Biology of dendritic cells in aging

Regulatory RNAs in immunosenescence

BACKGROUND

Immunosenescence is a multifactorial stress response to different intrinsic and extrinsic insults that cause immune deterioration and is accompanied by genomic or epigenomic perturbations. It is now widely recognized that genes and proteins contributing in the process of immunosenescence are regulated by various noncoding (nc) RNAs, including microRNAs (miRNAs), long ncRNAs, and circular RNAs.

AIMS

This review article aimed to evaluate the regulatore RNAs roles in the process of immunosenescence.

METHODS

We analyzed publications that were focusing on the different roles of regulatory RNAs on the several aspects of immunosenescence.

RESULTS

In the immunosenescence setting, ncRNAs have been found to play regulatory roles at both transcriptional and post-transcriptional levels. These factors cooperate to regulate the initiation of gene expression programs and sustaining the senescence phenotype and proinflammatory responses.

CONCLUSION

Immunosenescence is a complex process with pivotal alterations in immune function occurring with age. The extensive network that drive immunosenescence-related features are are mainly directed by a variety of regulatory RNAs such as miRNAs, lncRNAs, and circRNAs. Latest findings about regulation of senescence by ncRNAs in the innate and adaptive immune cells as well as their role in the immunosenescence pathways, provide a better understanding of regulatory RNAs function in the process of immunosenescence.

The impact of aging-induced gut microbiome dysbiosis on dendritic cells and lung diseases

Aging is an inevitable natural process that impacts every individual, and understanding its effect on the gut microbiome and dendritic cell (DC) functionality in elderly subjects is crucial. DCs are vital antigen-presenting cells (APCs) that orchestrate the immune response, maintaining immune tolerance to self-antigens and bridging innate and adaptive immunity. With aging, there is a shift toward nonspecific innate immunity, resulting in a decline in adaptive immune responses. This alteration raises significant concerns about managing the health of an elderly population. However, the precise impact of aging and microbiome changes on DC function and their implications in lung-associated diseases remain relatively understudied. To illuminate this subject, we will discuss recent advancements in understanding the connections between aging, gut dysbiosis, DCs, and lung diseases. Emphasizing the key concepts linking age-related gut microbiome changes and DC functions, we will focus on their relevance to overall health and immune response in elderly individuals. This article aims to improve our understanding of the intricate relationship between aging, gut microbiome, and DCs, potentially benefiting the management of age-associated diseases and promoting healthy aging.

The aging of the immune system and its implications for transplantation

By the last third of life, most mammals, including humans, exhibit a decline in immune cell numbers, immune organ structure, and immune defense of the organism, commonly known as immunosenescence. This decline leads to clinical manifestations of increased susceptibility to infections, particularly those caused by emerging and reemerging microorganisms, which can reach staggering levels-infection with SARS-CoV-2 has been 270-fold more lethal to older adults over 80 years of age, compared to their 18-39-year-old counterparts. However, while this would be expected to be beneficial to situations where hyporeactivity of the immune system may be desirable, this is not always the case. Here, we discuss the cellular and molecular underpinnings of immunosenescence as they pertain to outcomes of solid organ and hematopoietic transplantation.

Effects of Manipulation of Noradrenergic Activities on the Expression of Dopaminergic Phenotypes in Aged Rat Brains

This study investigated the effects of the pharmacological manipulation of noradrenergic activities on dopaminergic phenotypes in aged rats. Results showed that the administration of L-threo-3,4-dihydroxyphenylserine (L-DOPS) for 21 days significantly increased the expression of tyrosine hydroxylase (TH) and dopamine transporter (DAT) in the striatum and substantia nigra (SN) of 23-month-old rats. Furthermore, this treatment significantly increased norepinephrine/DA concentrations in the striatum and caused a deficit of sensorimotor gating as measured by prepulse inhibition (PPI). Next, old rats were injected with the α2-adrenoceptor antagonist 2-methoxy idazoxan or β2-adrenoceptor agonist salmeterol for 21 days. Both drugs produced similar changes of TH and DAT in the striatum and SN. Moreover, treatments with L-DOPS, 2-methoxy idazoxan, or salmeterol significantly increased the protein levels of phosphorylated Akt in rat striatum and SN. However, although a combination of 2-methoxy idazoxan and salmeterol resulted in a deficit of PPI in these rats, the administration of 2-methoxy idazoxan alone showed an opposite behavioral change. The in vitro experiments revealed that treatments with norepinephrine markedly increased mRNAs and proteins of ATF2 and CBP/p300 and reduced mRNA and proteins of HDAC2 and HDAC5 in MN9D cells. A ChIP assay showed that norepinephrine significantly increased CBP/p300 binding or reduced HDAC2 and HDAC5 binding on the TH promoter. The present results indicate that facilitating noradrenergic activity in the brain can improve the functions of dopaminergic neurons in aged animals. While this improvement may have biochemically therapeutic indication for the status involving the degeneration of dopaminergic neurons, it may not definitely include behavioral improvements, as indicated by using 2-methoxy idazoxan only.

SARS-CoV-2 multifaceted interaction with the human host. Part II: Innate immunity response, immunopathology, and epigenetics

The SARS-CoV-2 makes its way into the cell via the ACE2 receptor and the proteolytic action of TMPRSS2. In response to the SARS-CoV-2 infection, the innate immune response is the first line of defense, triggering multiple signaling pathways to produce interferons, pro-inflammatory cytokines and chemokines, and initiating the adaptive immune response against the virus. Unsurprisingly, the virus has developed strategies to evade detection, which can result in delayed, excessive activation of the innate immune system. The response elicited by the host depends on multiple factors, including health status, age, and sex. An overactive innate immune response can lead to a cytokine storm, inflammation, and vascular disruption, leading to the vast array of symptoms exhibited by COVID-19 patients. What is known about the expression and epigenetic regulation of the ACE2 gene and the various players in the host response are explored in this review.

