The frequency of regulatory CD3+CD8+CD28- CD25+ T lymphocytes in human peripheral blood increases with age

Impact of donor age and relationship on outcomes of peripheral blood haploidentical hematopoietic cell transplantation

Here we describe a retrospective analysis of outcomes in 299 patients who underwent peripheral blood haplo-HCT with PTCy from July 2009 through May 2021 and their association with donor characteristics. Patients had mostly acute leukemias and high or very high DRI. Multivariate analyses were conducted examining OS, NRM, relapse, cytokine release syndrome, acute and chronic GVHD. Donor characteristics included age, sex, relationship, ABO status, CMV status, and HLA match grade. Our analysis revealed increasing donor age was associated with higher NRM (compared to age <30; age 30-44 HR, 1.65; P = 0.110, age >44 HR, 1.80; P = 0.056) but lower relapse risk (compared to age <30; age 30-44 HR, 0.61; P = 0.034, age > 44 HR, 0.71; P = 0.132). There were no differences in CRS, aGVHD or cGVHD. We found no difference in outcomes based on the donor-recipient relationship. No differences were found based on HLA match grade or DRB1 match status. Increasing donor age was associated with lower relapse risk but higher NRM, resulting in no difference in OS based on donor age. Other donor factors including relationship (parent/sibling/child/ maternal), CMV status, donor sex, HLA match grade, and DRB1 status were not associated with outcomes.

Targeting the hallmarks of aging to improve influenza vaccine responses in older adults

Age-related declines in immune response pose a challenge in combating diseases later in life. Influenza (flu) infection remains a significant burden on older populations and often results in catastrophic disability in those who survive infection. Despite having vaccines designed specifically for older adults, the burden of flu remains high and overall flu vaccine efficacy remains inadequate in this population. Recent geroscience research has highlighted the utility in targeting biological aging to improve multiple age-related declines. Indeed, the response to vaccination is highly coordinated, and diminished responses in older adults are likely not due to a singular deficit, but rather a multitude of age-related declines. In this review we highlight deficits in the aged vaccine responses and potential geroscience guided approaches to overcome these deficits. More specifically, we propose that alternative vaccine platforms and interventions that target the hallmarks of aging, including inflammation, cellular senescence, microbiome disturbances, and mitochondrial dysfunction, may improve vaccine responses and overall immunological resilience in older adults. Elucidating novel interventions and approaches that enhance immunological protection from vaccination is crucial to minimize the disproportionate effect of flu and other infectious diseases on older adults.

Impact of aging on immune function in the pathogenesis of pulmonary diseases: potential for therapeutic targets

INTRODUCTION

Several immunological alterations that occur during pulmonary diseases often mimic alterations observed in the aged lung. From the molecular perspective, pulmonary diseases and aging partake in familiar mechanisms associated with significant dysregulation of the immune systems. Here, we summarized the findings of how aging alters immunity to respiratory conditions to identify age-impacted pathways and mechanisms that contribute to the development of pulmonary diseases.

AREAS COVERED

The current review examines the impact of age-related molecular alterations in the aged immune system during various lung diseases, such as COPD, IPF, Asthma, and alongside many others that could possibly improve on current therapeutic interventions. Moreover, our increased understanding of this phenomenon may play a primary role in shaping immunomodulatory strategies to boost outcomes in the elderly. Here, the authors present new insights into the context of lung-related diseases and describe the alterations in the functioning of immune cells during various pulmonary conditions altered with age.

EXPERT OPINION

The expert opinion provided the concepts on how aging alters immunity during pulmonary conditions, and suggests the associated mechanisms during the development of lung diseases. As a result, it becomes important to comprehend the complex mechanism of aging in the immune lung system.

Extremely Differentiated T Cell Subsets Contribute to Tissue Deterioration During Aging

There is a dramatic remodeling of the T cell compartment during aging. The most notorious changes are the reduction of the naive T cell pool and the accumulation of memory-like T cells. Memory-like T cells in older people acquire a phenotype of terminally differentiated cells, lose the expression of costimulatory molecules, and acquire properties of senescent cells. In this review, we focus on the different subsets of age-associated T cells that accumulate during aging. These subsets include extremely cytotoxic T cells with natural killer properties, exhausted T cells with altered cytokine production, and regulatory T cells that gain proinflammatory features. Importantly, all of these subsets lose their lymph node homing capacity and migrate preferentially to nonlymphoid tissues, where they contribute to tissue deterioration and inflammaging.

Cellular senescence is a key mediator of lung aging and susceptibility to infection

Aging results in systemic changes that leave older adults at much higher risk for adverse outcomes following respiratory infections. Much work has been done over the years to characterize and describe the varied changes that occur with aging from the molecular/cellular up to the organismal level. In recent years, the systemic accumulation of senescent cells has emerged as a key mediator of many age-related declines and diseases of aging. Many of these age-related changes can impair the normal function of the respiratory system and its capability to respond appropriately to potential pathogens that are encountered daily. In this review, we aim to establish the effects of cellular senescence on the disruption of normal lung function with aging and describe how these effects compound to leave an aged respiratory system at great risk when exposed to a pathogen. We will also discuss the role cellular senescence may play in the inability of most vaccines to confer protection against respiratory infections when administered to older adults. We posit that cellular senescence may be the point of convergence of many age-related immunological declines. Enhanced investigation into this area could provide much needed insight to understand the aging immune system and how to effectively ameliorate responses to pathogens that continue to disproportionately harm this vulnerable population.

Immunosenescence, aging and successful aging

Aging induces a series of immune related changes, which is called immunosenescence, playing important roles in many age-related diseases, especially neurodegenerative diseases, tumors, cardiovascular diseases, autoimmune diseases and coronavirus disease 2019(COVID-19). However, the mechanism of immunosenescence, the association with aging and successful aging, and the effects on diseases are not revealed obviously. In order to provide theoretical basis for preventing or controlling diseases effectively and achieve successful aging, we conducted the review and found that changes of aging-related phenotypes, deterioration of immune organ function and alterations of immune cell subsets participated in the process of immunosenescence, which had great effects on the occurrence and development of age-related diseases.

Circulating and Tumor-Infiltrating Immune Checkpoint-Expressing CD8+ Treg/T Cell Subsets and Their Associations with Disease-Free Survival in Colorectal Cancer Patients

Simple Summary

Colorectal cancer is one of the leading causes of global cancer-related mortality. Tumor-infiltrating effector immune cells play critical roles in tumor control, and their activity can dictate disease outcomes. In this study, we provide evidence of the associations between different CD8⁺ T cell subpopulations with disease-free survival (DFS) in CRC patients. We report associations between higher levels of certain circulating and tumor-infiltrating CD8⁺ T cell subsets and improved clinical outcomes in CRC patients.

