KLRG1 signaling induces defective Akt (ser473) phosphorylation and proliferative dysfunction of highly differentiated CD8+ T cells. Blood. 2009;113:6619-6628. [PMID: 19406987 DOI: 10.1182/blood-2009-01-199588]

OMIP-109: 45-color full spectrum flow cytometry panel for deep immunophenotyping of the major lineages present in human peripheral blood mononuclear cells with emphasis on the T cell memory compartment

The need for more in-depth exploration of the human immune system has moved the flow cytometry field forward with advances in instrumentation, reagent development and availability, and user-friendly implementation of data analysis methods. We developed a high-quality human 45-color panel, for comprehensive characterization of major cell lineages present in circulation including T cells, γδ T cells, NKT-like cells, B cells, NK cells, monocytes, basophils, dendritic cells, and ILCs. Assay optimization steps are described in detail to ensure that each marker in the panel was optimally resolved. In addition, we highlight the outstanding discernment of cell activation, exhaustion, memory, and differentiation states of CD4+ and CD8+ T cells using this 45-color panel. The panel enabled an in-depth description of very distinct phenotypes associated with the complexity of the T cell memory response. Furthermore, we present how this panel can be effectively used for cell sorting on instruments with a similar optical layout to achieve the same level of resolution. Functional evaluation of sorted specific rare cell subsets demonstrated significantly different patterns of immunological responses to stimulation, supporting functional and phenotypic differences within the T cell memory subsets. In summary, the combination of full spectrum profiling technology and careful assay design and optimization results in a high resolution multiparametric 45-color assay. This panel offers the opportunity to fully characterize immunological profiles present in peripheral blood in the context of infectious diseases, autoimmunity, neurodegeneration, immunotherapy, and biomarker discovery.

Combined Training Improves Gene Expression Related to Immunosenescence in Obese Type 2 Diabetic Individuals

Purpose: The aim of this study was to investigate the effects of moderate combined training (CT) on both the gene expression of pro- and anti-inflammatory markers and senescence in the immune system in peripheral blood mononuclear cells (PBMCs) and subcutaneous adipose tissue (SAT) of obese middle-aged individuals with type 2 diabetes (T2D). Methods: Thirty obese individuals (50.2 ± 9.4 years; body mass index: 31.8 ± 2.3 kg/m²) with T2D underwent 16 weeks of a CT group [CT; aerobic (50-60% of VO2max) plus resistance (50-75% of 1RM) training; 3 times/week, 70 min/session; n = 16)] or a control group (CG, n = 14). Nutritional patterns, muscle strength (1RM), cardiorespiratory fitness (VO2max), waist circumference (WC), body composition (Air Displacement Plethysmograph) and blood collections for biochemical (serum leptin, IL-2, IL-4, IL-6, IL-10, TNF-α and anti-CMV) and molecular (gene expression of leptin, IL-2, IL-4, IL-6, IL-10, TNF-α, PD-1, P16ink4a, CCR7, CD28 and CD27 in PBMCs and SAT) analyses were assessed before (Pre) and after (Post) the 16 weeks of the experimental period. Results: Significant decreases were observed in WC and IL4, TNF-α, PD-1 and CD27 expression in PBMCs for CT. Furthermore, significant increases were observed in 1RM and VO2max for CT after the experimental period. Conclusion: Moderate CT contributed to a reduction in the gene expression of markers associated to chronic inflammation and immunosenescence in PBMCs of obese middle-aged individuals with T2D.

Unraveling the genetic and molecular landscape of sepsis and acute kidney injury: A comprehensive GWAS and machine learning approach

OBJECTIVES

This study aimed to explore the underlying mechanisms of sepsis and acute kidney injury (AKI), including sepsis-associated AKI (SA-AKI), a frequent complication in critically ill sepsis patients.

METHODS

GWAS data was analyzed for genetic association between AKI and sepsis. Then, we systematically applied three distinct machine learning algorithms (LASSO, SVM-RFE, RF) to rigorously identify and validate signature genes of SA-AKI, assessing their diagnostic and prognostic value through ROC curves and survival analysis. The study also examined the functional and immunological aspects of these genes, potential drug targets, and ceRNA networks. A mouse model of sepsis was created to test the reliability of these signature genes.

RESULTS

LDSC confirmed a positive genetic correlation between AKI and sepsis, although no significant shared loci were found. Bidirectional MR analysis indicated mutual increased risks of AKI and sepsis. Then, 311 key genes common to sepsis and AKI were identified, with 42 significantly linked to sepsis prognosis. Six genes, selected through LASSO, SVM-RFE, and RF algorithms, showed excellent predictive performance for sepsis, AKI, and SA-AKI. The models demonstrated near-perfect AUCs in both training and testing datasets, and a perfect AUC in a sepsis mouse model. Significant differences in immune cells, immune-related pathways, HLA, and checkpoint genes were found between high- and low-risk groups. The study identified 62 potential drug treatments for sepsis and AKI and constructed a ceRNA network.

CONCLUSIONS

The identified signature genes hold potential clinical applications, including prognostic evaluation and targeted therapeutic strategies for sepsis and AKI. However, further research is needed to confirm these findings.

The role of KLRG1: a novel biomarker and new therapeutic target

Killer cell lectin-like receptor G1 (KLRG1) is an immune checkpoint receptor expressed predominantly in NK and T-cell subsets that downregulates the activation and proliferation of immune cells and participates in cell-mediated immune responses. Accumulating evidence has demonstrated the importance of KLRG1 as a noteworthy disease marker and therapeutic target that can influence disease onset, progression, and prognosis. Blocking KLRG1 has been shown to effectively mitigate the effects of downregulation in various mouse tumor models, including solid tumors and hematologic malignancies. However, KLRG1 inhibitors have not yet been approved for human use, and the understanding of KLRG1 expression and its mechanism of action in various diseases remains incomplete. In this review, we explore alterations in the distribution, structure, and signaling pathways of KLRG1 in immune cells and summarize its expression patterns and roles in the development and progression of autoimmune diseases, infectious diseases, and cancers. Additionally, we discuss the potential applications of KLRG1 as a tool for tumor immunotherapy.

Chronic immune activation and accelerated immune aging among HIV-infected adults receiving suppressive antiretroviral therapy for at least 12 years in an African cohort

Background

HIV-associated alterations innate and adaptive immune cell compartments are reminiscent of the process of immune aging.

Objectives

We described immune aging phenotypes among ART-treated HIV-infected adults relative to age-matched HIV-negative counterparts.

Methods

In a cross-sectional comparative study of HIV-infected adults with CD4≥500 cells/μl after at least 12 years of suppressive ART and age-and-gender-matched HIV-negative individuals, immune activation and immune aging phenotypes were measured, using multi-color flowcytometry.

Results

ART-treated HIV-infected individuals had higher body mass index (P = 0.004), waist-hip circumference (P = 0.041), hip circumference (P < 0.001), and diastolic blood pressure (P = 0.012) and immune activation (CD4+CD38+HLADR+; median 4.15,IQR(1.030,14.6)] relative to the HIV-negative age-matched individuals [median 3.14,IQR(1.030, 6.68)]; P=0.0034. Immune aging markers [CD4+CD57+T-cells; median 13.00 IQR (0.45,64.1)] were higher among HIV-infected ART-treated adults<50 years relative to HIV-negative<50 years[median 8.020,IQR(0.004,21.2)]; P=0.0010. Naïve CD4 T-cells, Central memory CD4 T-cells, Terminal Effector Memory T cells (TEMRA: CD27-CD45RA + CCR7-) and immune senescence CD4/CD8+CD28-/CD57+ T-cells were similar among ART-treated HIV-infected individuals<45 years relative to 60 years-and-older HIV-negative counterparts≥; p = 0.0932, p = 0.05357, p = 0.0950 and p = 0.5714 respectively.

Conclusion

ART-treated adults are immunologically two decades older than their HIV-negative counterparts. Accelerated immune aging among individuals aging with HIV underscores the need for an HIV cure to avert the unprecedented complications of accelerated immune senescence and the associated NCD risk in African settings with protracted exposure to endemic co-infections.

