Human CD8+ CD57- TEMRA cells: Too young to be called "old"

Exhaustion of CD8pos central memory regulatory T cell differentiation is involved in renal allograft rejection

Background

The role of regulatory CD8pos T cells (CD8pos Tregs) and cytotoxic CD8pos responder T cells (CD8pos Tresps) in maintaining stable graft function in kidney transplant recipients (KTR) remains largely unclear. The pathogenesis of graft deterioration in case of rejection involves the exhaustive differentiation of both CD8pos T cell subsets, but the causal mechanisms have not yet been identified.

Methods

In this study, we separately investigated the differentiation of CD8posTregs/Tresps in 134 stable KTR with no evidence of renal graft rejection, in 41 KTR diagnosed with biopsy-confirmed rejection at enrolment and in 5 patients who were unremarkable at enrolment, but developed rejection within three years of enrolment. We were investigating whether changed differentiation of CCR7posCD45RAposCD31pos recent thymic emigrant (RTE) cells via CD45RAnegCD31pos memory (CD31pos memory) cells (pathway 1), via direct proliferation (pathway 2), or via CCR7posCD45RA+CD31neg resting mature naïve (MN) cells (pathway 3) into CD45RAnegCD31neg memory (CD31neg memory) cells affects the CD8pos Treg/Tresp ratio or identifies a CD8pos Treg/Tresp subset that predicts or confirms renal allograft rejection.

Results

We found that RTE Treg differentiation via pathway 1 was age-independently increased in KTR, who developed graft rejection during the follow-up period, leading to abundant MN Treg and central memory Treg (CM Treg) production and favoring a strongly increased CD8pos Treg/Tresp ratio. In KTR with biopsy-confirmed rejection at the time of enrolment, an increased differentiation of RTE Tregs into CCR7negCD45RAposCD31neg terminally differentiated effector memory (CD31neg TEMRA Tregs) and CD31pos memory Tregs was observed. CD31neg memory Treg production was maintained by alternative differentiation of resting MN Tregs, resulting in increased effector memory Treg (EM Treg) production, while the CD8pos Treg/Treg ratio was unaffected. An altered differentiation of CD8pos Tresps was not observed, shifting the Treg/Tresp ratio in favor of Tregs.

Conclusions

Our results show that exhaustive CD8pos Treg differentiation into CM Tregs may lead to future rejection, with a shift towards EM Treg production and an accumulation of CD31neg TEMRA Tregs in KTR with current rejection.

CD57+ EMRA CD8+ T cells in cancer patients over 70: associations with prior chemotherapy and response to anti-PD-1/PD-L1 therapy

BACKGROUND

Immune ageing complicates cancer treatment in older individuals. While immunotherapy targeting the PD-1/PD-L1 pathway can reinvigorate T cells, these cells tend to become senescent with age. This study investigates different CD8+ T cell subsets usually associated with senescence, in cancer patients over 70 years old who are undergoing anti-PD-1/PD-L1 immunotherapy, and examines the relationship between these senescent cells and prior chemotherapy exposure. We analyzed data from the Elderly Cancer Patient (ELCAPA) cohort, which included 35 patients enrolled between March 2018 and March 2021.

RESULTS

Flow cytometry and unsupervised analysis were employed to characterize Effector Memory CD45RA+ (EMRA) and CD8+ T cell senescence at baseline, before initiating PD-1/PD-L1 therapy. EMRA cells were found to overexpress CD57 and KLRG1 compared to overall CD8+ T cells. Chemotherapy prior to anti-PD-1/PD-L1 was associated with an increased proportion of CD57+ EMRA CD8+ T cells (p = 0.009) and its granzyme B (GRZB) subset (p = 0.007). Using a 10% cut-off to define positivity, the six-month non-response tends to be associated with the CD57+ GRZB+ EMRA positivity (p = 0.097). Other CD8+ T cell subsets (EMRA, CD57+, or KLRG1+), usually associated with senescence, showed no significant association with previous chemotherapy or response to anti-PD-1/anti-PD-L1 therapy.

CONCLUSIONS

These findings underscore the impact of prior chemotherapy on expanding the pool of senescent T cells, particularly CD57+ EMRA CD8+ T and CD57+ GRZB+ EMRA CD8+ T cells, whose expansion could potentially affect the effectiveness of anti-PD-1/PD-L1 immunotherapy in elderly patients. This highlights the need for tailored approaches in this population.

Immune aging and infectious diseases

ABSTRACT

The rise in global life expectancy has led to an increase in the older population, presenting significant challenges in managing infectious diseases. Aging affects the innate and adaptive immune systems, resulting in chronic low-grade inflammation (inflammaging) and immune function decline (immunosenescence). These changes would impair defense mechanisms, increase susceptibility to infections and reduce vaccine efficacy in older adults. Cellular senescence exacerbates these issues by releasing pro-inflammatory factors, further perpetuating chronic inflammation. Moreover, comorbidities, such as cardiovascular disease and diabetes, which are common in older adults, amplify immune dysfunction, while immunosuppressive medications further complicate responses to infections. This review explores the molecular and cellular mechanisms driving inflammaging and immunosenescence, focusing on genomic instability, telomere attrition, and mitochondrial dysfunction. Additionally, we discussed how aging-associated immune alterations influence responses to bacterial, viral, and parasitic infections and evaluated emerging antiaging strategies, aimed at mitigating these effects to improve health outcomes in the aging population.

Prognostic implications of a CD8+ TEMRA to CD4+Treg imbalance in mandibular fracture healing: a prospective analysis of immune profiles

Introduction

Open reduction and fixation are the standard of care for treating mandibular fractures and usually lead to successful healing. However, complications such as delayed healing, non-union, and infection can compromise patient outcomes and increase healthcare costs. The initial inflammatory response, particularly the response involving specific CD8+ T cell subpopulations, is thought to play a critical role in healing long bone fractures. In this study, we investigated the role of these immune cell profiles in patients with impaired healing of mandibular fractures.

Materials and methods

In this prospective study, we included patients with mandibular fractures surgically treated at Charité - Universitätsmedizin Berlin, Germany, between September 2020 and December 2022. We used follow-up imaging and clinical assessment to evaluate bone healing. In addition, we analyzed immune cell profiles using flow cytometry and quantified cytokine levels using electrochemiluminescence-based multiplex immunoassays in preoperative blood samples.

Results

Out of the 55 patients enrolled, 38 met the inclusion criteria (30 men and 8 women; mean age 32.18 years). Radiographic evaluation revealed 31 cases of normal healing and 7 cases of incomplete consolidation, including 1 case of non-union. Patients with impaired healing exhibited increased levels of terminally differentiated effector memory CD8+ T cells (TEMRA) and a higher TEMRA to regulatory T cell (Treg) ratio, compared with those with normal healing.

Conclusions

Our analysis of mandibular fracture cases confirms our initial hypothesis derived from long bone fracture healing: monitoring the TEMRA to Treg ratio in preoperative blood can be an early indicator of patients at risk of impaired bone healing. Radiologic follow-up enabled us to detect healing complications that might not be detected by clinical assessment only. This study highlights the potential of individual immune profiles to predict successful healing and may form the basis for future strategies to manage healing complications.

Boosting peripheral immunity to fight neurodegeneration in the brain

Reciprocal communication between the brain and the immune system is essential for maintaining lifelong brain function. This interaction is mediated, at least in part, by immune cells recruited from both the circulation and niches at the borders of the brain. Here, we describe how immune exhaustion and senescence, even if not primary causative factors, can accelerate neurodegenerative diseases. We emphasize the role of a compromised peripheral immune system in driving neurodegeneration and discuss strategies for harnessing peripheral immunity to effectively treat neurodegenerative diseases, including the underlying mechanisms and opportunities for clinical translation. Specifically, we highlight the potential of boosting the immune system by blocking inhibitory checkpoint molecules to harness reparative immune cells in helping the brain to fight against neurodegeneration.

