Decreased TNF-alpha synthesis by macrophages restricts cutaneous immunosurveillance by memory CD4+ T cells during aging

Tumor Necrosis Factor-Alpha: Ally and Enemy in Protean Cutaneous Sceneries

Skin is the forestage for a series of many-sided functions of tumor necrosis factor-alpha (TNF-α), a proinflammatory cytokine with staggering versatility and sizable implications for tissue homeostasis, immune responses, angiogenesis, apoptosis, local and systemic inflammation. An aberrant TNF-α-mediated crosstalk has been linked to the pathogenesis of acute and chronic skin inflammatory diseases, and indeed, TNF-α dysregulation can contribute to the development and progression of psoriasis, vitiligo, local damage following exposition to ultraviolet light radiations, cutaneous lupus erythematosus, and acne vulgaris. Therapies that target TNF-α are conspicuously used in the treatment of different skin disorders, aiming to modulate the in vivo immune functions triggered by many cutaneous cells, including keratinocytes, mast cells, or Langerhans cells, and reduce inflammation taking place within the skin. Herein, we focus on the key relationships between TNF-α and distinct skin non-neoplastic inflammatory or physiologic conditions, showing that a natural induction of TNF-α may have a protective significance but that TNF-α overproduction may be harmful or even lethal. Many questions remain unraveled in the therapeutic practice, and caution should be exercised due to eventual backlashes exerted by TNF-α in maintaining skin health or in provoking skin disease.

High all-cause mortality and increasing proportion of older adults with tuberculosis in Texas, 2008-2020

Pulmonary tuberculosis (PTB) elimination efforts must consider the global growth of the ageing population. Here we used TB surveillance data from Texas, United States (2008-2020; total n = 10656) to identify unique characteristics and outcomes in older adults (OA, ≥65 years) with PTB, compared to young adults (YA, 18-39 years) or middle-aged adults (40-64 years). We found that the proportion of OA with PTB increased from 15% in 2008 to 24% in 2020 (trend p < 0.05). Diabetes was highly prevalent in OA (32%) but not associated with adverse outcomes. Death was 13-fold higher in OA compared to YA and was 7% at the time of diagnosis which suggests diagnostic delays. However, once TB was suspected, we found no differences in culture, smear, or nucleic acid detection of mycobacteria (although less lung cavitations) in OA. During treatment, OA had less drug-resistant TB, few adverse reactions and adhered with TB treatment. We recommend training healthcare workers to 'think TB' in OA, for prompt treatment initiation to diminish deaths. Furthermore, OA should be added as a priority group to the latent TB treatment guidelines by the World Health Organization, to prevent TB disease in this highly vulnerable group.

Accumulation of immune-suppressive CD4 + T cells in aging - tempering inflammaging at the expense of immunity

The 'immune risk profile' has been shown to predict mortality in the elderly, highlighting the need to better understand age-related immune dysfunction. While aging leads to many defects affecting all arms of the immune system, this review is focused on the accrual of immuno-suppressive CD4 + T cell populations, including FoxP3 + regulatory T cells, and subsets of IL-10-producing T follicular helper cells. New data suggest that such accumulations constitute feedback mechanisms to temper the ongoing progressive low-grade inflammation that develops with age, the so-called "inflammaging", and by doing so, how they have the potential to promote healthier aging. However, they also impair effector immune responses, notably to infections, or vaccines. These studies also reinforce the idea that the aged immune system should not be considered as a poorly functional version of the young one, but more as a dynamic system in which CD4 + T cells, and other immune/non-immune subsets, differentiate, interact with their milieu and function differently than in young hosts. A better understanding of these unique interactions is thus needed to improve effector immune responses in the elderly, while keeping inflammaging under control.

Skin Cancer Microenvironment: What We Can Learn from Skin Aging?

Aging is a natural intrinsic process associated with the loss of fibrous tissue, a slower cell turnover, and a reduction in immune system competence. In the skin, the continuous exposition of environmental factors superimposes extrinsic damage, mainly due to ultraviolet radiation causing photoaging. Although not usually considered a pathogenic event, photoaging affects cutaneous biology, increasing the risk of skin carcinogenesis. At the cellular level, aging is typified by the rise of senescence cells a condition characterized by reduced or absent capacity to proliferate and aberrant hyper-secretory activity. Senescence has a double-edged sword in cancer biology given that senescence prevents the uncontrolled proliferation of damaged cells and favors their clearance by paracrine secretion. Nevertheless, the cumulative insults and the poor clearance of injured cells in the elderly increase cancer incidence. However, there are not conclusive data proving that aged skin represents a permissive milieu for tumor onset. On the other hand, tumor cells are capable of activating resident fibroblasts onto a pro-tumorigenic phenotype resembling those of senescent fibroblasts suggesting that aged fibroblasts might facilitate cancer progression. This review discusses changes that occur during aging that can prime neoplasm or increase the aggressiveness of melanoma and non-melanoma skin cancer.

Markers of the ageing macrophage: a systematic review and meta-analysis

Introduction

Ageing research is establishing macrophages as key immune system regulators that undergo functional decline. Due to heterogeneity between species and tissue populations, a plethora of data exist and the power of scientific conclusions can vary substantially. This meta-analysis by information content (MAIC) and systematic literature review (SLR) aims to determine overall changes in macrophage gene and protein expression, as well as function, with age.

Methods

PubMed was utilized to collate peer-reviewed literature relating to macrophage ageing. Primary studies comparing macrophages in at least two age groups were included. Data pertaining to gene or protein expression alongside method used were extracted for MAIC analysis. For SLR analysis, data included all macrophage-specific changes with age, as well as species, ontogeny and age of groups assessed.

Results

A total of 240 studies were included; 122 of which qualified for MAIC. The majority of papers focussed on changes in macrophage count/infiltration as a function of age, followed by gene and protein expression. The MAIC found iNOS and TNF to be the most commonly investigated entities, with 328 genes and 175 proteins showing consistent dysregulation with age across the literature. Overall findings indicate that cytokine secretion and phagocytosis are reduced and reactive oxygen species production is increased in the ageing macrophage.

Discussion

Collectively, our analysis identifies critical regulators in macrophage ageing that are consistently dysregulated, highlighting a plethora of targets for further investigation. Consistent functional changes with age found here can be used to confirm an ageing macrophage phenotype in specific studies and experimental models.

The central role of DNA damage in immunosenescence

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

Impact of aging on immunity in the context of COVID-19, HIV, and tuberculosis

Knowledge of aging biology needs to be expanded due to the continuously growing number of elderly people worldwide. Aging induces changes that affect all systems of the body. The risk of cardiovascular disease and cancer increases with age. In particular, the age-induced adaptation of the immune system causes a greater susceptibility to infections and contributes to the inability to control pathogen growth and immune-mediated tissue damage. Since the impact of aging on immune function, is still to be fully elucidated, this review addresses some of the recent understanding of age-related changes affecting key components of immunity. The emphasis is on immunosenescence and inflammaging that are impacted by common infectious diseases that are characterized by a high mortality, and includes COVID-19, HIV and tuberculosis.