Persistence of a Skewed Repertoire of NK Cells in People with HIV-1 on Long-Term Antiretroviral Therapy

HIV-1 infection greatly alters the NK cell phenotypic and functional repertoire. This is highlighted by the expansion of a rare population of FcRγ- NK cells exhibiting characteristics of traditional immunologic memory in people with HIV (PWH). Although current antiretroviral therapy (ART) effectively controls HIV-1 viremia and disease progression, its impact on HIV-1-associated NK cell abnormalities remains unclear. To address this, we performed a longitudinal analysis detailing conventional and memory-like NK cell characteristics in n = 60 PWH during the first 4 y of ART. Throughout this regimen, a skewed repertoire of cytokine unresponsive FcRγ- memory-like NK cells persisted and accompanied an overall increase in NK surface expression of CD57 and KLRG1, suggestive of progression toward immune senescence. These traits were linked to elevated serum inflammatory biomarkers and increasing Ab titers to human CMV, with human CMV viremia detected in approximately one-third of PWH at years 1-4 of ART. Interestingly, 40% of PWH displayed atypical NK cell subsets, representing intermediate stages of NK-poiesis based on single-cell multiomic trajectory analysis. Our findings indicate that NK cell irregularities persist in PWH despite long-term ART, underscoring the need to better understand the causative mechanisms that prevent full restoration of immune health in PWH.

OPA1 mutation affects autophagy and triggers senescence in autosomal dominant optic atrophy plus fibroblasts

In several cases of mitochondrial diseases, the underlying genetic and bioenergetic causes of reduced oxidative phosphorylation (OxPhos) in mitochondrial dysfunction are well understood. However, there is still limited knowledge about the specific cellular outcomes and factors involved for each gene and mutation, which contributes to the lack of effective treatments for these disorders. This study focused on fibroblasts from a patient with Autosomal Dominant Optic Atrophy (ADOA) plus syndrome harboring a mutation in the Optic Atrophy 1 (OPA1) gene. By combining functional and transcriptomic approaches, we investigated the mitochondrial function and identified cellular phenotypes associated with the disease. Our findings revealed that fibroblasts with the OPA1 mutation exhibited a disrupted mitochondrial network and function, leading to altered mitochondrial dynamics and reduced autophagic response. Additionally, we observed a premature senescence phenotype in these cells, suggesting a previously unexplored role of the OPA1 gene in inducing senescence in ADOA plus patients. This study provides novel insights into the mechanisms underlying mitochondrial dysfunction in ADOA plus and highlights the potential importance of senescence in disease progression.

Senescent T Cells in Age-Related Diseases

Age-induced alterations in human immunity are often considered deleterious and are referred to as immunosenescence. The immune system monitors the number of senescent cells in the body, while immunosenescence may represent the initiation of systemic aging. Immune cells, particularly T cells, are the most impacted and involved in age-related immune function deterioration, making older individuals more prone to different age-related diseases. T-cell senescence can impact the effectiveness of immunotherapies that rely on the immune system's function, including vaccines and adoptive T-cell therapies. The research and practice of using senescent T cells as therapeutic targets to intervene in age-related diseases are in their nascent stages. Therefore, in this review, we summarize recent related literature to investigate the characteristics of senescent T cells as well as their formation mechanisms, relationship with various aging-related diseases, and means of intervention. The primary objective of this article is to explore the prospects and possibilities of therapeutically targeting senescent T cells, serving as a valuable resource for the development of immunotherapy and treatment of age-related diseases.

A silver bullet for ageing medicine?: clinical relevance of T-cell checkpoint receptors in normal human ageing

Immunosenescence describes dysregulation of the immune system with ageing manifested in both the innate and adaptive immunity, including changes in T-cell checkpoint signaling. Through complex and nuanced process, T-cells lose excitatory signaling pathways and upregulate their inhibitory signaling, leading to ineffective immune responses that contribute to the formation of the ageing phenotype. Here we expand on the expression, function, and clinical potential of targeting the T-cell checkpoint signaling in age and highlight interventions offering the most benefits to older adults' health. Notably, modifications in vaccination such as with mTOR inhibitors show immediate clinical relevance and good tolerability. Other proposed treatments, including therapies with monoclonal antibodies fail to show clinical efficacy or tolerability needed for implementation at present. Although T-cell co-signaling fits a valuable niche for translational scientists to manage immunosenescence, future study would benefit from the inclusion of older adults with multiple long-term conditions and polypharmacy, ensuring better applicability to actual patients seen in clinical settings.

Implications of Senescent T Cells for Cancer Immunotherapy

T-cell senescence is thought to result from the age-related loss of the ability to mount effective responses to pathogens and tumor cells. In addition to aging, T-cell senescence is caused by repeated antigenic stimulation and chronic inflammation. Moreover, we demonstrated that T-cell senescence was induced by treatment with DNA-damaging chemotherapeutic agents. The characteristics of therapy-induced senescent T (TIS-T) cells and general senescent T cells are largely similar. Senescent T cells demonstrate an increase in the senescence-associated beta-galactosidase-positive population, cell cycle arrest, secretion of senescence-associated secretory phenotypic factors, and metabolic reprogramming. Furthermore, senescent T cells downregulate the expression of the co-stimulatory molecules CD27 and CD28 and upregulate natural killer cell-related molecules. Moreover, TIS-T cells showed increased PD-1 expression. However, the loss of proliferative capacity and decreased expression of co-stimulatory molecules associated with T-cell senescence cause a decrease in T-cell immunocompetence. In this review, we discuss the characteristics of senescent T-cells, including therapy-induced senescent T cells.

CD28/PD1 co-expression: dual impact on CD8+ T cells in peripheral blood and tumor tissue, and its significance in NSCLC patients' survival and ICB response

BACKGROUND

Immune checkpoint blockade (ICB) has significantly prolonged survival of non-small cell lung cancer (NSCLC) patients, although most patients develop mechanisms of resistance. Recently single-cell RNA-sequencing (scRNA-Seq) revealed a huge T-cell phenotypic and (dys)functional state variability. Accordingly, T-cell exhaustion is recognized as a functional adaptation, with a dynamic progression from a long-lived "pre-exhausted stem-like progenitor" to a "terminally exhausted" state. In this scenario it is crucial to understand the complex interplay between co-stimulatory and inhibitory molecules in CD8+ T-cell functionality.

METHODS

To gain a baseline landscape of the composition, functional states, and transcriptomic signatures predictive of prognosis, we analyzed CD8+ T-cell subsets characterized by the presence/absence of PD1 and CD28 from periphery, adjacent non-tumor tissue and tumor site of a cohort of treatment-naïve NSCLC patients, by integrated multiparametric flow cytometry, targeted multi-omic scRNA-seq analyses, and computational pipelines.

RESULTS

Despite the increased PD1 levels, an improved PD1+CD28+ T-cell polyfunctionality was observed with the transition from periphery to tumor site, associated with lack of TIGIT, TIM-3 and LAG-3, but not with Ag-experienced-marker CD11a. Differently from CD28+ T cells, the increased PD1 levels in the tumor were associated with reduced functionality in PD1+CD28- T cells. CD11ahigh, although expressed only in a small fraction of this subset, still sustained its functionality. Absence of TIGIT, TIM-3 and CTLA-4, alone or combined, was beneficial to CD28- T cells. Notably, we observed distinct TRM phenotypes in the different districts, with CD28+ T cells more capable of producing TGFβ in the periphery, potentially contributing to elevated CD103 levels. In contrast CD28- TRM mainly produced CXCL13 within the tumor. ScRNA-seq revealed 5 different clusters for each of the two subsets, with distinctive transcriptional profiles in the three districts. By interrogating the TCGA dataset of patients with lung adenocarcinoma (LUAD) and metastatic NSCLC treated with atezolizumab, we found signatures of heterogeneous TRM and "pre-exhausted" long-lived effector memory CD8+ T cells associated with improved response to ICB only in the presence of CD28.

CONCLUSIONS

Our findings identify signatures able to stratify survival of LUAD patients and predict ICB response in advanced NSCLC. CD28 is advocated as a key determinant in the signatures identified, in both periphery and tumor site, thus likely providing feasible biomarkers of ICB response.

