophysiology. We further evaluated the expression of histone (de)acetylation-related genes in CD4+ T lymphocytes, using RNAseq. In these cells, we found a higher expression of KAT2B, PHF20, and ZEB2 and lower expression of KAT14 and JAD1 in patients with active EPF without treatment compared to controls from endemic regions. The encoded proteins cause epigenetic modifications related to immune cell differentiation and cell death, possibly affecting the immune response in patients with PF.

Cytotoxic CD4+ tissue-resident memory T cells are associated with asthma severity

BACKGROUND

Patients with severe uncontrolled asthma represent a distinct endotype with persistent airway inflammation and remodeling that is refractory to corticosteroid treatment. CD4+ TH2 cells play a central role in orchestrating asthma pathogenesis, and biologic therapies targeting their cytokine pathways have had promising outcomes. However, not all patients respond well to such treatment, and their effects are not always durable nor reverse airway remodeling. This observation raises the possibility that other CD4+ T cell subsets and their effector molecules may drive airway inflammation and remodeling.

METHODS

We performed single-cell transcriptome analysis of >50,000 airway CD4+ T cells isolated from bronchoalveolar lavage samples from 30 patients with mild and severe asthma.

FINDINGS

We observed striking heterogeneity in the nature of CD4+ T cells present in asthmatics' airways, with tissue-resident memory T (TRM) cells making a dominant contribution. Notably, in severe asthmatics, a subset of CD4+ TRM cells (CD103-expressing) was significantly increased, comprising nearly 65% of all CD4+ T cells in the airways of male patients with severe asthma when compared to mild asthma (13%). This subset was enriched for transcripts linked to T cell receptor activation (HLA-DRB1, HLA-DPA1) and cytotoxicity (GZMB, GZMA) and, following stimulation, expressed high levels of transcripts encoding for pro-inflammatory non-TH2 cytokines (CCL3, CCL4, CCL5, TNF, LIGHT) that could fuel persistent airway inflammation and remodeling.

CONCLUSIONS

Our findings indicate the need to look beyond the traditional T2 model of severe asthma to better understand the heterogeneity of this disease.

FUNDING

This research was funded by the NIH.

CAR+ and CAR- T cells share a differentiation trajectory into an NK-like subset after CD19 CAR T cell infusion in patients with B cell malignancies

Chimeric antigen receptor (CAR) T cell therapy is effective in treating B cell malignancies, but factors influencing the persistence of functional CAR+ T cells, such as product composition, patients' lymphodepletion, and immune reconstitution, are not well understood. To shed light on this issue, here we conduct a single-cell multi-omics analysis of transcriptional, clonal, and phenotypic profiles from pre- to 1-month post-infusion of CAR+ and CAR- T cells from patients from a CARTELL study (ACTRN12617001579381) who received a donor-derived 4-1BB CAR product targeting CD19. Following infusion, CAR+ T cells and CAR- T cells shows similar differentiation profiles with clonally expanded populations across heterogeneous phenotypes, demonstrating clonal lineages and phenotypic plasticity. We validate these findings in 31 patients with large B cell lymphoma treated with CD19 CAR T therapy. For these patients, we identify using longitudinal mass-cytometry data an association between NK-like subsets and clinical outcomes at 6 months with both CAR+ and CAR- T cells. These results suggest that non-CAR-derived signals can provide information about patients' immune recovery and be used as correlate of clinically relevant parameters.

Cytolytic circumsporozoite-specific memory CD4+ T cell clones are expanded during Plasmodium falciparum infection

Clinical immunity against Plasmodium falciparum infection develops in residents of malaria endemic regions, manifesting in reduced clinical symptoms during infection and in protection against severe disease but the mechanisms are not fully understood. Here, we compare the cellular and humoral immune response of clinically immune (0-1 episode over 18 months) and susceptible (at least 3 episodes) during a mild episode of Pf malaria infection in a malaria endemic region of Malawi, by analysing peripheral blood samples using high dimensional mass cytometry (CyTOF), spectral flow cytometry and single-cell transcriptomic analyses. In the clinically immune, we find increased proportions of circulating follicular helper T cells and classical monocytes, while the humoral immune response shows characteristic age-related differences in the protected. Presence of memory CD4+ T cell clones with a strong cytolytic ZEB2+ T helper 1 effector signature, sharing identical T cell receptor clonotypes and recognizing the Pf-derived circumsporozoite protein (CSP) antigen are found in the blood of the Pf-infected participants gaining protection. Moreover, in clinically protected participants, ZEB2+ memory CD4+ T cells express lower level of inhibitory and chemotactic receptors. We thus propose that clonally expanded ZEB2+ CSP-specific cytolytic memory CD4+ Th1 cells may contribute to clinical immunity against the sporozoite and liver-stage Pf malaria.

