Senescent T cells: Beneficial and detrimental roles

Immunosenescence Profile Is Associated With Increased Susceptibility to Severe COVID-19

In this study, we tested the hypothesis that the immunosenescence profile could account for the disproportional susceptibility of the elderly to severe forms of COVID-19. The immunological profiles of volunteers residing in endemic and non-endemic areas for chronic infectious diseases were analyzed at the early stage of SARS-CoV-2 infection. A unique signature of inflammatory plasma mediators was identified in COVID-19 volunteers when compared to individuals with other flu-like syndromes. COVID-19 severity correlated with high levels of inflammatory mediators; among them, CXCL9, a serum marker of aging. Patients who progressed to hospitalization displayed high frequencies of CD8+ and CD4+ T cells expressing exhaustion and senescence markers and showed reduced and more mature B cell repertoires, which are typical of senescence. They also had an acceleration of epigenetic age measured by DNA methylation. Therefore, severe COVID-19 correlated with phenotypic, functional, and epigenetic features of accelerated immunosenescence at the onset of infection.

T-cell senescence: Unlocking the tumor immune "Dark Box" - A multidimensional analysis from mechanism to tumor immunotherapeutic intervention

Immunosenescence is the dysfunction of the immune system that occurs with age, a process that is complex and characterized by several features, of which T-cell senescence is one of the key manifestations. In the tumor microenvironment, senescent T cells lead to the inability of tumor cells to be effectively eliminated, triggering immunosuppression, which in turn affects the efficacy of immunotherapy. This is a strong indication that T-cell senescence significantly weakens the immune function of the body, making individuals, especially elderly patients with cancer, more vulnerable to cancer attacks. Despite the many challenges, T-cell senescence is important as a potential therapeutic target. This review provides insights into the molecular mechanisms of T-cell senescence and its research advances in patients with cancer, especially in older adults, and systematically analyzes potential intervention strategies, including molecular mechanism-based interventions, the use of immune checkpoint inhibitors, and CAR-T cell therapy. It is hoped that this will establish a theoretical framework for T-cell senescence in the field of tumor immunology and provide a scientific and prospective reference basis for subsequent in-depth research and clinical practice on senescent T cells.

Advances in T Cell-Based Cancer Immunotherapy: From Fundamental Mechanisms to Clinical Prospects

T cells and their T cell receptors (TCRs) play crucial roles in the adaptive immune system's response against pathogens and tumors. However, immunosenescence, characterized by declining T cell function and quantity with age, significantly impairs antitumor immunity. Recent years have witnessed remarkable progress in T cell-based cancer treatments, driven by a deeper understanding of T cell biology and innovative screening technologies. This review comprehensively examines T cell maturation mechanisms, T cell-mediated antitumor responses, and the implications of thymic involution on T cell diversity and cancer prognosis. We discuss recent advances in adoptive T cell therapies, including tumor-infiltrating lymphocyte (TIL) therapy, engineered T cell receptor (TCR-T) therapy, and chimeric antigen receptor T cell (CAR-T) therapy. Notably, we highlight emerging DNA-encoded library technologies in mammalian cells for high-throughput screening of TCR-antigen interactions, which are revolutionizing the discovery of novel tumor antigens and optimization of TCR affinity. The review also explores strategies to overcome challenges in the solid tumor microenvironment and emerging approaches to enhance the efficacy of T cell therapy. As our understanding of T cell biology deepens and screening technologies advances, T cell-based immunotherapies show increasing promise for delivering durable clinical benefits to a broader patient population.