Reliable Hallmarks and Biomarkers of Senescent Lymphocytes

The phenomenon of accumulation of senescent adaptive immunity cells in the elderly is attracting attention due to the increasing risk of global epidemics and aging of the global population. Elderly people are predisposed to various infectious and age-related diseases and are at higher risk of vaccination failure. The accumulation of senescent cells increases age-related background inflammation, "Inflammaging", causing lymphocyte exhaustion and cardiovascular, neurodegenerative, autoimmune and cancer diseases. Here, we present a comprehensive contemporary review of the mechanisms and phenotype of senescence in the adaptive immune system. Although modern research has not yet identified specific markers of aging lymphocytes, several sets of markers facilitate the separation of the aging population based on normal memory and exhausted cells for further genetic and functional analysis. The reasons for the higher predisposition of CD8+ T-lymphocytes to senescence compared to the CD4+ population are also discussed. We point out approaches for senescent-lymphocyte-targeting markers using small molecules (senolytics), antibodies and immunization against senescent cells. The suppression of immune senescence is the most relevant area of research aimed at developing anti-aging and anti-cancer therapy for prolonging the lifespan of the global population.

Sub-lethal doses of chemotherapeutic agents induce senescence in T cells and upregulation of PD-1 expression

Cellular senescence is a stable cell cycle arrest, usually in response to internal and/or external stress, including telomere dysfunction, abnormal cellular growth, and DNA damage. Several chemotherapeutic drugs, such as melphalan (MEL) and doxorubicin (DXR), induce cellular senescence in cancer cells. However, it is not clear whether these drugs induce senescence in immune cells. We evaluated the induction of cellular senescence in T cells were derived from human peripheral blood mononuclear cells (PBMNCs) in healthy donors using sub-lethal doses of chemotherapeutic agents. The PBMNCs were kept overnight in RPMI 1640 medium with 2% phytohemagglutinin and 10% fetal bovine serum and then cultured in RPMI 1640 with 20 ng/mL IL-2 and sub-lethal doses of chemotherapeutic drugs (2 μM MEL and 50 nM DXR) for 48 h. Sub-lethal doses of chemotherapeutic agents induced phenotypes associated with senescence, such as the formation of γH2AX nuclear foci, cell proliferation arrest, and induction of senescence-associated beta-galactosidase (SA-β-Gal) activity, (control vs. MEL, DXR; median mean fluorescence intensity (MFI) 1883 (1130-2163) vs. 2233 (1385-2254), 2406.5 (1377-3119), respectively) in T cells. IL6 and SPP1 mRNA, which are senescence-associated secretory phenotype (SASP) factors, were significantly upregulated by sublethal doses of MEL and DXR compared to the control (P = 0.043 and 0.018, respectively). Moreover, sub-lethal doses of chemotherapeutic agents significantly enhanced the expression of programmed death 1 (PD-1) on CD3 + CD4 + and CD3 + CD8 + T cells compared to the control (CD4 + T cells; P = 0.043, 0.043, and 0.043, respectively, CD8 + T cells; P = 0.043, 0.043, and 0.043, respectively). Our results suggest that sub-lethal doses of chemotherapeutic agents induce senescence in T cells and tumor immunosuppression by upregulating PD-1 expression on T cells.

Heterogeneity of memory T cells in aging

Immune memory is a requisite and remarkable property of the immune system and is the biological foundation of the success of vaccinations in reducing morbidity from infectious diseases. Some vaccines and infections induce long-lasting protection, but immunity to other vaccines and particularly in older adults rarely persists over long time periods. Failed induction of an immune response and accelerated waning of immune memory both contribute to the immuno-compromised state of the older population. Here we review how T cell memory is influenced by age. T cell memory is maintained by a dynamic population of T cells that are heterogeneous in their kinetic parameters under homeostatic condition and their function. Durability of T cell memory can be influenced not only by the loss of a clonal progeny, but also by broader changes in the composition of functional states and transition of T cells to a dysfunctional state. Genome-wide single cell studies on total T cells have started to provide insights on the influence of age on cell heterogeneity over time. The most striking findings were a trend to progressive effector differentiation and the activation of pro-inflammatory pathways, including the emergence of CD4+ and CD8+ cytotoxic subsets. Genome-wide data on antigen-specific memory T cells are currently limited but can be expected to provide insights on how changes in T cell subset heterogeneity and transcriptome relate to durability of immune protection.

Endotoxemia Associated with Liver Disease Correlates with Systemic Inflammation and T Cell Exhaustion in Hepatitis C Virus Infection

Both acute and chronic hepatitis C virus (HCV) infections are characterized by inflammation. HCV and reduced liver blood filtration contribute to inflammation; however, the mechanisms of systemic immune activation and dysfunction as a result of HCV infection are not clear. We measured circulating inflammatory mediators (IL-6, IP10, sCD163, sCD14), indices of endotoxemia (EndoCab, LBP, FABP), and T cell markers of exhaustion and senescence (PD-1, TIGIT, CD57, KLRG-1) in HCV-infected participants, and followed a small cohort after direct-acting anti-viral therapy. IL-6, IP10, Endocab, LBP, and FABP were elevated in HCV participants, as were T cell co-expression of exhaustion and senescence markers. We found positive associations between IL-6, IP10, EndoCab, LBP, and co-expression of T cell markers of exhaustion and senescence. We also found numerous associations between reduced liver function, as measured by plasma albumin levels, and T cell exhaustion/senescence, inflammation, and endotoxemia. We found positive associations between liver stiffness (TE score) and plasma levels of IL-6, IP10, and LBP. Lastly, plasma IP10 and the proportion of CD8 T cells co-expressing PD-1 and CD57 decreased after initiation of direct-acting anti-viral therapy. Although associations do not prove causality, our results support the model that translocation of microbial products, resulting from decreased liver blood filtration, during HCV infection drives chronic inflammation that results in T cell exhaustion/senescence and contributes to systemic immune dysfunction.

The central role of DNA damage in immunosenescence

Ageing is the biggest risk factor for the development of multiple chronic diseases as well as increased infection susceptibility and severity of diseases such as influenza and COVID-19. This increased disease risk is linked to changes in immune function during ageing termed immunosenescence. Age-related loss of immune function, particularly in adaptive responses against pathogens and immunosurveillance against cancer, is accompanied by a paradoxical gain of function of some aspects of immunity such as elevated inflammation and increased incidence of autoimmunity. Of the many factors that contribute to immunosenescence, DNA damage is emerging as a key candidate. In this review, we discuss the evidence supporting the hypothesis that DNA damage may be a central driver of immunosenescence through senescence of both immune cells and cells of non-haematopoietic lineages. We explore why DNA damage accumulates during ageing in a major cell type, T cells, and how this may drive age-related immune dysfunction. We further propose that existing immunosenescence interventions may act, at least in part, by mitigating DNA damage and restoring DNA repair processes (which we term "genoprotection"). As such, we propose additional treatments on the basis of their evidence for genoprotection, and further suggest that this approach may provide a viable therapeutic strategy for improving immunity in older people.

High-dimensional analysis of 16 SARS-CoV-2 vaccine combinations reveals lymphocyte signatures correlating with immunogenicity

The range of vaccines developed against severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) provides a unique opportunity to study immunization across different platforms. In a single-center cohort, we analyzed the humoral and cellular immune compartments following five coronavirus disease 2019 (COVID-19) vaccines spanning three technologies (adenoviral, mRNA and inactivated virus) administered in 16 combinations. For adenoviral and inactivated-virus vaccines, heterologous combinations were generally more immunogenic compared to homologous regimens. The mRNA vaccine as the second dose resulted in the strongest antibody response and induced the highest frequency of spike-binding memory B cells irrespective of the priming vaccine. Priming with the inactivated-virus vaccine increased the SARS-CoV-2-specific T cell response, whereas boosting did not. Distinct immune signatures were elicited by the different vaccine combinations, demonstrating that the immune response is shaped by the type of vaccines applied and the order in which they are delivered. These data provide a framework for improving future vaccine strategies against pathogens and cancer.