Identification of different functions of CD8+ T cell subpopulations by a novel monoclonal antibody

The explicit identification of CD8+ T cell subpopulation is important for deciphering the role of CD8+ T cells for protecting our body against invading pathogens and cancer. Our generated monoclonal antibody (mAb), named FE-1H10, recognized two novel subpopulations of peripheral blood CD8+ T cells, FE-1H10+ and FE-1H10- CD8+ T cells. The molecule recognized by mAb FE-1H10 (FE-1H10 molecules) had a higher distribution on effector memory CD8+ T cell subsets. The functions of FE-1H10- and FE-1H10+ CD8+ T cells were investigated. T cell proliferation assays revealed that FE-1H10- CD8+ T cells exhibited a higher proliferation rate than FE-1H10+ CD8+ T cells, whereas FE-1H10+ CD8+ T cells produced higher levels of IFN-γ and TNF-α than FE-1H10- CD8+ T cells. In T cell cytotoxicity assays, FE-1H10+ CD8+ T cells were able to kill target cells better than FE-1H10- CD8+ T cells. RNA-sequencing analysis confirmed that these subpopulations were distinct: FE-1H10+ CD8+ T cells have higher expression of genes involved in effector functions (IFNG, TNF, GZMB, PRF1, GNLY, FASL, CX3CR1) while FE-1H10- CD8+ T cells have greater expression of genes related to memory CD8+ T cell populations (CCR7, SELL, TCF7, CD40LG). The results suggested that mAb FE-1H10 identifies two novel distinctive CD8+ T cell subpopulations. The FE-1H10+ CD8+ T cells carried a superior functionality in response to tumour cells. The uncover of these novel CD8+ T cell subpopulations may be the basis knowledge of an optional immunotherapy for the selection of potential CD8+ T cells in cancer treatment.

Inflammaging: The Next Challenge-Exploring the Role of Gut Microbiota, Environmental Factors, and Sex Differences

The term 'inflammaging' has been coined to describe the chronic state of inflammation derived from ongoing cycles of tissue damage and the subsequent immune responses. This inflammatory status contributes to the decline of organs and physiological functions, accelerates the aging process, and increases the risk of age-related illnesses and death. During aging, the gut microbiota (GM) undergoes significant changes, including a decreased diversity of species, a decline in beneficial bacteria, and a rise in proinflammatory ones, resulting in persistent low-grade inflammation. Moreover, environmental factors, such as diet and medications, contribute to age-related changes in GM and immune function, preventing or promoting inflammaging. This narrative review aims to clarify the underlying mechanisms of inflammaging and to specifically investigate the influence of GM and several environmental factors on these mechanisms, while also exploring potential differences related to sex. Moreover, lifestyle and pharmacological interventions will be suggested to promote healthy aging.

SIT1 identifies circulating hypoactive T cells with elevated cytotoxic molecule secretion in systemic lupus erythematosus patients

This study aims to elucidate the expression and functionality of SIT1 in circulating CD8/CD4 + T cells in humans and to delineate its significance in systemic lupus erythematosus (SLE) patients. We employed multiparametric flow cytometry to investigate the expression of SIT1 in circulating CD8/CD4 + T cells and their respective subsets, comparing healthy controls (HCs) with SLE patients. Furthermore, we assessed the levels of granzyme B, perforin, IL-17, and IFN-γ in SIT1-related CD8/CD4 + T cells from both HCs and SLE patients, both before and after PMA stimulation. Clinically, we conducted receiver operating characteristic curve analysis and correlation analysis to evaluate the clinical relevance of SIT1-related CD8/CD4 + T cells in SLE patients. SIT1 exhibited higher expression in CD4 + T cells, with SIT1 - T cells demonstrating elevated levels of granzyme B, perforin, and IFN-γ compared to SIT1 + T cells. PMA-stimulated T cells exhibited reduced SIT1 expression compared to unstimulated T cells. SLE patients displayed increased SIT1 + proportions in CD8 + T cells and decreased SIT1 + CD4 + T cell numbers. Additionally, SIT1 + cells in SLE patients exhibited significantly higher levels of granzyme B and perforin compared to HCs. SIT1 + cells demonstrated significant associations with clinical indicators in SLE patients, with indicators related to SIT1 proving valuable in the diagnosis of SLE patients. SIT1 is inversely correlated with T cell activation. In SLE patients, SIT1 expression is altered in T cells concomitant with an augmented secretion of cytotoxic molecules. This upregulation may contribute to the pathogenesis of SLE and enhance its diagnostic potential.

Mass cytometry reveals atypical immune profile notably impaired maturation of memory CD4 T with Gb3-related CD27 expression in CD4 T cells in Fabry disease

Fabry disease (FD) is an X-linked disease characterized by an accumulation of glycosphingolipids, notably of globotriaosylceramide (Gb3) and globotriaosylsphingosine (lysoGb3) leading to renal failure, cardiomyopathy, and cerebral strokes. Inflammatory processes are involved in the pathophysiology. We investigated the immunological phenotype of peripheral blood mononuclear cells in Fabry patients depending on the clinical phenotype, treatment, Gb3, and lysoGb3 levels and the presence of anti-drug antibodies (ADA). Leucocytes from 41 male patients and 20 controls were analyzed with mass cytometry using both unsupervised and supervised algorithms. FD patients had an increased expression of CD27 and CD28 in memory CD45- and CD45 + CCR7-CD4 T cells (respectively p < 0.014 and p < 0.02). Percentage of CD45RA-CCR7-CD27 + CD28+ cells in CD4 T cells was correlated with plasma lysoGb3 (r = 0.60; p = 0.0036) and phenotype (p < 0.003). The correlation between Gb3 and CD27 in CD4 T cells almost reached significance (r = 0.33; p = 0.058). There was no immune profile associated with the presence of ADA. Treatment with agalsidase beta was associated with an increased proportion of Natural Killer cells. These findings provide valuable insights for understanding FD, linking Gb3 accumulation to inflammation, and proposing new prognostic biomarkers.

Terminally differentiated effector memory T cells associate with cognitive and AD-related biomarkers in an aging-based community cohort

BACKGROUND AND PURPOSE

The immune response changes during aging and the progression of Alzheimer's disease (AD) and related dementia (ADRD). Terminally differentiated effector memory T cells (called TEMRA) are important during aging and AD due to their cytotoxic phenotype and association with cognitive decline. However, it is not clear if the changes seen in TEMRAs are specific to AD-related cognitive decline specifically or are more generally correlated with cognitive decline. This study aimed to examine whether TEMRAs are associated with cognition and plasma biomarkers of AD, neurodegeneration, and neuroinflammation in a community-based cohort of older adults.

METHODS

Study participants from a University of Kentucky Alzheimer's Disease Research Center (UK-ADRC) community-based cohort of aging and dementia were used to test our hypothesis. There were 84 participants, 44 women and 40 men. Participants underwent physical examination, neurological examination, medical history, cognitive testing, and blood collection to determine plasma biomarker levels (Aβ42/Aβ40 ratio, total tau, Neurofilament Light chain (Nf-L), Glial Fibrillary Acidic Protein (GFAP)) and to isolate peripheral blood mononuclear cells (PBMCs). Flow cytometry was used to analyze PBMCs from study participants for effector and memory T cell populations, including CD4+ and CD8+ central memory T cells (TCM), Naïve T cells, effector memory T cells (TEM), and effector memory CD45RA+ T cells (TEMRA) immune cell markers.

RESULTS

CD8+ TEMRAs were positively correlated with Nf-L and GFAP. We found no significant difference in CD8+ TEMRAs based on cognitive scores and no associations between CD8+ TEMRAs and AD-related biomarkers. CD4+ TEMRAs were associated with cognitive impairment on the MMSE. Gender was not associated with TEMRAs, but it did show an association with other T cell populations.

CONCLUSION

These findings suggest that the accumulation of CD8+ TEMRAs may be a response to neuronal injury (Nf-L) and neuroinflammation (GFAP) during aging or the progression of AD and ADRD. As our findings in a community-based cohort were not clinically-defined AD participants but included all ADRDs, this suggests that TEMRAs may be associated with changes in systemic immune T cell subsets associated with the onset of pathology.

Adaptive immune changes associate with clinical progression of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most frequent cause of dementia. Recent evidence suggests the involvement of peripheral immune cells in the disease, but the underlying mechanisms remain unclear.

METHODS

We comprehensively mapped peripheral immune changes in AD patients with mild cognitive impairment (MCI) or dementia compared to controls, using cytometry by time-of-flight (CyTOF).

RESULTS

We found an adaptive immune signature in AD, and specifically highlight the accumulation of PD1+ CD57+ CD8+ T effector memory cells re-expressing CD45RA in the MCI stage of AD. In addition, several innate and adaptive immune cell subsets correlated to cerebrospinal fluid (CSF) biomarkers of AD neuropathology and measures for cognitive decline. Intriguingly, subsets of memory T and B cells were negatively associated with CSF biomarkers for tau pathology, neurodegeneration and neuroinflammation in AD patients. Lastly, we established the influence of the APOE ε4 allele on peripheral immunity.

