Identification of the novel FOXP3-dependent Treg cell transcription factor MEOX1 by high-dimensional analysis of human CD4+ T cells

CD4+ T cells play a central role in the adaptive immune response through their capacity to activate, support and control other immune cells. Although these cells have become the focus of intense research, a comprehensive understanding of the underlying regulatory networks that orchestrate CD4+ T cell function and activation is still incomplete. Here, we analyzed a large transcriptomic dataset consisting of 48 different human CD4+ T cell conditions. By performing reverse network engineering, we identified six common denominators of CD4+ T cell functionality (CREB1, E2F3, AHR, STAT1, NFAT5 and NFATC3). Moreover, we also analyzed condition-specific genes which led us to the identification of the transcription factor MEOX1 in Treg cells. Expression of MEOX1 was comparable to FOXP3 in Treg cells and can be upregulated by IL-2. Epigenetic analyses revealed a permissive epigenetic landscape for MEOX1 solely in Treg cells. Knockdown of MEOX1 in Treg cells revealed a profound impact on downstream gene expression programs and Treg cell suppressive capacity. These findings in the context of CD4+ T cells contribute to a better understanding of the transcriptional networks and biological mechanisms controlling CD4+ T cell functionality, which opens new avenues for future therapeutic strategies.

Parallel recovery of chromatin accessibility and gene expression dynamics from frozen human regulatory T cells

Epigenetic features such as DNA accessibility dictate transcriptional regulation in a cell type- and cell state- specific manner, and mapping this in health vs. disease in clinically relevant material is opening the door to new mechanistic insights and new targets for therapy. Assay for Transposase Accessible Chromatin Sequencing (ATAC-seq) allows chromatin accessibility profiling from low cell input, making it tractable on rare cell populations, such as regulatory T (Treg) cells. However, little is known about the compatibility of the assay with cryopreserved rare cell populations. Here we demonstrate the robustness of an ATAC-seq protocol comparing primary Treg cells recovered from fresh or cryopreserved PBMC samples, in the steady state and in response to stimulation. We extend this method to explore the feasibility of conducting simultaneous quantitation of chromatin accessibility and transcriptome from a single aliquot of 50,000 cryopreserved Treg cells. Profiling of chromatin accessibility and gene expression in parallel within the same pool of cells controls for cellular heterogeneity and is particularly beneficial when constrained by limited input material. Overall, we observed a high correlation of accessibility patterns and transcription factor dynamics between fresh and cryopreserved samples. Furthermore, highly similar transcriptomic profiles were obtained from whole cells and from the supernatants recovered from ATAC-seq reactions. We highlight the feasibility of applying these techniques to profile the epigenomic landscape of cells recovered from cryopreservation biorepositories.

An intrinsic role of IL-33 in Treg cell-mediated tumor immunoevasion

Regulatory T (T_reg) cells accumulate into tumors hindering the success of cancer immunotherapy. Yet, therapeutic targeting of T_reg cells shows limited efficacy or leads to autoimmunity. The molecular mechanisms that guide T_reg cell stability in tumors, remain elusive. Herein, we identify a cell-intrinsic role of the alarmin IL-33 in the functional stability of T_reg cells. Specifically, IL-33-deficient T_reg cells demonstrated attenuated suppressive properties in vivo and facilitated tumor regression in an ST2 (IL-33 receptor)-independent fashion. Upon activation, Il33^–/– T_reg cells exhibited epigenetic reprogramming with increased chromatin accessibility of the Ifng locus leading to elevated interferon-γ (IFN-γ) production in an NF-κB–T-bet-dependent manner. IFN-γ was essential for T_reg cell defective function since its ablation restored Il33^–/– T_reg cell suppressive properties. Importantly, genetic ablation of Il33 potentiated the therapeutic effect of immunotherapy. Our findings reveal a novel and therapeutically important intrinsic role of IL-33 in T_reg cell stability in cancer.

Enzymatic Activity of HPGD in Treg Cells Suppresses Tconv Cells to Maintain Adipose Tissue Homeostasis and Prevent Metabolic Dysfunction

Regulatory T cells (Treg cells) are important for preventing autoimmunity and maintaining tissue homeostasis, but whether Treg cells can adopt tissue- or immune-context-specific suppressive mechanisms is unclear. Here, we found that the enzyme hydroxyprostaglandin dehydrogenase (HPGD), which catabolizes prostaglandin E₂ (PGE₂) into the metabolite 15-keto PGE₂, was highly expressed in Treg cells, particularly those in visceral adipose tissue (VAT). Nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ)-induced HPGD expression in VAT Treg cells, and consequential Treg-cell-mediated generation of 15-keto PGE₂ suppressed conventional T cell activation and proliferation. Conditional deletion of Hpgd in mouse Treg cells resulted in the accumulation of functionally impaired Treg cells specifically in VAT, causing local inflammation and systemic insulin resistance. Consistent with this mechanism, humans with type 2 diabetes showed decreased HPGD expression in Treg cells. These data indicate that HPGD-mediated suppression is a tissue- and context-dependent suppressive mechanism used by Treg cells to maintain adipose tissue homeostasis.