Transplantation of Marginal Organs: Immunological Aspects and Therapeutic Perspectives in Kidney Transplantation

Recent data from the World Population Prospects projects that, by 2050, nearly all regions in the world will have a quarter or more of the population aged 60 and above. Chronic kidney disease (CKD) has a high global prevalence (~13%) worldwide, and the prevalence of chronic kidney disease and end-stage kidney disease increase with age. Kidney transplantation remains the best therapeutic option for end-stage kidney disease, offering a survival benefit in comparison with dialysis maintenance for most patients. This review focuses on immunological aspects of kidney transplantation in older patients and marginal donors, i.e., 60 years or older deceased kidney donors or 50–59 years old deceased kidney donors with comorbidities. Clinical outcomes of kidney recipients in terms of renal and patient survival are more than acceptable even for patients over 70. In this population, the first cause of graft loss is death with a functional graft. However, the inherent issues of these transplantations are the acceptance or refusal of frail kidney from an old donor and the increased immunogenicity of these organs in balance with potential frail and immunosenescent recipients. Finally, the immunosuppressive regimen itself is a challenge for the future of the transplant, to prevent adverse effects such as nephrotoxicity and higher risk of infections or cancer in a population already at risk. Belatacept may have a good place in the immunosuppressive strategy to improve efficacy and the safety posttransplantation.

Blocking the FSTL1-DIP2A Axis Improves Anti-tumor Immunity

Immune dysfunction is a strong factor in the resistance of cancer to treatment. Blocking immune checkpoint pathways is a promising approach to improve anti-tumor immunity, but the clinical efficacies are still limited. We previously identified follistatin-like 1 (FSTL1) as a determinant of immune dysfunction mediated by mesenchymal stromal/stem cells (MSCs) and immunoregulatory cells. Here, we demonstrate that blocking FSTL1 but not immune checkpoint pathways significantly suppresses cancer progression and metastasis in several mouse tumor models with increased MSCs. Expression of DIP2A (the receptor of FSTL1) in tumor cells is critical for FSTL1-induced immunoresistance. FSTL1/DIP2A co-positivity in tumor tissues correlates with poor prognosis in NSCLC patients. Thus, breaking the FSTL1-DIP2A axis may be a useful strategy for successfully inducing anti-tumor immunity.

Aging and the Immune System: the Impact of Immunosenescence on Viral Infection, Immunity and Vaccine Immunogenicity

Immunosenescence is characterized by a progressive deterioration of the immune system associated with aging. Multiple components of both innate and adaptive immune systems experience aging-related changes, such as alterations in the number of circulating monocytic and dendritic cells, reduced phagocytic activities of neutrophils, limited diversity in B/T cell repertoire, T cell exhaustion or inflation, and chronic production of inflammatory cytokines known as inflammaging. The elderly are less likely to benefit from vaccinations as preventative measures against infectious diseases due to the inability of the immune system to mount a successful defense. Therefore, aging is thought to decrease the efficacy and effectiveness of vaccines, suggesting aging-associated decline in the immunogenicity induced by vaccination. In this review, we discuss aging-associated changes in the innate and adaptive immunity and the impact of immunosenescence on viral infection and immunity. We further explore recent advances in strategies to enhance the immunogenicity of vaccines in the elderly. Better understanding of the molecular mechanisms underlying immunosenescence-related immune dysfunction will provide a crucial insight into the development of effective elderly-targeted vaccines and immunotherapies.

Immunosenescence: A systems-level overview of immune cell biology and strategies for improving vaccine responses

Immunosenescence contributes to a decreased capacity of the immune system to respond effectively to infections or vaccines in the elderly. The full extent of the biological changes that lead to immunosenescence are unknown, but numerous cell types involved in innate and adaptive immunity exhibit altered phenotypes and function as a result of aging. These manifestations of immunosenescence at the cellular level are mediated by dysregulation at the genetic level, and changes throughout the immune system are, in turn, propagated by numerous cellular interactions. Environmental factors, such as nutrition, also exert significant influence on the immune system during aging. While the mechanisms that govern the onset of immunosenescence are complex, systems biology approaches allow for the identification of individual contributions from each component within the system as a whole. Although there is still much to learn regarding immunosenescence, systems-level studies of vaccine responses have been highly informative and will guide the development of new vaccine candidates, novel adjuvant formulations, and immunotherapeutic drugs to improve vaccine responses among the aging population.

Blood immune cell biomarkers in lung cancer

Characterization of host immune cell parameters prior to treatment is expected to identify biomarkers predictive of clinical outcome as well as to elucidate why some patients fail to respond to immunotherapy. We monitored blood immune cells from 58 patients with non-small- cell lung cancer (NSCLC) undergoing surgery of the primary tumor and from 50 age-matched healthy volunteers. Complete leukocyte blood count, the number of circulating dendritic cells (DC), HLA-DR^low monocytes and several lymphocytic subpopulations were determined by eight-color flow cytometry. Furthermore, the prognostic value of the immune cell parameters investigated was evaluated by patients' survival analysis. Compared to the control group, blood of NSCLC patients contained more neutrophils resulting in a higher neutrophil-to-lymphocyte ratio (NLR), but a lower number of blood DC, in particular of plasmacytoid DC (pDC), natural killer (NK) cells and naive CD4⁺ and CD8⁺ T cells. Furthermore, a higher frequency of CD4⁺ regulatory T cells (Treg) and HLA-DR^low monocytes was detected, and smoking had a significant impact on these values. HLA-DR^low monocytes were positively correlated to the number of neutrophils, monocytes and NLR, but negatively associated with the number of pDC and naive CD4⁺ T cells. The frequency of Treg, HLA-DR^low monocytes and naive CD4⁺ and CD8⁺ T cells as well as the ratios of CD4/HLA-DR^low monocytes and HLA-DR^low monocytes/pDC correlated with patient's overall survival. Next to Treg, HLA-DR^low monocytes and naive T cells represent prognostic markers for NSCLC patients and might be useful for monitoring of patients' responses to immunotherapies in future studies.

Effects of Acute and Chronic Exercise on Immunological Parameters in the Elderly Aged: Can Physical Activity Counteract the Effects of Aging?