Comorbidities and clinical complications associated with SARS-CoV-2 infection: an overview

The novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) causes major challenges to the healthcare system. SARS-CoV-2 infection leads to millions of deaths worldwide and the mortality rate is found to be greatly associated with pre-existing clinical conditions. The existing dataset strongly suggests that cardiometabolic diseases including hypertension, coronary artery disease, diabetes and obesity serve as strong comorbidities in coronavirus disease (COVID-19). Studies have also shown the poor outcome of COVID-19 in patients associated with angiotensin-converting enzyme-2 polymorphism, cancer chemotherapy, chronic kidney disease, thyroid disorder, or coagulation dysfunction. A severe complication of COVID-19 is mostly seen in people with compromised medical history. SARS-CoV-2 appears to attack the respiratory system causing pneumonia, acute respiratory distress syndrome, which lead to induction of severe systemic inflammation, multi-organ dysfunction, and death mostly in the patients who are associated with pre-existing comorbidity factors. In this article, we highlighted the key comorbidities and a variety of clinical complications associated with COVID-19 for a better understanding of the etiopathogenesis of COVID-19.

E-Cadherin Expression Distinguishes Mouse from Human Hematopoiesis in the Basophil and Erythroid Lineages

E-cadherin is a key regulator of epithelial cell-cell adhesion, the loss of which accelerates tumor growth and invasion. E-cadherin is also expressed in hematopoietic cells as well as epithelia. The function of hematopoietic E-cadherin is, however, mostly elusive. In this study, we explored the validity of mouse models to functionally investigate the role of hematopoietic E-cadherin in human hematopoiesis. We generated a hematopoietic-specific E-cadherin knockout mouse model. In mice, hematopoietic E-cadherin is predominantly expressed within the basophil lineage, the expression of which is dispensable for the generation of basophils. However, neither E-cadherin mRNA nor protein were detected in human basophils. In contrast, human hematopoietic E-cadherin marks the erythroid lineage. E-cadherin expression in hematopoiesis thereby revealed striking evolutionary differences between the basophil and erythroid cell lineage in humans and mice. This is remarkable as E-cadherin expression in epithelia is highly conserved among vertebrates including humans and mice. Our study therefore revealed that the mouse does not represent a suitable model to study the function of E-cadherin in human hematopoiesis and an alternative means to study the role of E-cadherin in human erythropoiesis needs to be developed.

Role of PARP Inhibitors in Cancer Immunotherapy: Potential Friends to Immune Activating Molecules and Foes to Immune Checkpoints

Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) induce cytotoxic effects as single agents in tumors characterized by defective repair of DNA double-strand breaks deriving from BRCA1/2 mutations or other abnormalities in genes associated with homologous recombination. Preclinical studies have shown that PARPi-induced DNA damage may affect the tumor immune microenvironment and immune-mediated anti-tumor response through several mechanisms. In particular, increased DNA damage has been shown to induce the activation of type I interferon pathway and up-regulation of PD-L1 expression in cancer cells, which can both enhance sensitivity to Immune Checkpoint Inhibitors (ICIs). Despite the recent approval of ICIs for a number of advanced cancer types based on their ability to reinvigorate T-cell-mediated antitumor immune responses, a consistent percentage of treated patients fail to respond, strongly encouraging the identification of combination therapies to overcome resistance. In the present review, we analyzed both established and unexplored mechanisms that may be elicited by PARPi, supporting immune reactivation and their potential synergism with currently used ICIs. This analysis may indicate novel and possibly patient-specific immune features that might represent new pharmacological targets of PARPi, potentially leading to the identification of predictive biomarkers of response to their combination with ICIs.

Sex differences exist in adult heart group 2 innate lymphoid cells

Background

Group 2 innate lymphoid cells (ILC2s) are the most dominant ILCs in heart tissue, and sex-related differences exist in mouse lung ILC2 phenotypes and functions; however, it is still unclear whether there are sex differences in heart ILC2s.

Results

Compared with age-matched wild-type (WT) male mice, 8-week-old but not 3-week-old WT female mice harbored an obviously greater percentage and number of heart ILC2s in homeostasis. However, the percentage of killer-cell lectin-like receptor G1 (Klrg1)⁻ ILC2s was higher, but the Klrg1⁺ ILC2s were lower in female mice than in male mice in both heart tissues of 3- and 8-week-old mice. Eight-week-old Rag2^−/− mice also showed sex differences similar to those of age-matched WT mice. Regarding surface marker expression, compared to age-matched male mice, WT female mice showed higher expression of CD90.2 and Ki67 and lower expression of Klrg1 and Sca-1 in heart total ILC2s. There was no sex difference in IL-4 and IL-5 secretion by male and female mouse heart ILC2s. Increased IL-33 mRNA levels within the heart tissues were also found in female mice compared with male mice. By reanalyzing published single-cell RNA sequencing data, we found 2 differentially expressed genes between female and male mouse heart ILC2s. Gene set variation analysis revealed that the glycine, serine and threonine metabolism pathway was upregulated in female heart ILC2s. Subcluster analysis revealed that one cluster of heart ILC2s with relatively lower expression of Semaphorin 4a and thioredoxin interacting protein but higher expression of hypoxia-inducible lipid droplet-associated.

Conclusions

These results revealed greater numbers of ILC2s, higher expression of CD90.2, reduced Klrg1 and Sca-1 expression in the hearts of female mice than in male mice and no sex difference in IL-4 and IL-5 production in male and female mouse heart ILC2s. These sex differences in heart ILC2s might be due to the heterogeneity of IL-33 within the heart tissue.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12865-022-00525-0.

KLMab-1: An Anti-human KLRG1 Monoclonal Antibody for Immunocytochemistry

Immune checkpoint molecules have received attention as targets of cancer immunotherapy. Killer cell lectin-like receptor subfamily G member 1 (KLRG1) is one of the immune checkpoint molecules expressed in CD4⁺ T, CD8⁺ T, and natural killer (NK) cells. KLRG1 exhibits antiviral and antitumor immunity, and its expression in T and NK cells is upregulated by viral infectious diseases and some tumors. Thus, monoclonal antibodies (mAbs) for KLRG1 would be useful tools for the diagnosis and immunotherapy against viral infectious diseases and cancers. We have developed anti-human KLRG1 (hKLRG1) mAb (clone KLMab-1, mouse IgG₁, kappa) by the Cell-Based Immunization and Screening method. We have also demonstrated that KLMab-1 recognizes both exogenous and endogenous hKLRG1 in flow cytometry. In this study, we first showed that KLMab-1 and its recombinant mAb (recKLMab-1) bound to exogenous hKLRG1 overexpressed in Chinese hamster ovary (CHO)-K1 cells, but not in parental CHO-K1 cells, in immunocytochemistry. We next showed that both mAbs detected endogenous hKLRG1 expressed in human NK cells. These results demonstrate that KLMab-1 and recKLMab-1 are available for immunocytochemistry.

Immune senescence in multiple myeloma-a role for mitochondrial dysfunction?

Age-related immune dysfunction is primarily mediated by immunosenescence which results in ineffective clearance of infective pathogens, poor vaccine responses and increased susceptibility to multi-morbidities. Immunosenescence-related immunometabolic abnormalities are associated with accelerated aging, an inflammatory immune response (inflammaging) and ultimately frailty syndromes. In addition, several conditions can accelerate the development of immunosenescence, including cancer. This is a bi-directional interaction since inflammaging may create a permissive environment for tumour development. Multiple myeloma (MM) is a mature B-cell malignancy that presents in the older population. MM exemplifies the interaction of age- (Host Response Biology; HRB) and disease-related immunological dysfunction, contributing to the development of a frailty syndrome which impairs the therapeutic impact of recent advances in treatment strategies. Understanding the mechanisms by which accelerated immunological aging is induced and the ways in which a tumour such as MM influences this process is key to overcoming therapeutic barriers. A link between cellular mitochondrial dysfunction and the acquisition of an abnormal immune phenotype has recently been described and has widespread physiological consequence beyond the impact on the immune system. Here we outline our current understanding of normal immune aging, describe the mechanism of immunometabolic dysfunction in accelerating this process, and propose the role these processes are playing in the pathogenesis of MM.