Early-to-mid stage idiopathic Parkinson's disease shows enhanced cytotoxicity and differentiation in CD8 T-cells in females

Neuroinflammation in the brain contributes to the pathogenesis of Parkinson's disease (PD), but the potential dysregulation of peripheral immunity has not been systematically investigated for idiopathic PD (iPD). Here we showed an elevated peripheral cytotoxic immune milieu, with more terminally-differentiated effector memory (TEMRA) CD8 T, CD8+ NKT cells and circulating cytotoxic molecules in fresh blood of patients with early-to-mid iPD, especially females, after analyzing > 700 innate and adaptive immune features. This profile, also reflected by fewer CD8+FOXP3+ T cells, was confirmed in another subcohort. Co-expression between cytotoxic molecules was selectively enhanced in CD8 TEMRA and effector memory (TEM) cells. Single-cell RNA-sequencing analysis demonstrated the accelerated differentiation within CD8 compartments, enhanced cytotoxic pathways in CD8 TEMRA and TEM cells, while CD8 central memory (TCM) and naïve cells were already more-active and transcriptionally-reprogrammed. Our work provides a comprehensive map of dysregulated peripheral immunity in iPD, proposing candidates for early diagnosis and treatments.

Single-cell dynamics of liver development in postnatal pigs

The postnatal development of the liver, an essential organ for metabolism and immunity, remains poorly characterized at the single-cell resolution. Here, we generated single-nucleus and single-cell transcriptomes of 84,824 pig liver cells at four postnatal time points: day 30, 42, 150, and 730. We uncovered 23 cell types, including three rare cell types: plasmacytoid dendritic cells, CAVIN3+IGF2+ endothelial cells, and EBF1+ fibroblasts. The latter two were verified by multiplex immunohistochemistry. Trajectory and gene regulatory analyses revealed 33 genes that encode transcription factors associated with hepatocyte development and function, including NFIL3 involved in regulating hepatic metabolism. We characterized the spatiotemporal heterogeneity of liver endothelial cells, identified and validated leucine zipper protein 2 (LUZP2) as a novel adult liver sinusoidal endothelial cell-specific transcription factor. Lymphoid cells (NK and T cells) governed the immune system of the pig liver since day 30. Furthermore, we identified a cluster of tissue-resident NK cells, which displayed virus defense functions, maintained proliferative features at day 730, and manifested a higher conservative transcription factor expression pattern in humans than in mouse liver. Our study presents the most comprehensive postnatal liver development single-cell atlas and demonstrates the metabolic and immune changes across the four age stages.

Cardinal features of immune memory in innate lymphocytes

The ability of vertebrates to 'remember' previous infections had once been attributed exclusively to adaptive immunity. We now appreciate that innate lymphocytes also possess memory properties akin to those of adaptive immune cells. In this Review, we draw parallels from T cell biology to explore the key features of immune memory in innate lymphocytes, including quantity, quality, and location. We discuss the signals that trigger clonal or clonal-like expansion in innate lymphocytes, and highlight recent studies that shed light on the complex cellular and molecular crosstalk between metabolism, epigenetics, and transcription responsible for differentiating innate lymphocyte responses towards a memory fate. Additionally, we explore emerging evidence that activated innate lymphocytes relocate and establish themselves in specific peripheral tissues during infection, which may facilitate an accelerated response program akin to those of tissue-resident memory T cells.

Zeb2 regulates differentiation of long-lived effector of invariant natural killer T cells

After activation, some invariant natural killer T (iNKT) cells are differentiated into Klrg1+ long-lived effector NKT1 cells. However, the regulation from the effector phase to the memory phase has not been elucidated. Zeb2 is a zinc finger E homeobox-binding transcription factor and is expressed in a variety of immune cells, but its function in iNKT cell differentiation remains also unknown. Here, we show that Zeb2 is dispensable for development of iNKT cells in the thymus and their maintenance in steady state peripheral tissues. After ligand stimulation, Zeb2 plays essential roles in the differentiation to and maintenance of Klrg1+ Cx3cr1+GzmA+ iNKT cell population derived from the NKT1 subset. Our results including single-cell-RNA-seq analysis indicate that Zeb2 regulates Klrg1+ long-lived iNKT cell differentiation by preventing apoptosis. Collectively, this study reveals the crucial transcriptional regulation by Zeb2 in establishment of the memory iNKT phase through driving differentiation of Klrg1+ Cx3cr1+GzmA+ iNKT population.