Abstract

T cells in the tumor microenvironment (TME) have diverse roles in anti-tumor immunity, including orchestration of immune responses and anti-tumor cytotoxic attack. However, different T cell subsets may have opposing roles in tumor progression, especially in inflammation-related cancers such as colorectal cancer (CRC). In this study, we phenotypically characterized CD3⁺CD4^- (CD8⁺) T cells in colorectal tumor tissues (TT), normal colon tissues (NT) and in circulation of CRC patients. We investigated the expression levels of key immune checkpoints (ICs) and Treg-related markers in CD8⁺ T cells. Importantly, we investigated associations between different tumor-infiltrating CD8⁺ T cell subpopulations and disease-free survival (DFS) in CRC patients. We found that FoxP3 expression and ICs including PD-1, CTLA-4, TIM-3, and LAG-3 were significantly increased in tumor-infiltrating CD8⁺ T cells compared with NT and peripheral blood. In the TME, we found that TIM-3 expression was significantly increased in patients with early stages and absent lymphovascular invasion (LVI) compared to patients with advanced stages and LVI. Importantly, we report that high levels of certain circulating CD8⁺ T cell subsets (TIM-3-expressing, FoxP3⁻Helios⁻TIM-3⁺ and FoxP3⁻Helios⁺TIM-3⁺ cells) in CRC patients were associated with better DFS. Moreover, in the TME, we report that elevated levels of CD25⁺ and TIM-3⁺ T cells, and FoxP3⁺Helios⁻TIM-3⁺ Tregs were associated with better DFS.

CD8+ T-Cells in Juvenile-Onset SLE: From Pathogenesis to Comorbidities

Diagnosis of systemic lupus erythematosus (SLE) in childhood [juvenile-onset (J) SLE], results in a more severe disease phenotype including major organ involvement, increased organ damage, cardiovascular disease risk and mortality compared to adult-onset SLE. Investigating early disease course in these younger JSLE patients could allow for timely intervention to improve long-term prognosis. However, precise mechanisms of pathogenesis are yet to be elucidated. Recently, CD8+ T-cells have emerged as a key pathogenic immune subset in JSLE, which are increased in patients compared to healthy individuals and associated with more active disease and organ involvement over time. CD8+ T-cell subsets have also been used to predict disease prognosis in adult-onset SLE, supporting the importance of studying this cell population in SLE across age. Recently, single-cell approaches have allowed for more detailed analysis of immune subsets in JSLE, where type-I IFN-signatures have been identified in CD8+ T-cells expressing high levels of granzyme K. In addition, JSLE patients with an increased cardiometabolic risk have increased CD8+ T-cells with elevated type-I IFN-signaling, activation and apoptotic pathways associated with atherosclerosis. Here we review the current evidence surrounding CD8+ T-cell dysregulation in JSLE and therapeutic strategies that could be used to reduce CD8+ T-cell inflammation to improve disease prognosis.

Molecular Mechanisms of Immunosenescene and Inflammaging: Relevance to the Immunopathogenesis and Treatment of Multiple Sclerosis

Aging is characterized, amongst other features, by a complex process of cellular senescence involving both innate and adaptive immunity, called immunosenescence and associated to inflammaging, a low-grade chronic inflammation. Both processes fuel each other and partially explain increasing incidence of cancers, infections, age-related autoimmunity, and vascular disease as well as a reduced response to vaccination. Multiple sclerosis (MS) is a lifelong disease, for which considerable progress in disease-modifying therapies (DMTs) and management has improved long-term survival. However, disability progression, increasing with age and disease duration, remains. Neurologists are now involved in caring for elderly MS patients, with increasing comorbidities. Aging of the immune system therefore has relevant implications for MS pathogenesis, response to DMTs and the risks mediated by these treatments. We propose to review current evidence regarding markers and molecular mechanisms of immunosenescence and their relevance to understanding MS pathogenesis. We will focus on age-related changes in the innate and adaptive immune system in MS and other auto-immune diseases, such as systemic lupus erythematosus and rheumatoid arthritis. The consequences of these immune changes on MS pathology, in interaction with the intrinsic aging process of central nervous system resident cells will be discussed. Finally, the impact of immunosenescence on disease evolution and on the safety and efficacy of current DMTs will be presented.

Immune system aging and the aging-related diseases in the COVIID-19 era

The interest in the process of aging, and specifically in how aging affects the working of our immune system, has recently enormously grown among both specialists (immunologists and gerontologists) and representatives of other disciplines of health sciences. An obvious reason for this interest is the current pandemics of COVID-19, known to affect the elderly more than younger people. In this paper current knowledge about mechanisms and complex facets of human immune system aging is presented, stemming from the knowledge about the working of various parts of the immune system, and leading to understanding of immunological mechanisms of chronic, inflammatory, aging-related diseases and of COVID-19.

Newly Found Peacekeeper: Potential of CD8+ Tregs for Graft-Versus-Host Disease

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the most effective and potentially curative treatment for a variety of hematologic malignancies. However, graft-versus-host disease (GVHD) is a major obstacle that limits wide application of allo-HSCT, despite the development of prophylactic strategies. Owing to experimental and clinical advances in the field, GVHD is characterized by disruption of the balance between effector and regulatory immune cells, resulting in higher inflammatory cytokine levels. A reduction in regulatory T cells (Tregs) has been associated with limiting recalibration of inflammatory overaction and maintaining immune tolerance. Moreover, accumulating evidence suggests that immunoregulation may be useful for preventing GVHD. As opposed to CD4⁺ Tregs, the CD8⁺ Tregs population, which constitutes an important proportion of all Tregs, efficiently attenuates GVHD while sparing graft-versus-leukemic (GVL) effects. CD8⁺ Tregs may provide another form of cellular therapy for preventing GVHD and preserving GVL effects, and understanding the underlying mechanisms that different from those of CD4⁺ Tregs is significant. In this review, we summarize preclinical experiments that have demonstrated the role of CD8⁺ Tregs during GVHD and attempted to obtain optimized CD8⁺ Tregs. Notably, although optimized CD8⁺ Tregs have obvious advantages, more exploration is needed to determine how to apply them in the clinic.

Harnessing CD8+CD28- Regulatory T Cells as a Tool to Treat Autoimmune Disease

T regulatory cell therapy presents a novel therapeutic strategy for patients with autoimmune diseases or who are undergoing transplantation. At present, the CD4⁺ Treg population has been extensively characterized, as a result of defined phenotypic and functional readouts. In this review article, we discuss the development and biology of CD8⁺ Tregs and their role in murine and human disease indications. A subset of CD8⁺ Tregs that lack the surface expression of CD28 (CD8⁺CD28⁻ Treg) has proved efficacious in preclinical models. CD8⁺CD28⁻ Tregs are present in healthy individuals, but their impaired functionality in disease renders them less effective in mediating immunosuppression. We primarily focus on harnessing CD8⁺ Treg cell therapy in the clinic to support current treatment for patients with autoimmune or inflammatory conditions.

Inflammaging, an Imbalanced Immune Response That Needs to Be Restored for Cancer Prevention and Treatment in the Elderly

Nowadays, new advances in society and health have brought an increased life expectancy. However, at the same time, aging comes with complications that impact the development of autoimmunity, neurodegenerative diseases and cancer. These complications affect the quality of life and impact the public health system. Specifically, with aging, a low-grade chronic sterile systemic inflammation with self-reactivity in the absence of acute infection occurs termed inflammaging. Inflammaging is related to an imbalanced immune response that can be either naturally acquired with aging or accelerated due to external triggers. Different molecules, metabolites and inflammatory forms of cell death are highly involved in these processes. Importantly, adoptive cellular immunotherapy is a modality of treatment for cancer patients that administers ex vivo expanded immune cells in the patient. The manipulation of these cells confers them enhanced proinflammatory properties. A general consequence of proinflammatory events is the development of autoimmune diseases and cancer. Herein, we review subsets of immune cells with a pertinent role in inflammaging, relevant proteins involved in these inflammatory events and external triggers that enhance and accelerate these processes. Moreover, we mention relevant preclinical studies that demonstrate associations of chronic inflammation with cancer development.