Immunosenescence is characterized by deterioration of the immune system caused by aging which induces changes to innate and adaptive immunity. Immunosenescence affects function and phenotype of immune cells, such as expression and function of receptors for immune cells which contributes to loss of immune function (chemotaxis, intracellular killing). Moreover, these alterations decrease the response to pathogens, which leads to several age-related diseases including cardiovascular disease, Alzheimer's disease, and diabetes in older individuals. Furthermore, increased risk of autoimmune disease and chronic infection is increased with an aging immune system, which is characterized by a pro-inflammatory environment, ultimately leading to accelerated biological aging. During the last century, sedentarism rose dramatically, with a concomitant increase in certain type of cancers (such as breast cancer, colon, or prostate cancer), and autoimmune disease. Numerous studies on physical activity and immunity, with focus on special populations (i.e., people with diabetes, HIV patients) demonstrate that chronic exercise enhances immunity. However, the majority of previous work has focused on either a pathological population or healthy young adults whilst research in elderly populations is scarce. Research conducted to date has primarily focused on aerobic and resistance exercise training and its effect on immunity. This review focuses on the potential for exercise training to affect the aging immune system. The concept is that some lifestyle strategies such as high-intensity exercise training may prevent disease through the attenuation of immunosenescence. In this context, we take a top-down approach and review the effect of exercise and training on immunological parameters in elderly at rest and during exercise in humans, and how they respond to different modes of training. We highlight the impact of these different exercise modes on immunological parameters, such as cytokine and lymphocyte concentration in elderly individuals.

Elderly dendritic cells respond to LPS/IFN-γ and CD40L stimulation despite incomplete maturation

There is evidence that dendritic cells (DCs) undergo age-related changes that modulate their function with their key role being priming antigen-specific effector T cells. This occurs once DCs develop into antigen-presenting cells in response to stimuli/danger signals. However, the effects of aging on DC responses to bacterial lipopolysaccharide (LPS), the pro-inflammatory cytokine interferon (IFN)-γ and CD40 ligand (CD40L) have not yet been systematically evaluated. We examined responses of blood myeloid (m)DC1s, mDC2s, plasmacytoid (p)DCs, and monocyte-derived DCs (MoDCs) from young (21–40 years) and elderly (60–84 years) healthy human volunteers to LPS/IFN-γ or CD40L stimulation. All elderly DC subsets demonstrated comparable up-regulation of co-stimulatory molecules (CD40, CD80 and/or CD86), intracellular pro-inflammatory cytokine levels (IFN-γ, tumour necrosis factor (TNF)-α, IL-6 and/or IL-12), and/or secreted cytokine levels (IFN-α, IFN-γ, TNF-α, and IL-12) to their younger counterparts. Furthermore, elderly-derived LPS/IFN-γ or CD40L-activated MoDCs induced similar or increased levels of CD8⁺ and CD4⁺ T cell proliferation, and similar T cell functional phenotypes, to their younger counterparts. However, elderly LPS/IFN-γ-activated MoDCs were unreliable in their ability to up-regulate chemokine (IL-8 and monocyte chemoattractant protein (MCP)-1) and IL-6 secretion, implying an inability to dependably induce an inflammatory response. A key age-related difference was that, unlike young-derived MoDCs that completely lost their ability to process antigen, elderly-derived MoDCs maintained their antigen processing ability after LPS/IFN-γ maturation, measured using the DQ-ovalbumin assay; this response implies incomplete maturation that may enable elderly DCs to continuously present antigen. These differences may impact on the efficacy of anti-pathogen and anti-tumour immune responses in the elderly.

Considerations for successful cancer immunotherapy in aged hosts

Improvements in understanding cancer immunopathogenesis have now led to unprecedented successes in immunotherapy to treat numerous cancers. Although aging is the most important risk factor for cancer, most pre-clinical cancer immunotherapy studies are undertaken in young hosts. This review covers age-related immune changes as they affect cancer immune surveillance, immunopathogenesis and immune therapy responses. Declining T cell function with age can impede efficacy of age-related cancer immunotherapies, but examples of successful approaches to breach this barrier have been reported. It is further recognized now that immune functions with age do not simply decline, but that they change in potentially detrimental ways. For example, detrimental immune cell populations can become predominant during aging (notably pro-inflammatory cells), the prevalence or function of suppressive cells can increase (notably myeloid derived suppressor cells), drugs can have age-specific effects on immune cells, and attributes of the aged microenvironment can impede or subvert immunity. Key advances in these and related areas will be reviewed as they pertain to cancer immunotherapy in the aged, and areas requiring additional study and some speculations on future research directions will be addressed. We prefer the term Age Related Immune Dysfunction (ARID) as most encompassing the totality of age-associated immune changes.

Modulation of dendritic cell and T cell cross-talk during aging: The potential role of checkpoint inhibitory molecules

Dendritic cells (DCs) undergo continuous changes throughout life, and there is evidence that elderly DCs have a reduced capacity to stimulate T cells, which may contribute to impaired anti-tumour immune responses in elderly people with cancer. Changes in checkpoint inhibitory molecules/pathways during aging may be one mechanism that impairs the ability of elderly DCs to activate T cells. However, little is currently known regarding the combined effects of aging and cancer on DC and T cell inhibitory molecules/pathways. In this review, we discuss our current understanding of the influence of aging and cancer on key DC and T cell inhibitory molecules/pathways, the potential underlying cellular and molecular mechanisms contributing to their modulation, and the possibility of therapeutically targeting inhibitory molecules in elderly cancer patients.

Considerations for successful cancer immunotherapy in aged hosts

Immunotherapy is now experiencing unprecedented successes in treating various cancers based on new understandings of cancer immunopathogenesis. Nonetheless, although ageing is the biggest risk factor for cancer, the majority of cancer immunotherapy preclinical studies are conducted in young hosts. This review will explore age-related changes in immunity as they relate to cancer immune surveillance, immunopathogenesis and responses to immunotherapy. Although it is recognized that declining T cell function with age poses a great challenge to developing effective age-related cancer immunotherapies, examples of successful approaches to overcome this hurdle have been developed. Further, it is now recognized that immune functions do not simply decline with age, but rather change in ways than can be detrimental. For example, with age, specific immune cell populations with detrimental functions can become predominant (such as cells producing proinflammatory cytokines), suppressive cells can become more numerous or more suppressive (such as myeloid-derived suppressor cells), drugs can affect aged immune cells distinctly and the aged microenvironment is becoming recognized as a significant barrier to address. Key developments in these and other areas will be surveyed as they relate to cancer immunotherapy in aged hosts, and areas in need of more study will be assessed with some speculations for the future. We propose the term 'age-related immune dysfunction' (ARID) as best representative of age-associated changes in immunity.