CONCLUSIONS

Our findings illustrate significant peripheral immune alterations associated with both early and late clinical stages of AD, emphasizing the necessity for further investigation into how these changes influence underlying brain pathology.

The Impact of Immune System Aging on Infectious Diseases

Immune system aging is becoming a field of increasing public health interest because of prolonged life expectancy, which is not paralleled by an increase in health expectancy. As age progresses, innate and adaptive immune systems undergo changes, which are defined, respectively, as inflammaging and immune senescence. A wealth of available data demonstrates that these two conditions are closely linked, leading to a greater vulnerability of elderly subjects to viral, bacterial, and opportunistic infections as well as lower post-vaccination protection. To face this novel scenario, an in-depth assessment of the immune players involved in this changing epidemiology is demanded regarding the individual and concerted involvement of immune cells and mediators within endogenous and exogenous factors and co-morbidities. This review provides an overall updated description of the changes affecting the aging immune system, which may be of help in understanding the underlying mechanisms associated with the main age-associated infectious diseases.

PRaG 3.0 therapy for human epidermal growth factor receptor 2-positive metastatic pancreatic ductal adenocarcinoma: A case report

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC) is a highly fatal disease with limited effective treatment especially after first-line chemotherapy. The human epidermal growth factor receptor 2 (HER-2) immunohistochemistry (IHC) positive is associated with more aggressive clinical behavior and shorter overall survival in PDAC.

CASE SUMMARY

We present a case of multiple metastatic PDAC with IHC mismatch repair proficient but HER-2 IHC weakly positive at diagnosis that didn't have tumor regression after first-line nab-paclitaxel plus gemcitabine and PD-1 inhibitor treatment. A novel combination therapy PRaG 3.0 of RC48 (HER2-antibody-drug conjugate), radiotherapy, PD-1 inhibitor, granulocyte-macrophage colony-stimulating factor and interleukin-2 was then applied as second-line therapy and the patient had confirmed good partial response with progress-free-survival of 6.5 months and overall survival of 14.2 month. She had not developed any grade 2 or above treatment-related adverse events at any point. Percentage of peripheral CD8+Temra and CD4+Temra were increased during first two activation cycles of PRaG 3.0 treatment containing radiotherapy but deceased to the baseline during the maintenance cycles containing no radiotherapy.

CONCLUSION

PRaG 3.0 might be a novel strategy for HER2-positive metastatic PDAC patients who failed from previous first-line approach and even PD-1 immunotherapy but needs more data in prospective trials.

Immune dysfunction in patients with end stage kidney disease; Immunosenescence - Review

The body's defense against environmental factors is realized by physical barriers and cells of both the innate and adaptive immune systems. Patients with end stage kidney disease (ESKD), especially those treated by hemodialysis, have changes in both the function and the number or percent of different leukocyte subsets. Changes were described at the level of monocytes and lymphocyte subsets, which are associated with immunodeficiencies and pro-inflammatory status correlated with degenerative changes and increased cardiovascular risk. These abnormalities have been compared over the past years with alterations appearing as a result ageing. Also, similitudes regarding immunosenescence observed in ESKD patients, in combination with chronic inflammation, are described as the so-called "inflammaging syndrome".

HIIT Induces Stronger Shifts within the Peripheral T Cell Compartment Independent of Sex

Acute exercise induces changes within the T-cell compartment, especially in cytotoxic CD8+ memory subsets, depending on exercise intensity and duration. It is unclear whether exercise-induced changes in major T-cell subsets differ in response to acute high-intensity interval training (HIIT) or moderate-intensity continuous training (MICT) and whether sex-specific effects exist. Twenty-four recreationally active runners (females: n=12, 27.8±4.1years, 54.4±4.6 ml*kg-1*min-1; males: n=12, 31.6±3.8years, 58.9±7.7 ml*kg-1*min-1) participated in this randomized controlled crossover study, and conducted an energy- and duration-matched HIIT and MICT session. Blood was sampled before (T1), immediately (T2) and 1 h after exercise (T3). Flow cytometry was used to identify T-cell populations. HIIT decreased the proportion of CD8+ T-cells more pronounced at T3 compared to MICT (p=0.007), induced a significantly stronger increase in the CD8+ effector memory (TEM) cell proportion at T2 (p=0.032), and decreased CD4+ central memory proportion more pronounced at T2 (p=0.029). A decrease below baseline CD8+ TEM proportion at T3 was observed only after HIIT (p<0.001). No interaction effects between sexes were revealed. Taken together, HIIT represents a more potent stimulus to induce shifts mainly within the cytotoxic CD8+ T-cell compartment, thereby giving implications to investigate the role of HIIT on the cell´s effector phenotype and function in more detail.

Cytotoxic CD8+ Temra cells show loss of chromatin accessibility at genes associated with T cell activation

As humans age, their memory T cell compartment expands due to the lifelong exposure to antigens. This expansion is characterized by terminally differentiated CD8+ T cells (Temra), which possess NK cell-like phenotype and are associated with chronic inflammatory conditions. Temra cells are predominantly driven by the sporadic reactivation of cytomegalovirus (CMV), yet their epigenomic patterns and cellular heterogeneity remain understudied. To address this gap, we correlated their gene expression profiles with chromatin openness and conducted single-cell transcriptome analysis, comparing them to other CD8+ subsets and CMV-responses. We confirmed that Temra cells exhibit high expression of genes associated with cytotoxicity and lower expression of costimulatory and chemokine genes. The data revealed that CMV-responsive CD8+ T cells (Tcmv) were predominantly derived from a mixed population of Temra and memory cells (Tcm/em) and shared their transcriptomic profiles. Using ATAC-seq analysis, we identified 1449 differentially accessible chromatin regions between CD8+ Temra and Tcm/em cells, of which only 127 sites gained chromatin accessibility in Temra cells. We further identified 51 gene loci, including costimulatory CD27, CD28, and ICOS genes, whose chromatin accessibility correlated with their gene expression. The differential chromatin regions Tcm/em cells were enriched in motifs that bind multiple transcriptional activators, such as Jun/Fos, NFkappaB, and STAT, whereas the open regions in Temra cells mainly contained binding sites of T-box transcription factors. Our single-cell analysis of CD8+CCR7loCD45RAhi sorted Temra population showed several subsets of Temra and NKT-like cells and CMC1+ Temra populations in older individuals that were shifted towards decreased cytotoxicity. Among CD8+CCR7loCD45RAhi sorted cells, we found a decreased proportion of IL7R+ Tcm/em-like and MAIT cells in individuals with high levels of CMV antibodies (CMVhi). These results shed new light on the molecular and cellular heterogeneity of CD8+ Temra cells and their relationship to aging and CMV infection.

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.

HELIOS-expressing human CD8 T cells exhibit limited effector functions

Introduction

The transcription factor HELIOS is primarily known for its expression in CD4 regulatory T cells, both in humans and mice. In mice, HELIOS is found in exhausted CD8 T cells. However, information on human HELIOS+ CD8 T cells is limited and conflicting.

Methods

In this study, we characterized by flow cytometry and transcriptomic analyses human HELIOS+ CD8 T cells.

Results

These T cells primarily consist of memory cells and constitute approximately 21% of blood CD8 T cells. In comparison with memory HELIOS- T-BEThigh CD8 T cells that displayed robust effector functions, the memory HELIOS+ T-BEThigh CD8 T cells produce lower amounts of IFN-γ and TNF-α and have a lower cytotoxic potential. We wondered if these cells participate in the immune response against viral antigens, but did not find HELIOS+ cells among CD8 T cells recognizing CMV peptides presented by HLA-A2 and HLA-B7. However, we found HELIOS+ CD8 T cells that recognize a CMV peptide presented by MHC class Ib molecule HLA-E. Additionally, a portion of HELIOS+ CD8 T cells is characterized by the expression of CD161, often used as a surface marker for identifying TC17 cells. These CD8 T cells express TH17/TC17-related genes encoding RORgt, RORa, PLZF, and CCL20.

Discussion

Our findings emphasize that HELIOS is expressed across various CD8 T cell populations, highlighting its significance beyond its role as a transcription factor for Treg or exhausted murine CD8 T cells. The significance of the connection between HELIOS and HLA-E restriction is yet to be understood.