Regulatory KIR+ RA+ T cells accumulate with age and are highly activated during viral respiratory disease

Severe respiratory viral infectious diseases such as influenza and COVID‐19 especially affect the older population. This is partly ascribed to diminished CD8⁺ T‐cell responses a result of aging. The phenotypical diversity of the CD8⁺ T‐cell population has made it difficult to identify the impact of aging on CD8⁺ T‐cell subsets associated with diminished CD8⁺ T‐cell responses. Here we identify a novel human CD8⁺ T‐cell subset characterized by expression of Killer‐cell Immunoglobulin‐like Receptors (KIR⁺) and CD45RA (RA⁺). These KIR⁺RA⁺ T cells accumulated with age in the blood of healthy individuals (20–82 years of age, n = 50), expressed high levels of aging‐related markers of T‐cell regulation, and were functionally capable of suppressing proliferation of other CD8⁺ T cells. Moreover, KIR⁺RA⁺ T cells were a major T‐cell subset becoming activated in older adults suffering from an acute respiratory viral infection (n = 36), including coronavirus and influenza virus infection. In addition, older adults with influenza A infection showed that higher activation status of their KIR⁺RA⁺ T cells associated with longer duration of respiratory symptoms. Together, our data indicate that KIR⁺RA⁺ T cells are a unique human T‐cell subset with regulatory properties that may explain susceptibility to viral respiratory disease at old age.

Impact of donor age and kinship on clinical outcomes after T-cell-replete haploidentical transplantation with PT-Cy

Donor selection contributes to improve clinical outcomes of T-cell-replete haploidentical stem cell transplantation (haplo-SCT) with posttransplant cyclophosphamide (PT-Cy). The impact of donor age and other non-HLA donor characteristics remains a matter of debate. We performed a multicenter retrospective analysis on 990 haplo-SCTs with PT-Cy. By multivariable analysis, after adjusting for donor/recipient kinship, increasing donor age and peripheral blood stem cell graft were associated with a higher risk of grade 2 to 4 acute graft-versus-host-disease (aGVHD), whereas 2-year cumulative incidence of moderate-to-severe chronic GVHD was higher for transplants from female donors into male recipients and after myeloablative conditioning. Increasing donor age was associated with a trend for higher nonrelapse mortality (NRM) (hazard ratio [HR], 1.05; P = .057) but with a significant reduced risk of disease relapse (HR, 0.92; P = .001) and improved progression-free survival (PFS) (HR, 0.97; P = .036). Increasing recipient age was a predictor of worse overall survival (OS). Risk of relapse was higher (HR, 1.39; P < .001) in patients aged ≤40 years receiving a transplant from a parent as compared with a sibling. Moreover, OS and PFS were lower when the donor was the mother rather than the father. Pretransplant active disease status was an invariably independent predictor of worse clinical outcomes, while recipient positive cytomegalovirus serostatus and hematopoietic cell transplant comorbidity index >3 were associated with worse OS and PFS. Our results suggest that younger donors may reduce the incidence of aGVHD and NRM, though at higher risk of relapse. A parent donor, particularly the mother, is not recommended in recipients ≤40 years.

Regular Exercise May Restore Certain Age-Related Alterations of Adaptive Immunity and Rebalance Immune Regulation

Age-related changes of the immune system lead to an increased morbidity and mortality due to enhanced vulnerability to infectious diseases and malignancies. Recent studies revealed the important effects of physical activity on immune functions, which may largely depend on the type of exercise, its intensity and duration. However, limited information is available regarding the immunological effects of sport activities in older ages. The aim of our study was to examine the changes in a wide spectrum of lymphocyte subtypes after regular workout among healthy elderly individuals. We enrolled 29 elderly women with sedentary lifestyle (mean age: 67.03 ± 3.74 years) to take part in a 6-week long functional conditioning gymnastic exercise program. The percentages of peripheral natural killer (NK), NKT cells, T and B lymphocyte subtypes (early-/late-activated T, naïve and memory T, cytotoxic T (Tc), T-helper (Th)1, Th2, Th17, T regulatory type 1 (Tr1), CD4⁺CD127^lo/-CD25^bright Treg, as well as naïve and memory B cells) were determined by flow cytometry. Evaluation of the changes in functional capability of Treg cells was based on in vitro functional assays. At the end of exercise program, in parallel with improvements in body composition and physical performance, significant changes in naïve and memory lymphocyte ratios were observed. Importantly, levels of naïve Tc cells elevated, ratios of effector memory Tc cells decreased and distribution of memory B cells rearranged as well. Additionally, proportions of late-activated HLA-DR⁺ T cells increased, while percentages of anti-inflammatory interleukin (IL)-10 producing Tr1 cells, as well as immunosuppressive CD4⁺CD127^lo/-CD25^bright Treg cells decreased following the exercise workout. Changes observed after the regular exercise program indicate an improvement in the age-related redistribution of certain naïve and memory cell proportions and a retuned immune regulation in older ages.

Systemic effect of radiotherapy before or after nivolumab in lung cancer: an observational, retrospective, multicenter study

BACKGROUND

The combination of radiotherapy (RT) and programmed death 1 inhibitors seems to increase antitumor immune responses.

OBJECTIVE

To assess the outcome and the role of the best combination sequence, i.e. immunotherapy given before, during, and/or after RT, in patients with non-small cell lung cancer (NSCLC).

METHODS

We conducted an observational, retrospective analysis of 95 consecutive patients with advanced NSCLC who received any radiotherapy treatment and nivolumab, as clinically indicated. Median overall survival (OS) and the 95% confidence interval (CI) were estimated with the Kaplan-Meier method. Cox model was used to obtain hazard ratio (HR) and associated 95% CI with statistical inference by log-rank statistic.

RESULTS

Median OS was 11.9 months (95% CI, 6.6-17.2). Patients who received radiotherapy during an immune checkpoint inhibitor treatment started more than 60 days before showed a better outcome than patients who started immunotherapy over 60 days after RT ending (HR, 2.90 [1.37-6.12], p = 0.005; median OS, 22.4 months vs 8.6 months, p = 0.005). Median progression-free survival was 6.3 months (95% CI, 4.6-8.0).

CONCLUSIONS

This study shows that combining irradiation with nivolumab for the treatment of advanced NSCLC leads to improved OS. The optimal time window for the combination of RT and immunotherapy seems to play a critical role for therapeutic antitumor response derived by abscopal effect.

The Complex Role of Regulatory T Cells in Immunity and Aging

The immune system is a tightly regulated network which allows the development of defense mechanisms against foreign antigens and tolerance toward self-antigens. Regulatory T cells (Treg) contribute to immune homeostasis by maintaining unresponsiveness to self-antigens and suppressing exaggerated immune responses. Dysregulation of any of these processes can lead to serious consequences. Classically, Treg cell functions have been described in CD4⁺ T cells, but other immune cells also harbour the capacity to modulate immune responses. Regulatory functions have been described for different CD8⁺ T cell subsets, as well as other T cells such as γδT cells or NKT cells. In this review we describe the diverse populations of Treg cells and their role in different scenarios. Special attention is paid to the aging process, which is characterized by an altered composition of immune cells. Treg cells can contribute to the development of various age-related diseases but they are poorly characterized in aged individuals. The huge diversity of cells that display immune modulatory functions and the lack of universal markers to identify Treg make the expanding field of Treg research complex and challenging. There are still many open questions that need to be answered to solve the enigma of regulatory T cells.