Dynamic polarization of tumor-associated macrophages and their interaction with intratumoral T cells in an inflamed tumor microenvironment: from mechanistic insights to therapeutic opportunities

Immunotherapy has brought a paradigm shift in the treatment of tumors in recent decades. However, a significant proportion of patients remain unresponsive, largely due to the immunosuppressive tumor microenvironment (TME). Tumor-associated macrophages (TAMs) play crucial roles in shaping the TME by exhibiting dual identities as both mediators and responders of inflammation. TAMs closely interact with intratumoral T cells, regulating their infiltration, activation, expansion, effector function, and exhaustion through multiple secretory and surface factors. Nevertheless, the heterogeneous and plastic nature of TAMs renders the targeting of any of these factors alone inadequate and poses significant challenges for mechanistic studies and clinical translation of corresponding therapies. In this review, we present a comprehensive summary of the mechanisms by which TAMs dynamically polarize to influence intratumoral T cells, with a focus on their interaction with other TME cells and metabolic competition. For each mechanism, we also discuss relevant therapeutic opportunities, including non-specific and targeted approaches in combination with checkpoint inhibitors and cellular therapies. Our ultimate goal is to develop macrophage-centered therapies that can fine-tune tumor inflammation and empower immunotherapy.

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.

The dark side of Tregs during aging

In the last century, we have seen a dramatic rise in the number of older persons globally, a trend known as the grey (or silver) tsunami. People live markedly longer than their predecessors worldwide, due to remarkable changes in their lifestyle and in progresses made by modern medicine. However, the older we become, the more susceptible we are to a series of age-related pathologies, including infections, cancers, autoimmune diseases, and multi-morbidities. Therefore, a key challenge for our modern societies is how to cope with this fragile portion of the population, so that everybody could have the opportunity to live a long and healthy life. From a holistic point of view, aging results from the progressive decline of various systems. Among them, the distinctive age-dependent changes in the immune system contribute to the enhanced frailty of the elderly. One of these affects a population of lymphocytes, known as regulatory T cells (Tregs), as accumulating evidence suggest that there is a significant increase in the frequency of these cells in secondary lymphoid organs (SLOs) of aged animals. Although there are still discrepancies in the literature about modifications to their functional properties during aging, mounting evidence suggests a detrimental role for Tregs in the elderly in the context of bacterial and viral infections by suppressing immune responses against non-self-antigens. Interestingly, Tregs seem to also contribute to the reduced effectiveness of immunizations against many pathogens by limiting the production of vaccine-induced protective antibodies. In this review, we will analyze the current state of understandings about the role of Tregs in acute and chronic infections as well as in vaccination response in both humans and mice. Lastly, we provide an overview of current strategies for Treg modulation with potential future applications to improve the effectiveness of vaccines in older individuals.

A subset of gut leukocytes has telomerase-dependent "hyper-long" telomeres and require telomerase for function in zebrafish

BACKGROUND

Telomerase, the enzyme capable of elongating telomeres, is usually restricted in human somatic cells, which contributes to progressive telomere shortening with cell-division and ageing. T and B-cells cells are somatic cells that can break this rule and can modulate telomerase expression in a homeostatic manner. Whereas it seems intuitive that an immune cell type that depends on regular proliferation outbursts for function may have evolved to modulate telomerase expression it is less obvious why others may also do so, as has been suggested for macrophages and neutrophils in some chronic inflammation disease settings. The gut has been highlighted as a key modulator of systemic ageing and is a key tissue where inflammation must be carefully controlled to prevent dysfunction. How telomerase may play a role in innate immune subtypes in the context of natural ageing in the gut, however, remains to be determined.

RESULTS

Using the zebrafish model, we show that subsets of gut immune cells have telomerase-dependent"hyper-long" telomeres, which we identified as being predominantly macrophages and dendritics (mpeg1.1+ and cd45+mhcII+). Notably, mpeg1.1+ macrophages have much longer telomeres in the gut than in their haematopoietic tissue of origin, suggesting that there is modulation of telomerase in these cells, in the gut. Moreover, we show that a subset of gut mpeg1.1+ cells express telomerase (tert) in young WT zebrafish, but that the relative proportion of these cells decreases with ageing. Importantly, this is accompanied by telomere shortening and DNA damage responses with ageing and a telomerase-dependent decrease in expression of autophagy and immune activation markers. Finally, these telomerase-dependent molecular alterations are accompanied by impaired phagocytosis of E. coli and increased gut permeability in vivo.

CONCLUSIONS

Our data show that limiting levels of telomerase lead to alterations in gut immunity, impacting on the ability to clear pathogens in vivo. These are accompanied by increased gut permeability, which, together, are likely contributors to local and systemic tissue degeneration and increased susceptibility to infection with ageing.

Photoaging: UV radiation-induced inflammation and immunosuppression accelerate the aging process in the skin

Background

Excessive exposure of the skin to UV radiation (UVR) triggers a remodeling of the immune system and leads to the photoaging state which is reminiscent of chronological aging. Over 30 years ago, it was observed that UVR induced an immunosuppressive state which inhibited skin contact hypersensitivity.

Methods

Original and review articles encompassing inflammation and immunosuppression in the photoaging and chronological aging processes were examined from major databases including PubMed, Scopus, and Google Scholar.

Results

Currently it is known that UVR treatment can trigger a cellular senescence and inflammatory state in the skin. Chronic low-grade inflammation stimulates a counteracting immunosuppression involving an expansion of immunosuppressive cells, e.g., regulatory T cells (Treg), myeloid-derived suppressor cells (MDSC), and regulatory dendritic cells (DCreg). This increased immunosuppressive activity not only suppresses the function of effector immune cells, a state called immunosenescence, but it also induces bystander degeneration of neighboring cells. Interestingly, the chronological aging process also involves an accumulation of pro-inflammatory senescent cells and signs of chronic low-grade inflammation, called inflammaging. There is also clear evidence that inflammaging is associated with an increase in anti-inflammatory and immunosuppressive activities which promote immunosenescence.

Conclusion

It seems that photoaging and normal aging evoke similar processes driven by the remodeling of the immune system. However, it is likely that there are different molecular mechanisms inducing inflammation and immunosuppression in the accelerated photoaging and the chronological aging processes.

Cellular Carcinogenesis: Role of Polarized Macrophages in Cancer Initiation

Simple Summary

Inflammation is a hallmark of many cancers. Macrophages are key participants in innate immunity and important drivers of inflammation. When chronically polarized beyond normal homeostatic responses to infection, injury, or aging, macrophages can express several pro-carcinogenic phenotypes. In this review, evidence supporting polarized macrophages as endogenous sources of carcinogenesis is discussed. In addition, the depletion or modulation of macrophages by small molecule inhibitors and probiotics are reviewed as emerging strategies in cancer prevention.

Abstract

Inflammation is an essential hallmark of cancer. Macrophages are key innate immune effector cells in chronic inflammation, parainflammation, and inflammaging. Parainflammation is a form of subclinical inflammation associated with a persistent DNA damage response. Inflammaging represents low-grade inflammation due to the dysregulation of innate and adaptive immune responses that occur with aging. Whether induced by infection, injury, or aging, immune dysregulation and chronic macrophage polarization contributes to cancer initiation through the production of proinflammatory chemokines/cytokines and genotoxins and by modulating immune surveillance. This review presents pre-clinical and clinical evidence for polarized macrophages as endogenous cellular carcinogens in the context of chronic inflammation, parainflammation, and inflammaging. Emerging strategies for cancer prevention, including small molecule inhibitors and probiotic approaches, that target macrophage function and phenotype are also discussed.

Establishment of an Ex Vivo Tissue Culture Model for Evaluation of Antitumor Efficacy in Clear Cell Renal Cell Carcinoma

There are many potential immunotherapeutic targets for cancer immunotherapy, which should be assessed for efficacy before they enter clinical trials. Here we established an ex vivo cultured patient-derived tumor tissue model to evaluate antitumor effectiveness of one VISTA inhibitor, given that our previous study showed that VISTA was selectively highly expressed in human clear cell renal cell carcinoma (ccRCC) tumors. We observed that all the tested patients responded to the anti-VISTA monoclonal antibody as manifested by TNF-α production, but only a small fraction were responders to the anti-PD-1 antibody. Co-blockade of VISTA and PD-1 resulted in a synergistic effect in 20% of RCC patients. Taken together, these findings indicate that this ex vivo tumor slice culture model represents a viable tool to evaluate antitumor efficacies for the inhibitors of immune checkpoints and further supports that VISTA could serve as a promising target for immunotherapy in ccRCC.