Single-cell profiling reveals unique features of diabetogenic T cells in anti-PD-1-induced type 1 diabetes mice

Immune-related adverse events (irAEs) are a notable complication of PD-1 cancer immunotherapy. A better understanding of how these iatrogenic diseases compare with naturally arising autoimmune diseases is needed for treatment and monitoring of irAEs. We identified differences in anti-PD-1-induced type 1 diabetes (T1D) and spontaneous T1D in non-obese diabetic (NOD) mice by performing single-cell RNA-seq and TCR-seq on T cells from the pancreas, pancreas-draining lymph node (pLN), and blood of mice with PD-1-induced T1D or spontaneous T1D. In the pancreas, anti-PD-1 resulted in expansion of terminally exhausted/effector-like CD8+ T cells, an increase in T-bethi CD4+FoxP3- T cells, and a decrease in memory CD4+FoxP3- and CD8+ T cells in contrast to spontaneous T1D. Notably, anti-PD-1 caused increased TCR sharing between the pancreas and the periphery. Moreover, T cells in the blood of anti-PD-1-treated mice expressed markers that differed from spontaneous T1D, suggesting that the blood may provide a window to monitor irAEs rather than relying exclusively on the autoimmune target organ.

Control of nutrient uptake by IRF4 orchestrates innate immune memory

Natural killer (NK) cells are innate cytotoxic lymphocytes with adaptive immune features, including antigen specificity, clonal expansion and memory. As such, NK cells share many transcriptional and epigenetic programs with their adaptive CD8+ T cell siblings. Various signals ranging from antigen, co-stimulation and proinflammatory cytokines are required for optimal NK cell responses in mice and humans during virus infection; however, the integration of these signals remains unclear. In this study, we identified that the transcription factor IRF4 integrates signals to coordinate the NK cell response during mouse cytomegalovirus infection. Loss of IRF4 was detrimental to the expansion and differentiation of virus-specific NK cells. This defect was partially attributed to the inability of IRF4-deficient NK cells to uptake nutrients required for survival and memory generation. Altogether, these data suggest that IRF4 is a signal integrator that acts as a secondary metabolic checkpoint to orchestrate the adaptive response of NK cells during viral infection.

Hallmarks of CD8+ T cell dysfunction are established within hours of tumor antigen encounter before cell division

Tumor-specific CD8+ T cells (TST) in patients with cancer are dysfunctional and unable to halt cancer progression. TST dysfunction, also known as exhaustion, is thought to be driven by chronic T cell antigen receptor (TCR) stimulation over days to weeks. However, we know little about the interplay between CD8+ T cell function, cell division and epigenetic remodeling within hours of activation. Here, we assessed early CD8+ T cell differentiation, cell division, chromatin accessibility and transcription in tumor-bearing mice and acutely infected mice. Surprisingly, despite robust activation and proliferation, TST had near complete effector function impairment even before undergoing cell division and had acquired hallmark chromatin accessibility features previously associated with later dysfunction/exhaustion. Moreover, continued tumor/antigen exposure drove progressive epigenetic remodeling, 'imprinting' the dysfunctional state. Our study reveals the rapid divergence of T cell fate choice before cell division in the context of tumors versus infection.

In vitro modeling of CD8+ T cell exhaustion enables CRISPR screening to reveal a role for BHLHE40

Identifying molecular mechanisms of exhausted CD8 T cells (Tex) is a key goal of improving immunotherapy of cancer and other diseases. However, high-throughput interrogation of in vivo Tex can be costly and inefficient. In vitro models of Tex are easily customizable and quickly generate high cellular yield, enabling CRISPR screening and other high-throughput assays. We established an in vitro model of chronic stimulation and benchmarked key phenotypic, functional, transcriptional, and epigenetic features against bona fide in vivo Tex. We leveraged this model of in vitro chronic stimulation in combination with CRISPR screening to identify transcriptional regulators of T cell exhaustion. This approach identified several transcription factors, including BHLHE40. In vitro and in vivo validation defined a role for BHLHE40 in regulating a key differentiation checkpoint between progenitor and intermediate Tex subsets. By developing and benchmarking an in vitro model of Tex, then applying high-throughput CRISPR screening, we demonstrate the utility of mechanistically annotated in vitro models of Tex.

Graded expression of the chemokine receptor CX3CR1 marks differentiation states of human and murine T cells and enables cross-species interpretation

T cells differentiate into functionally distinct states upon antigen encounter. These states are delineated by different cell surface markers for murine and human T cells, which hamper cross-species translation of T cell properties. We aimed to identify surface markers that reflect the graded nature of CD8+ T cell differentiation and delineate functionally comparable states in mice and humans. CITEseq analyses revealed that graded expression of CX3CR1, encoding the chemokine receptor CX3CR1, correlated with the CD8+ T cell differentiation gradient. CX3CR1 expression distinguished human and murine CD8+ and CD4+ T cell states, as defined by migratory and functional properties. Graded CX3CR1 expression, refined with CD62L, accurately captured the high-dimensional T cell differentiation continuum. Furthermore, the CX3CR1 expression gradient delineated states with comparable properties in humans and mice in steady state and on longitudinally tracked virus-specific CD8+ T cells in both species. Thus, graded CX3CR1 expression provides a strategy to translate the behavior of distinct T cell differentiation states across species.