Early β-amyloid accumulation in the brain is associated with peripheral T cell alterations

INTRODUCTION

Fast and minimally invasive approaches for early diagnosis of Alzheimer's disease (AD) are highly anticipated. Evidence of adaptive immune cells responding to cerebral β-amyloidosis has raised the question of whether immune markers could be used as proxies for β-amyloid accumulation in the brain.

METHODS

Here, we apply multidimensional mass-cytometry combined with unbiased machine-learning techniques to immunophenotype peripheral blood mononuclear cells from a total of 251 participants in cross-sectional and longitudinal studies.

RESULTS

We show that increases in antigen-experienced adaptive immune cells in the blood, particularly CD45RA-reactivated T effector memory (TEMRA) cells, are associated with early accumulation of brain β-amyloid and with changes in plasma AD biomarkers in still cognitively healthy subjects.

DISCUSSION

Our results suggest that preclinical AD pathology is linked to systemic alterations of the adaptive immune system. These immunophenotype changes may help identify and develop novel diagnostic tools for early AD assessment and better understand clinical outcomes.

Terminally differentiated effector memory T cells associate with cognitive and AD-related biomarkers in an aging-based community cohort

Background and Purpose

The immune response changes during aging and the progression of Alzheimer's disease (AD) and related dementia (ADRD). Terminally differentiated effector memory T cells (called TEMRA) are important during aging and AD due to their cytotoxic phenotype and association with cognitive decline. However, it is not clear if the changes seen in TEMRAs are specific to AD-related cognitive decline specifically or are more generally correlated with cognitive decline. This study aimed to examine whether TEMRAs are associated with cognition and plasma biomarkers of AD, neurodegeneration, and neuroinflammation in a community-based cohort of older adults.

Methods

Study participants from a University of Kentucky Alzheimer's Disease Research Center (UK-ADRC) community-based cohort of aging and dementia were used to test our hypothesis. There were 84 participants, 44 women and 40 men. Participants underwent physical examination, neurological examination, medical history, cognitive testing, and blood collection to determine plasma biomarker levels (Aβ42/Aβ40 ratio, total tau, Neurofilament Light chain (Nf-L), Glial Fibrillary Acidic Protein (GFAP)) and to isolate peripheral blood mononuclear cells (PBMCs). Flow cytometry was used to analyze PBMCs from study participants for effector and memory T cell populations, including CD4+ and CD8+ central memory T cells (TCM), Naïve T cells, effector memory T cells (TEM), and effector memory CD45RA+ T cells (TEMRA) immune cell markers.

Results

CD8+ TEMRAs were positively correlated with Nf-L and GFAP. We found no significant difference in CD8+ TEMRAs based on cognitive scores and no associations between CD8+ TEMRAs and AD-related biomarkers. CD4+ TEMRAs were associated with cognitive impairment on the MMSE. Gender was not associated with TEMRAs, but it did show an association with other T cell populations.

Conclusion

These findings suggest that the accumulation of CD8+ TEMRAs may be a response to neuronal injury (Nf-L) and neuroinflammation (GFAP) during aging or the progression of AD and ADRD. As our findings in a community-based cohort were not clinically-defined AD participants but included all ADRDs, this suggests that TEMRAs may be associated with changes in systemic immune T cell subsets associated with the onset of pathology.

The role of TEMRA cell-mediated immune senescence in the development and treatment of HIV disease

Human Immunodeficiency Virus (HIV) has plagued human society for a long time since its discovery, causing a large number of patients to suffer and costing hundreds of millions of medical services every year. Scientists have found that HIV and antiretroviral therapy accelerate immune aging by inducing mitochondrial dysfunction, and that terminal effector memory T cells (TEMRA cells) are crucial in immune aging. This specific subset of effector memory T cells has terminally differentiated properties and exhibits high cytotoxicity and proinflammatory capacity. We therefore explored and described the interplay between exhaustion features, essential markers, functions, and signaling pathways from previous studies on HIV, antiretroviral therapy, immune senescence, and TEMRA cells. Their remarkable antiviral capacity is then highlighted by elucidating phenotypic changes in TEMRA cells during HIV infection, describing changes in TEMRA cells before, during, and after antiretroviral therapy and other drug treatments. Their critical role in complications and cytomegalovirus (CMV)-HIV superinfection is highlighted. These studies demonstrate that TEMRA cells play a key role in the antiviral response and immune senescence during HIV infection. Finally, we review current therapeutic strategies targeting TEMRA cells that may be clinically beneficial, highlight their potential role in HIV-1 vaccine development, and provide perspectives and predictions for related future applications.

G Protein-Coupled Receptor 56 Characterizes CTLs and Reflects the Progression of Lung Cancer Patients

CTLs play important roles in host immune responses to tumors. CD4 CTLs are characterized by their ability to secrete cytotoxic effector molecules, such as granzyme B and perforin, and kill target cells in a MHC class II-restricted manner. However, the cell surface markers of CD4 CTLs remain unknown, which hinders their separation and research on their function. In this study, we performed a bioinformatics analysis and experimental validation that revealed that G protein-coupled receptor 56 (GPR56) is a cell surface marker that can be used to characterize CD4 CTLs. We found that GPR56 and granzyme B were coexpressed in extremely high levels in human peripheral blood T cells, and that anti-GPR56 stimulation significantly upregulated the expression of granzyme B in both CD4+GPR56+ and CD8+GPR56+ T cells. These findings suggest that GPR56 expression and the GPR56 signaling pathway could contribute directly to the toxic function of either CD4+ or CD8+ T cells. We also used GPR56 as a biomarker to investigate the clinical significance of CD4 CTLs. GPR56+ T cell levels were increased in patients with lung cancer, and GPR56 expression was significantly correlated with lung cancer progression. A further analysis revealed an increase in exhausted cell states in lung cancer patients because of upregulation of programmed cell death protein 1 expression in GPR56+ T cells. The findings of this study suggest that GPR56 characterizes the cytotoxic states of either CD4+ or CD8+ T cells.

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

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

Activation of telomerase by TA-65 enhances immunity and reduces inflammation post myocardial infarction

Myocardial infarction (MI) accelerates immune ageing characterised by lymphopenia, expansion of terminally differentiated CD8+ T-lymphocytes (CD8+ TEMRA) and inflammation. Pre-clinical data showed that TA-65, an oral telomerase activator, reduced immune ageing and inflammation after MI. We conducted a double blinded randomised controlled pilot trial evaluating the use of TA-65 to reduce immune cell ageing in patients following MI. Ninety MI patients aged over 65 years were randomised to either TA-65 (16 mg daily) or placebo for 12 months. Peripheral blood leucocytes were analysed by flow cytometry. The pre-defined primary endpoint was the proportion of CD8+ T-lymphocytes which were CD8+ TEMRA after 12 months. Secondary outcomes included high-sensitivity C-reactive protein (hsCRP) levels. Median age of participants was 71 years. Proportions of CD8+ TEMRA did not differ after 12 months between treatment groups. There was a significant increase in mean total lymphocyte count in the TA-65 group after 12 months (estimated treatment effect: + 285 cells/μl (95% CI: 117-452 cells/ μ l, p < 0.004), driven by significant increases from baseline in CD3+, CD4+, and CD8+ T-lymphocytes, B-lymphocytes and natural killer cells. No increase in lymphocyte populations was seen in the placebo group. At 12 months, hsCRP was 62% lower in the TA-65 group compared to placebo (1.1 vs. 2.9 mg/L). Patients in the TA-65 arm experienced significantly fewer adverse events (130 vs. 185, p = 0.002). TA-65 did not alter CD8+ TEMRA but increased all major lymphocyte subsets and reduced hsCRP in elderly patients with MI after 12 months.

Vaccination provides superior in vivo recall capacity of SARS-CoV-2-specific memory CD8 T cells

Memory CD8 T cells play an important role in the protection against breakthrough infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Whether the route of antigen exposure impacts these cells at a functional level is incompletely characterized. Here, we compare the memory CD8 T cell response against a common SARS-CoV-2 epitope after vaccination, infection, or both. CD8 T cells demonstrate comparable functional capacity when restimulated directly ex vivo, independent of the antigenic history. However, analysis of T cell receptor usage shows that vaccination results in a narrower scope than infection alone or in combination with vaccination. Importantly, in an in vivo recall model, memory CD8 T cells from infected individuals show equal proliferation but secrete less tumor necrosis factor (TNF) compared with those from vaccinated people. This difference is negated when infected individuals have also been vaccinated. Our findings shed more light on the differences in susceptibility to re-infection after different routes of SARS-CoV-2 antigen exposure.