Skin Aging, Cellular Senescence and Natural Polyphenols

The skin, being the barrier organ of the body, is constitutively exposed to various stimuli impacting its morphology and function. Senescent cells have been found to accumulate with age and may contribute to age-related skin changes and pathologies. Natural polyphenols exert many health benefits, including ameliorative effects on skin aging. By affecting molecular pathways of senescence, polyphenols are able to prevent or delay the senescence formation and, consequently, avoid or ameliorate aging and age-associated pathologies of the skin. This review aims to provide an overview of the current state of knowledge in skin aging and cellular senescence, and to summarize the recent in vitro studies related to the anti-senescent mechanisms of natural polyphenols carried out on keratinocytes, melanocytes and fibroblasts. Aged skin in the context of the COVID-19 pandemic will be also discussed.

Promises and challenges of senolytics in skin regeneration, pathology and ageing

The research of the last two decades has defined a crucial role of cellular senescence in both the physiology and pathology of skin, and senescent cells have been detected in conditions including development, regeneration, aging, and disease. The pathophysiology of cellular senescence in skin is complex as the phenotype of senescence pertains to several different cell types including fibroblasts, keratinocytes and melanocytes, among others. Paradoxically, the transient presence of senescent cells is believed to be beneficial in the context of development and wound healing, while the chronic presence of senescent cells is detrimental in the context of aging, diseases, and chronic wounds, which afflict predominantly the elderly. Identifying strategies to prevent senescence induction or reduce senescent burden in the skin could broadly benefit the aging population. Senolytics, drugs known to specifically eliminate senescent cells while preserving non-senescent cells, are being intensively studied for use in the clinical setting. Here, we review recent research on skin senescence, on the methods for the detection of senescent cells and describe promises and challenges related to the application of senolytic drugs. This article is part of the Special Issue - Senolytics - Edited by Joao Passos and Diana Jurk.

Insulin/IGF-1 signaling promotes immunosuppression via the STAT3 pathway: impact on the aging process and age-related diseases

BACKGROUND

The insulin/IGF-1 signaling pathway has a major role in the regulation of longevity both in Caenorhabditis elegans and mammalian species, i.e., reduced activity of this pathway extends lifespan, whereas increased activity accelerates the aging process. The insulin/IGF-1 pathway controls protein and energy metabolism as well as the proliferation and differentiation of insulin/IGF-1-responsive cells. Insulin/IGF-1 signaling also regulates the functions of the innate and adaptive immune systems. The purpose of this review was to elucidate whether insulin/IGF-1 signaling is linked to immunosuppressive STAT3 signaling which is known to promote the aging process.

METHODS

Original and review articles encompassing the connections between insulin/IGF-1 and STAT3 signaling were examined from major databases including Pubmed, Scopus, and Google Scholar.

RESULTS

The activation of insulin/IGF-1 receptors stimulates STAT3 signaling through the JAK and AKT-driven signaling pathways. STAT3 signaling is a major activator of immunosuppressive cells which are able to counteract the chronic low-grade inflammation associated with the aging process. However, the activation of STAT3 signaling stimulates a negative feedback response through the induction of SOCS factors which not only inhibit the activity of insulin/IGF-1 receptors but also that of many cytokine receptors. The inhibition of insulin/IGF-1 signaling evokes insulin resistance, a condition known to be increased with aging. STAT3 signaling also triggers the senescence of both non-immune and immune cells, especially through the activation of p53 signaling.

CONCLUSIONS

Given that cellular senescence, inflammaging, and counteracting immune suppression increase with aging, this might explain why excessive insulin/IGF-1 signaling promotes the aging process.

Immunosuppressive network promotes immunosenescence associated with aging and chronic inflammatory conditions

The functional competence of the immune system gradually declines with aging, a process called immunosenescence. The age-related remodelling of the immune system affects both adaptive and innate immunity. In particular, a chronic low-grade inflammation, termed inflammaging, is associated with the aging process. Immunosenescence not only is present in inflammaging state, but it also occurs in several pathological conditions in conjunction with chronic inflammation. It is known that persistent inflammation stimulates a counteracting compensatory immunosuppression intended to protect host tissues. Inflammatory mediators enhance myelopoiesis and induce the generation of immature myeloid-derived suppressor cells (MDSC) which in mutual cooperation stimulates the immunosuppressive network. Immunosuppressive cells, especially MDSCs, regulatory T cells (Treg), and M2 macrophages produce immunosuppressive factors, e.g., TGF-β, IL-10, ROS, arginase-1 (ARG1), and indoleamine 2,3-dioxygenase (IDO), which suppress the functions of CD4/CD8T and B cells as well as macrophages, natural killer (NK) cells, and dendritic cells. The immunosuppressive armament (i) inhibits the development and proliferation of immune cells, (ii) decreases the cytotoxic activity of CD8T and NK cells, (iii) prevents antigen presentation and antibody production, and (iv) suppresses responsiveness to inflammatory mediators. These phenotypes are the hallmarks of immunosenescence. Immunosuppressive factors are able to control the chromatin landscape, and thus, it seems that the immunosenescence state is epigenetically regulated.

Interferon Gamma Release Assays for Detection of Latent Mycobacterium tuberculosis in Elderly Hispanics

Background:

Interferon gamma release assays (IGRAs) are used to detect latent Mycobacterium tuberculosis (M.tb) infection (LTBI) in adults, but their performance in older people is not well-established. We evaluated IGRAs for LTBI detection in older Hispanic recent TB contacts (ReC) or community controls (CoC).

Methods:

Cross-sectional assessment of LTBI with T-SPOT.TB and/or QuantiFERON-Gold in-tube or –Plus assay in older (≥60 years) and adult (18–50 years) Hispanic people.

Results:

We enrolled 193 CoC (119 adults, 74 older persons) and 459 ReC (361 adults, 98 older persons). LTBI positivity increased with age in CoC (19%–59%, P<0.001), but was similar in ReC (59%–69%, P=0.329). Older people had lower concordance between IGRAs (kappa 0.465 vs 0.688 in adults) and more inconclusive results (indeterminate/borderline 11.6% vs 5.8% in adults, P=0.012). With simultaneous IGRAs, inconclusive results were resolved as positive or negative with the other IGRA. The magnitude of response to M.tb peptides in IGRAs was similar among age groups, but responsiveness to mitogens was lower in older people.

Conclusions:

IGRAs are suitable for LTBI detection in older people. Discordant and inconclusive findings are more prevalent in older people, but results are resolved when IGRA is repeated with a different IGRA test.

The old guard: Age-related changes in microglia and their consequences

Among all major organs, the brain is one of the most susceptible to the inexorable effects of aging. Throughout the last decades, several studies in human cohorts and animal models have revealed a plethora of age-related changes in the brain, including reduced neurogenesis, oxidative damage, mitochondrial dysfunction and cell senescence. As the main immune effectors and first responders of the nervous tissue, microglia are at the center of these events. These cells experience irrevocable changes as a result from cumulative exposure to environmental triggers, such as stress, infection and metabolic dysregulation. The age-related immunosenescent phenotype acquired by microglia is characterized by profound modifications in their transcriptomic profile, secretome, morphology and phagocytic activity, which compromise both their housekeeping and defensive functions. As a result, aged microglia are no longer capable of establishing effective immune responses and sustaining normal synaptic activity, directly contributing to age-associated cognitive decline and neurodegeneration. This review discusses how lifestyle and environmental factors drive microglia dysfunction at the molecular and functional level, also highlighting possible interventions to reverse aging-associated damage to the nervous and immune systems.