Identification of the association of CD28+ CD244+ Tc17/IFN-γ cells with chronic hepatitis C virus infection

CD8+ T cells play multiple and complex immunological roles including antiviral, regulatory, and exhaustive effects in hepatitis C virus (HCV) infected patients. Some CD8+ T-cell subsets were confirmed to be closely related to HCV infection such as TCM , TEM , TEM RA, Tc17, and CD8+ Treg. Herein, we report a new subset of interleukin (IL)-17/interferon (IFN)-γ producing CD8+ T (Tc17/IFN-γ) cells that markedly correlate with CD28+ CD244+ cells, IL-17 levels, and HCV RNA in HCV patients. During early treatment with peg-IFN-a2a plus ribavirin, the imbalance of these Tc17/IFN-γ cells could be partially restored, together with normalized serum alanine aminotransferase but not aspartate transaminase. Also, we analyzed the dynamic change of the percentage of this T cells subset in patients with different outcome after 4-week course of treatment with peg-IFN-a2a plus ribavirin and found that the percentage of CD8+ CD28+ CD244+ T cells significantly decreased in recovered patients but not in nonrecovered patients. In vitro, CD28+ CD244+ T cells were the only CD8+ T-cell group that secreted both IL-17 and IFN-γ in this axis and blockade with anti-CD244 antibodies significantly reduced cytokine production. Taken together, this study demonstrates that the frequency and regulatory functions of CD28+ CD244+ Tc17/IFN-γ cells may play an important role in persistent HCV infection.

Monocyte and T Cell Immune Phenotypic Profiles Associated With Age Advancement Differ Between People With HIV, Lifestyle-Comparable Controls and Blood Donors

Motivation

People with HIV on successful antiretroviral therapy show signs of premature aging and are reported to have higher rates of age-associated comorbidities. HIV-associated immune dysfunction and inflammation have been suggested to contribute to this age advancement and increased risk of comorbidities.

Method

Partial least squares regression (PLSR) was used to explore associations between biological age advancement and immunological changes in the T cell and monocyte compartment in people with HIV (n=40), comparable HIV-negative individuals (n=40) participating in the Comorbidity in Relation to AIDS (COBRA) cohort, and blood donors (n=35).

Results

We observed that age advancement in all three groups combined was associated with a monocyte immune phenotypic profile related to inflammation and a T cell immune phenotypic associated with immune senescence and chronic antigen exposure. Interestingly, a unique monocyte and T cell immune phenotypic profile predictive for age advancement was found within each group. An inflammatory monocyte immune phenotypic profile associated with age advancement in HIV-negative individuals, while the monocyte profile in blood donors and people with HIV was more reflective of loss of function. The T cell immune phenotypic profile in blood donors was related to loss of T cell function, whereas the same set of markers were related to chronic antigen stimulation and immune senescence in HIV-negative individuals. In people with HIV, age advancement was related to changes in the CD4⁺ T cell compartment and more reflective of immune recovery after cART treatment.

Impact

The identified monocyte and T cell immune phenotypic profiles that were associated with age advancement, were strongly related to inflammation, chronic antigen exposure and immune senescence. While the monocyte and T cell immune phenotypic profile within the HIV-negative individuals reflected those observed in the combined three groups, a distinct profile related to immune dysfunction, was observed within blood donors and people with HIV. These data suggest that varying exposures to lifestyle and infection-related factors may be associated with specific changes in the innate and adaptive immune system, that all contribute to age advancement.

Immunosenescence is both functional/adaptive and dysfunctional/maladaptive

Alterations in the immune system with aging are considered to underlie many age-related diseases. However, many elderly individuals remain healthy until even a very advanced age. There is also an increase in numbers of centenarians and their apparent fitness. We should therefore change our unilaterally detrimental consideration of age-related immune changes. Recent data taking into consideration the immunobiography concept may allow for meaningful distinctions among various aging trajectories. This implies that the aging immune system has a homeodynamic characteristic balanced between adaptive and maladaptive aspects. The survival and health of an individual depends from the equilibrium of this balance. In this article, we highlight which parts of the aging of the immune system may be considered adaptive in contrast to those that may be maladaptive.

Role of Regulatory T Cells in Disturbed Immune Homeostasis in Patients With Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is a complex chronic disease in which T cell-mediated pulmonary inflammation has been shown to play a key role. Accumulating evidence shows that COPD has many of the characteristics of an autoimmune response. An adaptive immune response directed against lung self-antigens, which are released during the initial innate inflammatory response and are triggered by constant exposure to cigarette smoke and epithelial injury, drives the persistent inflammatory response found in smokers. The development and severity of adaptive inflammation depend on the level of tolerance to self-antigens. For these reasons, the effect of regulatory T (Treg) cells on adaptive immunity in COPD patients is of particular interest and could be targeted therapeutically. The disturbance in immune homeostasis caused by changes in the number or function of Treg cells, which is related to cigarette smoke exposure, may be of importance in understanding the development and progression of COPD.

Restored immune cell functions upon clearance of senescence in the irradiated splenic environment

Some studies show eliminating senescent cells rejuvenate aged mice and attenuate deleterious effects of chemotherapy. Nevertheless, it remains unclear whether senescence affects immune cell function. We provide evidence that exposure of mice to ionizing radiation (IR) promotes the senescent‐associated secretory phenotype (SASP) and expression of p16^INK4a in splenic cell populations. We observe splenic T cells exhibit a reduced proliferative response when cultured with allogenic cells in vitro and following viral infection in vivo. Using p16‐3MR mice that allow elimination of p16^INK4a‐positive cells with exposure to ganciclovir, we show that impaired T‐cell proliferation is partially reversed, mechanistically dependent on p16^INK4a expression and the SASP. Moreover, we found macrophages isolated from irradiated spleens to have a reduced phagocytosis activity in vitro, a defect also restored by the elimination of p16^INK4a expression. Our results provide molecular insight on how senescence‐inducing IR promotes loss of immune cell fitness, which suggest senolytic drugs may improve immune cell function in aged and patients undergoing cancer treatment.

Epigenomic drivers of immune dysfunction in aging

Aging inevitably leads to reduced immune function, leaving the elderly more susceptible to infections, less able to respond to pathogen challenges, and less responsive to preventative vaccinations. No cell type is exempt from the ravages of age, and extensive studies have found age-related alterations in the frequencies and functions of both stem and progenitor cells, as well as effector cells of both the innate and adaptive immune systems. The intrinsic functional reduction in immune competence is also associated with low-grade chronic inflammation, termed "inflamm-aging," which further perpetuates immune dysfunction. While many of these age-related cellular changes are well characterized, understanding the molecular changes that underpin the functional decline has proven more difficult. Changes in chromatin are increasingly appreciated as a causative mechanism of cellular and organismal aging across species. These changes include increased genomic instability through loss of heterochromatin and increased DNA damage, telomere attrition, and epigenetic alterations. In this review, we discuss the connections between chromatin, immunocompetence, and the loss of function associated with mammalian immune aging. Through understanding the molecular events which underpin the phenotypic changes observed in the aged immune system, it is hoped that the aged immune system can be restored to provide youthful immunity once more.

Sicilian centenarian offspring are more resistant to immune ageing

BACKGROUND

Immunosenescence constitutes a major indirect cause of morbidity and mortality in the elderly. Previous analysis of immune signatures in a cohort of centenarian offspring showed an intermediate immunophenotype between age-matched and younger controls.