An "unexpected" role for EMT transcription factors in hematological development and malignancy

The epithelial to mesenchymal transition (EMT) is a fundamental developmental process essential for normal embryonic development. It is also important during various pathogenic processes including fibrosis, wound healing and epithelial cancer cell metastasis and invasion. EMT is regulated by a variety of cell signalling pathways, cell-cell interactions and microenvironmental cues, however the key drivers of EMT are transcription factors of the ZEB, TWIST and SNAIL families. Recently, novel and unexpected roles for these EMT transcription factors (EMT-TFs) during normal blood cell development have emerged, which appear to be largely independent of classical EMT processes. Furthermore, EMT-TFs have also begun to be implicated in the development and pathogenesis of malignant hematological diseases such as leukemia and lymphoma, and now present themselves or the pathways they regulate as possible new therapeutic targets within these malignancies. In this review, we discuss the ZEB, TWIST and SNAIL families of EMT-TFs, focusing on what is known about their normal roles during hematopoiesis as well as the emerging and "unexpected" contribution they play during development and progression of blood cancers.

Get me out of here: Sphingosine 1-phosphate signaling and T cell exit from tissues during an immune response

During an immune response, the duration of T cell residence in lymphoid and non-lymphoid tissues likely affects T cell activation, differentiation, and memory development. The factors that govern T cell transit through inflamed tissues remain incompletely understood, but one important determinant of T cell exit from tissues is sphingosine 1-phosphate (S1P) signaling. In homeostasis, S1P levels are high in blood and lymph compared to lymphoid organs, and lymphocytes follow S1P gradients out of tissues into circulation using varying combinations of five G-protein coupled S1P receptors. During an immune response, both the shape of S1P gradients and the expression of S1P receptors are dynamically regulated. Here we review what is known, and key questions that remain unanswered, about how S1P signaling is regulated in inflammation and in turn how S1P shapes immune responses.

Inhibitory IL-10-producing CD4+ T cells are T-bet-dependent and facilitate cytomegalovirus persistence via coexpression of arginase-1

Inhibitory CD4+ T cells have been linked with suboptimal immune responses against cancer and pathogen chronicity. However, the mechanisms that underpin the development of these regulatory cells, especially in the context of ongoing antigen exposure, have remained obscure. To address this knowledge gap, we undertook a comprehensive functional, phenotypic, and transcriptomic analysis of interleukin (IL)-10-producing CD4+ T cells induced by chronic infection with murine cytomegalovirus (MCMV). We identified these cells as clonally expanded and highly differentiated TH1-like cells that developed in a T-bet-dependent manner and coexpressed arginase-1 (Arg1), which promotes the catalytic breakdown of L-arginine. Mice lacking Arg1-expressing CD4+ T cells exhibited more robust antiviral immunity and were better able to control MCMV. Conditional deletion of T-bet in the CD4+ lineage suppressed the development of these inhibitory cells and also enhanced immune control of MCMV. Collectively, these data elucidated the ontogeny of IL-10-producing CD4+ T cells and revealed a previously unappreciated mechanism of immune regulation, whereby viral persistence was facilitated by the site-specific delivery of Arg1.

Insights into phenotypic and functional CD8+ TRM heterogeneity

Cytotoxic CD8+ T cells recognize and eliminate infected or cancerous cells. A subset of CD8+ memory T cells called tissue-resident memory T cells (TRM ) resides in peripheral tissues, monitors the periphery for pathogen invasion, and offers a rapid and potent first line of defense at potential sites of re-infection. TRM cells are found in almost all tissues and are transcriptionally and epigenetically distinct from circulating memory populations, which shows their ability to acclimate to the tissue environment to allow for long-term survival. Recent work and the broader availability of single-cell profiling have highlighted TRM heterogeneity among different tissues, as well as identified specialized subsets within individual tissues, that are time and infection dependent. TRM cell phenotypic and transcriptional heterogeneity has implications for understanding TRM function and longevity. This review aims to summarize and discuss the latest findings on CD8+ TRM heterogeneity using single-cell molecular profiling and explore the potential implications for immune protection and the design of immune therapies.