Age-related changes in ocular mucosal tolerance: Lessons learned from gut and respiratory tract immunity

The ocular surface is the part of the visual system directly exposed to the environment, and it comprises the cornea, the first refractive tissue layer and its surrounding structures. The ocular surface has evolved to keep the cornea smooth and wet, a prerequisite for proper sight, and also protected. To this aim, the ocular surface is a bona fide mucosal niche with an immune system capable of fighting against dangerous pathogens. However, due to the potential harmful effects of uncontrolled inflammation, the ocular surface has several mechanisms to keep the immune response in check. Specifically, the ocular surface is maintained inflammation-free and functional by a particular form of peripheral tolerance known as mucosal tolerance, markedly different from the immune privilege of intraocular structures. Remarkably, conjunctival tolerance is akin to the oral and respiratory tolerance mechanisms found in the gut and airways, respectively. And also similarly, this form of immunoregulation in the eye is affected by ageing just as it is in the digestive and respiratory tracts. With ageing comes an increased prevalence of immune-based ocular surface disorders, which could be related to an age-related impairment of conjunctival tolerance. The purpose of this review was to summarize the present knowledge of ocular mucosal tolerance and how it is affected by the ageing process in the light of the current literature on mucosal immunoregulation of the gut and airways.

Feed-forward regulation between cellular senescence and immunosuppression promotes the aging process and age-related diseases

Aging is a progressive degenerative process involving a chronic low-grade inflammation and the accumulation of senescent cells. One major issue is to reveal the mechanisms which promote the deposition of pro-inflammatory senescent cells within tissues. The accumulation involves mechanisms which increase cellular senescence as well as those inhibiting the clearance of senescent cells from tissues. It is known that a persistent inflammatory state evokes a compensatory immunosuppression which inhibits pro-inflammatory processes by impairing the functions of effector immune cells, e.g., macrophages, T cells and natural killer (NK) cells. Unfortunately, these cells are indispensable for immune surveillance and the subsequent clearance of senescent cells, i.e., the inflammation-induced counteracting immunosuppression prevents the cleansing of host tissues. Moreover, senescent cells can also repress their own clearance by expressing inhibitors of immune surveillance and releasing the ligands of NKG2D receptors which impair their surveillance by NK and cytotoxic CD8⁺ T cells. It seems that cellular senescence and immunosuppression establish a feed-forward process which promotes the aging process and age-related diseases. I will examine in detail the immunosuppressive mechanisms which impair the surveillance and clearance of pro-inflammatory senescent cells with aging. In addition, I will discuss several therapeutic strategies to halt the degenerative feed-forward circuit associated with the aging process and age-related diseases.

Aging and the immune response in diabetic peripheral neuropathy

A large proportion of older individuals with diabetes go on to develop diabetic peripheral neuropathy (DPN). DPN is associated with an increase in inflammatory cells within the peripheral nerve, activation of nuclear factor kappa-light-chain-enhancer of activated B cells and receptors for advanced glycation end products/advanced glycation end products pathways, aberrant cytokine expression, oxidative stress, ischemia, as well as pro-inflammatory changes in the bone marrow; all processes that may be exacerbated with age. We review the immunological features of DPN and discuss whether age-related changes in relevant immunological areas may contribute to age being a risk factor for DPN.

The ocular surface immune system through the eyes of aging

Since the last century, advances in healthcare, housing, and education have led to an increase in life expectancy. Longevity is accompanied by a higher prevalence of age-related diseases, such as cancer, autoimmunity, diabetes, and infection, and part of this increase in disease incidence relates to the significant changes that aging brings about in the immune system. The eye is not spared by aging either, presenting with age-related disorders of its own, and interestingly, many of these diseases have immune pathophysiology. Being delicate organs that must be exposed to the environment in order to capture light, the eyes are endowed with a mucosal environment that protects them, the so-called ocular surface. As in other mucosal sites, immune responses at the ocular surface need to be swift and potent to eliminate threats but are at the same time tightly controlled to prevent excessive inflammation and bystander damage. This review will detail how aging affects the mucosal immune response of the ocular surface as a whole and how this process relates to the higher incidence of ocular surface disease in the elderly.

Can blocking inflammation enhance immunity during aging?

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

Basal-like breast cancer with low TGFβ and high TNFα pathway activity is rich in activated memory CD4 T cells and has a good prognosis

Basal-like breast cancer (BLBC) is a type of high-grade invasive breast cancer with high risk of recurrence, metastases, and poor survival. Immune activation in BLBC is a key factor that influences both cancer progression and therapeutic response, although its molecular mechanisms are not well clarified. In this study, we examined five cancer immunity-related pathways (IFNα, IFNγ, STAT3, TGFβ and TNFα) in four large independent breast cancer cohorts (n = 6,381) and their associations with the prognosis of breast cancer subtypes. Activities of the 5 pathways were calculated based on corresponding pathway signatures and associations between pathways and clinical outcomes were examined by survival analysis. Among the five PAM50-based subtypes, BLBC had the highest IFNα, IFNγ, TNFα pathway activities, and the lowest TGFβ activity. The IFNα, IFNγ, TNFα pathway activities were negatively correlated with BLBC recurrence. In contrast, positive association and no association with BLBC recurrence were observed for TGFβ and STAT3 pathways, respectively. TNFα/TGFβ pathway combination improved the prediction of recurrence and chemotherapy response of BLBCs. Immune cell subset analysis in BLBC showed that M0, M1 and M2 macrophage levels were associated with either TNFα or TGFβ pathways, whereas the level of activated memory CD4 T cells were associated with both pathways. Moreover, this T cell subset was most abundant in BLBCs with low TGFβ and high TNFα pathway activities. These results suggested that cooperation of TNFα and TGFβ signaling may be involved in the regulation of memory T cells and anti-cancer immunity in BLBCs. Our data also demonstrate that TNFα/TGFβ pathway combination may represent a better biomarker for BLBC prognosis and clinical management.

Immunosenescence Study of T Cells: A Systematic Review

Background

Aging is accompanied by alterations in immune response which leads to increased susceptibility to infectious diseases, cancer, autoimmunity, and inflammatory disorders. This decline in immune function is termed as immunosenescence; however, the mechanisms are not fully elucidated. Experimental approaches of adaptive immunity, particularly for T cells, have been the main focus of immunosenescence research. This systematic review evaluates and discusses T cell markers implicated in immunosenescence.

Objective

To determine the best flow cytometry markers of circulating T cells associated with immunosenescence.

Methods

We systematically queried PubMed, MEDLINE, EBSCO, and BVS databases for original articles focused on two age groups of healthy humans: 18–44 (young adults) and >60 (older adults) years. In accordance with the Cochrane methodology, we synthesized data through qualitative descriptions and quantitative random effects meta-analysis due to extensive heterogeneity.

Results

A total of 36 studies conducted in the last 20 years were included for the qualitative analysis and four out of these studies were used to perform the meta-analysis. A significant decrease in naïve T cell subset was observed in older adults compared to young adults. Primary markers used to identify senescent cells were loss of CD28 and increased expression of CD57 and KLRG1 in terminally-differentiated memory T cell subset in older adults. Moreover, we observed an increase in proinflammatory cytokines and decrease in telomere length in old adult T cells. It was not possible to perform quantitative synthesis on cell markers, cytokines, and telomere length because of the significant variations between the groups, which is attributed to differences in protocols and unreported measurements, thus generating a high risk of bias.

Conclusions

Heterogeneity among studies in terms of data report, measurement techniques and high risk of bias were major impediments for performing a robust statistical analysis that could aid the identification of eligible flow cytometry markers of immunosenescence phenotype in T cells.