Prospective Evaluation of CD45RA+/CCR7- Effector Memory T (TEMRA) Cell Subsets in Patients with Primary and Secondary Brain Tumors during Radiotherapy of the Brain within the Scope of the Prospective Glio-CMV-01 Clinical Trial

Radiotherapy (RT) of the brain is a common treatment for patients with high-grade gliomas and brain metastases. It has previously been shown that reactivation of cytomegalovirus (CMV) frequently occurs during RT of the brain. This causes neurological decline, demands antiviral treatment, and is associated with a worse prognosis. CMV-specific T cells are characterized by a differentiated effector memory phenotype and CD45RA+ CCR7- effector memory T (T_EMRA) cells were shown to be enriched in CMV seropositive individuals. In this study, we investigated the distribution of T_EMRA cells and their subsets in the peripheral blood of healthy donors and, for the first time, prospectively within the scope of the prospective Glio-CMV-01 clinical trial of patients with high-grade glioma and brain metastases during radiation therapy as a potential predictive marker. First, we developed a multicolor flow cytometry-based assay to monitor the frequency and distribution of T_EMRA cells in a longitudinal manner. The CMV serostatus and age were considered as influencing factors. We revealed that patients who had a reactivation of CMV have significantly higher amounts of CD8+ T_EMRA cells. Further, the distribution of the subsets of T_EMRA cells based on the expression of CD27, CD28, and CD57 is highly dependent on the CMV serostatus. We conclude that the percentage of CD8+ T_EMRA cells out of all CD8+ T cells has the potential to serve as a biomarker for predicting the risk of CMV reactivation during RT of the brain. Furthermore, this study highlights the importance of taking the CMV serostatus into account when analyzing T_EMRA cells and their subsets.

The Function of Memory CD8+ T Cells in Immunotherapy for Human Diseases

Memory T (Tm) cells protect against Ags that they have previously contacted with a fast and robust response. Therefore, developing long-lived Tm cells is a prime goal for many vaccines and therapies to treat human diseases. The remarkable characteristics of Tm cells have led scientists and clinicians to devise methods to make Tm cells more useful. Recently, Tm cells have been highlighted for their role in coronavirus disease 2019 vaccines during the ongoing global pandemic. The importance of Tm cells in cancer has been emerging. However, the precise characteristics and functions of Tm cells in these diseases are not completely understood. In this review, we summarize the known characteristics of Tm cells and their implications in the development of vaccines and immunotherapies for human diseases. In addition, we propose to exploit the beneficial characteristics of Tm cells to develop strategies for effective vaccines and overcome the obstacles of immunotherapy.

Tracking Peripheral Memory T Cell Subsets in Advanced Nonsmall Cell Lung Cancer Treated with Hypofractionated Radiotherapy and PD-1 Blockade

Hypofractionated radiotherapy (HFRT) or chemotherapy combined with programmed death-1 (PD-1) blockade has achieved good clinical control in advanced nonsmall cell lung cancer (NSCLC). However, the relative influence of HFRT + PD-1 blockade and chemo-immunotherapy on peripheral memory T cell subsets in NSCLC responders has not been evaluated in clinical practice. Thirty-nine patients with advanced NSCLC were enrolled. The frequencies of naive (Tn; CD45RA+CCR7+), central memory (Tcm; CD45RA-CCR7+), effector memory (Tem; CD45RA-CCR7-), and effector memory RA (TemRA; CD45RA+CCR7-) T cell subsets and PD-1 expression were analyzed in CD4+ and CD8+ T cells using flow cytometry from peripheral blood samples. The correlations of memory T cell subsets and PD-1 expression with overall survival in HFRT + PD-1 blockade group were examined using the Kaplan-Meier method. Patients with partial response to HFRT + PD-1 blockade showed reduction in Tn and expansion in TemRA cell subpopulations among CD8+ T cells and reduced PD-1+CD4+ and PD-1+CD8+ T cells, all of which were significantly correlated with overall survival. The responders to chemo-immunotherapy showed expansion of the TemRA and decrease of Tcm in CD8+ T cell subpopulation. Our findings show that HFRT+PD-1 blockade and chemo-immunotherapy combination therapies induce differential memory T cell subset differentiation, offering predictive markers for treatment response. Clinical Trial Information: https://clinicaltrials.gov/ct2/show/ChiCTR-1900027768.

Pregnancy imparts distinct systemic adaptive immune function

PROBLEM

Pregnancy represents a state of systemic immune activation that is primarily driven by alterations in circulating innate immune cells. Recent studies have suggested that cellular adaptive immune components, T cells and B cells, also undergo changes throughout gestation. However, the phenotypes and functions of such adaptive immune cells are poorly understood. Herein, we utilized high-dimensional flow cytometry and functional assays to characterize T-cell and B-cell responses in pregnant and non-pregnant women.

METHODS

Peripheral blood mononuclear cells from pregnant (n = 20) and non-pregnant (n = 25) women were used for phenotyping of T-cell and B-cell subsets. T-cell proliferation and B-cell activation were assessed by flow cytometry after in vitro stimulation, and lymphocyte cytotoxicity was evaluated by using a cell-based assay. Statistical comparisons were performed with linear mixed-effects models.

RESULTS

Pregnancy was associated with modestly enhanced basal activation of peripheral CD4+ T cells. Both CD4+ and CD8+ T cells from pregnant women showed increased activation-induced proliferation; yet, a reduced proportion of these cells expressed activation markers compared to non-pregnant women. There were no differences in peripheral lymphocyte cytotoxicity between study groups. A greater proportion of B cells from pregnant women displayed memory-like and activated phenotypes, and such cells exhibited higher activation following stimulation.

CONCLUSION

Maternal circulating T cells and B cells display distinct responses during pregnancy. The former may reflect the unique capacity of T cells to respond to potential threats without undergoing aberrant activation, thereby preventing systemic inflammatory responses that can lead to adverse perinatal consequences.

Are CD45RO+ and CD45RA- genuine markers for bovine memory T cells?

Effective vaccination induces memory T cells, which protect the host against pathogen re-infections. Therefore, detection of memory T cells is essential for evaluating vaccine efficacy, which was originally dependent on cytokine induction assays. Currently, two isoforms of CD45 tyrosine phosphatase, CD45RO expression and CD45RA exclusion (CD45RO+/ CD45RA-) are used extensively for detecting memory T cells in cattle. The CD45RO+/CD45RA- markers were first established in humans around three decades ago, and were adopted in cattle soon after. However, in the last two decades, some published data in humans have challenged the initial paradigm, and required multiple markers for identifying memory T cells. On the contrary, memory T cell detection in cattle still mostly relies on CD45RO+/CD45RA- despite some controversial evidence. In this review, we summarized the current literature to examine if CD45RO+/CD45RA- are valid markers for detecting memory T cells in cattle. It seems CD45RA and CD45RO (CD45RA/RO) as markers for identifying bovine memory T cells are questionable.

Gain-of-function defects in toll-like receptor 8 shed light on the interface between immune system and bone marrow failure disorders

In this article, we will share lessons that patients with gain-of-function defects in Toll-like receptor 8 (TLR8-GOF) can teach us about the interface between bone marrow failure (BMF) disorders and inborn errors of immunity (IEI), subsequently referred to as “Interface Disorders”. TLR8-GOF is a relatively young entity (from a discovery standpoint) that—through both similar and dissimilar disease characteristics—can increase our understanding of interface disorders, for example, as it pertains to pathophysiology, the genetic mechanism of disease, and related diagnostics and therapeutics. From a genetics point of view, TLR8-GOF joins a growing list of (interface) disorders that can cause disease both with germline and somatic (mosaic) genetic variants. This not only has repercussions for the diagnostic workup of these disorders, inasmuch that routine genetic testing may miss somatic variants, but has therapeutic implications as well, for example, with the approach to curative treatment, such as hematopoietic stem cell transplantation. Following an introduction and schematic rendering of the interface, we will review the salient features of TLR8-GOF, with the understanding that the phenotype of this new disorder is likely not written in stone yet. In keeping with the principle of “Form Follows Function”, we will discuss specific immunological biomarkers that can be measured in clinical laboratories and highlight key disease features that pertain to TLR8-GOF, and can be found in several interface disorders. As can be seen from a schematic representation, the interface provides not only opportunities for learning and collaboration with respect to shared diagnostics but also the potential for drug repurposing and precision therapeutics. Ideally, collaboration also focuses on education and teaching, such that cross-fertilization and collaboration across these disciplines can create a framework for complementary research.