140 Endocrine Profiling in Prepubertal Stallions with Abnormal Testicular Development

The use of anti-Müllerian hormone (AMH) as a biomarker for assessment of male gonadal activity has become increasingly widespread. Aberrant AMH concentration successfully detects cryptorchids or pathologic testes in postpubertal stallions, but the ability to use AMH to identify stallions with testicular pathologies during their prepubertal life has not been analysed so far. The objectives of this work were to (1) assess AMH, testosterone, LH, and FSH dynamics in male horses with or without testicular pathologies during the first year of life; and (2) find a reliable diagnostic approach that would enable the identification of animals that will develop abnormal testes at an early stage. Warmblood colts (n = 16) born from February to May on the same stud farm were used. Blood samples for hormone determinations were collected from birth onwards every 4 weeks until the age of 1 year. At 2 years, testicular development was assessed, total testicular volume calculated. and a blood sample collected. Concentrations of AMH, testosterone, LH, and FSH were determined in all samples; AMH (AL-115, Ansh Laboratories, Webster, TX, USA) and testosterone (DE1559, Demeditec, Kiel-Wellsee, Germany) concentrations were determined by ELISA, whereas LH and FSH concentrations were determined by radioimmunoassay. Statistical analysis (SPSS Statistics 24; IBM/SPSS, Armonk, NY, USA) was performed by ANOVA using a general linear model for repeated measures. In 2 stallions, unilateral cryptorchism, and in other 4 stallions, subnormal total testicular volume (<mean minus SD) were diagnosed at 2 years. Concentrations of AMH, testosterone, and FSH changed over time (P < 0.001) but were similar (P > 0.05) within the first year of life irrespective of testicular morphology and location. Concentration of LH at birth was lower (P = 0.05) in stallions with abnormal testes (0.3 ± 0.2 ng mL−1) than in controls (0.6 ± 0.2 ng mL−1), but did not differ thereafter. At 2 years of age, AMH concentration was higher (P < 0.01) in stallions with abnormal testes (39.7 ± 12.7 ng mL−1) than in controls (8.0 ± 0.2 ng mL−1), but no group differences with regard to LH, FSH, and testosterone existed. There was a low but significant negative correlation between AMH and FSH (P < 0.001, r = –0.24), as well as between AMH and LH (P < 0.05, r = –0.15). Also, testosterone concentration was positively correlated with FSH (P < 0.05, r = 0.18) and LH (P < 0.05, r = 0.16) concentrations. In conclusion, AMH determination can be reliably used from 2 years onwards to identify stallions with abnormal testicular development, but it is inconclusive before puberty. We concluded that LH secretion in the perinatal period is involved in testicular development and descent in the horse.

Tumor-necrosis factor impairs CD4(+) T cell-mediated immunological control in chronic viral infection

Persistent viral infections are characterized by the simultaneous presence of chronic inflammation and T cell dysfunction. In prototypic models of chronicity--infection with human immunodeficiency virus (HIV) or lymphocytic choriomeningitis virus (LCMV)--we used transcriptome-based modeling to reveal that CD4(+) T cells were co-exposed not only to multiple inhibitory signals but also to tumor-necrosis factor (TNF). Blockade of TNF during chronic infection with LCMV abrogated the inhibitory gene-expression signature in CD4(+) T cells, including reduced expression of the inhibitory receptor PD-1, and reconstituted virus-specific immunity, which led to control of infection. Preventing signaling via the TNF receptor selectively in T cells sufficed to induce these effects. Targeted immunological interventions to disrupt the TNF-mediated link between chronic inflammation and T cell dysfunction might therefore lead to therapies to overcome persistent viral infection.

Silent period measurement revives as a valuable diagnostic tool with transcranial magnetic stimulation

Following magnetic transcranial stimulation (TCS) a post-excitatory pause can be observed in surface electromyographic (EMG) recordings from pre-innervated muscles. We studied the duration of this silent period (SP) in the abductor pollicis brevis muscle while varying the stimulus intensity (SI) and the amount of the voluntary tonic contraction in 23 normal adults aged 20-78 years. A multivariate linear regression analysis revealed a positive correlation of SP with SI and a slight negative correlation with age. In 11 hemiparetic patients a relative increase of the SP was found on the affected side despite normal central motor conduction time. A marked shortening of the SP in relation to controls was observed in 6 parkinsonian patients.