An In Vitro Approach to Study Effects of Prebiotics and Probiotics on the Faecal Microbiota and Selected Immune Parameters Relevant to the Elderly

The aging process leads to alterations of gut microbiota and modifications to the immune response, such changes may be associated with increased disease risk. Prebiotics and probiotics can modulate microbiome changes induced by aging; however, their effects have not been directly compared. The aim of this study was to use anaerobic batch culture fermenters to assess the impact of various fermentable carbohydrates and microorganisms on the gut microbiota and selected immune markers. Elderly volunteers were used as donors for these experiments to enable relevance to an aging population. The impact of fermentation supernatants on immune markers relevant to the elderly were assessed in vitro. Levels of IL-1β, IL-6, IL-8, IL-10 and TNF-α in peripheral blood mononuclear cell culture supernatants were measured using flow cytometry. Trans-galactooligosaccharides (B-GOS) and inulin both stimulated bifidobacteria compared to other treatments (p<0.05). Fermentation supernatants taken from faecal batch cultures supplemented with B-GOS, inulin, B. bifidum, L. acidophilus and Ba. coagulans inhibited LPS induced TNF-α (p<0.05). IL-10 production, induced by LPS, was enhanced by fermentation supernatants from faecal batch cultures supplemented with B-GOS, inulin, B. bifidum, L. acidophilus, Ba. coagulans and Bac. thetaiotaomicron (p<0.05). To conclude, prebiotics and probiotics could lead to potentially beneficial effects to host health by targeting specific bacterial groups, increasing saccharolytic fermentation and decreasing inflammation associated with aging. Compared to probiotics, prebiotics led to greater microbiota modulation at the genus level within the fermenters.

The effects of proliferation and DNA damage on hematopoietic stem cell function determine aging

In most of the mammalian tissues, homeostasis as well as injury repair depend upon a small number of resident adult stem cells. The decline in tissue/organ function in aged organisms has been directly linked with poorly functioning stem cells. Altered function of hematopoietic stem cells (HSCs) is at the center of an aging hematopoietic system, a tissue with high cellular turnover. Poorly engrafting, myeloid-biased HSCs with higher levels of DNA damage accumulation are the hallmark features of an aged hematopoietic system. These cells show a higher proliferation rate than their younger counterparts. It was proposed that quiescence of these cells over long period of time leads to accumulation of DNA damage, eventually resulting in poor function/pathological conditions in hematopoietic system. However, various mouse models with premature aging phenotype also show highly proliferative HSCs. This review examines the evidence that links proliferation of HSCs with aging, which leads to functional changes in the hematopoietic system. Developmental Dynamics 245:739-750, 2016. © 2016 Wiley Periodicals, Inc.

Adaptive and Innate Immune Responses in Autism: Rationale for Therapeutic Use of Intravenous Immunoglobulin

Background

Autism is a complex polygenic neurodevelopmental disorder characterized by deficits in communication and social interactions as well as specific stereotypical behaviors. Both genetic and environmental factors appear to contribute to the pathogenesis of autism. Accumulating data including changes in immune responses, linkage to major histocompatibility complex antigens, and the presence of autoantibodies to neural tissues/antigens suggest that the immune system plays an important role in its pathogenesis.

Summary

In this brief review, we discuss the data regarding changes in both innate and adaptive immunity in autism and the evidence in favor of the role of the immune system, especially of maternal autoantibodies in the pathogenesis of a subset of patients with autism. The rationale for possible therapeutic use of intravenous immunoglobulin is also discussed.

DAMPs and influenza virus infection in ageing

Influenza A virus (IAV) is a serious global health problem worldwide due to frequent and severe outbreaks. IAV causes significant morbidity and mortality in the elderly population, due to the ineffectiveness of the vaccine and the alteration of T cell immunity with ageing. The cellular and molecular link between ageing and virus infection is unclear and it is possible that damage associated molecular patterns (DAMPs) may play a role in the raised severity and susceptibility of virus infections in the elderly. DAMPs which are released from damaged cells following activation, injury or cell death can activate the immune response through the stimulation of the inflammasome through several types of receptors found on the plasma membrane, inside endosomes after endocytosis as well as in the cytosol. In this review, the detriment in the immune system during ageing and the links between influenza virus infection and ageing will be discussed. In addition, the role of DAMPs such as HMGB1 and S100/Annexin in ageing, and the enhanced morbidity and mortality to severe influenza infection in ageing will be highlighted.

Loss of Phagocytic and Antigen Cross-Presenting Capacity in Aging Dendritic Cells Is Associated with Mitochondrial Dysfunction

Impaired functionality of dendritic cells (DCs) significantly contributes to decreased adaptive immune responses in aged hosts. The expression of MHC-peptide on the DC surface is the critical first step in T cell priming, but few studies have addressed the effect of aging on Ag acquisition, processing, and presentation by DCs. In this study, we show that aged murine DCs were less efficient in the cross-presentation of cell-associated Ag and subsequently in the cross-priming of CD8(+) T cells than were their young counterparts. The decreased cross-presentation was associated with a reduction in the frequency of CD8α DCs and merocytic (CD8α(-)CD11b(-))DCs that could endocytose cell-associated Ag, as well as the number and the size of the endocytosed particles in the DC that did internalize cell-associated materials. Mechanistically, phagocytic capacity has been associated with mitochondrial activity and membrane potential (Δψm). Aged DCs exhibited profound signs of mitochondrial dysfunction, illustrated by lower Δψm, reduced ATP turnover and coupling efficiency, decreased baseline oxidative phosphorylation, and greater proton leak and reactive oxygen species (ROS) production. Mimicking the aged metabolic phenotype in young DCs by pharmacologic manipulation indicated that the reductions in Δψm and ATP impeded the phagocytic capacity whereas ROS interfered with a later step in the cross-presentation process. Conversely, in vitro scavenging of ROS partially restored cross-presentation by aged DCs. Taken together, these data suggest that improvement of aged DC functionality might be feasible in the elderly by targeting metabolic dysfunction or its downstream sequelae, thereby opening new avenues for enhancing vaccine efficiency in this population.