The aging immune system in Alzheimer's and Parkinson's diseases

The neurodegenerative diseases Alzheimer's disease (AD) and Parkinson's disease (PD) both have a myriad of risk factors including genetics, environmental exposures, and lifestyle. However, aging is the strongest risk factor for both diseases. Aging also profoundly influences the immune system, with immunosenescence perhaps the most prominent outcome. Through genetics, mouse models, and pathology, there is a growing appreciation of the role the immune system plays in neurodegenerative diseases. In this review, we explore the intersection of aging and the immune system in AD and PD.

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.

High Frequencies of Phenotypically and Functionally Senescent and Exhausted CD56+CD57+PD-1+ Natural Killer Cells, SARS-CoV-2-Specific Memory CD4+ and CD8+ T cells Associated with Severe Disease in Unvaccinated COVID-19 Patients

Unvaccinated COVID-19 patients display a large spectrum of symptoms, ranging from asymptomatic to severe symptoms, the latter even causing death. Distinct Natural killer (NK) and CD4+ and CD8+ T cells immune responses are generated in COVID-19 patients. However, the phenotype and functional characteristics of NK cells and T-cells associated with COVID-19 pathogenesis versus protection remain to be elucidated. In this study, we compared the phenotype and function of NK cells SARS-CoV-2-specific CD4+ and CD8+ T cells in unvaccinated symptomatic (SYMP) and unvaccinated asymptomatic (ASYMP) COVID-19 patients. The expression of senescent CD57 marker, CD45RA/CCR7differentiation status, exhaustion PD-1 marker, activation of HLA-DR, and CD38 markers were assessed on NK and T cells from SARS-CoV-2 positive SYMP patients, ASYMP patients, and Healthy Donors (HD) using multicolor flow cytometry. We detected significant increases in the expression levels of both exhaustion and senescence markers on NK and T cells from SYMP patients compared to ASYMP patients and HD controls. In SYMP COVID-19 patients, the T cell compartment displays several alterations involving naive, central memory, effector memory, and terminally differentiated T cells. The senescence CD57 marker was highly expressed on CD8+ TEM cells and CD8+ TEMRA cells. Moreover, we detected significant increases in the levels of pro-inflammatory TNF-α, IFN-γ, IL-6, IL-8, and IL-17 cytokines from SYMP COVID-19 patients, compared to ASYMP COVID-19 patients and HD controls. The findings suggest exhaustion and senescence in both NK and T cell compartment is associated with severe disease in critically ill COVID-19 patients.

Crossing borders in Alzheimer's disease: A T cell's perspective

Alzheimer's disease (AD) is the most common form of dementia affecting millions of people worldwide. While different immunotherapies are imminent, currently only disease-modifying medications are available and a cure is lacking. Over the past decade, immunological interfaces of the central nervous system (CNS) and their role in neurodegenerative diseases received increasing attention. Specifically, emerging evidence shows that subsets of circulating CD8⁺ T cells cross the brain barriers and associate with AD pathology. To gain more insight into how the adaptive immune system is involved in disease pathogenesis, we here provide a comprehensive overview of the contribution of T cells to AD pathology, incorporating changes at the brain barriers. In addition, we review studies that provide translation of these findings by targeting T cells to combat AD pathology and cognitive decline. Importantly, these data show that immunological changes in AD are not confined to the CNS and that AD-associated systemic immune changes appear to affect brain homeostasis.

Immune Alterations in a Patient With Hyperornithinemia-Hyperammonemia-Homocitrullinuria Syndrome: A Case Report

The hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome is a rare autosomal recessive inborn error of the urea cycle caused by mutations in the SLC25A15 gene. Besides the well-known metabolic complications, patients often present intercurrent infections associated with acute hyperammonemia and metabolic decompensation. However, it is currently unknown whether intercurrent infections are associated with immunological alterations besides the known metabolic imbalances. Herein, we describe the case of a 3-years-old girl affected by the HHH syndrome caused by two novel SLC25A15 gene mutations associated with immune phenotypic and functional alterations. She was admitted to the hospital with an episode of recurrent otitis, somnolence, confusion, and lethargy. Laboratory tests revealed severe hyperammonemia, elevated serum levels of liver transaminases, hemostasis alterations, hyperglutaminemia and strikingly increased orotic aciduria. Noteworthy, serum protein electrophoresis showed a reduction in the gamma globulin fraction. Direct sequencing of the SLC25A15 gene revealed two heterozygous non-conservative substitutions in the exon 5: c.649G>A (p.Gly217Arg) and c.706A>G (p.Arg236Gly). In silico analysis indicated that both mutations significantly impair protein structure and function and are consistent with the patient clinical status confirming the diagnosis of HHH syndrome. In addition, the immune analysis revealed reduced levels of serum IgG and striking phenotypic and functional alterations in the T and B cell immune compartments. Our study has identified two non-previously described mutations in the SLC25A15 gene underlying the HHH syndrome. Moreover, we are reporting for the first time functional and phenotypic immunologic alterations in this rare inborn error of metabolism that would render the patient immunocompromised and might be related to the high frequency of intercurrent infections observed in patients bearing urea cycle disorders. Our results point out the importance of a comprehensive analysis to gain further insights into the underlying pathophysiology of the disease that would allow better patient care and quality of life.

Tacrolimus-resistant SARS-CoV-2-specific T cell products to prevent and treat severe COVID-19 in immunosuppressed patients

Solid organ transplant (SOT) recipients receive therapeutic immunosuppression that compromises their immune response to infections and vaccines. For this reason, SOT patients have a high risk of developing severe coronavirus disease 2019 (COVID-19) and an increased risk of death from severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. Moreover, the efficiency of immunotherapies and vaccines is reduced due to the constant immunosuppression in this patient group. Here, we propose adoptive transfer of SARS-CoV-2-specific T cells made resistant to a common immunosuppressant, tacrolimus, for optimized performance in the immunosuppressed patient. Using a ribonucleoprotein approach of CRISPR-Cas9 technology, we have generated tacrolimus-resistant SARS-CoV-2-specific T cell products from convalescent donors and demonstrate their specificity and function through characterizations at the single-cell level, including flow cytometry, single-cell RNA (scRNA) Cellular Indexing of Transcriptomes and Epitopes (CITE), and T cell receptor (TCR) sequencing analyses. Based on the promising results, we aim for clinical validation of this approach in transplant recipients. Additionally, we propose a combinatory approach with tacrolimus, to prevent an overshooting immune response manifested as bystander T cell activation in the setting of severe COVID-19 immunopathology, and tacrolimus-resistant SARS-CoV-2-specific T cell products, allowing for efficient clearance of viral infection. Our strategy has the potential to prevent severe COVID-19 courses in SOT or autoimmunity settings and to prevent immunopathology while providing viral clearance in severe non-transplant COVID-19 cases.