AIMS

To confirm and extend the previous studies performing further phenotypical analysis in centenarian offspring and controls.

METHODS

Analysis of Treg cells, γδ T cells, mucosal-associated invariant T cells, and senescent immune T cells was performed in centenarian offspring and controls.

RESULTS

We report significant differences between elderly and centenarian offspring in most of the studied subsets, showing that centenarian offspring subsets present an intermediate phenotyping between elderly and younger people.

CONCLUSION

The whole present data confirm and extend the previous results showing that centenarian offspring retain more youthful immunological parameters and that the exhaustion of the immune system is less evident than in elderly without centenarian parents, though further investigations are warranted.

Terminally differentiated CD8+ T cells and CD57-FOXP3+CD8+ T cells are highly associated with the efficacy of immunotherapy using activated autologous lymphocytes

Treatment with activated autologous lymphocytes (AALs) has demonstrated mixed results for cancer treatment. Preliminary results revealed that the proportion of cluster of differentiation (CD)8⁺CD57⁺ T cells is significantly increased in AALs, indicating that they are able to determine treatment outcome. Therefore, the role of CD8⁺CD57⁺ T cells in AAL efficacy was investigated. T lymphocytes were isolated from 35 patients with stage IV gastric carcinomas (17 men and 18 women; aged 41-84 years) receiving immunotherapy using AALs (IAAL). Using fluorescence activated cell sorting, CD8, CD27, CD57, and forkhead box protein 3 (FOXP3) expression was investigated on CD8⁺ T cell populations in CD8⁺ T cell differentiation prior to and following in vitro culture. The association between these populations and progression-free survival (PFS) was analyzed using Cox univariate, and multivariate analyses and Kaplan-Meier survival analysis. CD57 expression was negative in early-differentiated CD8⁺ T cells (CD27⁺CD8⁺CD57^-), and positive in intermediate- (CD27⁺CD8⁺CD57⁺) and terminal- (CD27^-CD8⁺CD57⁺) differentiated CD8⁺ T cells. Univariate analysis revealed a significant association between terminal-CD8⁺ T cells and longer PFS times (P=0.035), whereas CD57^-FOXP3⁺CD8⁺ T cells were associated with shorter PFS times. Multivariate analysis revealed that CD57^-FOXP3⁺CD8⁺ T cells was an independent poor prognostic factor, whereas CD57⁺FOXP3⁺CD8⁺ T cells were not associated with PFS. Although IAAL increased the proportion of terminal-CD8⁺ T cells relative to the pre-culture proportions, patients with a high CD57^-FOXP3⁺CD8⁺ T cell percentage exhibited repressed terminal-CD8⁺ T cell induction, leading to poor patient prognosis. Terminally differentiated CD27^-CD8⁺CD57⁺ T cells were responsible for the effectiveness of AALs; however, CD57^-FOXP3⁺CD8⁺ T cells abrogated their efficacy, possibly by inhibiting their induction.

The influence and impact of ageing and immunosenescence (ISC) on adaptive immunity during multiple sclerosis (MS) and the animal counterpart experimental autoimmune encephalomyelitis (EAE)

The human ageing process encompasses mechanisms that effect a decline in homeostasis with increased susceptibility to disease and the development of chronic life-threatening illness. Increasing age affects the immune system which undergoes a progressive loss of efficiency, termed immunosenescence (ISC), to impact on quantitative and functional aspects of innate and adaptive immunity. The human demyelinating disease multiple sclerosis (MS) and the corresponding animal model experimental autoimmune encephalomyelitis (EAE) are strongly governed by immunological events that primarily involve the adaptive arm of the immune response. MS and EAE are frequently characterised by a chronic pathology and a protracted disease course which thereby creates the potential for exposure to the inherent, on-going effects and consequences of ISC. Collective evidence is presented to confirm the occurrence of established and unendorsed biological markers of ISC during the development of both diseases. Moreover, results are discussed from studies during the course of MS and EAE that reveal a premature upregulation of ISC-related biomarkers which indicates untimely alterations to the adaptive immune system. The effects of ISC and a prematurely aged immune system on autoimmune-associated neurodegenerative conditions such as MS and EAE are largely unknown but current evaluation of data justifies and encourages further investigation.

Human T cell immunosenescence and inflammation in aging

The aging process is driven by a finite number of inter-related mechanisms that ultimately lead to the emergence of characteristic phenotypes, including increased susceptibility to multiple chronic diseases, disability, and death. New assays and analytical tools have become available that start to unravel some of these mechanisms. A prevailing view is that aging leads to an imbalance between stressors and stress-buffering mechanisms that causes loss of compensatory reserve and accumulation of unrepaired damage. Central to this paradigm are changes in the immune system and the chronic low-grade proinflammatory state that affect many older individuals, even when they are apparently healthy and free of risk factors. Independent of chronological age, high circulating levels of proinflammatory markers are associated with a high risk of multiple adverse health outcomes in older persons. In this review, we discuss current theories about causes and consequences of the proinflammatory state of aging, with a focus on changes in T cell function. We examine the role of NF-κB activation and its dysregulation and how NF-κB activity differs among subgroups of T cells. We explore emerging hypotheses about immunosenescence and changes in T cell behavior with age, including consideration of the T cell antigen receptor and regulatory T cells (T_regs). We conclude by illustrating how research using advanced technology is uncovering clues at the core of inflammation and aging. Some of the preliminary work in this field is already improving our understanding of the complex mechanisms by which immunosenescence of T cells is intertwined during human aging.

CD8+ T Cells That Coexpress RORγt and T-bet Are Functionally Impaired and Expand in Patients with Distal Bile Duct Cancer

CD8⁺ T cells that express retinoic acid-related orphan receptor (ROR)γt (T_C17 cells) have been shown to promote procarcinogenic inflammation and contribute to a tolerogenic microenvironment in tumors. We investigated their phenotype and functional properties in relationship to the pathogenesis of human distal bile duct cancer (DBDC). DBDC patients had an elevated level of type 17 immune responses and the frequency of CD8⁺RORγt⁺ T cells (T_C17 cells) was increased in peripheral blood. The CD8⁺RORγt⁺ T cells represented a highly activated subset and produced IL-17A in equal amount as CD4⁺RORγt⁺ T cells (T_H17 cells). Most CD8⁺RORγt⁺ T cells coexpressed T-bet, a lineage transcription factor for T_H1 and T_C1 development, suggesting that CD8⁺RORγt⁺ T cells undergo plasticity toward a T_C17/1-like phenotype with coproduction of IL-17A and INF-γ. In comparison with CD8⁺RORγt^- T cells, the CD8⁺RORγt⁺ T cells had a higher level of TCR signaling and were terminally differentiated and exhausted. These cells also had impaired ability to re-express perforin after degranulation and reduced cytotoxic immune function. A subset of CD8⁺RORγt⁺ T cells expressing a low level of programmed cell death protein 1 and a high level of OX40 were associated with reduced patient survival. In conclusion, CD8⁺RORγt⁺ T cells are proinflammatory and functionally impaired and may contribute to the pathogenesis of DBDC.