17β-Estradiol influences in vitro response of aged rat splenic conventional dendritic cells to TLR4 and TLR7/8 agonists in an agonist specific manner

This study was undertaken considering that, despite the broad use of the unopposed estrogen replacement therapy in elderly women, data on estrogen influence on the functional capacity of dendritic cells (DCs), and consequently immune response are limited. We examined the influence of 17β-estradiol on phenotype, cytokine secretory profile, and allostimulatory and polarizing capacity of splenic (OX62+) conventional DCs from 26-month-old (aged) Albino Oxford rats matured in vitro in the presence of LPS, a TLR4 agonist, and R848, a TLR7/8 agonist. In the presence of 17β-estradiol, DCs from aged rats exhibited an impaired ability to mature upon stimulation with LPS, as shown by the lower surface density of MHC II and costimulatory CD80 and CD86 molecules. 17β-Estradiol alone enhanced CD40 expression in OX62+ DCs without affecting the expression of other costimulatory molecules, thereby confirming that the expression of this molecule is regulated independently from the regulation of other costimulatory molecules. However, although R848 upregulated the expression of MHC II and CD80 and CD40 costimulatory molecules on DCs, 17β-estradiol diminished the effect of this TLR agonist only on MHC II expression. In conjunction, the previous findings suggest that LPS and R848 elicit changes in the expression of costimulatory molecules via triggering differential intracellular signaling pathways. Furthermore, 17β-estradiol diminished the stimulatory influence of both LPS- and R848-matured OX62+ DCs on allogeneic CD4+ T lymphocyte proliferation in a mixed lymphocyte reaction (MLR). Moreover, as shown in MLR, the exposure to 17β-estradiol during LPS- and R848-induced maturation diminished Th1- and enhanced Th17-driving capacity and reduced Th1-driving capacity of OX62+ DCs, respectively. This suggests that LPS and R848 affect not only the surface phenotype, but also functional characteristics of OX62+ DCs triggering distinct intracellular signaling pathways. Collectively, the findings indicate that estrogen directly acting on OX62+ DCs, may affect CD4+ lymphocyte-dependent immune response in aged female rats.

Dysfunction of dendritic cells in aged C57BL/6 mice leads to failure of natural killer cell activation and of tumor eradication

The reciprocal activation of dendritic cells (DCs) and natural killer cells (NKs) plays a key role in both innate and adaptive immunity. The effect of aging on this cross-talk, a critical step in virus disease control and tumor immunology, has not been reported. Splenic DCs and NKs were purified from both young and old C57BL/6 mice and cocultured in the presence of polyinosinic:polycytidylic acid (poly I:C). The resulting activation of NKs was measured as expression of CD69 and secretion of IFN-γ. However, DCs from old mice could not activate NKs from either young or old mice in vitro or in vivo. In contrast, DCs from young mice efficiently activated NKs from both young and old mice. DCs from old mice were deficient in poly I:C-stimulated secretion of IL-15, IL-18, and IFN-α. Gene expression analysis revealed many other differences between DCs of old and young mice. Young mice strongly eradicated MHC class I-negative NK-sensitive RMA-S lymphoma mutant tumor cells, but old mice did not, in concert with the previous report that mousepox kills aged, but not young, C57BL/6 mice. Furthermore, a similar dysfunction of DC and its key role in NK activation was found in 27 out of 55 healthy human donors.

Naive T cells: the crux of cellular immune aging?

When encountering foreign antigens, naïve T cells become activated and differentiate into effector and memory T cells. They represent therefore the primary source to mount an immune response against pathogens or tumors. Recent evidence of both quantitative and qualitative alterations of naïve T cells has accumulated in aged mice, indicating that the successful generation of primary T cell responses from the naïve T cell pool may be compromised with old age. However, the vast majority of the data supporting compromised naïve T cell priming efficacy with old age have been produced in animal models, and the situation is much less clear in humans. In the elderly, the involution of the thymus and the associated decline in thymic output result in a decreased number of naïve T cells, which is partially compensated by homeostatic proliferation. Emerging evidence suggest that alterations of the TCR repertoire diversity and intrinsic defects of old CD4(+) naïve T cells may impact on their responsiveness to antigenic stimulation. Increasing focus on the study of naïve T cells (in particular CD8(+)) in old humans are needed to fill the gaps in our understanding of reduced cellular immunity with aging.

Ocular surface disease and dacryoadenitis in aging C57BL/6 mice

Dry eye in humans displays increased prevalence in the aged and in women. Here, we investigated the ocular surfaces and lacrimal glands of aged mice of both sexes. We surveyed three different ages [young, middle-aged (6 to 9 months), and elderly] by investigating severity markers of dry eye disease (DED). We observed an age-dependent dry eye phenotype as early as 6 to 9 months: increased corneal surface irregularity, increased corneal barrier disruption, conjunctival CD4(+) T-cell infiltration, and loss of mucin-filled goblet cells. Expression of interferon-γ, IL-17 mRNA transcripts was increased in the conjunctiva and IL-17A, matrix metallopeptidase 9, and chemokine ligand 20 in the corneas of elderly mice. Elderly male mice develop more of a skewed response of type 1 T helper cell, whereas female mice have a bias toward type 17 T helper cell in the conjunctiva. In the lacrimal gland, an increase in CD4(+) and CD8(+) T cells and B cells and a decrease in activated dendritic cells were observed. Adoptive transfer of CD4(+) T cells isolated from elderly mice transferred DED into young immunodeficient recipients, which was more pronounced from male donors. Our findings show the development of DED in aging mice. Pathogenic CD4(+) T cells that develop with aging are capable of transferring DED from older mice to naive immunodeficient recipients. Taken together, our results indicate that age-related autoimmunity contributes to development of DED with aging.

Immunosenescence and immune response in organ transplantation

The immune system undergoes a complex and continuous remodeling with aging. Immunosenescence results into both quantitative and qualitative changes of specific cellular subpopulations that have major impact on allorecognition and alloresponse, and consequently on graft rejection and tolerance. Here, we are going to review the immunological changes associated with the aging process relevant for transplantation. Interventions to selectively target changes associated with the senescence process seem promising therapeutic strategies to improve transplantation outcome.

Preoperative cerebrospinal fluid cytokine levels and the risk of postoperative delirium in elderly hip fracture patients

Background

Aging and neurodegenerative disease predispose to delirium and are both associated with increased activity of the innate immune system resulting in an imbalance between pro- and anti-inflammatory mediators in the brain. We examined whether hip fracture patients who develop postoperative delirium have altered levels of inflammatory mediators in cerebrospinal fluid (CSF) prior to surgery.

Methods

Patients were 75 years and older and admitted for surgical repair of an acute hip fracture. CSF samples were collected preoperatively. In an exploratory study, we measured 42 cytokines and chemokines by multiplex analysis. We compared CSF levels between patients with and without postoperative delirium and examined the association between CSF cytokine levels and delirium severity. Delirium was diagnosed with the Confusion Assessment Method; severity of delirium was measured with the Delirium Rating Scale Revised-98. Mann–Whitney U tests or Student t-tests were used for between-group comparisons and the Spearman correlation coefficient was used for correlation analyses.