Canonical BAF complex activity shapes the enhancer landscape that licenses CD8+ T cell effector and memory fates

CD8+ T cells provide host protection against pathogens by differentiating into distinct effector and memory cell subsets, but how chromatin is site-specifically remodeled during their differentiation is unclear. Due to its critical role in regulating chromatin and enhancer accessibility through its nucleosome remodeling activities, we investigated the role of the canonical BAF (cBAF) chromatin remodeling complex in antiviral CD8+ T cells during infection. ARID1A, a subunit of cBAF, was recruited early after activation and established de novo open chromatin regions (OCRs) at enhancers. Arid1a deficiency impaired the opening of thousands of activation-induced enhancers, leading to loss of TF binding, dysregulated proliferation and gene expression, and failure to undergo terminal effector differentiation. Although Arid1a was dispensable for circulating memory cell formation, tissue-resident memory (Trm) formation was strongly impaired. Thus, cBAF governs the enhancer landscape of activated CD8+ T cells that orchestrates TF recruitment and activity and the acquisition of specific effector and memory differentiation states.

STAT4 increases the phenotypic and functional heterogeneity of intestinal tissue-resident memory T cells

Tissue-resident memory T cells (Trms) are an important subset of lymphocytes that are lodged within non-lymphoid tissues and carry out diverse functions to control local pathogen replication. CD103 has been used to broadly define subsets of Trms within the intestine, with CD103+ and CD103- subsets having unique transcriptional profiles and effector functions. Here we identify signal transducer and activator of transcription 4 (STAT4) as an important regulator of CD103- Trm differentiation. STAT4-deficient cells trafficked to the intestine and localized to areas of infection but displayed impaired Trm differentiation with fewer CD103- Trms. Single-cell RNA-sequencing demonstrated that STAT4-deficiency led to a reduction in CD103- Trm subsets and expansion of a single population of CD103+ cells. Alterations in Trm populations were due, in part, to STAT4-mediated inhibition of transforming growth factor (TGF)-β-driven expression of Trm signature genes. STAT4-dependent Trm populations expressed genes associated with cytokine production and cell migration, and STAT4-deficient Trm cells had altered localization within the tissue and reduced effector function after reactivation in vivo. Overall, our data indicate that STAT4 leads to increased differentiation of CD103- Trms, in part by modulating the expression of TGF-β-regulated genes, and results in increased Trm heterogeneity and function within the intestinal tissue.

Identification of CD8 + T-Cell-Immune Cell Communications in Ileal Crohn's Disease

INTRODUCTION

Crohn's disease (CD) is a major subtype of inflammatory bowel disease (IBD), a spectrum of chronic intestinal disorders caused by dysregulated immune responses to gut microbiota. Although transcriptional and functional changes in a number of immune cell types have been implicated in the pathogenesis of IBD, the cellular interactions and signals that drive these changes have been less well-studied.

METHODS

We performed Cellular Indexing of Transcriptomes and Epitopes by sequencing on peripheral blood, colon, and ileal immune cells derived from healthy subjects and patients with CD. We applied a previously published computational approach, NicheNet, to predict immune cell types interacting with CD8 + T-cell subsets, revealing putative ligand-receptor pairs and key transcriptional changes downstream of these cell-cell communications.

RESULTS

As a number of recent studies have revealed a potential role for CD8 + T-cell subsets in the pathogenesis of IBD, we focused our analyses on identifying the interactions of CD8 + T-cell subsets with other immune cells in the intestinal tissue microenvironment. We identified ligands and signaling pathways that have implicated in IBD, such as interleukin-1β, supporting the validity of the approach, along with unexpected ligands, such as granzyme B, which may play previously unappreciated roles in IBD.

DISCUSSION

Overall, these findings suggest that future efforts focused on elucidating cell-cell communications among immune and nonimmune cell types may further our understanding of IBD pathogenesis.

Bcl11b sustains multipotency and restricts effector programs of intestinal-resident memory CD8+ T cells

The networks of transcription factors (TFs) that control intestinal-resident memory CD8⁺ T (T_RM) cells, including multipotency and effector programs, are poorly understood. In this work, we investigated the role of the TF Bcl11b in T_RM cells during infection with Listeria monocytogenes using mice with post-activation, conditional deletion of Bcl11b in CD8⁺ T cells. Conditional deletion of Bcl11b resulted in increased numbers of intestinal T_RM cells and their precursors as well as decreased splenic effector and circulating memory cells and precursors. Loss of circulating memory cells was in part due to increased intestinal homing of Bcl11b^-/- circulating precursors, with no major alterations in their programs. Bcl11b^-/- T_RM cells had altered transcriptional programs, with diminished expression of multipotent/multifunctional (MP/MF) program genes, including Tcf7, and up-regulation of the effector program genes, including Prdm1. Bcl11b also limits the expression of Ahr, another TF with a role in intestinal CD8⁺ T_RM cell differentiation. Deregulation of T_RM programs translated into a poor recall response despite T_RM cell accumulation in the intestine. Reduced expression of MP/MF program genes in Bcl11b^-/- T_RM cells was linked to decreased chromatin accessibility and a reduction in activating histone marks at these loci. In contrast, the effector program genes displayed increased activating epigenetic status. These findings demonstrate that Bcl11b is a frontrunner in the tissue residency program of intestinal memory cells upstream of Tcf1 and Blimp1, promoting multipotency and restricting the effector program.