Pro-tumorigenic role of type 2 diabetes-induced cellular senescence in colorectal cancer

Colorectal cancer (CRC) is the second leading cause of cancer-related mortality worldwide. The disease still remains incurable and highly lethal in the advanced stage, representing a global health concern. Therefore, it is essential to understand the causes and risk factors leading to its development. Because age-related cellular senescence and type 2 diabetes (T2D) have been recognised as risk factors for CRC development, the recent finding that type 2 diabetic patients present an elevated circulating volume of senescent cells raises the question whether type 2 diabetes facilitates the process of CRC tumorigenesis by inducing premature cell senescence. In this review, we will discuss the mechanisms according to which T2D induces cellular senescence and the role of type 2 diabetes-induced cellular senescence in the pathogenesis and progression of colorectal cancer. Lastly, we will explore the current therapeutic approaches and challenges in targeting senescence.

Inflammation, Immune Senescence, and Dysregulated Immune Regulation in the Elderly

An optimal immune response requires the appropriate interaction between the innate and the adaptive arms of the immune system as well as a proper balance of activation and regulation. After decades of life, the aging immune system is continuously exposed to immune stressors and inflammatory assaults that lead to immune senescence. In this review, we will discuss inflammaging in the elderly, specifically concentrating on IL-6 and IL-1b in the context of T lymphocytes, and how inflammation is related to mortality and morbidities, specifically cardiovascular disease and cancer. Although a number of studies suggests that the anti-inflammatory cytokine TGF-b is elevated in the elderly, heightened inflammation persists. Thus, the regulation of the immune response and the ability to return the immune system to homeostasis is also important. Therefore, we will discuss cellular alterations in aging, concentrating on senescent T cells and CD4+ CD25+ FOXP3+ regulatory T cells (Tregs) in aging

The Yin and Yang of Targeting KLRG1+ Tregs and Effector Cells

The literature surrounding KLRG1 has primarily focused on NK and CD8⁺ T cells. However, there is evidence that the most suppressive Tregs express KLRG1. Until now, the role of KLRG1 on Tregs has been mostly overlooked and remains to be elucidated. Here we review the current literature on KLRG1 with an emphasis on the KLRG1⁺ Treg subset role during cancer development and autoimmunity. KLRG1 has been recently proposed as a new checkpoint inhibitor target, but these studies focused on the effects of KLRG1 blockade on effector cells. We propose that when designing anti-tumor therapies targeting KLRG1, the effects on both effector cells and Tregs will have to be considered.

Co-Expression of TIGIT and Helios Marks Immunosenescent CD8+ T Cells During Aging

Aging leads to alterations in the immune system that result in ineffective responsiveness against pathogens. Features of this process, collectively known as immunosenescence, accumulate in CD8⁺ T cells with age and have been ascribed to differentiation of these cells during the course of life. Here we aimed to identify novel markers in CD8⁺ T cells associated with immunosenescence. Furthermore, we assessed how these markers relate to the aging-related accumulation of highly differentiated CD27^-CD28^- cells. We found that co-expression of the transcription factor Helios and the aging-related marker TIGIT identifies CD8⁺ T cells that fail to proliferate and show impaired induction of activation markers CD69 and CD25 in response to stimulation in vitro. Despite this, in blood of older adults we found TIGIT⁺Helios⁺ T cells to become highly activated during an influenza-A virus infection, but these higher frequencies of activated TIGIT⁺Helios⁺ T cells associate with longer duration of coughing. Moreover, in healthy individuals, we found that TIGIT⁺Helios⁺ CD8⁺ T cells accumulate with age in the highly differentiated CD27^-CD28^- population. Interestingly, TIGIT⁺Helios⁺ CD8⁺ T cells also accumulate with age among the less differentiated CD27⁺CD28^- T cells before their transit into the highly differentiated CD27^-CD28^- stage. This finding suggests that T cells with immunosenescent features become prominent at old age also within the earlier differentiation states of these cells. Our findings show that co-expression of TIGIT and Helios refines the definition of immunosenescent CD8⁺ T cells and challenge the current dogma of late differentiation stage as proxy for T-cell immunosenescence.

Central memory T cells are the most effective precursors of resident memory T cells in human skin

The circulating precursor cells that give rise to human resident memory T cells (T_RM) are poorly characterized. We used an in vitro differentiation system and human skin-grafted mice to study T_RM generation from circulating human memory T cell subsets. In vitro T_RM differentiation was associated with functional changes, including enhanced IL-17A production and FOXP3 expression in CD4⁺ T cells and granzyme B production in CD8⁺ T cells, changes that mirrored the phenotype of T cells in healthy human skin. Effector memory T cells (T_EM) had the highest conversion rate to T_RM in vitro and in vivo, but central memory T cells (T_CM) persisted longer in the circulation, entered the skin in larger numbers, and generated increased numbers of T_RM. In summary, T_CM are highly efficient precursors of human skin T_RM, a feature that may underlie their known association with effective long-term immunity.

An old problem with new solutions: Strategies to improve vaccine efficacy in the elderly

Vaccination is the most effective measure to protect against infections. However, with increasing age, there is a progressive decline in the ability of the immune system to both protect against infection and develop protective immunity from vaccination. This age-related decline of the immune system is due to age-related changes in both the innate and adaptive immune systems. With an aging world population and increased risk of pandemics, there is a need to continue to develop strategies to increase vaccine responses in the elderly. Here, the major age-related changes that occur in both the innate and adaptive immune responses that impair the response to vaccination in the elderly will be highlighted. Existing and future strategies to improve vaccine efficacy in the elderly will then be discussed, including adjuvants, delivery methods, and formulation. These strategies provide mechanisms to improve the efficacy of existing vaccines and develop novel vaccines for the elderly.

Aging-associated immune system changes in multiple myeloma: The dark side of the moon

Multiple myeloma (MM) is a disease of the elderly. Changes that occur in the immune system with aging, also known as immunosenescence, have been associated with decreased tumor immunosurveillance and are thought to contribute to the development of MM and other cancers in the elderly. Once MM establishes itself in the bone marrow, immunosenescence related changes have been observed in the immune tumor microenvironment (iTME) and are driven by the malignant cells. The efficacy of novel immunotherapies used to treat MM has been blunted by detrimental iTME changes that occur at later disease stages and are, to some extent, driven by prior therapies. In this review, we discuss general changes that occur in the immune system with aging as well as our current knowledge of immunosenescence in MM. We discuss the differences and overlap between T cell senescence and exhaustion as well as potential methods to prevent or reverse immunosenescence. We focus predominantly on T cell immunosenescence which has been better evaluated in this disease and is more pertinent to novel MM immunotherapies. Our lack of understanding of the drivers of immunosenescence at each stage of the disease, from precursor stages to heavily pretreated MM, represents a major barrier to improving the efficacy of novel and existing therapies.

Group-2 Innate Lymphoid Cells Promote HCC Progression Through CXCL2-Neutrophil-Induced Immunosuppression

BACKGROUND AND AIMS

Due to their inherent characteristics, the function of group-2 innate lymphoid cells (ILC2s) varies in a context-dependent manner. ILC2s are involved in certain liver diseases; however, their involvement in HCC is unknown. In the present study, we assessed the role of an HCC-derived ILC2 population in tumor progression.

APPROACH AND RESULTS

Through FACS and single-cell RNA sequencing, we discovered that ILC2s were highly enriched in human HCC and correlated significantly with tumor recurrence and worse progression-free survival as well as overall survival in patients. Mass cytometry identified a subset of HCC-derived ILC2s that had lost the expression of killer cell lectin-like receptor subfamily G, member 1 (KLRG1). Distinct from their circulating counterparts, these hepatic ILC2s highly expressed CD69 and an array of tissue resident-related genes. Furthermore, reduction of E-cadherin in tumor cells caused the loss of KLRG1 expression in ILC2s, leading to their increased proliferation and subsequent accumulation in HCC sites. The KLRG1^- ILC2 subset showed elevated production of chemotaxis factors, including C-X-C motif chemokine (C-X-C motif) ligand (CXCL)-2 and CXCL8, which in turn recruited neutrophils to form an immunosuppressive microenvironment, leading to tumor progression. Accordingly, restoring KLRG1 in ILC2s, inhibiting CXCL2 in ILC2s, or depleting neutrophils inhibited tumor progression in a murine HCC model.

CONCLUSIONS

We identified HCC-associated ILC2s as an immune regulatory cell type that promotes tumor development, suggesting that targeting these ILC2s might lead to new treatments for HCC.