Chronic Kidney Failure Provokes the Enrichment of Terminally Differentiated CD8+ T Cells, Impairing Cytotoxic Mechanisms After Kidney Transplantation

Chronic kidney failure (KF) provokes the development of immune senescent CD8⁺ cytotoxic T cells, affecting the occurrence of graft rejection, viral infections, and malignancies after kidney transplantation. In this study, we analyzed the impact of KF, subsequent dialysis treatment, and kidney transplantation on the differentiation of CD8⁺CD31⁺CD45RA⁺CCR7⁺ recent thymic emigrant (CCR7⁺ RTE) Tregs/Tresps into CD8⁺CD31^-CD45RA^- memory (CD31^- memory) Tregs/Tresps and its effect on the release of cytokines, Fas receptor, Fas ligand as well as cytotoxic mediators by naïve, central memory (CM), effector memory (EM), and terminally differentiated effector memory (TEMRA) Tresps. We found that normal age-dependent differentiation of CD8⁺ Tregs/Tresps generally differs in the way that TEMRA cells only arise in Tresps. Compared to healthy controls, KF patients revealed an age-independently decreased frequency of CCR7⁺ RTE Tregs/Tresps, but increased frequencies of CCR7⁺ MN Tregs/Tresps and CD31^- memory Tregs/Tresps, suggesting an increased differentiation via CD31⁺CD45RA^- memory (CD31⁺ memory) Tregs/Tresps into CD31^- memory Tregs/Tresps. Intensified differentiation via CD31⁺ memory Tresps increased the emergence of apoptosis-resistant CM Tresps with strong Fas ligand-mediated cytotoxicity. CCR7⁺ RTE Tresp proliferation generated TEMRA Tresps, secreting high levels of cytotoxic mediators. In dialysis and transplant patients, CD31⁺ TEMRA Tregs/Tresps accumulated, proposing an impaired CCR7⁺ RTE Treg/Tresp differentiation via CD31⁺ memory Tregs/Tresps into CD31^- memory Tregs/Tresps. Increased percentages of CD31^- TEMRA Tresps, but not of CD31^- TEMRA Tregs, were observed in all patient groups, indicating impaired proliferation of CCR7⁺ RTE Tresps, but not of CCR7⁺ RTE Tregs, into CD31^- memory Tregs/Tresps. In transplant patients, CCR7⁺ RTE Tregs accumulated, while frequencies of CCR7⁺ RTE Tresps were decreased, suggesting that the immunosuppressive therapy only prevented excessive CCR7⁺ RTE Treg differentiation but not that of CCR7⁺ RTE Tresps. Presumably, this caused the accumulation of TEMRA Tresps with decreased release of cytotoxic mediators, such as perforin. In conclusion, we propose that chronic KF affects both the differentiation of CD8⁺ Tregs and CD8⁺ Tresps. However, the immunosuppressive therapy after transplantation may successfully prevent excessive Treg differentiation, but not as suffciently that of Tresps. Therefore, the risk for graft rejection may be reduced, while the susceptibility for infections and malignancies may be increased in these patients.

Intersection Between Large Granular Lymphocyte Leukemia and Rheumatoid Arthritis

Large granular lymphocyte (LGL) leukemia, a rare hematologic malignancy, has long been associated with rheumatoid arthritis (RA), and the diseases share numerous common features. This review aims to outline the parallels and comparisons between the diseases as well as discuss the potential mechanisms for the relationship between LGL leukemia and RA. RA alone and in conjunction with LGL leukemia exhibits cytotoxic T-cell (CTL) expansions, HLA-DR4 enrichment, RA-associated autoantibodies, female bias, and unknown antigen specificity of associated T-cell expansions. Three possible mechanistic links between the pathogenesis of LGL leukemia and RA have been proposed, including LGL leukemia a) as a result of longstanding RA, b) as a consequence of RA treatment, or c) as a driver of RA. Several lines of evidence point towards LGL as a driver of RA. CTL involvement in RA pathogenesis is evidenced by citrullination and granzyme B cleavage that modifies the repertoire of self-protein antigens in target cells, particularly neutrophils, killed by the CTLs. Further investigations of the relationship between LGL leukemia and RA are warranted to better understand causal pathways and target antigens in order to improve the mechanistic understanding and to devise targeted therapeutic approaches for both disorders.

Canine memory T-cell subsets in health and disease

A more complete understanding of canine T-lymphocyte immunity is necessary for improving diagnostic and therapeutic approaches to canine diseases, developing cell-based canine immunotherapeutics, and evaluating dogs as large mammal models for comparative immunology research. The aim of this study was to utilize CD45RA (indicating antigen inexperience) and CD62L (indicating lymph node homing capability), to quantify canine memory T-cell subsets in healthy dogs and dogs with various diseases. Peripheral blood mononuclear cells (PBMCs) were prospectively collected from dogs belonging to one of four groups:dermatologic inflammation (n = 9), solid tumors (n = 9), lymphoma (n = 9), and age-/weight-matched healthy control dogs (n = 15). Dogs receiving prednisone or any other immunomodulating medication within two weeks were excluded. Flow cytometry was performed and T-cell subsets were defined as CD4+ or CD8+, and naïve (TN), central memory (CM), effector memory (EM), or terminal effector memory re-expressing CD45RA (TEMRA). T-cell subset proportions were compared between each disease group and their healthy age-/weight-matched controls using a Mann-Whitney test. Significantly increased %CD8+ TN (P = 0.036) and decreased %CD8+ TEMRA (P = 0.045) were detected in dogs with dermatologic inflammation compared to healthy controls. Furthermore, %CD4+ TN positively correlated with Canine Atopic Dermatitis Extent and Severity Index (CADESI) score within the inflammation group (ρ = 0.817, P = 0.011). No significant differences between either cancer group and their healthy controls were detected. Taken together, these data indicate that dermatologic inflammation can alter proportions of peripheral blood T-cell subsets, possibly due to the migration of antigen-specific T-cells into tissues. Furthermore, these findings support the utility of CD45RA and CD62L in characterizing clinical canine immune responses.

Transcriptional Analysis of Total CD8+ T Cells and CD8+CD45RA- Memory T Cells From Young and Old Healthy Blood Donors

Memory CD8⁺ T cells accumulate with aging, while the naïve T cell compartment decreases, leading to an increased susceptibility to infections and a decreased vaccine efficiency. To get deeper insights into the underlying mechanisms, this study aims to determine the age-dependent expression profile of total versus memory CD8⁺ T cells from young and old donors. Total CD8⁺ and CD8⁺CD45RA^- memory T cells isolated from young (<30 years) and old (>60 years) donors were stimulated with anti-CD3 and anti-CD28 antibodies for 48h before analyzing the cytokine secretion and activation markers by flow cytometry and changes in the expression profiles using RNA sequencing. Gene ontology (GO) term enrichment analyses were performed for up-regulated and uniquely expressed transcripts identified in the T cell populations of both age groups. Total and memory CD8⁺ T cells from old donors expressed significantly higher CD25 levels and have an increased cytokine secretion. While approximately 1,500 up-regulated transcripts were identified in all groups, CD8⁺CD45RA^- memory T cells of old donors had approximately 500 more uniquely expressed transcripts. Four GO terms related to the JAK-STAT pathway were identified for up-regulated transcripts in the total CD8⁺ T cells of old donors, whereas CD8⁺CD45RA^- memory T cells GO terms related to adjacent pathways, like JNK and MAPK/ERK, were found. Additionally, the unique transcripts of CD8⁺CD45RA^- memory T cells of old donors were related to the JNK, MAPK and IL-12 pathways. For both T cell populations of the old donors, cytokine and JAK-STAT pathway transcripts were up-regulated. Thus, an age-dependent effect was observed on the transcriptomes of total and memory CD8⁺ T cells. The CD8⁺ CD45RA^- memory T cells from old donors maintained the increased cytokine secretion of the total CD8⁺ T cell population and the increased JAK-STAT pathway transcripts, which have an impact on inflammation and senescence.

Single-Cell Immunogenomic Approach Identified SARS-CoV-2 Protective Immune Signatures in Asymptomatic Direct Contacts of COVID-19 Cases

The response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is largely impacted by the level of virus exposure and status of the host immunity. The nature of protection shown by direct asymptomatic contacts of coronavirus disease 2019 (COVID-19)-positive patients is quite intriguing. In this study, we have characterized the antibody titer, SARS-CoV-2 surrogate virus neutralization, cytokine levels, single-cell T-cell receptor (TCR), and B-cell receptor (BCR) profiling in asymptomatic direct contacts, infected cases, and controls. We observed significant increase in antibodies with neutralizing amplitude in asymptomatic contacts along with cytokines such as Eotaxin, granulocyte-colony stimulating factor (G-CSF), interleukin 7 (IL-7), migration inhibitory factor (MIF), and macrophage inflammatory protein-1α (MIP-1α). Upon single-cell RNA (scRNA) sequencing, we explored the dynamics of the adaptive immune response in few representative asymptomatic close contacts and COVID-19-infected patients. We reported direct asymptomatic contacts to have decreased CD4⁺ naive T cells with concomitant increase in CD4⁺ memory and CD8⁺ Temra cells along with expanded clonotypes compared to infected patients. Noticeable proportions of class switched memory B cells were also observed in them. Overall, these findings gave an insight into the nature of protection in asymptomatic contacts.