In Vitro Modeling of CD8 T Cell Exhaustion Enables CRISPR Screening to Reveal a Role for BHLHE40

Identifying novel molecular mechanisms of exhausted CD8 T cells (T ex ) is a key goal of improving immunotherapy of cancer and other diseases. However, high-throughput interrogation of in vivo T ex can be costly and inefficient. In vitro models of T ex are easily customizable and quickly generate high cellular yield, offering an opportunity to perform CRISPR screening and other high-throughput assays. We established an in vitro model of chronic stimulation and benchmarked key phenotypic, functional, transcriptional, and epigenetic features against bona fide in vivo T ex . We leveraged this model of in vitro chronic stimulation in combination with pooled CRISPR screening to uncover transcriptional regulators of T cell exhaustion. This approach identified several transcription factors, including BHLHE40. In vitro and in vivo validation defined a role for BHLHE40 in regulating a key differentiation checkpoint between progenitor and intermediate subsets of T ex . By developing and benchmarking an in vitro model of T ex , we demonstrate the utility of mechanistically annotated in vitro models of T ex , in combination with high-throughput approaches, as a discovery pipeline to uncover novel T ex biology.

Differentially expressed transcript isoforms associate with resistance to tuberculin skin test and interferon gamma release assay conversion

BACKGROUND

A mechanistic understanding of uncommon immune outcomes such as resistance to infection has led to the development of novel therapies. Using gene level analytic methods, we previously found distinct monocyte transcriptional responses associated with resistance to Mycobacterium tuberculosis (Mtb) infection defined as persistently negative tuberculin skin test (TST) and interferon gamma release assay (IGRA) reactivity among highly exposed contacts (RSTR phenotype).

OBJECTIVE

Using transcript isoform analyses, we aimed to identify novel RSTR-associated genes hypothesizing that previous gene-level differential expression analysis obscures isoform-specific differences that contribute to phenotype.

MATERIALS AND METHODS

Monocytes from 49 RSTR versus 52 subjects with latent Mtb infection (LTBI) were infected with M. tuberculosis (H37Rv) or left unstimulated (media) prior to RNA isolation and sequencing. RSTR-associated gene expression was then identified using differential transcript isoform analysis.

RESULTS

We identified 81 differentially expressed transcripts (DETs) in 70 genes (FDR <0.05) comparing RSTR and LTBI phenotypes with the majority (n = 79 DETs) identified under Mtb-stimulated conditions. Seventeen of these genes were previously identified with gene-level bulk RNAseq analyses including genes in the IFNγ response that had increased expression among LTBI subjects, findings consistent with a clinical phenotype based on IGRA reactivity. Among the subset of 23 genes with positive differential expression among Mtb-infected RSTR monocytes, 13 were not previously identified. These novel DET genes included PDE4A and ZEB2, which each had multiple DETs with higher expression among RSTR subjects, and ACSL4 and GAPDH that each had a single transcript isoform associated with RSTR.

CONCLUSION AND LIMITATIONS

Transcript isoform-specific analyses identify transcriptional associations, such as those associated with resistance to TST/IGRA conversion, that are obscured when using gene-level approaches. These findings should be validated with additional RSTR cohorts and whether the newly identified candidate resistance genes directly influence the monocyte Mtb response requires functional study.

Prolidase Deficiency Causes Spontaneous T Cell Activation and Lupus-like Autoimmunity

Prolidase deficiency (PD) is a multisystem disorder caused by mutations in the PEPD gene, which encodes a ubiquitously expressed metallopeptidase essential for the hydrolysis of dipeptides containing C-terminal proline or hydroxyproline. PD typically presents in childhood with developmental delay, skin ulcers, recurrent infections, and, in some patients, autoimmune features that can mimic systemic lupus erythematosus. The basis for the autoimmune association is uncertain, but might be due to self-antigen exposure with tissue damage, or indirectly driven by chronic infection and microbial burden. In this study, we address the question of causation and show that Pepd-null mice have increased antinuclear autoantibodies and raised serum IgA, accompanied by kidney immune complex deposition, consistent with a systemic lupus erythematosus-like disease. These features are associated with an accumulation of CD4 and CD8 effector T cells in the spleen and liver. Pepd deficiency leads to spontaneous T cell activation and proliferation into the effector subset, which is cell intrinsic and independent of Ag receptor specificity or antigenic stimulation. However, an increase in KLRG1+ effector CD8 cells is not observed in mixed chimeras, in which the autoimmune phenotype is also absent. Our findings link autoimmune susceptibility in PD to spontaneous T cell dysfunction, likely to be acting in combination with immune activators that lie outside the hemopoietic system but result from the abnormal metabolism or loss of nonenzymatic prolidase function. This knowledge provides insight into the role of prolidase in the maintenance of self-tolerance and highlights the importance of treatment to control T cell activation.