Changes in blood lymphocyte numbers with age in vivo and their association with the levels of cytokines/cytokine receptors

Background

Alterations in the number and composition of lymphocytes and their subsets in blood are considered a hallmark of immune system aging. However, it is unknown whether the rates of change of lymphocytes are stable or change with age, or whether the inter-individual variations of lymphocyte composition are stable over time or undergo different rates of change at different ages. Here, we report a longitudinal analysis of T- and B-cells and their subsets, and NK cells in the blood of 165 subjects aged from 24 to 90 years, with each subject assessed at baseline and an average of 5.6 years follow-up.

Results

The rates of change of T-(CD4⁺ and CD8⁺) and B-cells, and NK cells were relative stable throughout the adult life. A great degree of individual variations in numbers of lymphocytes and their subsets and in the rates of their changes with age was observed. Among them, CD4⁺ T cells exhibited the highest degree of individual variation followed by NK cells, CD8⁺ T cells, and B cells. Different types of lymphocytes had distinct trends in their rates of change which did not appear to be influenced by CMV infection. Finally, the rates of CD4⁺, CD8⁺ T cells, naive CD4⁺ and naïve CD8⁺ T cells were closely positively correlated.

Conclusion

Our findings provide evidence that the age-associated changes in circulating lymphocytes were at relative stable rates in vivo in a highly individualized manner and the levels of selected cytokines/cytokine receptors in serum might influence these age-associated changes of lymphocytes in circulation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12979-016-0079-7) contains supplementary material, which is available to authorized users.

Abnormal phenotypic distribution of regulatory and effector T cells in octogenarian and nonagenarian women

INTRODUCTION

aging is associated with several immunologic changes. Regulatory (Treg) and effector T cells are involved in the pathogenesis of infectious, neoplastic, and autoimmune diseases. Little is known about the effects of aging on the frequency and function of these T cell subpopulations.

METHODS

peripheral blood mononuclear cells (PBMC) were obtained from 26 young (under 44 years old) and 18 elderly (above 80 years old) healthy women. T cell subpopulations were analyzed by flow cytometry.

RESULTS

elderly individuals had lower frequency of several activated effector T cell phenotypes as compared with young individuals: CD3+CD4+CD25+ (3.82±1.93 versus 9.53±4.49; p<0.0001); CD3+CD4+CD25+CD127+(2.39±1.19 versus 7.26±3.84; p<0.0001); CD3+CD4+CD25+ (0.41±0.22 versus 1.86±0.85, p<0.0001); and CD3+CD4+CD25highCD127+(0.06±0.038 versus 0.94±0.64, p<0.0001). Treg (CD3+CD4+CD25+CD127øFoxp3+) presented lower frequency in elderly individuals as compared to young adults (0.34±0.18 versus 0.76±0.48; p=0.0004) and its frequency was inversely correlated with age in the whole group (r=-0.439; p=0.013). The elderly group showed higher frequency of two undefined CD25øFoxp3+ phenotypes: CD3+CD4+CD25øFoxp3+(15.05±7.34 versus 1.65±1.71; p<0.0001) and CD3+CD4+CD25øCD127øFoxp3+(13.0±5.52 versus 3.51±2.87; p<0.0001).

CONCLUSIONS

the altered proportion of different T cell subsets herein documented in healthy elderly women may be relevant to the understanding of the immunologic behavior and disease susceptibility patterns observed in geriatric patients.

A varying T cell subtype explains apparent tobacco smoking induced single CpG hypomethylation in whole blood

Background

Many recent epigenetic studies report that cigarette smoking reduces DNA methylation in whole blood at the single CpG site cg19859270 within the GPR15 gene.

Results

Within two independent cohorts, we confirmed the differentially expression of the GPR15 gene when smokers and non-smokers subjects are compared. By validating the GPR15 protein expression at the cellular level, we found that the observed decreased methylation at this site in white blood cells (WBC) of smokers is mainly caused by the high proportion of CD3+GPR15+ expressing T cells in peripheral blood. In current smokers, the percentage of GPR15+ cells among CD3+ T cells in peripheral blood is significantly higher (15.5 ± 7.2 %, mean ± standard deviation) compared to non-smokers (3.7 ± 1.6 %). Treatment of peripheral blood mononuclear cell (PBMC) cultures with aqueous cigarette smoke extract did not induce a higher proportion of this T cell subtype.

Conclusions

Our results underline that DNA hypomethylation at cg19859270 site, observed in WBCs of smokers, did not arise by direct effect of tobacco smoking compounds on methylation of DNA but rather by the enrichment of a tobacco-smoking-induced lymphocyte population in the peripheral blood.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-015-0113-1) contains supplementary material, which is available to authorized users.

The expression of molecule CD28 and CD38 on CD4⁺/CD8⁺ T lymphocytes in thymus and spleen elicited by Schistosoma japonicum infection in mice model

Schistosomiasis caused by human schistosomes such as Schistosoma japonicum (S. japonicum) is considered as an immune-related disease. It was demonstrated that specific cytokine antibodies' response elicited by S. japonicum infection was gradually downregulated with the progress of the disease, resulting in a Th1/Th2 polarization and suppression of immune response. CD28 (cluster of differentiation 28) is one of the proteins expressed on T cells that provide co-stimulatory signals required for T cell activation and survival, and CD38 is an activating marker of T lymphocyte with high expression in many acute or chronic infections. The immune signature of CD28null T cells in the peripheral circulation associates with chronic inflammation in many diseases, such as HIV and CMV infection. In the thymus, CD28 expression on developing thymocytes appears to play a role for their selection, and it synergizes with CD38 to induce apoptosis of DP (double-positive) thymocytes. Few reports about CD28 and CD38 have been published in schistosomiasis. Here, we investigated the dynamic patterns of the expression of molecules CD28 and CD38 on CD4(+)/CD8(+) T lymphocytes of the thymus and spleen in mice model with S. japonicum infection. Our data indicated that at an early period of infection, the frequency of CD8(+)CD28(-) T cell in the spleen decreased significantly, but higher at chronic infection than that in control. However, it demonstrated an increasing trend in the thymus with the progression of infection. The frequency of CD4(+)CD28(-) T cells increased from acute infection in the thymus, while from chronic infection in the spleen. The expression of CD38 on CD8(+) T cells began to increase at 4 weeks post infection both in the thymus and spleen; its elevated expression on CD4(+) T cells emerged at 6 weeks post infection in the thymus and at 10 weeks post infection in the spleen. Praziquantel (PZQ) treatment could partially restore the frequency of CD28(+) T cell of CD4(+) T cells and CD38(+) T cell of CD8(+)/CD4(+) T cells in the spleen and CD38(+) T cell in the thymus. We hypothesized that the reactivation of S. japonicum infection may trigger expansion of CD28(-) T cells and hence mediate systemic inflammation. We speculated that CD8(+)CD28(-) T cell might be involved in immune modulation and CD8(+)CD28(-) T cell may be a crucial part in pathogenesis, which can provide further knowledge of the sophisticated mechanism of immuno-downregulation in schistosomiasis and potential treatment target.

Interference of therapeutic antibodies used in desensitization protocols on lymphocytotoxicity crossmatch results

BACKGROUND

Therapeutic antibodies used to desensitize patients awaiting a human leukocyte antigen (HLA) or ABO-mismatched graft are suspected to interfere with the lymphocytotoxicity crossmatch (LCT-XM) test when they are present in the tested sera because of their potential ability to activate or inhibit the complement.

METHODS

The most frequent therapeutic antibodies (Abs) used in desensitization protocols (intravenous immunoglobulins, rituximab, basiliximab, eculizumab, antithymocyte globulin) were added to a negative- or a positive-control serum at various concentrations, and tested in vitro in a LCT-XM test.