Novel modulation of T effector memory cells-expressing CD45RA by prednisone in inoperable advanced type B thymoma patients

Due to the covert onset of thymoma, nearly 30% of patients are diagnosed at stage III or IV, losing the opportunity for surgical treatment. We have initiated the application of prednisone in treating refractory thymoma and explored biomarkers to identify potential cases that might benefit from prednisone treatment. In a study involving 96 patients with thymoma, we confirmed a significant tumor shrinkage with prednisone acetate treatment. A reduced diameter ratio indicated that type B1 and B2 thymomas exhibited the most obvious response to prednisone acetate, especially type B2 thymoma. However, the reduced diameter ratio was < 30% in type A, AB, and B3 thymomas. Immunofluorescence and flow cytometry of tumor tissues indicated that TEMRA (T Effector Memory-Expressing CD45RA) cells primarily exist in type B thymoma. However, the percentage of interleukin-8 + TEMRA cells decreased only in B1 and B2 thymoma tissues after prednisone acetate treatment. These findings are particularly significant for patients with type B thymoma with stage III or IV.

The PARP inhibitor olaparib promotes senescence in murine macrophages

Cellular senescence is a multifaceted process involving cell cycle arrest, telomere shortening, and the accumulation of DNA damage associated with aging and cellular stress. It is marked by persistent cell cycle arrest and DNA damage accumulation, and plays an increasingly recognized role in age-related diseases and cancer therapy. Olaparib, a poly (ADP-ribose) polymerase (PARP) inhibitor, is approved for use in ovarian cancer treatment. We hypothesized that olaparib may influence senescence by inhibiting DNA damage repair, and investigated its effects on non-senescent and replicatively senescent murine macrophages (RAW 264.7 cells). Senescent cells exhibited elevated baseline levels of PARP1 expression, PARylation, and DNA damage relative to non-senescent control cells. Olaparib amplified these differences by upregulating senescence markers (SA-β-gal and p21), inhibiting proliferation, and exacerbating DNA damage. Many of its effects were more pronounced in senescent cells. At higher concentrations (10-30 µM), olaparib induced significant cytotoxicity through mixed apoptotic and necrotic mechanisms, with senescent cells exhibiting a predominantly necrotic response. Interestingly, both mitochondrial activity and cellular bioenergetics were elevated in senescent cells at baseline, and were more severely impaired by olaparib compared to non-senescent control cells. These findings underscore olaparib's enhanced cytotoxic and pro-senescent effects in senescent immune cells and suggest potential implications for its use in elderly cancer patients with an increased burden of senescent cells.

CD8+ TEMRAs in severe asthma associate with asthma symptom duration and escape proliferation arrest

Aberrant immune response is a hallmark of asthma, with 5%-10% of patients suffering from severe disease exhibiting poor response to standard treatment. A better understanding of the immune responses contributing to disease heterogeneity is critical for improving asthma management. T cells are major players in the orchestration of asthma, in both mild and severe disease, but it is unclear whether specific T cell subsets influence asthma symptom duration. Here we show a significant association of airway CD8+ effector memory T cells re-expressing CD45RA (TEMRAs), but not CD8+CD45RO+ or tissue-resident memory T cells, with asthma duration in patients with severe asthma (SA) but not mild to moderate asthma (MMA). Higher frequencies of IFN-γ+CD8+ TEMRAs compared with IFN-γ+CD45RO+ T cells were detected in SA airways, and the TEMRAs from patients with SA but not MMA proliferated ex vivo, although both expressed cellular senescence-associated biomarkers. Prompted by the transcriptomic profile of SA CD8+ TEMRAs and proliferative response to IL-15, airway IL15 expression was higher in patients with SA compared with MMA. Additionally, IL15 expression in asthmatic airways negatively correlated with lung function. Our findings add what we believe is a new dimension to understanding asthma heterogeneity, identifying IL-15 as a potential target for treatment.

Enhancing immunity during ageing by targeting interactions within the tissue environment

Immunity declines with age. This results in a higher risk of age-related diseases, diminished ability to respond to new infections and reduced response to vaccines. The causes of this immune dysfunction are cellular senescence, which occurs in both lymphoid and non-lymphoid tissue, and chronic, low-grade inflammation known as 'inflammageing'. In this Review article, we highlight how the processes of inflammation and senescence drive each other, leading to loss of immune function. To break this cycle, therapies are needed that target the interactions between the altered tissue environment and the immune system instead of targeting each component alone. We discuss the relative merits and drawbacks of therapies that are directed at eliminating senescent cells (senolytics) and those that inhibit inflammation (senomorphics) in the context of tissue niches. Furthermore, we discuss therapeutic strategies designed to directly boost immune cell function and improve immune surveillance in tissues.