CXCR6 promotes dermal CD8+ T cell survival and transition to long-term tissue residence

Tissue resident memory T cells (TRM) provide important protection against infection, and yet the interstitial signals necessary for their formation and persistence remain incompletely understood. Here we show that antigen-dependent induction of the chemokine receptor, CXCR6, is a conserved requirement for TRM formation in peripheral tissue after viral infection. CXCR6 was dispensable for the early accumulation of antigen-specific CD8+ T cells in skin and did not restrain their exit. Single cell sequencing indicated that CXCR6-/- CD8+ T cells were also competent to acquire a transcriptional program of residence but exhibited deficiency in multiple pathways that converged on survival and metabolic signals necessary for memory. As such, CXCR6-/- CD8+ T cells exhibited increased rates of apoptosis relative to controls in the dermis, leading to inefficient TRM formation. CXCR6 expression may therefore represent a common mechanism across peripheral non-lymphoid tissues and inflammatory states that increases the probability of long-term residence.

scMINER: a mutual information-based framework for identifying hidden drivers from single-cell omics data

The sparse nature of single-cell omics data makes it challenging to dissect the wiring and rewiring of the transcriptional and signaling drivers that regulate cellular states. Many of the drivers, referred to as "hidden drivers", are difficult to identify via conventional expression analysis due to low expression and inconsistency between RNA and protein activity caused by post-translational and other modifications. To address this issue, we developed scMINER, a mutual information (MI)-based computational framework for unsupervised clustering analysis and cell-type specific inference of intracellular networks, hidden drivers and network rewiring from single-cell RNA-seq data. We designed scMINER to capture nonlinear cell-cell and gene-gene relationships and infer driver activities. Systematic benchmarking showed that scMINER outperforms popular single-cell clustering algorithms, especially in distinguishing similar cell types. With respect to network inference, scMINER does not rely on the binding motifs which are available for a limited set of transcription factors, therefore scMINER can provide quantitative activity assessment for more than 6,000 transcription and signaling drivers from a scRNA-seq experiment. As demonstrations, we used scMINER to expose hidden transcription and signaling drivers and dissect their regulon rewiring in immune cell heterogeneity, lineage differentiation, and tissue specification. Overall, activity-based scMINER is a widely applicable, highly accurate, reproducible and scalable method for inferring cellular transcriptional and signaling networks in each cell state from scRNA-seq data. The scMINER software is publicly accessible via: https://github.com/jyyulab/scMINER.

scMINER: a mutual information-based framework for identifying hidden drivers from single-cell omics data

The sparse nature of single-cell omics data makes it challenging to dissect the wiring and rewiring of the transcriptional and signaling drivers that regulate cellular states. Many of the drivers, referred to as "hidden drivers", are difficult to identify via conventional expression analysis due to low expression and inconsistency between RNA and protein activity caused by post-translational and other modifications. To address this issue, we developed scMINER, a mutual information (MI)-based computational framework for unsupervised clustering analysis and cell-type specific inference of intracellular networks, hidden drivers and network rewiring from single-cell RNA-seq data. We designed scMINER to capture nonlinear cell-cell and gene-gene relationships and infer driver activities. Systematic benchmarking showed that scMINER outperforms popular single-cell clustering algorithms, especially in distinguishing similar cell types. With respect to network inference, scMINER does not rely on the binding motifs which are available for a limited set of transcription factors, therefore scMINER can provide quantitative activity assessment for more than 6,000 transcription and signaling drivers from a scRNA-seq experiment. As demonstrations, we used scMINER to expose hidden transcription and signaling drivers and dissect their regulon rewiring in immune cell heterogeneity, lineage differentiation, and tissue specification. Overall, activity-based scMINER is a widely applicable, highly accurate, reproducible and scalable method for inferring cellular transcriptional and signaling networks in each cell state from scRNA-seq data. The scMINER software is publicly accessible via: https://github.com/jyyulab/scMINER.