Methods for Characterization of Senescent Circulating and Tumor-Infiltrating T-Cells: An Overview from Multicolor Flow Cytometry to Single-Cell RNA Sequencing

Immunosenescence is the general term used to describe the aging-associated decline of immunological function that explains the higher susceptibility to infectious diseases and cancer, increased autoimmunity, or the reduced effectiveness of vaccinations. Senescence of CD8+ T-cells has been described in all these conditions.The most important classical markers of T senescent cells are the cell cycle inhibitors p16ink4a, p21, and p53, together with positivity for SA-βgal expression and the acquirement of a peculiar IFNγ -based secretory phenotype commonly defined SASP (Senescence Associated Secretory Phenotype). Other surface markers are the CD28 and CD27 loss together with gain of expression of CD45RA, CD57, TIGIT, and/or KLRG1. However, this characterization could not be sufficient to distinguish from truly senescent cells and exhausted T-cells. Furthermore, more complexity is added by the wide heterogeneity of T-cells subset in aged individuals or in the tumor microenvironment. A combined analysis by multicolor flow cytometry for surface and intracellular markers integrated with gene-expression arrays and single-cell RNA sequencing is required to develop effective interventions for therapeutic modulation of specific T-cell subsets. The RNASeq offers the great possibility to reveal at single-cell resolution the exact molecular hallmarks of senescent CD8+ T-cells without the limitations of bulk analysis. Furthermore, the comprehensive integration of multidimensional approaches (genomics, epigenomics, proteomics, metabolomics) will increase our global understanding of how immunosenescence of T-cells is interlinked to human aging.

Hedgehog interacting protein-expressing lung fibroblasts suppress lymphocytic inflammation in mice

Chronic obstructive pulmonary disease (COPD) is mainly caused by cigarette smoking and characterized by chronic inflammation in vulnerable individuals. However, it is unknown how genetic factors may shape chronic inflammation in COPD. To understand how hedgehog interacting protein, encoded by HHIP gene identified in the genome-wide association study in COPD, plays a role in inflammation, we utilized Hhip^+/– mice that present persistent inflammation and emphysema upon aging similar to that observed in human COPD. By performing single-cell RNA sequencing of the whole lung from mice at different ages, we found that Hhip^+/– mice developed a cytotoxic immune response with a specific increase in killer cell lectin-like receptor G1–positive CD8⁺ T cells with upregulated Ifnγ expression recapitulating human COPD. Hhip expression was restricted to a lung fibroblast subpopulation that had increased interaction with CD8⁺ T lymphocytes in Hhip^+/– compared with Hhip^+/+ during aging. Hhip-expressing lung fibroblasts had upregulated IL-18 pathway genes in Hhip^+/– lung fibroblasts, which was sufficient to drive increased levels of IFN-γ in CD8⁺ T cells ex vivo. Our finding provides insight into how a common genetic variation contributes to the amplified lymphocytic inflammation in COPD.

Polyfunctional KLRG-1+CD57+ Senescent CD4+ T Cells Infiltrate Tumors and Are Expanded in Peripheral Blood From Breast Cancer Patients

Senescent T cells have been described during aging, chronic infections, and cancer; however, a comprehensive study of the phenotype, function, and transcriptional program of this T cell population in breast cancer (BC) patients is missing. Compared to healthy donors (HDs), BC patients exhibit an accumulation of KLRG-1⁺CD57⁺ CD4⁺ and CD8⁺ T cells in peripheral blood. These T cells infiltrate tumors and tumor-draining lymph nodes. KLRG-1⁺CD57⁺ CD4⁺ and CD8⁺ T cells from BC patients and HDs exhibit features of senescence, and despite their inhibitory receptor expression, they produce more effector cytokines and exhibit higher expression of Perforin, Granzyme B, and CD107a than non-senescent subsets. When compared to blood counterparts, tumor-infiltrating senescent CD4⁺ T cells show similar surface phenotype but reduced cytokine production. Transcriptional profiling of senescent CD4⁺ T cells from the peripheral blood of BC patients reveals enrichment in genes associated with NK or CD8⁺-mediated cytotoxicity, TCR-mediated stimulation, and cell exhaustion compared to non-senescent T cells. Comparison of the transcriptional profile of senescent CD4⁺ T cells from peripheral blood of BC patients with those of HDs highlighted marked similarities but also relevant differences. Senescent CD4⁺ T cells from BC patients show enrichment in T-cell signaling, processes involved in DNA replication, p53 pathways, oncogene-induced senescence, among others compared to their counterparts in HDs. High gene expression of CD4, KLRG-1, and B3GAT1 (CD57), which correlates with increased overall survival for BC patients, underscores the usefulness of the evaluation of the frequency of senescent CD4⁺ T cells as a biomarker in the follow-up of patients.

Type I interferon mediated induction of somatostatin leads to suppression of ghrelin and appetite thereby promoting viral immunity in mice

Loss of appetite (anorexia) is a typical behavioral response to infectious diseases that often reduces body weight. Also, anorexia can be observed in cancer and trauma patients, causing poor quality of life and reduced prospects of positive therapeutic outcomes. Although anorexia is an acute symptom, its initiation and endocrine regulation during antiviral immune responses are poorly understood. During viral infections, plasmacytoid dendritic cells (pDCs) produce abundant type I interferon (IFN-I) to initiate first-line defense mechanisms. Here, by targeted ablation of pDCs and various in vitro and in vivo mouse models of viral infection and inflammation, we identified that IFN-I is a significant driver of somatostatin (SST). Consequently, SST suppressed the hunger hormone ghrelin that led to severe metabolic changes, anorexia, and rapid body weight loss. Furthermore, during vaccination with Modified Vaccinia Ankara virus (MVA), the SST-mediated suppression of ghrelin was critical to viral immune response, as ghrelin restrained the production of early cytokines by natural killer (NK) cells and pDCs, and impaired the clonal expansion of CD8⁺ T cells. Thus, the hormonal modulation of ghrelin through SST and the cytokine IFN-I is fundamental for optimal antiviral immunity, which comes at the expense of calorie intake.

Exercise and the immune system: taking steps to improve responses to cancer immunotherapy

The remarkable success of cancer immunotherapies has provided new hope to cancer patients. Unfortunately, a significant proportion of patients remain unable to respond to immunotherapy or maintain durable clinical responses. The lack of objective responses likely results from profound immune dysfunction often observed in patients with cancer. There is substantial evidence that exercise and physical activity can reduce incidence and improve outcomes in cancer patients. As the immune system is highly responsive to exercise, one potential avenue to improve immune function is through exercise and physical activity. A single event of dynamic exercise results in the substantial mobilization of leukocytes with increased functional capacities into the circulation. Chronic, or long-term, exercise leads to higher physical fitness in terms of greater cardiorespiratory function and/or muscle strength and endurance. High aerobic capacity, as measured by maximal oxygen uptake, has been associated with the reduction of dysfunctional T cells and improvements in the abundance of some T cell populations. To be sure, however, the mechanisms of exercise-mediated immune changes are both extensive and diverse. Here, we examine the evidence and theorize how acute and chronic exercise could be used to improve responses to cancer immunotherapies including immune checkpoint inhibitors, dendritic cell vaccines, natural killer cell therapies, and adoptive T cell therapies such as chimeric antigen receptor (CAR) T cells. Although the parameters of optimal exercise to yield defined outcomes remain to be determined, the available current data provide a compelling justification for additional human studies and clinical trials investigating the adjuvant use of exercise in immuno-oncology.

Functions and clinical significance of KLRG1 in the development of lung adenocarcinoma and immunotherapy

BACKGROUND

As a marker of differentiation, Killer cell lectin like receptor G1 (KLRG1) plays an inhibitory role in human NK cells and T cells. However, its clinical role remains inexplicit. This work intended to investigate the predictive ability of KLRG1 on the efficacy of immune-checkpoint inhibitor in the treatment of lung adenocarcinoma (LUAD), as well as contribute to the possible molecular mechanisms of KLRG1 on LUAD development.