A subtype of T cells impedes tissue repair in aged spinal cord after injury

In this issue of Neuron, Kong et al.1 identify targetable natural killer-like T cells that seed the intact aged human and murine spinal cords and increase further after injury. These cells impede myeloid-cell-dependent wound healing in the aged injured cord through expressing natural killer cell granule protein 7 (NKG7).

Clonally expanded, targetable, natural killer-like NKG7 T cells seed the aged spinal cord to disrupt myeloid-dependent wound healing

Spinal cord injury (SCI) increasingly affects aged individuals, where functional impairment and mortality are highest. However, the aging-dependent mechanisms underpinning tissue damage remain elusive. Here, we find that natural killer-like T (NKLT) cells seed the intact aged human and murine spinal cord and multiply further after injury. NKLT cells accumulate in the spinal cord via C-X-C motif chemokine receptor 6 and ligand 16 signaling to clonally expand by engaging with major histocompatibility complex (MHC)-I-expressing myeloid cells. NKLT cells expressing natural killer cell granule protein 7 (Nkg7) disrupt myeloid-cell-dependent wound healing in the aged injured cord. Nkg7 deletion in mice curbs NKLT cell degranulation to normalize the myeloid cell phenotype, thus promoting tissue repair and axonal integrity. Monoclonal antibodies neutralizing CD8+ T cells after SCI enhance neurological recovery by promoting wound healing. Our results unveil a reversible role for NKG7+CD8+ NKLT cells in exacerbating tissue damage, suggesting a clinically relevant treatment for SCI.

CX3CR1+ age-associated CD4+ T cells contribute to synovial inflammation in late-onset rheumatoid arthritis

BACKGROUND

Recent evidence suggests that clonally expanded cytotoxic T cells play a role in various autoimmune diseases. Late-onset rheumatoid arthritis (LORA) exhibits unique characteristics compared to other RA forms, suggesting distinct immunological mechanisms. This study aimed to examine the involvement of cytotoxic T cells in LORA.

METHODS

Fresh peripheral blood samples were collected from 78 treatment-naïve active RA patients, 12 with difficult-to-treat RA, and 16 healthy controls. Flow cytometry was employed to measure the proportions of CX3CR1+cytotoxic CD4+ and CD8+ T cells in these samples. Additionally, immunohistochemical staining was performed on lymphoid node and synovial biopsy samples from patients with RA.

RESULTS

CX3CR1+cytotoxic CD4+ T cells were specifically increased in untreated, active patients with LORA, displaying features of CXCR3mid age-associated T helper cells known as "ThA". CX3CR1⁺CD4⁺ T cells were identified as a cytotoxic ThA subset, as nearly all of these cells specifically expressed granzyme B. These cells were observed in enlarged lymph nodes and were found to infiltrate synovial tissues from patients with LORA. The proportions of CX3CR1+CD4+ T cells positively correlated with arthritis activity in LORA. The number of cells decreased after treatment with methotrexate, tumor necrosis factor inhibitors, and interleukin-6 inhibitors, whereas T-cell activation modulators did not affect them. Moreover, PD-1+CD38+CX3CR1+CD4+ T cells were identified as a treatment-resistant T cell subset that was characteristically increased in difficult-to-treat RA. CX3CR1+CD8+ T cells showed no significant difference between RA patients and healthy individuals, and no correlation with disease activity was observed. However, a correlation with age was observed in RA patients.

CONCLUSIONS

Our findings suggest that the immunopathogenesis of RA differs by age of onset, with CX3CR1+ age-associated cytotoxic CD4+ T cells playing a significant role in LORA. Additionally, the presence of a specific CX3CR1+ T cell subset may be linked to treatment resistance.