Recruitment of inflammatory monocytes by senescent fibroblasts inhibits antigen-specific tissue immunity during human aging

We have previously shown that healthy older adults exhibit reduced cutaneous immune responses during a varicella zoster virus (VZV) antigen challenge that correlated with a nonspecific inflammatory response to the injection itself. Here we found that needle damage during intradermal injections in older adults led to an increase in the number of cutaneous senescent fibroblasts expressing CCL2, resulting in the local recruitment of inflammatory monocytes. These infiltrating monocytes secreted prostaglandin E2, which inhibited resident memory T cell activation and proliferation. Pretreatment of older participants with a p38 mitogen-activated protein kinase inhibitor in vivo decreased CCL2 expression and inhibited monocyte recruitment and secretion of prostaglandin E2. This coincided with an increased response to VZV antigen challenge in the skin. Our results point to a series of molecular and cellular mechanisms that link cellular senescence, tissue damage, excessive inflammation and reduced immune responsiveness in human skin and demonstrate that tissue-specific immunity can be restored in older adults by short-term inhibition of inflammatory responses.

Blockade of CCL2/CCR2 Signaling Pathway Exerts Anti-Inflammatory Effects and Attenuates Gestational Diabetes Mellitus in a Genetic Mice Model

The chemokine (C-C motif) ligand 2 (CCL2) and its receptor CCR2 are involved in gestational diabetes mellitus (GDM). The present study aims to explore the effects of CCL2 blocking on GDM. Serum CCL2, interleukin (IL)-6, and tumor necrosis factor (TNF)-α were determined in GDM patients and healthy volunteers. C57BL/KsJdb/+mouse was used as the GDM model and CCL2 antibody (αCCL2) was applied. Flow cytometry was applied to determine the frequency of macrophages. Quantitative reverse transcription PCR (RT-qPCR) and western blot were determined to detect the mRNA and protein expressions, respectively. Enzyme-linked immunosorbent assay (ELISA) was applied to determine the levels of inflammatory cytokines and serum insulin. Serum CCL2 was correlated with inflammatory cytokines (IL-6 and TNF-α) in the GDM patients. Besides, the results showed high expressions of CCL2 in the visceral adipose tissue (VAT) and placenta tissue in the GDM mice. Flow cytometry and immunohistochemistry (IHC) staining showed the accumulations of macrophages in these tissues. Treatment of αCCL2 attenuated the GDM symptoms and ameliorated the inflammation. Furthermore, the treatment of αCCL2 improved reproductive outcomes in the GDM mice. Blockade of CCL2 attenuated GDM symptoms and reduced inflammatory cytokines in a genetic mice model.

Age-related transcriptome changes in melanoma patients with tumor-positive sentinel lymph nodes

Age is an important factor for determining the outcome of melanoma patients. Sentinel lymph node (SLN) status is also a strong predictor of survival for melanoma. Paradoxically, older melanoma patients have a lower incidence of SLN metastasis but a higher mortality rate when compared with their younger counterparts. The mechanisms that underlie this phenomenon remain unknown. This study uses three independent datasets of RNA samples from patients with melanoma metastatic to the SLN to identify age-related transcriptome changes in SLNs and their association with outcome. Microarray was applied to the first dataset of 97 melanoma patients. NanoString was performed in the second dataset to identify the specific immune genes and pathways that are associated with recurrence in younger versus older patients. qRT-PCR analysis was used in the third dataset of 36 samples to validate the differentially expressed genes (DEGs) from microarray and NanoString. These analyses show that FOS, NR4A, and ITGB1 genes were significantly higher in older melanoma patients with positive SLNs. IRAK3- and Wnt10b-related genes are the major pathways associated with recurrent melanoma in younger and older patients with tumor-positive SLNs, respectively. This study aims to elucidate age-related differences in SLNs in the presence of nodal metastasis.

The impact of ageing on monocytes and macrophages

Ageing is a global burden. Increasing age is associated with increased incidence of infections and cancer and decreased vaccine efficacy. This increased morbidity observed with age, is believed to be due in part to a decline in adaptive immunity, termed immunosenescence. However not all aspects of immunity decrease with age as ageing presents with systemic low grade chronic inflammation, characterised by elevated concentrations of mediators such as IL-6, TNFα and C Reactive protein (CRP). Inflammation is a strong predictor of morbidity and mortality, and chronic inflammation is known to be detrimental to a functioning immune system. Although the source of the inflammation is much discussed, the key cells which are believed to facilitate the inflammageing phenomenon are the monocytes and macrophages. In this review we detail how macrophage and monocyte phenotype and function change with age. The impact of ageing on macrophages includes decreased phagocytosis and immune resolution, increased senescent-associated markers, increased inflammatory cytokine production, reduced autophagy, and a decrease in TLR expression. With monocytes there is an increase in circulating CD16⁺ monocytes, decreased type I IFN production, and decreased efferocytosis. In conclusion, we believe that monocytes and macrophages contribute to immunosenescence and inflammageing and as a result have an important role in defective immunity with age.

Dysregulation of leukocyte trafficking in ageing: Causal factors and possible corrective therapies

Ageing is a universal biological phenomenon that is accompanied by the development of chronic, low-grade inflammation and remodelling of the immune system resulting in compromised immune function. In this review, we explore how the trafficking of innate and adaptive immune cells under homeostatic and inflammatory conditions is dysregulated in ageing. We particularly highlight the age-related changes in the expression of adhesion molecules and chemokine receptor/ligands, and the accumulation of senescent cells that drive modulated leukocyte trafficking. These age-related changes to leukocyte trafficking are multifactorial and specific to leukocyte subset, tissue, type of vascular bed, and inflammatory status. However, dysregulated leukocyte trafficking ultimately affects immune responses in older adults. We therefore go on to discuss approved drugs, including anti-integrins, anti-chemokines and statins, as well as novel therapeutics that may be used to target dysregulated leukocyte trafficking in ageing, improve immune responses and delay the onset of age-related diseases.

Vitamin D3 replacement enhances antigen-specific immunity in older adults

Introduction

Ageing is associated with increased number of infections, decreased vaccine efficacy and increased systemic inflammation termed inflammageing. These changes are reflected by reduced recall responses to varicella zoster virus (VZV) challenge in the skin of older adults. Vitamin D deficiency is more common in the old and has been associated with frailty and increased inflammation. In addition, vitamin D increases immunoregulatory mechanisms and therefore has the potential to inhibit inflammageing.

Objectives

We investigated the use of vitamin D₃ replacement to enhance cutaneous antigen-specific immunity in older adults (≥65 years).

Methods

Vitamin D insufficient older adults (n = 18) were administered 6400IU of vitamin D₃/day orally for 14 weeks. Antigen-specific immunity to VZV was assessed by clinical score assessment of the injection site and transcriptional analysis of skin biopsies collected from challenged injection sites pre- and post-vitamin D₃ replacement.

Results

We showed that older adults had reduced VZV-specific cutaneous immune response and increased non-specific inflammation as compared to young. Increased non-specific inflammation observed in the skin of older adults negatively correlated with vitamin D sufficiency. We showed that vitamin D₃ supplementation significantly increased the response to cutaneous VZV antigen challenge in older adults. This enhancement was associated with a reduction in inflammatory monocyte infiltration with a concomitant enhancement of T cell recruitment to the site of antigen challenge in the skin.

Conclusion

Vitamin D₃ replacement can boost antigen-specific immunity in older adults with sub-optimal vitamin D status.