Sepsis-induced changes in differentiation, maintenance, and function of memory CD8 T cell subsets

Formation of long-lasting memory lymphocytes is one of the foundational characteristics of adaptive immunity and the basis of many vaccination strategies. Following the rapid expansion and contraction of effector CD8 T cells, the surviving antigen (Ag)-specific cells give rise to the memory CD8 T cells that persist for a long time and are phenotypically and functionally distinct from their naïve counterparts. Significant heterogeneity exists within the memory CD8 T cell pool, as different subsets display distinct tissue localization preferences, cytotoxic ability, and proliferative capacity, but all memory CD8 T cells are equipped to mount an enhanced immune response upon Ag re-encounter. Memory CD8 T cells demonstrate numerical stability under homeostatic conditions, but sepsis causes a significant decline in the number of memory CD8 T cells and diminishes their Ag-dependent and -independent functions. Sepsis also rewires the transcriptional profile of memory CD8 T cells, which profoundly impacts memory CD8 T cell differentiation and, ultimately, the protective capacity of memory CD8 T cells upon subsequent stimulation. This review delves into different aspects of memory CD8 T cell subsets as well as the immediate and long-term impact of sepsis on memory CD8 T cell biology.

T follicular helper 17 (Tfh17) cells are superior for immunological memory maintenance

A defining feature of successful vaccination is the ability to induce long-lived antigen-specific memory cells. T follicular helper (Tfh) cells specialize in providing help to B cells in mounting protective humoral immunity in infection and after vaccination. Memory Tfh cells that retain the CXCR5 expression can confer protection through enhancing humoral response upon antigen re-exposure but how they are maintained is poorly understood. CXCR5⁺ memory Tfh cells in human blood are divided into Tfh1, Tfh2, and Tfh17 cells by the expression of chemokine receptors CXCR3 and CCR6 associated with Th1 and Th17, respectively. Here, we developed a new method to induce Tfh1, Tfh2, and Tfh17-like (iTfh1, iTfh2, and iTfh17) mouse cells in vitro. Although all three iTfh subsets efficiently support antibody responses in recipient mice with immediate immunization, iTfh17 cells are superior to iTfh1 and iTfh2 cells in supporting antibody response to a later immunization after extended resting in vivo to mimic memory maintenance. Notably, the counterpart human Tfh17 cells are selectively enriched in CCR7⁺ central memory Tfh cells with survival and proliferative advantages. Furthermore, the analysis of multiple human cohorts that received different vaccines for HBV, influenza virus, tetanus toxin or measles revealed that vaccine-specific Tfh17 cells outcompete Tfh1 or Tfh2 cells for the persistence in memory phase. Therefore, the complementary mouse and human results showing the advantage of Tfh17 cells in maintenance and memory function supports the notion that Tfh17-induced immunization might be preferable in vaccine development to confer long-term protection.

Clonal lineage tracing reveals mechanisms skewing CD8+ T cell fate decisions in chronic infection

Although recent evidence demonstrates heterogeneity among CD8+ T cells during chronic infection, developmental relationships and mechanisms underlying their fate decisions remain incompletely understood. Using single-cell RNA and TCR sequencing, we traced the clonal expansion and differentiation of CD8+ T cells during chronic LCMV infection. We identified immense clonal and phenotypic diversity, including a subset termed intermediate cells. Trajectory analyses and infection models showed intermediate cells arise from progenitor cells before bifurcating into terminal effector and exhausted subsets. Genetic ablation experiments identified that type I IFN drives exhaustion through an IRF7-dependent mechanism, possibly through an IFN-stimulated subset bridging progenitor and exhausted cells. Conversely, Zeb2 was critical for generating effector cells. Intriguingly, some T cell clones exhibited lineage bias. Mechanistically, we identified that TCR avidity correlates with an exhausted fate, whereas SHP-1 selectively restricts low-avidity effector cell accumulation. Thus, our work elucidates novel mechanisms underlying CD8+ T cell fate determination during persistent infection and suggests two potential pathways leading to exhaustion.

Identification of two migratory colon ILC2 populations differentially expressing IL-17A and IL-5/IL-13

Group 2 innate lymphoid cells (ILC2s) play important tissue resident roles in anti-parasite immunity, allergic immune response, tissue homeostasis, and tumor immunity. ILC2s are considered tissue resident cells with little proliferation at steady state. Recent studies have shown that a subset of small intestinal ILC2s could leave their residing tissues, circulate and migrate to different organs, including lung, liver, mesenteric LN and spleen, upon activation. However, it remains unknown whether other ILC populations with migratory behavior exist. In this study, we find two major colon ILC2 populations with potential to migrate to the lung in response to IL-25 stimulation. One subset expresses IL-17A and resembles inflammatory ILC2s (iILC2s) but lacks CD27 expression, whereas the other expresses CD27 but not IL-17A. In addition, the IL-17A⁺ ILC2s express lower levels of CD127, CD25, and ST2 than CD27⁺ ILC2s, which express higher levels of IL-5 and IL-13. Surprisingly, we found that both colon ILC2 populations still maintained their colonic features of preferential expression of IL-17A and CD27, IL-5/IL-13, respectively. Together, our study identifies two migratory colon ILC2 subsets with unique surface markers and cytokine profiles which are critical in regulating lung and colon immunity and homeostasis.