Results

Sixty-one patients were included, of whom 23 patients (37.7%) developed postsurgical delirium. Concentrations of Fms-like tyrosine kinase-3 (P=0.021), Interleukin-1 receptor antagonist (P=0.032) and Interleukin-6 (P=0.005) were significantly lower in patients who developed delirium postoperatively.

Conclusions

Our findings fit the hypothesis that delirium after surgery results from a dysfunctional neuroinflammatory response: stressing the role of reduced levels of anti-inflammatory mediators in this process.

Trial registration

The Effect of Taurine on Morbidity and Mortality in the Elderly Hip Fracture Patient.

Registration number: NCT00497978. Local ethical protocol number: NL16222.094.07.

Mice with heterozygous deficiency of manganese superoxide dismutase (SOD2) have a skin immune system with features of "inflamm-aging"

Dendritic cells (DC) are central in regulating skin immunity. Immunosenescence is associated with a chronic inflammatory state. Little is known about the contribution of DC to "inflamm-aging". When determining langerhans cell (LC) numbers, we found a 60 % reduction of LC in aged epidermis. Reactive oxygen species(ROS) are linked with aging. The mitochondrial manganese superoxide dismutase (SOD2) is in the first line of antioxidant defense. We investigated the function of DC from SOD2 heterozygous mice (SOD2+/-) and found that at 4 months of age LC numbers are not altered, but activated LC have impaired expression of MHC-II and CD44. Immature SOD2+/- DC produced increased proinflammatory IL-6 and chemokines CXCL1 and CXCL2. Upon challenge SOD2+/- DC accumulated ROS. When activating SOD2+/- DC by LPS they less efficiently upregulated MHC-II, CD86 and CD44. Surprisingly, in vivo contact hypersensitivity (CHS) was enhanced in SOD2+/- mice although SOD2+/- DC were less potent in stimulating wt T cells. However, SOD2+/- T cells showed increased proliferation, even when stimulated with SOD2+/- DC, possibly explaining the increased CHS. Our findings suggest that SOD2 is a molecular candidate in the regulation of "inflamm-aging" conveying both immunosuppressive and proinflammatory signals through alteration of DC and T cell functions.

Immunosenescence and organ transplantation

Increasing numbers of elderly transplant recipients and a growing demand for organs from older donors impose pressing challenges on transplantation medicine. Continuous and complex modifications of the immune system in parallel to aging have a major impact on transplant outcome and organ quality. Both, altered alloimmune responses and increased immunogenicity of organs present risk factors for inferior patient and graft survival. Moreover, a growing body of knowledge on age-dependent modifications of allorecognition and alloimmune responses may require age-adapted immunosuppression and organ allocation. Here, we summarize relevant aspects of immunosenescence and their possible clinical impact on organ transplantation.

The immune system in the elderly: a fair fight against diseases?

The immune system is a very dynamic network, consisting of various innate and adaptive cells acting via direct cell–cell contact, as well as indirect messaging mediated by soluble factors. Changes in the number or quality of receptors involved in these events alter the capacity of the immune system to respond properly. There is an increasing awareness that many chronic infections and diseases, such as cytomegalovirus, impact on the immune system. Concurrently, there are changes in immune profiles of healthy, as well as ill, elderly individuals. All these changes translate into obvious signs of immunological aging that are more profound in diseases. This review will discuss the manifestation of different diseases in the elderly and how the immune system behaves in such situations.

Innate immunosenescence: effect of aging on cells and receptors of the innate immune system in humans

Components of the innate immune response, including neutrophils and macrophages, are the first line of defense against infections. Their role is to initiate an inflammatory response, phagocyte and kill pathogens, recruit natural killer cells (NK), and facilitate the maturation and migration of dendritic cells that will initiate the adaptive immune response. Extraordinary advances have been made in the last decade on the knowledge of the receptors and mechanisms used by cells of the innate immunity not only to sense and eliminate the pathogen but also to communicate each other and collaborate with cells of adaptive immunity to mount an effective immune response. The analysis of innate immunity in elderly humans has evidenced that aging has a profound impact on the phenotype and functions of these cells. Thus altered expression and/or function of innate immunity receptors and signal transduction leading to defective activation and decreased chemotaxis, phagocytosis and intracellular killing of pathogens have been described. The phenotype and function of NK cells from elderly individuals show significant changes that are compatible with remodeling of the different NK subsets, with a decrease in the CD56bright subpopulation and accumulation of the CD56dim cells, in particular those differentiated NK cells that co-express CD57, as well as a decreased expression of activating natural cytotoxicity receptors. These alterations can be responsible of the decreased production of cytokines and the lower per-cell cytotoxicity observed in the elderly. Considering the relevance of these cells in the initiation of the immune response, the possibility to reactivate the function of innate immune cells should be considered in order to improve the response to pathogens and to vaccination in the elderly.

Enumeration of human peripheral blood dendritic cells throughout the life

Human aging is associated with immunosenescence, a process characterized by alterations in numerical and functional features of immune system components. Dendritic cells (DCs) are the main antigen-presenting cells, playing a pivotal role in adaptive and innate immunity. Therefore, we investigated the distribution of human circulating DCs throughout the life, in order to contribute to the knowledge of the physiological background underlying the aging of immune system. Cytofluorimetric analysis of peripheral blood samples by all-aged healthy population showed a significant decrease of circulating DCs and of their two main subsets among age. This reduction was limited to the plasmacytoid cell subtype when young and old subjects were analyzed separately. The analysis of circulating Treg cell number in a cohort of the subjects showed a significant reduction with increasing age and a positive significant correlation to myeloid or plasmacytoid absolute numbers. In conclusion, this work provides a large set of data of normal reference values of peripheral blood dendritic cells in healthy population suitable for comparative clinical studies concerning pathological immune dysfunctions.