Targeting Inflammation and Immunosenescence to Improve Vaccine Responses in the Elderly

One of the most appreciated consequences of immunosenescence is an impaired response to vaccines with advanced age. While most studies report impaired antibody responses in older adults as a correlate of vaccine efficacy, it is now widely appreciated that this may fail to identify important changes occurring in the immune system with age that may affect vaccine efficacy. The impact of immunosenescence on vaccination goes beyond the defects on antibody responses as T cell-mediated responses are reshaped during aging and certainly affect vaccination. Likewise, age-related changes in the innate immune system may have important consequences on antigen presentation and priming of adaptive immune responses. Importantly, a low-level chronic inflammatory status known as inflammaging has been shown to inhibit immune responses to vaccination and pharmacological strategies aiming at blocking baseline inflammation can be potentially used to boost vaccine responses. Yet current strategies aiming at improving immunogenicity in the elderly have mainly focused on the use of adjuvants to promote local inflammation. More research is needed to understand the role of inflammation in vaccine responses and to reconcile these seemingly paradoxical observations. Alternative approaches to improve vaccine responses in the elderly include the use of higher vaccine doses or alternative routes of vaccination showing only limited benefits. This review will explore novel targets and potential new strategies for enhancing vaccine responses in older adults, including the use of anti-inflammatory drugs and immunomodulators.

Immunesenescence: A Predisposing Risk Factor for the Development of COVID-19?

Bearing a strong resemblance to the phenotypic and functional remodeling of the immune system that occurs during aging (termed immunesenescence), the immune response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of Coronavirus disease 2019 (COVID-19), is characterized by an expansion of inflammatory monocytes, functional exhaustion of lymphocytes, dysregulated myeloid responses and the presence of highly activated senescent T cells. Alongside advanced age, male gender and pre-existing co-morbidities [e.g., obesity and type 2 diabetes (T2D)] are emerging as significant risk factors for COVID-19. Interestingly, immunesenescence is more profound in males when compared to females, whilst accelerated aging of the immune system, termed premature immunesenescence, has been described in obese subjects and T2D patients. Thus, as three distinct demographic groups with an increased susceptibility to COVID-19 share a common immune profile, could immunesenescence be a generic contributory factor in the development of severe COVID-19? Here, by focussing on three key aspects of an immune response, namely pathogen recognition, elimination and resolution, we address this question by discussing how immunesenescence may weaken or exacerbate the immune response to SARS-CoV-2. We also highlight how aspects of immunesenescence could render potential COVID-19 treatments less effective in older adults and draw attention to certain therapeutic options, which by reversing or circumventing certain features of immunesenescence may prove to be beneficial for the treatment of groups at high risk of severe COVID-19.

Exosomal vesicles enhance immunosuppression in chronic inflammation: Impact in cellular senescence and the aging process

Exosomes represent an evolutionarily conserved signaling pathway which can act as an alarming mechanism in responses to diverse stresses, e.g. chronic inflammation activates the budding of exosomal vesicles in both immune and non-immune cells. Exosomes can contain both pro- and anti-inflammatory cargos but in chronic inflammation, exosomes mostly carry immunosuppressive cargos, e.g. enzymes and miRNAs. The aging process is associated with chronic low-grade inflammation and the accumulation of pro-inflammatory senescent cells into tissues. There is clear evidence that aging increases the number of exosomes in both the circulation and tissues. Especially, the secretion of immunosuppressive exosomes robustly increases from senescent cells. There are observations that the exosomes from senescent cells are involved in the expansion of senescence into neighbouring cells. Interestingly, the age-related exosomes contain immune suppressive cargos which enhance the immunosuppression within recipient immune cells, i.e. tissue-resident and recruited immune cells including M2 macrophages, myeloid-derived suppressor cells (MDSC), and regulatory T cells (Treg). It seems that increased immunosuppression with aging impairs the clearance of senescent cells and their accumulation within tissues augments the aging process.

The Pathobiology of Skin Aging: New Insights into an Old Dilemma

Long considered both physiologic and inevitable, skin aging is a degenerative phenomenon whereby both intrinsic and environmental factors conspire to produce an authentic disease. The consequences of this disorder are many and varied, ranging from atrophy and fragility to defective repair to deficient immunity and vulnerability to certain infections. The pathobiologic basis for skin aging remains poorly understood. At a cellular level, stem cell dysfunction and attrition appear to be key events, and both genetic and epigenetic factors are involved in a complex interplay that over time results in deterioration of our main protective interface with the external environment. Past and current understanding of the cellular and molecular intricacies of skin aging provide a foundation for future approaches designed to thwart the aging phenotype. Herein, the authors provide a review of current insights into skin aging, including the mechanisms of skin aging, the role of stem cells in skin aging and the implications of skin aging for the microbiome and for the development of cancer. Conquest of the oft overlooked disease of skin aging should have broad implications that transcend the integument and inform novel approaches to retarding aging and age-related dysfunction in those internal organs that youthful skin was designed to envelop and safeguard.

ER stress activates immunosuppressive network: implications for aging and Alzheimer's disease

The endoplasmic reticulum (ER) contains stress sensors which recognize the accumulation of unfolded proteins within the lumen of ER, and subsequently these transducers stimulate the unfolded protein response (UPR). The ER sensors include the IRE1, PERK, and ATF6 transducers which activate the UPR in an attempt to restore the quality of protein folding and thus maintain cellular homeostasis. If there is excessive stress, UPR signaling generates alarmins, e.g., chemokines and cytokines, which activate not only tissue-resident immune cells but also recruit myeloid and lymphoid cells into the affected tissues. ER stress is a crucial inducer of inflammation in many pathological conditions. A chronic low-grade inflammation and cellular senescence have been associated with the aging process and many age-related diseases, such as Alzheimer’s disease. Currently, it is known that immune cells can exhibit great plasticity, i.e., they are able to display both pro-inflammatory and anti-inflammatory phenotypes in a context-dependent manner. The microenvironment encountered in chronic inflammatory conditions triggers a compensatory immunosuppression which defends tissues from excessive inflammation. Recent studies have revealed that chronic ER stress augments the suppressive phenotypes of immune cells, e.g., in tumors and other inflammatory disorders. The activation of immunosuppressive network, including myeloid-derived suppressor cells (MDSC) and regulatory T cells (Treg), has been involved in the aging process and Alzheimer’s disease. We will examine in detail whether the ER stress-related changes found in aging tissues and Alzheimer’s disease are associated with the activation of immunosuppressive network, as has been observed in tumors and many chronic inflammatory diseases.

How Inflammation Blunts Innate Immunity in Aging

The collective loss of immune protection during aging leads to poor vaccine responses and an increased severity of infection for the elderly. Here, we review our current understanding of effects of aging on the cellular and molecular dysregulation of innate immune cells as well as the relevant tissue milieu which influences their functions. The innate immune system is composed of multiple cell types which provide distinct and essential roles in tissue surveillance and antigen presentation as well as early responses to infection or injury. Functional defects that arise during aging lead to a reduced dynamic range of responsiveness, altered cytokine dynamics, and impaired tissue repair. Heightened inflammation influences both the dysregulation of innate immune responses as well as surrounding tissue microenvironments which have a critical role in development of a functional immune response. In particular, age-related physical and inflammatory changes in the skin, lung, lymph nodes, and adipose tissue reflect disrupted architecture and spatial organization contributing to diminished immune responsiveness. Underlying mechanisms include altered transcriptional programming and dysregulation of critical innate immune signaling cascades. Further, we identify signaling functions of bioactive lipid mediators which address chronic inflammation and may contribute to the resolution of inflammation to improve innate immunity during aging.