METHODS

Using data from the Gene Expression Omnibus, the Cancer Genome Atlas and the Genotype-Tissue Expression, we compared the expression of KLRG1 and its related genes Bruton tyrosine kinase (BTK), C-C motif chemokine receptor 2 (CCR2), Scm polycomb group protein like 4 (SCML4) in LUAD and normal lung tissues. We also established stable LUAD cell lines with KLRG1 gene knockdown and investigated the effect of KLRG1 knockdown on tumor cell proliferation. We further studied the prognostic value of the four factors in terms of overall survival (OS) in LUAD. Using data from the Gene Expression Omnibus, we further investigated the expression of KLRG1 in the patients with different responses after immunotherapy.

RESULTS

The expression of KLRG1, BTK, CCR2 and SCML4 was significantly downregulated in LUAD tissues compared to normal controls. Knockdown of KLRG1 promoted the proliferation of A549 and H1299 tumor cells. And low expression of these four factors was associated with unfavorable overall survival in patients with LUAD. Furthermore, low expression of KLRG1 also correlated with poor responses to immunotherapy in LUAD patients.

CONCLUSION

Based on these findings, we inferred that KLRG1 had significant correlation with immunotherapy response. Meanwhile, KLRG1, BTK, CCR2 and SCML4 might serve as valuable prognostic biomarkers in LUAD.

Combination blockade of KLRG1 and PD-1 promotes immune control of local and disseminated cancers

Checkpoint blockade therapy is effective against many cancers; however, new targets need to be identified to treat patients who do not respond to current treatment or demonstrate immune escape. Here, we showed that blocking the inhibitory receptor Killer cell lectin-like receptor G1 (KLRG1) enhances anti-tumor immunity mediated by NK cells and CD8⁺ T cells. We found that loss of KLRG1 signaling alone significantly decreased melanoma and breast cancer tumor growth in the lungs of mice. In addition, we demonstrated that KLRG1 blockade can synergize with PD-1 checkpoint therapy to increase the therapeutic efficacy compared to either treatment alone. This effect was even observed with tumors that do not respond to PD-1 checkpoint therapy. Double blockade therapy led to significantly decreased tumor size, increased frequency and activation of CD8⁺ T cells, and increased NK cell frequency and maturation in the tumor microenvironment. These findings demonstrate that KLRG1 is a novel checkpoint inhibitor target that affects NK and T cell anti-tumor immunity, both alone and in conjunction with established immunotherapies.

Δ133p53α enhances metabolic and cellular fitness of TCR-engineered T cells and promotes superior antitumor immunity

Background

Tumor microenvironment-associated T cell senescence is a key limiting factor for durable effective cancer immunotherapy. A few studies have demonstrated the critical role of the tumor suppressor TP53-derived p53 isoforms in cellular senescence process of non-immune cells. However, their role in lymphocytes, in particular tumor-antigen (TA) specific T cells remain largely unexplored.

Methods

Human T cells from peripheral blood were retrovirally engineered to coexpress a TA-specific T cell receptor and the Δ133p53α-isoform, and characterized for their cellular phenotype, metabolic profile and effector functions.

Results

Phenotypic analysis of Δ133p53α-modified T cells revealed a marked reduction of the T-cell inhibitory molecules (ie, CD160 and TIGIT), a lower frequency of senescent-like CD57⁺ and CD160⁺ CD8⁺ T cell populations, and an increased number of less differentiated CD28⁺ T cells. Consistently, we demonstrated changes in the cellular metabolic program toward a quiescent T cell state. On a functional level, Δ133p53α-expressing T cells acquired a long-term proliferative capacity, showed superior cytokine secretion and enhanced tumor-specific killing in vitro and in mouse tumor model. Finally, we demonstrated the capacity of Δ133p53α to restore the antitumor response of senescent T cells isolated from multiple myeloma patients.

Conclusion

This study uncovered a broad effect of Δ133p53α isoform in regulating T lymphocyte function. Enhancing fitness and effector functions of senescent T cells by modulation of p53 isoforms could be exploited for future translational research to improve cancer immunotherapy and immunosenescence-related diseases.

An atypical KLRG1 in Nile tilapia involves in adaptive immunity as a potential marker for activated T lymphocytes

Killer cell lectin-like receptor G subfamily 1 (KLRG1) is a receptor generally expressed on effector CD8⁺ T cells or NK cells at terminal differentiation stage, and it will be highly induced for lymphocyte cytotoxicity upon pathogen infection or lymphocyte activation. However, little is known about the character or function of KLRG1 in lower vertebrates. In present study, we reappraised a molecule that previously defined as KLRG1 in the genomic sequence of Nile tilapia Oreochromis niloticus, and identified it as an atypical KLRG1-like molecule (defined as On-KLRG1-L), and illustrated its potential function serving as a marker representing effector T lymphocytes of fish species. On-KLRG1-L consists of two C-type lectin-like domains (CTLDs) without transmembrane region, and the tertiary structure of the CTLD is highly alike to that in mouse KLRG1. As a CTLD-containing protein, the recombinant On-KLRG1-L could bind PGN and several microbes in vitro. On-KLRG1-L was widely expressed in immune-associated tissues, with the highest expression level in the gill. Once Nile tilapia is infected by Aeromonas hydrophila, mRNA level of On-KLRG1-L in spleen lymphocytes were significantly up-regulated on 5 days after infection. Meanwhile, On-KLRG1-L protein was also induced on 5 or 8 days after A. hydrophila infection. Furthermore, we found both mRNA and protein levels of On-KLRG1-L were dramatically enhanced within several hours after spleen lymphocytes were activated by T cell-specific mitogen PHA in vitro. More importantly, the ratio of On-KLRG1-L⁺ T cells was also augmented after PHA stimulation. The observations suggested that the KLRG1-like molecule from Nile tilapia participated in lymphocyte activation and anti-bacterial adaptive immune response, and could serve as an activation marker of T lymphocytes. Our study thus provided new evidences to understand lymphocyte-mediated adaptive immunity of teleost.

Hallmarks of T cell aging

The aged adaptive immune system is characterized by progressive dysfunction as well as increased autoimmunity. This decline is responsible for elevated susceptibility to infection and cancer, as well as decreased vaccination efficacy. Recent evidence indicates that CD4⁺ T cell-intrinsic alteratins contribute to chronic inflammation and are sufficient to accelerate an organism-wide aging phenotype, supporting the idea that T cell aging plays a major role in body-wide deterioration. In this Review, we propose ten molecular hallmarks to represent common denominators of T cell aging. These hallmarks are grouped into four primary hallmarks (thymic involution, mitochondrial dysfunction, genetic and epigenetic alterations, and loss of proteostasis) and four secondary hallmarks (reduction of the TCR repertoire, naive-memory imbalance, T cell senescence, and lack of effector plasticity), and together they explain the manifestation of the two integrative hallmarks (immunodeficiency and inflammaging). A major challenge now is weighing the relative impact of these hallmarks on T cell aging and understanding their interconnections, with the final goal of defining molecular targets for interventions in the aging process.

Compromised DNA Repair Promotes the Accumulation of Regulatory T Cells With an Aging-Related Phenotype and Responsiveness

Decline of immune function during aging has in part been ascribed to the accumulation of regulatory T cells (Tregs) and decreased T-cell responses with age. Aside from changes to T cells that occur over a lifetime, the impact of intracellular aging processes such as compromised DNA repair on T cells remains incompletely defined. Here we aimed to define the impact of compromised DNA repair on T-cell phenotype and responsiveness by studying T cells from mice with a deficiency in their DNA excision-repair gene Ercc1. These Ercc1 mutant (Ercc1^−/Δ7) mice show accumulation of nuclear DNA damage resulting in accelerated aging. Similarly to wild-type aged mice, Ercc1^−/Δ7 mice accumulated Tregs with reduced CD25 and increased PD-1 expression among their naive T cells. Ercc1-deficiency limited the capacity of Tregs, helper T cells, and cytotoxic T cells to proliferate and upregulate CD25 in response to T-cell receptor- and IL-2-mediated stimulation. The recent demonstration that the mammalian target of rapamycin (mTOR) may impair DNA repair lead us to hypothesize that changes induced in the T-cell population by compromised DNA repair may be slowed down or reversed by blocking mTOR with rapamycin. In vivo dietary treatment of Ercc1^−/Δ7 mice with rapamycin did not reduce Treg levels, but highly increased the proportion of CD25⁺ and PD-1⁺ memory Tregs instead. Our study elucidates that compromised DNA repair promotes the accumulation of Tregs with an aging-related phenotype and causes reduced T-cell responsiveness, which may be independent of mTOR activation.