RESULTS

Rituximab turned the LCT-XM positive on B cells at 0.2 μg/mL and antithymocyte globulin turned the LCT-XM positive with T and B cells at 20 μg/mL and 200 μg/mL, respectively. Treatment with dithiothreitol sera, supplemented with rituximab (0.2 and 2 μg/mL) and antithymocyte globulins (20 and 200 μg/mL), partially or totally reduced this positive interference. Intravenous immunoglobulin, eculizumab, and basiliximab did not trigger any interference with the negative control serum. In a positive LCT-XM, eculizumab did not annihilate activation of the rabbit complement. Intravenous immunoglobulins (25 g/L) could partially or totally reduced lysis score of positive crossmatch with weak lysis scores.

CONCLUSION

If eculizumab within the serum did not annihilate rabbit complement activation and basiliximab did not interfere with the crossmatch reaction, treatments based on rituximab, antithymocyte globulin and intravenous immunoglobulins need to be taken into account when interpreting a positive or negative crossmatch test.

T-cell ageing in end-stage renal disease patients: Assessment and clinical relevance

End-stage renal disease (ESRD) patients have a defective T-cell-mediated immune system which is related to excessive premature ageing of the T-cell compartment. This is likely to be caused by the uremia-associated pro-inflammatory milieu, created by loss of renal function. Therefore, ESRD patients are highly susceptible for infections, have an increased risk for virus-associated cancers, respond poorly to vaccination and have an increased risk for atherosclerotic diseases. Three ageing parameters can be used to assess an immunological T-cell age. First, thymic output can be determined by assessing the T-cell receptor excision circles-content together with CD31 expression within the naïve T cells. Second, the telomere length of T cells and third the T-cell differentiation status are also indicators of T-cell ageing. Analyses based on these parameters in ESRD patients revealed that the immunological T-cell age is increased by on average 20 years compared to the chronological age. After kidney transplantation (KTx) the aged T-cell phenotype persists although the pro-inflammatory milieu is diminished. This might be explained by epigenetic modifications at hematopoietic stem cells level. Assessment of an immunological T-cell age could be an important tool to identify KTx recipients who are at risk for allograft rejection or to prevent over-immunosuppression.

Targeting regulatory T cells to improve vaccine immunogenicity in early life

Human newborns and infants are bombarded with multiple pathogens on leaving the sterile intra-uterine environment, and yet have suboptimal innate immunity and limited immunological memory, thus leading to increased susceptibility to infections in early life. They are thus the target age group for a host of vaccines against common bacterial and viral pathogens. They are also the target group for many vaccines in development, including those against tuberculosis (TB), malaria, and HIV infection. However, neonatal and infant responses too many vaccines are suboptimal, and in the case of the polysaccharide vaccines, it has been necessary to develop the alternative conjugated formulations in order to induce immunity in early life. Immunoregulatory factors are an intrinsic component of natural immunity necessary to dampen or control immune responses, with the caveat that they may also decrease immunity to infections or lead to chronic infection. This review explores the key immunoregulatory factors at play in early life, with a particular emphasis on regulatory T cells (Tregs). It goes on to explore the role that Tregs play in limiting vaccine immunogenicity, and describes animal and human studies in which Tregs have been depleted in order to enhance vaccine responses. A deeper understanding of the role that Tregs play in limiting or controlling vaccine-induced immunity would provide strategies to improve vaccine immunogenicity in this critical age group. New adjuvants and drugs are being developed that can transiently suppress Treg function, and their use as part of human vaccination strategies against infections is becoming a real prospect for the future.

Ageing and respiratory infections: the airway of ageing

Respiratory infections are a leading cause of infectious disease burden worldwide especially among the elderly. Furthermore, a direct relationship between ageing and susceptibility to infections has been reported, which may be caused by impaired immune function, frailty and degree of exposure to infectious diseases. Many complex changes, including structural and age-associated decline in immunity are associated with increased pulmonary diseases worldwide and result in a high age-related disease burden. The common respiratory infections that present serious risks for the elderly include influenza, respiratory syncytial virus, and a number of bacterial pathogens including pneumococcus and tuberculosis. Vaccines are available for a limited number of these pathogens including influenza, pneumococcal and pertussis vaccines. This mini review article examines the age-related changes in immune function that predispose the elderly population to respiratory infections and potential loss of vaccine efficacy with a focus on ageing and influenza infections.

A Trichosanthin-derived peptide suppresses type 1 immune responses by TLR2-dependent activation of CD8(+)CD28(-) Tregs

A group of 15-aa-long Trichosanthin-derived peptides was synthesized and screened based on their differential abilities to induce low-responsiveness in mouse strains with high and low susceptibility. One of them was conjugated to form a homo-tetramer Tk-tPN. At concentrations of 0.1-50 μg/ml, Tk-tPN activated CD8(+)CD28(-) Tregs in vitro to induce immune suppression as effectively as the native Trichosanthin but did not exhibit cytotoxicity. In EAE mice which were pre-treated with Tk-tPN or Tk-tPN-activated CD8(+) T cells, a marked attenuation of clinical scores was recorded together with an expansion of the CD8(+)CD28(-) Treg from 2.2% to 36.1% in vivo. A pull-down assay and signal transduction analyses indicated that the ability of Tk-tPN to convert the CD8(+)CD28(-) Treg-related cytokine secretion pattern from type 1 to type 2 depends on the TLR2-initiated signaling in macrophages. The high production of IL-4/IL-10 by the Tk-tPN-activated CD8(+)CD28(-) Treg suggests the value of using Tk-tPN as a therapeutic reagent for Th1-dominant immunological diseases.

Alloanergization of human T cells results in expansion of alloantigen-specific CD8(+) CD28(-) suppressor cells

Allostimulation with concurrent costimulatory blockade induces alloantigen-specific hyporesponsiveness in responder T cells ("alloanergization"). Alloanergized responder cells also acquire alloantigen-specific suppressive activity, suggesting this strategy induces active immune tolerance. While this acquired suppressive activity is mediated primarily by CD4(+) FOXP3(+) cells, other cells, most notably CD8(+) suppressor cells, have also been shown to ameliorate human alloresponses. To determine whether alloanergization expands CD8(+) cells with allosuppressive phenotype and function, we used mixed lymphocyte cultures in which costimulatory blockade was provided by belatacept, an FDA-approved, second-generation CTLA-4-immunoglobulin fusion protein that blocks CD28-mediated costimulation, as an in vitro model of HLA-mismatched transplantation. This strategy resulted in an eightfold expansion of CD8(+) CD28(-) T cells which potently and specifically suppressed alloresponses of both CD4(+) and CD8(+) T cells without reducing the frequency of a range of functional pathogen-specific T cells. This CD8-mediated allosuppression primarily required cell-cell contact. In addition, we observed expansion of CD8(+) CD28(-) T cells in vivo in patients undergoing alloanergized HLA-mismatched bone marrow transplantation. Use of costimulatory blockade-mediated alloanergization to expand allospecific CD8(+) CD28(-) suppressor cells merits exploration as an approach to inducing or supporting immune tolerance to alloantigens after allogeneic transplantation.