Multiple outcomes of the germline p16INK4a mutation affecting senescence and immunity in human skin

The integrated behaviour of multiple senescent cell types within a single human tissue leading to the development of malignancy is unclear. Patients with Familial Melanoma Syndrome (FMS) have heterozygous germline defects in the CDKN2A gene coding for the cyclin inhibitor p16INK4a. Melanocytes within skin biopsies from FMS patients express significantly less p16INK4a but express higher levels of the DNA-damage protein 𝛾H2AX a than fibroblastic cells. However, patient fibroblasts also exhibit defects since senescent cells do not increase in the skin during ageing and fibroblasts isolated from the skin of patients have increased replicative capacity compared to control fibroblasts in vitro, culminating in abnormal nuclear morphology. Patient derived fibroblasts also secreted less SASP than control cells. Predisposition of FMS patients to melanoma may therefore result from integrated dysregulation of senescence in multiple cell types in vivo. The inherently greater levels of DNA damage and the overdependence of melanocytes on p16 for cell cycle inhibition after DNA damage makes them exquisitely susceptible to malignant transformation. This may be accentuated by senescence-related defects in fibroblasts, in particular reduced SASP secretion that hinders recruitment of T cells in the steady state and thus reduces cutaneous immunosurveillance in vivo.

Benefit delayed immunosenescence by regulating CD4+T cells: A promising therapeutic target for aging-related diseases

CD4+T cells play a notable role in immune protection at different stages of life. During aging, the interaction between the body's internal and external environment and CD4+T cells results in a series of changes in the CD4+T cells pool making it involved in immunosenescence. Many studies have extensively examined the subsets and functionality of CD4+T cells within the immune system, highlighted their pivotal role in disease pathogenesis, progression, and therapeutic interventions. However, the underlying mechanism of CD4+T cells senescence and its intricate association with diseases remains to be elucidated and comprehensively understood. By summarizing the immunosenescent progress and network of CD4+T cell subsets, we reveal the crucial role of CD4+T cells in the occurrence and development of age-related diseases. Furthermore, we provide new insights and theoretical foundations for diseases targeting CD4+T cell subsets aging as a treatment focus, offering novel approaches for therapy, especially in infections, cancers, autoimmune diseases, and other diseases in the elderly.

IL-15 in T-Cell Responses and Immunopathogenesis

IL-15 belongs to the common gamma chain cytokine family and has pleiotropic immunological functions. IL-15 is a homeostatic cytokine essential for the development and maintenance of NK cells and memory CD8+ T cells. In addition, IL-15 plays a critical role in the activation, effector functions, tissue residency, and senescence of CD8+ T cells. IL-15 also activates virtual memory T cells, mucosal-associated invariant T cells and γδ T cells. Recently, IL-15 has been highlighted as a major trigger of TCR-independent activation of T cells. This mechanism is involved in T cell-mediated immunopathogenesis in diverse diseases, including viral infections and chronic inflammatory diseases. Deeper understanding of IL-15-mediated T-cell responses and their underlying mechanisms could optimize therapeutic strategies to ameliorate host injury by T cell-mediated immunopathogenesis. This review highlights recent advancements in comprehending the role of IL-15 in relation to T cell responses and immunopathogenesis under various host conditions.

Multimodal profiling reveals tissue-directed signatures of human immune cells altered with age

The immune system comprises multiple cell lineages and heterogeneous subsets found in blood and tissues throughout the body. While human immune responses differ between sites and over age, the underlying sources of variation remain unclear as most studies are limited to peripheral blood. Here, we took a systems approach to comprehensively profile RNA and surface protein expression of over 1.25 million immune cells isolated from blood, lymphoid organs, and mucosal tissues of 24 organ donors aged 20-75 years. We applied a multimodal classifier to annotate the major immune cell lineages (T cells, B cells, innate lymphoid cells, and myeloid cells) and their corresponding subsets across the body, leveraging probabilistic modeling to define bases for immune variations across donors, tissue, and age. We identified dominant tissue-specific effects on immune cell composition and function across lineages for lymphoid sites, intestines, and blood-rich tissues. Age-associated effects were intrinsic to both lineage and site as manifested by macrophages in mucosal sites, B cells in lymphoid organs, and T and NK cells in blood-rich sites. Our results reveal tissue-specific signatures of immune homeostasis throughout the body and across different ages. This information provides a basis for defining the transcriptional underpinnings of immune variation and potential associations with disease-associated immune pathologies across the human lifespan.