Ptpn2 and KLRG1 regulate the generation and function of tissue-resident memory CD8+ T cells in skin

Tissue-resident memory T cells (T_RM cells) are key elements of tissue immunity. Here, we investigated the role of the regulator of T cell receptor and cytokine signaling, Ptpn2, in the formation and function of T_RM cells in skin. Ptpn2-deficient CD8⁺ T cells displayed a marked defect in generating CD69⁺ CD103⁺ T_RM cells in response to herpes simplex virus type 1 (HSV-1) skin infection. This was accompanied by a reduction in the proportion of KLRG1⁻ memory precursor cells and a transcriptional bias toward terminal differentiation. Of note, forced expression of KLRG1 was sufficient to impede T_RM cell formation. Normalizing memory precursor frequencies by transferring equal numbers of KLRG1⁻ cells restored T_RM generation, demonstrating that Ptpn2 impacted skin seeding with precursors rather than downstream T_RM cell differentiation. Importantly, Ptpn2-deficient T_RM cells augmented skin autoimmunity but also afforded superior protection from HSV-1 infection. Our results emphasize that KLRG1 repression is required for optimal T_RM cell formation in skin and reveal an important role of Ptpn2 in regulating T_RM cell functionality.

Markers of T Cell Exhaustion and Senescence and Their Relationship to Plasma TGF-β Levels in Treated HIV+ Immune Non-responders

Background: Immune non-responders (INR) are HIV+, ART-controlled (>2 yrs) people who fail to reconstitute their CD4 T cell numbers. Systemic inflammation and markers of T cell senescence and exhaustion are observed in INR. This study aims to investigate T cell senescence and exhaustion and their possible association with soluble immune mediators and to understand the immune profile of HIV-infected INR. Selected participants were <50 years old to control for the confounder of older age. Methods: Plasma levels of IL-6, IP10, sCD14, sCD163, and TGF-β and markers of T cell exhaustion (PD-1, TIGIT) and senescence (CD57, KLRG-1) were measured in ART-treated, HIV+ participants grouped by CD4 T cell counts (n = 63). Immune parameters were also measured in HIV-uninfected, age distribution-matched controls (HC; n = 30). Associations between T cell markers of exhaustion and senescence and plasma levels of immune mediators were examined by Spearman rank order statistics. Results: Proportions of CD4 T cell subsets expressing markers of exhaustion (PD-1, TIGIT) and senescence (CD57, KLRG-1) were elevated in HIV+ participants. When comparing proportions between INR and IR, INR had higher proportions of CD4 memory PD-1+, EM CD57+, TEM TIGIT+ and CD8 EM and TEM TIGIT+ cells. Plasma levels of IL-6, IP10, and sCD14 were elevated during HIV infection. IP10 was higher in INR. Plasma TGF-β levels and CD4 cycling proportions of T regulatory cells were lower in INR. Proportions of CD4 T cells expressing TIGIT, PD-1, and CD57 positively correlated with plasma levels of IL-6. Plasma levels of TGF-β negatively correlated with proportions of TIGIT+ and PD-1+ T cell subsets. Conclusions: INR have lower levels of TGF-β and decreased proportions of cycling CD4 T regulatory cells and may have difficulty controlling inflammation. IP10 is elevated in INR and is linked to higher proportions of T cell exhaustion and senescence seen in INR.

Can blocking inflammation enhance immunity during aging?

Aging is a global burden, and the increase in life span does not increase in parallel with health span. Therefore, older adults are currently living longer with chronic diseases, increased infections, and cancer. A characteristic of aging is the presence of chronic low-grade inflammation that is characterized by elevated concentrations of IL-6, TNF-α, and C-reactive protein, which has been termed inflammaging. Previous studies have demonstrated that chronic inflammation interferes with T-cell response and macrophage function and is also detrimental for vaccine responses. This raises the question of whether therapeutic strategies that reduce inflammation may be useful for improving immunity in older adults. In this review we discuss the potential causes of inflammaging, the cellular source of the inflammatory mediators, and the mechanisms by which inflammation may inhibit immunity. Finally, we describe existing interventions that target inflammation that have been used to enhance immunity during aging.

T cell markers recount the course of immunosenescence in healthy individuals and chronic kidney disease

Aging results in substantial changes in almost all cellular subpopulations within the immune system, including functional and phenotypic alterations. T lymphocytes, as the main representative population of cellular immunity, have been extensively studied in terms of modifications and adjustments during aging. Phenotypic alterations are attributed to three main mechanisms; a reduction of naïve T cell population with a shift to more differentiated forms, a subsequent oligoclonal expansion of naïve T cells characterized by repertoire restriction, and replicative insufficiency after repetitive activation. These changes and the subsequent phenotypic disorders are comprised in the term "immunosenescence". Similar changes seem to occur in chronic kidney disease, with T cells of young patients resembling those of healthy older individuals. A broad range of surface markers can be utilized to identify immunosenescent T cells. In this review, we will discuss the most important senescence markers and their potential connection with impaired renal function.

T-Cell Dysfunction as a Limitation of Adoptive Immunotherapy: Current Concepts and Mitigation Strategies

Simple Summary

T cells are immune cells that can be used to target infections or cancers. Adoptive T-cell immunotherapy leverages these properties and/or confers new features to T cells through ex vivo manipulations prior to their use in patients. However, as a “living drug,” the function of these cells can be hampered by several built-in physiological constraints and external factors that limit their efficacy. Manipulating T cells ex vivo can impart dysfunctional features to T cells through repeated stimulations and expansion, but it also offers many opportunities to improve the therapeutic potential of these cells, including emerging interventions to prevent or reverse T-cell dysfunction developing ex vivo or after transfer in patients. This review outlines the various forms of T-cell dysfunction, emphasizes how it affects various types of T-cell immunotherapy approaches, and describes current and anticipated strategies to limit T-cell dysfunction.

Abstract

Over the last decades, cellular immunotherapy has revealed its curative potential. However, inherent physiological characteristics of immune cells can limit the potency of this approach. Best defined in T cells, dysfunction associated with terminal differentiation, exhaustion, senescence, and activation-induced cell death, undermine adoptive cell therapies. In this review, we concentrate on how the multiple mechanisms that articulate the various forms of immune dysfunction impact cellular therapies primarily involving conventional T cells, but also other lymphoid subtypes. The repercussions of immune cell dysfunction across the full life cycle of cell therapy, from the source material, during manufacturing, and after adoptive transfer, are discussed, with an emphasis on strategies used during ex vivo manipulations to limit T-cell dysfunction. Applicable to cellular products prepared from native and unmodified immune cells, as well as genetically engineered therapeutics, the understanding and potential modulation of dysfunctional features are key to the development of improved cellular immunotherapies.

Hallmarks and detection techniques of cellular senescence and cellular ageing in immune cells

The ageing of the global population brings about unprecedented challenges. Chronic age-related diseases in an increasing number of people represent an enormous burden for health and social care. The immune system deteriorates during ageing and contributes to many of these age-associated diseases due to its pivotal role in pathogen clearance, tissue homeostasis and maintenance. Moreover, in order to develop treatments for COVID-19, we urgently need to acquire more knowledge about the aged immune system, as older adults are disproportionally and more severely affected. Changes with age lead to impaired responses to infections, malignancies and vaccination, and are accompanied by chronic, low-degree inflammation, which together is termed immunosenescence. However, the molecular and cellular mechanisms that underlie immunosenescence, termed immune cell senescence, are mostly unknown. Cellular senescence, characterised by an irreversible cell cycle arrest, is thought to be the cause of tissue and organismal ageing. Thus, better understanding of cellular senescence in immune populations at single-cell level may provide us with insight into how immune cell senescence develops over the life time of an individual. In this review, we will briefly introduce the phenotypic characterisation of aged innate and adaptive immune cells, which also contributes to overall immunosenescence, including subsets and function. Next, we will focus on the different hallmarks of cellular senescence and cellular ageing, and the detection techniques most suitable for immune cells. Applying these techniques will deepen our understanding of immune cell senescence and to discover potential druggable pathways, which can be modulated to reverse immune ageing.