Impaired NLRP3 inflammasome function in elderly mice during influenza infection is rescued by treatment with nigericin

The NLRP3 inflammasome is activated in the lung during influenza viral infection; however, the impact of aging on inflammasome function during influenza infection has not been examined. In this study, we show that elderly mice infected with a mouse-adapted strain of influenza produced lower levels of IL-1β during in vitro and in vivo infection. Dendritic cells from elderly mice exhibited decreased expression of ASC, NLRP3, and capase-1 but increased expression of pro-IL-1β, pro-IL-18, and pro-IL-33 compared with dendritic cells from young infected mice. Treatment with nigericin during influenza infection augmented IL-1β production, increased caspase-1 activity, and decreased morbidity and mortality in elderly mice. Our study demonstrates for the first time, to our knowledge, that during influenza viral infection, elderly mice have impaired NLRP3 inflammasome activity and that treatment with nigericin rescues NLRP3 activation in elderly hosts.

Donor age-specific injury and immune responses

Utilization rates of organs from elderly donors have shown the highest proportional increase during the last decade. Clinical reports support the concept of transplanting older organs. However, the engraftment of such organs has been linked to accelerated immune responses based on ageing changes per se and a proinflammatory environment subsequent to compromised injury and repair mechanism. We analyzed the clinical consequences of transplanting older donor organs and present mechanistic aspects correlating age, injury repair and effects on host immunoresponsiveness.

Age-related increases in PGD(2) expression impair respiratory DC migration, resulting in diminished T cell responses upon respiratory virus infection in mice

The morbidity and mortality associated with respiratory virus infection is felt most keenly among the elderly. T cells are necessary for viral clearance, and many age-dependent intrinsic T cell defects have been documented. However, the development of robust T cell responses in the lung also requires respiratory DCs (rDCs), which must process antigen and migrate to draining LNs (DLNs), and little is known about age-related defects in these T cell-extrinsic functions. Here, we show that increases in prostaglandin D(2) (PGD(2)) expression in mouse lungs upon aging correlate with a progressive impairment in rDC migration to DLNs. Decreased rDC migration resulted in diminished T cell responses and more severe clinical disease in older mice infected with respiratory viruses. Diminished rDC migration associated with virus-specific defects in T cell responses and was not a result of cell-intrinsic defect, rather it reflected the observed age-dependent increases in PGD(2) expression. Blocking PGD(2) function with small-molecule antagonists enhanced rDC migration, T cell responses, and survival. This effect correlated with upregulation on rDCs of CCR7, a chemokine receptor involved in DC chemotaxis. Our results suggest that inhibiting PGD(2) function may be a useful approach to enhance T cell responses against respiratory viruses in older humans.

Vaccination in the elderly

There is a general consensus that the elderly do not respond as well to vaccination as the young, but robust studies are few and far between. Most refer to influenza vaccination, but even here, adequate immunological and clinical data are surprisingly thin on the ground. The meta-analysis by Goodwin et al. from 2006 is still the most comprehensive that we have. They reviewed 31 antibody response studies comparing influenza vaccination efficacy in groups of elderly and younger adults. They reported that the adjusted odds ratio (OR) of responses in elderly versus young adults ranged from 0.24 to 0.59 for the three influenza antigens used in the vaccines. They concluded that rather than the estimated 70-90% clinical vaccine efficacy in younger adults, this figure was only 17-53% in the elderly, depending on which viruses were prevalent that year. They stated that 'this highlights the need for more immunogenic vaccine formulations for the elderly'. How to achieve this? There are three areas where we may consider alterations to increase vaccine efficacy: (i) make the vaccine more potent; (ii) use adjuvants to enhance immunity; and (iii) apply immune modulators or other interventions to alter host immunity generally. We will consider these three options, focusing on influenza vaccination, in this mini-review.

Plasmacytoid DC from aged mice down-regulate CD8 T cell responses by inhibiting cDC maturation after Encephalitozoon cuniculi infection

Age associated impairment of immune function results in inefficient vaccination, tumor surveillance and increased severity of infections. Several alterations in adaptive immunity have been observed and recent studies report age related declines in innate immune responses to opportunistic pathogens including Encephalitozoon cuniculi. We previously demonstrated that conventional dendritic cells (cDC) from 9-month-old animals exhibit sub-optimal response to E. cuniculi infection, suggesting that age associated immune senescence begins earlier than expected. We focused this study on how age affects plasmacytoid DC (pDC) function. More specifically how aged pDC affect cDC function as we observed that the latter are the predominant activators of CD8 T cells during this infection. Our present study demonstrates that pDC from middle-aged mice (12 months) suppress young (8 week old) cDC driven CD8 T cell priming against E. cuniculi infection. The suppressive effect of pDC from older mice decreased maturation of young cDC via cell contact. Aged mouse pDC exhibited higher expression of PD-L1 and blockade of their interaction with cDC via this molecule restored cDC maturation and T cell priming. Furthermore, the PD-L1 dependent suppression of cDC T cell priming was restricted to effector function of antigen-specific CD8 T cells not their expansion. To the best of our knowledge, the data presented here is the first report highlighting a cell contact dependent, PD-L1 regulated, age associated defect in a DC subpopulation that results in a sub-optimal immune response against E. cuniculi infection. These results have broad implications for design of immunotherapeutic approaches to enhance immunity for aging populations.

Morphology of the non-sensory tissue components in rat aging vomeronasal organ

With 30 figures, 3 histograms and 3 tables

SUMMARY

The vomeronasal organ (VNO) is a chemosensory organ that detects environmental pheromones. The morphology of the 'non-sensory' epithelium (NSE) of the VNO and its lamina propria, as well as how it relates to ageing has received little attention. Histological, histochemical, morphometric and ultrastructural techniques were used to study the morphological structure of the rat NSE in five adult (3 months old) and five aged (2-2.5 years old) male albino rats. In adult rats, the NSE contained dark and light columnar cells with predominance of the latter. The surface of the epithelial cells was covered with microvilli and/or cilia. The lamina propria contained serous vomeronasal glands (VNGs), smooth muscles with numerous variable-sized mitochondria, vessels including lymphatic capillaries and nerve bundles. The following changes were detected in aged rats. The NSE exhibited an increase in number of dark columnar cells. Some cells revealed a prominent cell coat, dense aggregation of filaments in the luminal cytoplasm and appearance of multinucleated cells. Their surface revealed malformed configuration. Large mitochondria (2 μm), formed by fusion, were frequently observed in the smooth muscle cells of the lamina propria. Lipid droplets were frequently detected both in the VNGs acini and in the lymphatic endothelium. Ageing affected both the cells of the tissues and the extracellular matrix.