Effects of Korean red ginseng on T-cell repopulation after autologous hematopoietic stem cell transplantation in childhood cancer patients

Background

Although the survival outcomes of childhood cancer patients have improved, childhood cancer survivors suffer from various degrees of immune dysfunction or delayed immune reconstitution. This study aimed to investigate the effect of Korean Red Ginseng (KRG) on T cell recovery in childhood cancer patients who underwent autologous hematopoietic stem cell transplantation (ASCT) from the perspective of inflammatory and senescent phenotypes.

Methods

This was a single-arm exploratory trial. The KRG group (n = 15) received KRG powder from month 1 to month 12 post-ASCT. We compared the results of the KRG group with those of the control group (n = 23). The proportions of T cell populations, senescent phenotypes, and cytokine production profiles were analyzed at 1, 3, 6, and 12 months post-ASCT using peripheral blood samples.

Results

All patients in the KRG group completed the treatment without any safety issues and showed a comparable T cell repopulation pattern to that in the control group. In particular, KRG administration influenced the repopulation of CD4+ T cells via T cell expansion and differentiation into effector memory cell re-expressing CD45RA (EMRA) cells. Although the KRG group showed an increase in the number of CD4+ EMRA cells, the expression of senescent and exhausted markers in these cells decreased, and the capacity for senescence-related cytokine production in the senescent CD28- subset was ameliorated.

Conclusions

These findings suggest that KRG promotes the repopulation of CD4+ EMRA T cells and regulates phenotypical and functional senescent changes after ASCT in pediatric patients with cancer.

Cellular senescence throws new insights into patient classification and pharmacological interventions for clinical management of hepatocellular carcinoma

BACKGROUND

Cellular senescence, a state of stable growth arrest, is intertwined with human cancers. However, characterization of cellular senescence-associated phenotypes in hepatocellular carcinoma (HCC) remains unexplored.

AIM

To address this issue, we delineated cellular senescence landscape across HCC.

METHODS

We enrolled two HCC datasets, TCGA-LIHC and International Cancer Genome Consortium (ICGC). Unsupervised clustering was executed to probe tumor heterogeneity based upon cellular senescence genes. Least absolute shrinkage and selection operator algorithm were utilized to define a cellular senescence-relevant scoring system. TRNP1 expression was measured in HCCs and normal tissues through immunohistochemistry, immunoblotting and quantitative real-time polymerase chain reaction. The influence of TMF-regulated nuclear protein (TRNP)1 on HCC senescence and growth was proven via a series of experiments.

RESULTS

TCGA-LIHC patients were classified as three cellular senescence subtypes, named C1-3. The robustness and reproducibility of these subtypes were proven in the ICGC cohort. C2 had the worst overall survival, C1 the next, and C3 the best. C2 presented the highest levels of immune checkpoints, abundance of immune cells, and immunogenetic indicators. Thus, C2 might possibly respond to immunotherapy. C2 had the lowest somatic mutation rate, while C1 presented the highest copy number variations. A cellular senescence-relevant gene signature was generated, which can predict patient survival, and chemo- or immunotherapeutic response. Experimentally, it was proven that TRNP1 presented the remarkable upregulation in HCCs. TRNP1 knockdown induced apoptosis and senescence of HCC cells and attenuated tumor growth.

CONCLUSION

These findings provide a systematic framework for assessing cellular senescence in HCC, which decode the tumor heterogeneity and tailor the pharmacological interventions to improve clinical management.