Activation of immunosuppressive network in the aging process

Chronic low-grade inflammation has a key role in the aging process, a state called inflammaging. It is known that the chronic inflammatory condition generates counteracting immunosuppressive state in many diseases. Inflammaging is also associated with an immune deficiency; generally termed as immunosenescence, although it is not known whether it represents the senescence of immune cells or the active remodeling of immune system. Evidence has accumulated since the 1970's indicating that immunosenescence might be caused by an increased activity of immunosuppressive cells rather than cellular senescence. Immune cells display remarkable plasticity; many of these cells can express both proinflammatory and immunosuppressive phenotypes in a context-dependent manner. The immunosuppressive network involves the regulatory subtypes of T (Treg) and B (Breg) cells as well as regulatory phenotypes of macrophages (Mreg), dendritic (DCreg), natural killer (NKreg), and type II natural killer T (NKT) cells. The immunosuppressive network also includes monocytic (M-MDSC) and polymorphonuclear (PMN-MDSC) myeloid-derived suppressor cells which are immature myeloid cells induced by inflammatory mediators. This co-operative network is stimulated in chronic inflammatory conditions preventing excessive inflammatory responses but at the same time they exert harmful effects on the immune system and tissue homeostasis. Recent studies have revealed that the aging process is associated with the activation of immunosuppressive network, especially the functions of MDSCs, Tregs, and Mregs are increased. I will briefly review the properties of the regulatory phenotypes of immune cells and examine in detail the evidences for an activation of immunosuppressive network with aging.

Defects in Antiviral T Cell Responses Inflicted by Aging-Associated miR-181a Deficiency

Generation of protective immunity to infections and vaccinations declines with age. Studies in healthy individuals have implicated reduced miR-181a expression in T cells as contributing to this defect. To understand the impact of miR-181a expression on antiviral responses, we examined LCMV infection in mice with miR-181ab1-deficient T cells. We found that miR-181a deficiency delays viral clearance, thereby biasing the immune response in favor of CD4 over CD8 T cells. Antigen-specific CD4 T cells in mice with miR-181a-deficient T cells expand more and have a broader TCR repertoire with preferential expansion of high-affinity T cells than in wild-type mice. Importantly, generation of antigen-specific miR-181a-deficient CD8 effector T cells is particularly impaired, resulting in lower frequencies of CD8 T cells in the liver even at time points when the infection has been cleared. Consistent with the mouse model, CD4 memory T cells in individuals infected with West Nile virus at older ages tend to be more frequent and of higher affinity.

Research Progress of Mechanisms and Drug Therapy For Atherosclerosis on Toll-Like Receptor Pathway

Recent reports have established atherosclerosis (AS) as a major factor in the pathogenetic process of cardiovascular diseases such as ischemic stroke and coronary heart disease. Although the possible pathogenesis of AS remains to be elucidated, a large number of investigations strongly suggest that the inhibition of toll-like receptors (TLRs) alleviates the severity of AS to some extent by suppressing vascular inflammation and the formation of atherosclerotic plaques. As pattern recognition receptors, TLRs occupy a vital position in innate immunity, mediating various signaling pathways in infective and sterile inflammation. This review summarizes the available data on the research progress of AS and the latest antiatherosclerotic drugs associated with TLR pathway.

Impact of Zostavax Vaccination on T-Cell Accumulation and Cutaneous Gene Expression in the Skin of Older Humans After Varicella Zoster Virus Antigen-Specific Challenge

Background

The live attenuated vaccine Zostavax was developed to prevent varicella zoster virus (VZV) reactivation that causes herpes zoster (shingles) in older humans. However, the impact of vaccination on the cutaneous response to VZV is not known.

Methods

We investigated the response to intradermal VZV antigen challenge before and after Zostavax vaccination in participants >70 years of age by immunohistological and transcriptomic analyses of skin biopsy specimens collected from the challenge site.

Results

Vaccination increased the proportion of VZV-specific CD4⁺ T cells in the blood and promoted the accumulation of both CD4⁺ and CD8⁺ T cells in the skin after VZV antigen challenge. However, Zostavax did not alter the proportion of resident memory T cells (CD4⁺ and CD8⁺) or CD4⁺Foxp3⁺ regulatory T cells in unchallenged skin. After vaccination, there was increased cutaneous T-cell proliferation at the challenge site and also increased recruitment of T cells from the blood, as indicated by an elevated T-cell migratory gene signature. CD8⁺ T-cell–associated functional genes were also highly induced in the skin after vaccination.

Conclusion

Zostavax vaccination does not alter the abundance of cutaneous resident memory T cells but instead increases the recruitment of VZV-specific T cells from the blood and enhances T-cell activation, particularly cells of the CD8⁺ subset, in the skin after VZV antigen challenge.

Soluble Factors Released From Activated T Lymphocytes Regulate C2C12 Myoblast Proliferation and Cellular Signaling, but Effects Are Blunted in the Elderly

The key objective of this work was to investigate the impact of young and old human lymphocyte secretomes on C2C12 myoblasts regeneration. Conditioned media were harvested from isolated young and older lymphocytes treated with (activated [AC]) or without (nonactivated [NA]), anti-CD3/CD28 activators for 4 days. AC conditioned media from older lymphocytes had decreased levels of amphiregulin (367 ± 208 pg/mL vs 904 ± 323 pg/mL; p = .018) and IGF-I (845 ± 88 ng/mL vs 1100 ± 48 ng/mL; p = .032) compared with younger AC lymphocytes. AC older versus younger lymphocytes had reduced expression of CD25 (24.6 ± 5.5%; p = .0003) and increased expression of FoxP3 (35 ± 15.7%; p = .032). Treatment of C2C12 myoblasts with young AC lymphocytes resulted in decreased expression of MyoD (0.46 ± 0.12; p =.004) and Myogenin (0.34 ± 0.05; p = .010) mRNA, increased activation of MEk1 (724 ± 140 mean fluorescent intensity [MFI]; p =.001) and ERK1/2 (3768 ± 314 MFI; p =.001), and a decreased activation of Akt (74.5 ± 4 MFI; p = .009) and mTOR (61.8 ± 7 MFI; p = .001) compared with old AC lymphocytes. By contrast, C2C12 myoblasts treated with older AC lymphocytes displayed increased expression of MyoD (0.7 ± 0.08; p =.004) and Myogenin (0.68 ± 0.05; p =.010) mRNA, decreased phosphorylation of MEk1 and ERK1/2 (528 ± 80 MFI; p = .008, and 1141 ± 668 MFI; p = .001, respectively), and increased Akt/mTOR activation (171 ± 35 MFI; p = .009, and 184 ± 33 MFI; p = .001, respectively). These data provide new evidence that differences between older and younger lymphocyte secretomes contribute to differential responses of C2C12 myoblasts in culture.

Immunosenescence: the potential role of myeloid-derived suppressor cells (MDSC) in age-related immune deficiency

The aging process is associated with chronic low-grade inflammation in both humans and rodents, commonly called inflammaging. At the same time, there is a gradual decline in the functional capacity of adaptive and innate immune systems, i.e., immunosenescence, a process not only linked to the aging process, but also encountered in several pathological conditions involving chronic inflammation. The hallmarks of immunosenescence include a decline in the numbers of naïve CD4+ and CD8+ T cells, an imbalance in the T cell subsets, and a decrease in T cell receptor (TCR) repertoire and signaling. Correspondingly, there is a decline in B cell lymphopoiesis and a reduction in antibody production. The age-related changes are not as profound in innate immunity as they are in adaptive immunity. However, there are distinct functional deficiencies in dendritic cells, natural killer cells, and monocytes/macrophages with aging. Interestingly, the immunosuppression induced by myeloid-derived suppressor cells (MDSC) in diverse inflammatory conditions also targets mainly the T and B cell compartments, i.e., inducing very similar alterations to those present in immunosenescence. Here, we will compare the immune profiles induced by immunosenescence and the MDSC-driven immunosuppression. Given that the appearance of MDSCs significantly increases with aging and MDSCs are the enhancers of other immunosuppressive cells, e.g., regulatory T cells (Tregs) and B cells (Bregs), it seems likely that MDSCs might remodel the immune system, thus preventing excessive inflammation with aging. We propose that MDSCs are potent inducers of immunosenescence.