Aging of the Innate Immune System: An Update

The relationship between advanced age and immunologic deficits is becoming an area of rapidly advancing research. Many of the clinical hurdles in the elderly population result from dysregulation of the immune system leading to the inability of the elderly to swiftly combat infection and to the increased incidence of chronic disease states and autoimmune conditions. Herein, we address the crucial alterations in the innate immune system that occur with advancing age. Specifically, we discuss how the effects of advanced age may lead to functional changes in the neutrophil, macrophage, dendritic cell, natural killer cell, and natural killer T cell populations in human and murine models that translate into aberrant innate immune responses. Furthermore, we elucidate how these changes may contribute to documented deficits in adaptive immunity as well as the pathological conditions and the increased morbidity and mortality seen in the elderly population.

Age-related changes in natural killer cell receptors from childhood through old age

Most studies on natural killer (NK) cells and aging have focused on overall cell numbers and global cytotoxic activity. NK cell functions are controlled by surface receptors belonging to three major families: killer cell immunoglobulin-like receptors (KIRs), natural cytotoxicity receptors (NCRs), and C-type lectins. The expression of these receptors was investigated from childhood through old age in T, NKT- and NK cells and also in the CD56(dim) (cytotoxic) and CD56(bright) (responsible for cytokine production) NK cell subsets. A decrease in the expression of activating receptors (NKp30 and NKp46) was observed in NK cells in elderly individuals. KIR expression was increased only in the CD56(bright) subset. Children presented similar results regarding expression of NKp30 and KIR, but not NKp46. NKG2D expression was decreased in T cells of elderly subjects. Analysis of KIR genotype revealed that KIR2DL5 and KIR2DS3 were significantly associated with old age. Cytotoxic activity was preserved from childhood through old age, suggesting that the increase of the absolute number of CD56(dim), observed in elderly, may represent a compensatory mechanism for the receptor expression alterations. This initial study provides the framework for more focused studies of this subject, which are necessary to determine whether the changing balance of NK receptor expression may influence susceptibility to infectious, inflammatory, and neoplastic diseases.

Expanding the universe of cytokines and pattern recognition receptors: galectins and glycans in innate immunity

Effective immunity relies on the recognition of pathogens and tumors by innate immune cells through diverse pattern recognition receptors (PRRs) that lead to initiation of signaling processes and secretion of pro- and anti-inflammatory cytokines. Galectins, a family of endogenous lectins widely expressed in infected and neoplastic tissues have emerged as part of the portfolio of soluble mediators and pattern recognition receptors responsible for eliciting and controlling innate immunity. These highly conserved glycan-binding proteins can control immune cell processes through binding to specific glycan structures on pathogens and tumors or by acting intracellularly via modulation of selective signaling pathways. Recent findings demonstrate that various galectin family members influence the fate and physiology of different innate immune cells including polymorphonuclear neutrophils, mast cells, macrophages, and dendritic cells. Moreover, several pathogens may actually utilize galectins as a mechanism of host invasion. In this review, we aim to highlight and integrate recent discoveries that have led to our current understanding of the role of galectins in host-pathogen interactions and innate immunity. Challenges for the future will embrace the rational manipulation of galectin-glycan interactions to instruct and shape innate immunity during microbial infections, inflammation, and cancer.

Preferential enhancement of older human T cell cytokine generation, chemotaxis, proliferation and survival by lenalidomide

Lenalidomide, an analog of thalidomide, modified responses of stimulated T cells from healthy young (ages 21-40 years) and old (≥ age 65 years) subjects. At 0.03 μM to 1 μM, lenalidomide enhanced generation of IL-2 and IFN-γ by T cell receptor-stimulated T cells of young subjects up to respective maximum increases of 17-fold and three-fold, but at 0.3 μM and 1 μM suppressed IL-17 generation. The same concentrations of lenalidomide enhanced IL-2 and IFN-γ generation by stimulated T cells of old subjects more, with greater respective maximal increases of up to 120-fold and six-fold, without suppressing IL-17 generation. Lenalidomide enhanced proliferation and suppressed apoptosis of stimulated T cells from old subjects, by IL-2-dependent mechanisms, and restored diminished T cell chemotactic responses to CCL21 and sphingosine 1-phosphate. The reversal of T cell abnormalities of immunosenescence by low concentrations of lenalidomide suggest a potential for improvement of immunity in the elderly.

Susceptibility of the aging lung to environmental injury

With an ever-increasing number of elderly individuals in the world, a better understanding of the issues associated with aging and the environment is needed. The respiratory system is one of the primary interfaces between the body and the external environment. An expanding number of studies suggest that the aging pulmonary system (>65 years) is at increased risk for adverse health effects from environmental insult, such as by air pollutants, infection, and climate change. However, the mechanism(s) for increased susceptibility in this subpopulation are not well understood. In this review, we provide a limited but comprehensive overview of how the lung ages, examples of environmental exposures associated with injury to the aging lung, and potential mechanisms underlying the increased vulnerability of the aging lung to injury from environmental factors.

The impact of varicella zoster virus: chronic pain

Herpes zoster (HZ) is a common condition that affects all age groups and both immunocompetent and immunocompromised individuals. However, it mainly impacts elderly and immunocompromised people and is associated with important and sometimes permanent detriment to quality of life and activities of daily living. Age-related decline in cell-mediated immunity (CMI) permits reactivation of varicella zoster virus (VZV) from latency. The risk of developing post-herpetic neuralgia (PHN) can be predicted using epidemiologically identified risk factors, thus indicating which patients may benefit most from protection by appropriate means, including vaccination. Despite increasing knowledge of the pathology causing PHN, the management modalities for acute HZ pain and PHN remain inadequate. Public, and probably physician, understanding of HZ and its complications is poor, potentially leading to low utilisation of HZ vaccination and delayed presentation for treatment.

Potential role of immunosenescence in cancer development

The incidence and prevalence of most cancers increase with age. The reasons for this may include tumor escape mechanisms and decreased immunosurveillance, but most are caused by the time required for carcinogenesis, according to most scientists. The immune system is a unique mechanism of defense against pathogens and possibly cancers; however, there is a body of evidence that the immune system of the aged is eroded, a phenomenon termed immunosenescence. There is a growing interest in immunosenescence and how it may contribute to the increased number of cancers with aging. Each arm of the immune system, innate and adaptive, is altered with aging, contributing to increased tumorigenesis. Understanding the contribution of immunosenescence to cancer development and progression may lead to better interventions for the elderly.