High CD4-to-CD8 ratio identifies an at-risk population susceptible to lethal COVID-19

Around half of people with severe COVID-19 requiring intensive care unit (ICU) treatment will survive, but it is unclear how the immune response to SARS-CoV-2 differs between ICU patients that recover and those that do not. We conducted whole-blood immunophenotyping of COVID-19 patients upon admission to ICU and during their treatment and uncovered marked differences in their circulating immune cell subsets. At admission, patients who later succumbed to COVID-19 had significantly lower frequencies of all memory CD8+ T cell subsets, resulting in increased CD4-to-CD8 T cell and neutrophil-to-CD8 T cell ratios. ROC and Kaplan-Meier analyses demonstrated that both CD4-to-CD8 and neutrophil-to-CD8 ratios at admission were strong predictors of in-ICU mortality. Therefore, we propose the use of the CD4-to-CD8 T cell ratio as a marker for the early identification of those individuals likely to require enhanced monitoring and/or pro-active intervention in ICU.

Association between senescence of T cells and disease activity in patients with systemic lupus erythematosus

Objectives

Systemic lupus erythematosus (SLE) patients are predisposed to chronic immune activation, leading to accelerated immunosenescence. The aging of the immune system causes the T cells to express several senescence markers such as CD57 and KLRG1, which produce pro-inflammatory cytokine interferon γ (IFN-γ). Immunosenescence was associated with high morbidity and mortality in other diseases. This research was conducted to prove the association between senescent T cells and SLE disease activity.

Material and methods

This research was an observational cross-sectional study on 53 women aged 16–45 years diagnosed with SLE based on SLICC 2012 criteria. All subjects were recorded for demographic and clinical data, and their SLE disease activity index (SLEDAI) score was measured to evaluate disease activity. Active disease was defined as SLEDAI score ≥ 3. The CD57 antigen and KLRG1 expression on CD4+ and CD8+ T cells were calculated from peripheral blood mononuclear cells (PBMC) by flow cytometry. Interferon γ was measured from serum using ELISA. The comparison was done using the Mann-Whitney U test, and correlation was tested using the Spearman test. Associations between variables were calculated using linear regression models.

Results

Systemic lupus erythematosus patients with active disease had markedly higher CD4+KLRG1+ (3.1 [1.3–5.5]% vs. 0.3 [0.1–0.5]%), CD8+CD57+ (11.6 ±7.1% vs. 2.4 ±2.0%, p = 0.000), and CD8+KLRG1+ T cell percentages (13.7 ±7.5% vs. 0.3 ±0.1%, p = 0.000), and IFN- γ levels (208.9 [148.3–233.8] vs. 146.7 [130.2–210.8] pg/ml, p = 0.048), compared to the inactive patients. Positive correlation and association was found between the CD8+CD57+ and CD8+KLRG1+ percentages with the SLEDAI score (p = 0.007 and p = 0.007, for the linear regression analysis, respectively).

Conclusions

Systemic lupus erythematosus patients showed significantly higher senescence T cell markers compared to controls, and the increase of T cell senescence, especially in the CD8 compartment, has some association with increased disease activity in patients with SLE.

CD8+ TILs in NSCLC differentiate into TEMRA via a bifurcated trajectory: deciphering immunogenicity of tumor antigens

Background

CD8⁺ tumor-infiltrating lymphocytes (TILs) comprise phenotypically and functionally heterogeneous subpopulations. Of these, effector memory CD45RA re-expressing CD8⁺ T cells (Temra) have been discovered and characterized as the most terminally differentiated subset. However, their exact ontogeny and physiological importance in association with tumor progression remain poorly understood.

Methods

We analyzed primary tumors and peripheral blood samples from 26 patients with non-small cell lung cancer and analyzed their phenotypes and functional characteristics using flow cytometry, RNA-sequencing, and bioinformatics.

Results

We found that tumor-infiltrating Temra (tilTemra) cells largely differ from peripheral blood Temra (pTemra), with distinct transcriptomes and functional properties. Notably, although majority of the pTemra was CD27⁻CD28⁻ double-negative (DN), a large fraction of tilTemra population was CD27⁺CD28⁺ double-positive (DP), a characteristic of early-stage, less differentiated effector cells. Trajectory analysis revealed that CD8⁺ TILs undergo a divergent sequence of events for differentiation into either DP or DN tilTemra. Such a differentiation toward DP tilTemra relied on persistent expression of CD27 and CD28 and was associated with weak T cell receptor engagement. Thus, a higher proportion of DP Temra was correlated with lower immunogenicity of tumor antigens and consequently lower accumulation of CD8⁺ TILs.

Conclusions

These data suggest a complex interplay between CD8⁺ T cells and tumors and define DP Temra as a unique subset of tumor-specific CD8⁺ TILs that are produced in patients with relatively low immunogenic cancer types, predicting immunogenicity of tumor antigens and CD8⁺ TIL counts, a reliable biomarker for successful cancer immunotherapy.

Integrated single-cell analysis unveils diverging immune features of COVID-19, influenza, and other community-acquired pneumonia

The exact immunopathophysiology of community-acquired pneumonia (CAP) caused by SARS-CoV-2 (COVID-19) remains clouded by a general lack of relevant disease controls. The scarcity of single-cell investigations in the broader population of patients with CAP renders it difficult to distinguish immune features unique to COVID-19 from the common characteristics of a dysregulated host response to pneumonia. We performed integrated single-cell transcriptomic and proteomic analyses in peripheral blood mononuclear cells from a matched cohort of eight patients with COVID-19, eight patients with CAP caused by Influenza A or other pathogens, and four non-infectious control subjects. Using this balanced, multi-omics approach, we describe shared and diverging transcriptional and phenotypic patterns-including increased levels of type I interferon-stimulated natural killer cells in COVID-19, cytotoxic CD8 T EMRA cells in both COVID-19 and influenza, and distinctive monocyte compositions between all groups-and thereby expand our understanding of the peripheral immune response in different etiologies of pneumonia.

High-dimensional and single-cell transcriptome analysis of the tumor microenvironment in angioimmunoblastic T cell lymphoma (AITL)

Angioimmunoblastic T-cell lymphoma (AITL) is an aggressive lymphoid malignancy associated with a poor clinical prognosis. The AITL tumor microenvironment (TME) is unique, featuring a minority population of malignant CD4+ T follicular helper (TFH) cells inter-mixed with a diverse infiltrate of multi-lineage immune cells. While much of the understanding of AITL biology to date has focused on characteristics of the malignant clone, less is known about the many non-malignant populations that comprise the TME. Recently, mutational consistencies have been identified between malignant cells and non-malignant B cells within the AITL TME. As a result, a significant role for non-malignant populations in AITL biology has been increasingly hypothesized. In this study, we have utilized mass cytometry and single-cell transcriptome analysis to identify several expanded populations within the AITL TME. Notably, we find that B cells within the AITL TME feature decreased expression of key markers including CD73 and CXCR5. Furthermore, we describe the expansion of distinct CD8+ T cell populations that feature an exhausted phenotype and an underlying expression profile indicative of dysfunction, impaired cytotoxicity, and upregulation of the chemokines XCL2 and XCL1.

Abdominal Obesity-Related Disturbance of Insulin Sensitivity Is Associated with CD8+ EMRA Cells in the Elderly

Aging and overweight increase the risk of developing type 2 diabetes mellitus. In this cross-sectional study, we aimed to investigate the potential mediating role of T-EMRA cells and inflammatory markers in the development of a decreased insulin sensitivity. A total of 134 healthy older volunteers were recruited (age 59.2 (_SD 5.6) years). T cell subpopulations were analyzed by flow cytometry. Furthermore, body composition, HOMA-IR, plasma tryptophan (Trp) metabolites, as well as cytokines and adipokines were determined. Using subgroup and covariance analyses, the influence of BMI on the parameters was evaluated. Moreover, correlation, multiple regression, and mediation analyses were performed. In the subgroup of participants with obesity, an increased proportion of CD8+EMRA cells and elevated concentrations of plasma kynurenine (KYN) were found compared to the lower-weight subgroups. Linear regression analysis revealed that an elevated HOMA-IR could be predicted by a higher proportion of CD8+EMRA cells and KYN levels. A mediation analysis showed a robust indirect effect of the Waist-to-hip ratio on HOMA-IR mediated by CD8+EMRA cells. Thus, the deleterious effects of abdominal obesity on glucose metabolism might be mediated by CD8+EMRA cells in the elderly. Longitudinal studies should validate this assumption and analyze the suitability of CD8+EMRA cells as early predictors of incipient prediabetes.