Regulatory T cells and the immune aging process: a mini-review

Constant exposure to new and persisting antigens and the need to replace cellular attrition with newly built cells lead to profound remodeling of the immune system after the age of 50 years. The impact of the immunosenescence process varies amongst the different cellular subsets represented within the immune system. Emerging data suggest that progressive aging significantly affects frequencies, subset distribution and functional competence of regulatory T cells (Tregs). Given the central role of Tregs in immune homeostasis, age-related loss of Treg function would be predicted to cause excessive immunity, encountered in elderly humans as a syndrome of chronic, smoldering inflammation as well as the age-related increase in the risk for autoimmunity. Conversely, age-dependent gain of Treg activity would result in failing immunity, such as the rising risk of malignancies and infections amongst the elderly. Emerging data suggest that some Treg populations, specifically naturally occurring Tregs, seem to accumulate with advancing age, whereas inducible Tregs appear to be less available in the older host. More studies are necessary to elucidate functional competence of old Tregs, with an emphasis on comparing the efficacy of young and old Tregs for defined functional domains. Mechanisms of declining Treg inducibility are not understood, but may provide an opportunity for targeted immunomodulation in the elderly. On the horizon is the potential to develop novel therapeutic interventions that target Tregs to make the elderly more efficient in fighting cancers and infections and dampen the risk for senescence-associated inflammation.

Perspectives on vaccine development for the elderly

Modern society is characterized by a steady increase in the aged population. Increasing numbers of elderly people are exposed to infectious diseases in addition to suffering from chronic non-communicable illnesses. Key differences exist between immune responses elicited against infectious agents in the elderly and in the youngest population. Responses in the aged are characterized by a physiological state of impaired immunity. Such state has forced scientist and vaccine manufacturers to re-think the way vaccines are designed and tested in the elderly. Multiple strategies have been used to overcome the consequences of immunosenescence including the use of higher antigen dose, adjuvanted vaccines, and alternative routes of immunization. However, the lack of understanding of the immune regulatory mechanisms underlying immunosenescence in the elderly represents one of the main hurdles in the pathway to produce effective vaccines for seniors. This article reviews in a succinct form the current state of the art on the development of vaccines for the elderly and critically assesses the past and current literature on this topic, while also proposing new avenues for future studies.

Human lymphocyte repertoires in ageing

Deterioration of adaptive immunity with ageing may reflect changes in the repertoire of T cells and B cells available to respond to antigenic challenges, due to altered proportions and absolute numbers of lymphocyte subpopulations as well as changes in the repertoire of antigen receptor genes expressed by these cells. High-throughput DNA sequencing (HTS) now facilitates examination of immunoglobulin and T cell receptor gene rearrangements, and initial studies using these methods to study immune system ageing in humans have demonstrated age-related alterations in the receptor populations within lymphocyte subsets, as well as in repertoires responding to vaccination. Accurate measurement of repertoire diversity remains an experimental challenge. Studies of larger numbers of human subjects, analysis of defined lymphocyte subpopulations including antigen-specific populations, and controlling for factors such as chronic viral infections, will be important for gaining additional understanding of the impact of ageing on human lymphocyte populations.

The impact of aging on regulatory T-cells

Age-related deviations of the immune system contribute to a higher likelihood of infections, cancer, and autoimmunity in the elderly. Senescence of T-lymphocytes is characterized by phenotypical and functional changes including the loss of characteristic T-cell surface markers, while an increase of stimulatory receptors, cytotoxicity as well as resistance against apoptosis is observed. One of the key mediators of immune regulation are naturally occurring regulatory T-cells (Tregs). Tregs express high levels of CD25 and the intracellular protein forkhead box P3; they exert their suppressive functions in contact-dependent as well as contact-independent manners. Quantitative and qualitative defects of Tregs were observed in patients with autoimmune diseases. Increased Treg activity was shown to suppress anti-tumor and anti-infection immunity. The effect of aging on Tregs, and the possible contribution of age-related changes of the Treg pool to the pathophysiology of diseases in the elderly are still poorly understood. Treg homeostasis depends on an intact thymic function and current data suggest that conversion of non-regulatory T-cells into Tregs as well as peripheral expansion of existing Tregs compensates for thymic involution after puberty to maintain constant Treg numbers. In the conventional T-cell subset, peripheral proliferation of T-cells is associated with replicative senescence leading to phenotypical and functional changes. For Tregs, different developmental stages were also described; however, replicative senescence of Tregs has not been observed yet.

The importance of the nurse cells and regulatory cells in the control of T lymphocyte responses

T lymphocytes from the immune system are bone marrow-derived cells whose development and activities are carefully supervised by two sets of accessory cells. In the thymus, the immature young T lymphocytes are engulfed by epithelial “nurse cells” and retained in vacuoles, where most of them (95%) are negatively selected and removed when they have an incomplete development or express high affinity autoreactive receptors. The mature T lymphocytes that survive to this selection process leave the thymus and are controlled in the periphery by another subpopulation of accessory cells called “regulatory cells,” which reduce any excessive immune response and the risk of collateral injuries to healthy tissues. By different times and procedures, nurse cells and regulatory cells control both the development and the functions of T lymphocyte subpopulations. Disorders in the T lymphocytes development and migration have been observed in some parasitic diseases, which disrupt the thymic microenvironment of nurse cells. In other cases, parasites stimulate rather than depress the functions of regulatory T cells decreasing T-mediated host damages. This paper is a short review regarding some features of these accessory cells and their main interactions with T immature and mature lymphocytes. The modulatory role that neurotransmitters and hormones play in these interactions is also revised.

Pathogenesis of pediatric multiple sclerosis

Onset of multiple sclerosis in childhood occurs in 3-5% of patients. There is limited, but growing knowledge about the underlying pathobiology of pediatric MS. It is crucial to better understand this area in order to address central questions in the field: 1) Can pediatric multiple sclerosis inform us about factors related to disease initiation and propagation? 2) What are the biomarkers of disease course in pediatric multiple sclerosis; 3) Does pediatric multiple sclerosis pathogenesis differ from adult-onset multiple sclerosis; 4) How can we optimize treatment in pediatric demyelinating diseases? 5) Can pediatric multiple sclerosis provide insights into the environmental risk factors for multiple sclerosis in general? Here we review the current knowledge of the pathogenesis of multiple sclerosis in children, and address the five questions raised above.

Regulatory T cells in γ irradiation-induced immune suppression

Sublethal total body γ irradiation (TBI) of mammals causes generalized immunosuppression, in part by induction of lymphocyte apoptosis. Here, we provide evidence that a part of this immune suppression may be attributable to dysfunction of immune regulation. We investigated the effects of sublethal TBI on T cell memory responses to gain insight into the potential for loss of vaccine immunity following such exposure. We show that in mice primed to an MHC class I alloantigen, the accelerated graft rejection T memory response is specifically lost several weeks following TBI, whereas identically treated naïve mice at the same time point had completely recovered normal rejection kinetics. Depletion in vivo with anti-CD4 or anti-CD25 showed that the mechanism involved cells consistent with a regulatory T cell (T reg) phenotype. The loss of the T memory response following TBI was associated with a relative increase of CD4+CD25+ Foxp3+ expressing T regs, as compared to the CD8+ T effector cells requisite for skin graft rejection. The radiation-induced T memory suppression was shown to be antigen-specific in that a third party ipsilateral graft rejected with normal kinetics. Remarkably, following the eventual rejection of the first MHC class I disparate skin graft, the suppressive environment was maintained, with markedly prolonged survival of a second identical allograft. These findings have potential importance as regards the immunologic status of T memory responses in victims of ionizing radiation exposure and apoptosis-inducing therapies.