T Lymphocytes and Their Potential Role in Dementia with Lewy Bodies

Dementia with Lewy bodies (DLB) is the second most common neurodegenerative cause of dementia. People with DLB have an inferior prognosis compared to Alzheimer's disease (AD), but the diseases overlap in their neuropathology and clinical syndrome. It is imperative that we enhance our understanding of the aetiology and pathogenesis of DLB. The impact of peripheral inflammation on the brain in dementia has been increasingly explored in recent years, with T lymphocyte recruitment into brain parenchyma identified in AD and Parkinson's disease. There is now a growing range of literature emerging on the potential role of innate and adaptive immune cells in DLB, including T lymphocytes. In this review, we examine the profile of T lymphocytes in DLB, focusing on studies of post-mortem brain tissue, cerebrospinal fluid, and the blood compartment. We present an integrated viewpoint on the results of these studies by proposing how changes to the T lymphocyte profile in the brain and periphery may relate to each other. Improving our understanding of T lymphocytes in DLB has the potential to guide the development of disease-modifying treatments.

Harnessing the immunomodulatory effects of exercise to enhance the efficacy of monoclonal antibody therapies against B-cell haematological cancers: a narrative review

Therapeutic monoclonal antibodies (mAbs) are standard care for many B-cell haematological cancers. The modes of action for these mAbs include: induction of cancer cell lysis by activating Fcγ-receptors on innate immune cells; opsonising target cells for antibody-dependent cellular cytotoxicity or phagocytosis, and/or triggering the classical complement pathway; the simultaneous binding of cancer cells with T-cells to create an immune synapse and activate perforin-mediated T-cell cytotoxicity against cancer cells; blockade of immune checkpoints to facilitate T-cell cytotoxicity against immunogenic cancer cell clones; and direct delivery of cytotoxic agents via internalisation of mAbs by target cells. While treatment regimens comprising mAb therapy can lead to durable anti-cancer responses, disease relapse is common due to failure of mAb therapy to eradicate minimal residual disease. Factors that limit mAb efficacy include: suboptimal effector cell frequencies, overt immune exhaustion and/or immune anergy, and survival of diffusely spread tumour cells in different stromal niches. In this review, we discuss how immunomodulatory changes arising from exposure to structured bouts of acute exercise might improve mAb treatment efficacy by augmenting (i) antibody-dependent cellular cytotoxicity, (ii) antibody-dependent cellular phagocytosis, (iii) complement-dependent cytotoxicity, (iv) T-cell cytotoxicity, and (v) direct delivery of cytotoxic agents.

Chronic inflammation and the hallmarks of aging

BACKGROUND

Recently, the hallmarks of aging were updated to include dysbiosis, disabled macroautophagy, and chronic inflammation. In particular, the low-grade chronic inflammation during aging, without overt infection, is defined as "inflammaging," which is associated with increased morbidity and mortality in the aging population. Emerging evidence suggests a bidirectional and cyclical relationship between chronic inflammation and the development of age-related conditions, such as cardiovascular diseases, neurodegeneration, cancer, and frailty. How the crosstalk between chronic inflammation and other hallmarks of aging underlies biological mechanisms of aging and age-related disease is thus of particular interest to the current geroscience research.

SCOPE OF REVIEW

This review integrates the cellular and molecular mechanisms of age-associated chronic inflammation with the other eleven hallmarks of aging. Extra discussion is dedicated to the hallmark of "altered nutrient sensing," given the scope of Molecular Metabolism. The deregulation of hallmark processes during aging disrupts the delicate balance between pro-inflammatory and anti-inflammatory signaling, leading to a persistent inflammatory state. The resultant chronic inflammation, in turn, further aggravates the dysfunction of each hallmark, thereby driving the progression of aging and age-related diseases.

MAIN CONCLUSIONS

The crosstalk between chronic inflammation and other hallmarks of aging results in a vicious cycle that exacerbates the decline in cellular functions and promotes aging. Understanding this complex interplay will provide new insights into the mechanisms of aging and the development of potential anti-aging interventions. Given their interconnectedness and ability to accentuate the primary elements of aging, drivers of chronic inflammation may be an ideal target with high translational potential to address the pathological conditions associated with aging.