Characterization of donor and recipient CD8+ tissue-resident memory T cells in transplant nephrectomies

Tissue-resident memory T (T_RM) cells are characterized by their surface expression of CD69 and can be subdivided in CD103+ and CD103− T_RM cells. The origin and functional characteristics of T_RM cells in the renal allograft are largely unknown. To determine these features we studied T_RM cells in transplant nephrectomies. T_RM cells with a CD103+ and CD103− phenotype were present in all samples (n = 13) and were mainly CD8+ T cells. Of note, donor-derived T_RM cells were only detectable in renal allografts that failed in the first month after transplantation. Grafts, which failed later, mainly contained recipient derived T_RM cells. The gene expression profiles of the recipient derived CD8+ T_RM cells were studied in more detail and showed a previously described signature of tissue residence within both CD103+ and CD103− T_RM cells. All CD8+ T_RM cells had strong effector abilities through the production of IFNγ and TNFα, and harboured high levels of intracellular granzyme B and low levels of perforin. In conclusion, our results demonstrate that donor and recipient T_RM cells reside in the rejected renal allograft. Over time, the donor-derived T_RM cells are replaced by recipient T_RM cells which have features that enables these cells to aggressively respond to the allograft.

Aged human skin accumulates mast cells with altered functionality that localize to macrophages and vasoactive intestinal peptide-positive nerve fibres

BACKGROUND

Skin health declines with age and this is partially attributed to immunosenescence. Mast cells (MCs) are innate immune cells that coordinate tissue immune responses integral to skin homeostasis and disease.

OBJECTIVES

To understand how MCs contribute to human skin ageing, we investigated how intrinsic ageing impacts MC phenotype and MC relationships with other immune cells and skin structures.

METHODS

In photoprotected skin biopsies from young (≤ 30 years) and aged (≥ 75 years) individuals, immunostaining and spatial morphometry were performed to identify changes in MC phenotype, number, distribution and interaction with the vasculature and nerve fibres. Quantitative polymerase chain reaction was used to measure changes in gene expression related to immune cell activity and neuropeptide signalling.

RESULTS

Skin MCs, macrophages and CD8+ T cells increased in number in intrinsically aged vs. young skin by 40%, 44% and 90%, respectively (P < 0·05), while CD4+ T cells and neutrophils were unchanged. In aged skin, MCs were more numerous in the papillary dermis and showed a reduced incidence of degranulation (50% lower than in young, P < 0·01), a conserved tryptase-chymase phenotype and coexpression of granzyme B. In aged skin, MCs increased their association with macrophages (~ 48% vs. ~27%, P < 0·05) and nerve fibres (~29% vs. 16%, P < 0·001), while reducing their interactions with blood vessels (~34% vs. 45%, P < 0·001). Additionally, we observed modulation of gene expression of vasoactive intestinal peptide (VIP; increased) and substance P (decreased) with age; this was associated with an increased frequency of VIP+ nerve fibres (around three times higher in aged skin, P < 0·05), which were strongly associated with MCs (~19% in aged vs. 8% in young, P < 0·05).

CONCLUSIONS

In photoprotected skin we observed an accumulation of MCs with increasing age. These MCs have both altered functionality and distribution within the skin, which supports a role for these cells in altered tissue homeostasis during ageing.

Oxidative Stress and Nutraceuticals in the Modulation of the Immune Function: Current Knowledge in Animals of Veterinary Interest

In the veterinary sector, many papers deal with the relationships between inflammation and oxidative stress. However, few studies investigate the mechanisms of action of oxidised molecules in the regulation of immune cells. Thus, authors often assume that these events, sometime leading to oxidative stress, are conserved among species. The aim of this review is to draw the state-of-the-art of the current knowledge about the role of oxidised molecules and dietary antioxidant compounds in the regulation of the immune cell functions and suggest some perspectives for future investigations in animals of veterinary interest.

Age-Related Differential Stimulation of Immune Response by Babesia microti and Borrelia burgdorferi During Acute Phase of Infection Affects Disease Severity

Lyme disease is the most prominent tick-borne disease with 300,000 cases estimated by CDC every year while ~2,000 cases of babesiosis occur per year in the United States. Simultaneous infection with Babesia microti and Borrelia burgdorferi are now the most common tick-transmitted coinfections in the U.S.A., and they are a serious health problem because coinfected patients show more intense and persisting disease symptoms. B. burgdorferi is an extracellular spirochete responsible for systemic Lyme disease while B. microti is a protozoan that infects erythrocytes and causes babesiosis. Immune status and spleen health are important for resolution of babesiosis, which is more severe and even fatal in the elderly and splenectomized patients. Therefore, we investigated the effect of each pathogen on host immune response and consequently on severity of disease manifestations in both young, and 30 weeks old C3H mice. At the acute stage of infection, Th1 polarization in young mice spleen was associated with increased IFN-γ and TNF-α producing T cells and a high Tregs/Th17 ratio. Together, these changes could help in the resolution of both infections in young mice and also prevent fatality by B. microti infection as observed with WA-1 strain of Babesia. In older mature mice, Th2 polarization at acute phase of B. burgdorferi infection could play a more effective role in preventing Lyme disease symptoms. As a result, enhanced B. burgdorferi survival and increased tissue colonization results in severe Lyme arthritis only in young coinfected mice. At 3 weeks post-infection, diminished pathogen-specific antibody production in coinfected young, but not older mice, as compared to mice infected with each pathogen individually may also contribute to increased inflammation observed due to B. burgdorferi infection, thus causing persistent Lyme disease observed in coinfected mice and reported in patients. Thus, higher combined proinflammatory response to B. burgdorferi due to Th1 and Th17 cells likely reduced B. microti parasitemia significantly only in young mice later in infection, while the presence of B. microti reduced humoral immunity later in infection and enhanced tissue colonization by Lyme spirochetes in these mice even at the acute stage, thereby increasing inflammatory arthritis.

The role of myeloid-derived suppressor cells (MDSC) in the inflammaging process

A chronic low-grade inflammation is one of the hallmarks of the aging process. This gradually augmenting inflammatory state has been termed inflammaging. Inflammaging is associated with increased myelopoiesis in the bone marrow. This myelopoiesis-biased process increases the generation not only of mature myeloid cells, e.g. monocytes, macrophages, and neutrophils, but also immature myeloid progenitors and myeloid-derived suppressor cells (MDSCs). It is known that the aging process is associated with a significant increase in the presence of MDSCs in the bone marrow, blood, spleen, and peripheral lymph nodes. Consequently, MDSCs will become recruited into inflamed tissues where they suppress acute inflammatory responses and trigger the resolution of inflammation. However, if the perpetrator cannot be eliminated, the long-term presence of MDSCs suppresses the host's immune defence and increases the susceptibility to infections and tumorigenesis. Chronic immunosuppression also impairs the clearance of waste products and dead cells, impairs energy metabolism, and disturbs tissue proteostasis. This immunosuppressive state is reminiscent of the immunosenescence observed in inflammaging. It seems that proinflammatory changes in tissues with aging stimulate the myelopoietic production of MDSCs which subsequently induces immunosenescence and maintains the chronic inflammaging process. We will briefly describe the functions of MDSCs and then examine in detail how inflammaging enhances the generation MDSCs and how MDSCs are involved in the control of immunosenescence occurring in inflammaging.