B Cell Dysfunction Associated With Aging and Autoimmune Diseases

Immunosenescence: A new direction in anti-aging research

The immune system is a major regulatory system of the body, that is composed of immune cells, immune organs, and related signaling factors. As an organism ages, observable age-related changes in the function of the immune system accumulate in a process described as 'immune aging. Research has shown that the impact of aging on immunity is detrimental, with various dysregulated responses that affect the function of immune cells at the cellular level. For example, increased aging has been shown to result in the abnormal chemotaxis of neutrophils and decreased phagocytosis of macrophages. Age-related diminished functionality of immune cell types has direct effects on host fitness, leading to poorer responses to vaccination, more inflammation and tissue damage, as well as autoimmune disorders and the inability to control infections. Similarly, age impacts the function of the immune system at the organ level, resulting in decreased hematopoietic function in the bone marrow, a gradual deficiency of catalase in the thymus, and thymic atrophy, resulting in reduced production of related immune cells such as B cells and T cells, further increasing the risk of autoimmune disorders in the elderly. As the immune function of the body weakens, aging cells and inflammatory factors cannot be cleared, resulting in a cycle of increased inflammation that accumulates over time. Cumulatively, the consequences of immune aging increase the likelihood of developing age-related diseases, such as Alzheimer's disease, atherosclerosis, and osteoporosis, among others. Therefore, targeting the age-related changes that occur within cells of the immune system might be an effective anti-aging strategy. In this article, we summarize the relevant literature on immune aging research, focusing on its impact on aging, in hopes of providing new directions for anti-aging research.

Clinical, Immunological, and Genetic Features in Patients with NFKB1 and NFKB2 Mutations: a Systematic Review

BACKGROUND

Inborn errors of immunity (IEIs) encompass various diseases with diverse clinical and immunological symptoms. Determining the genotype-phenotype of different variants in IEI entity precisely is challenging, as manifestations can be heterogeneous even in patients with the same mutated gene.

OBJECTIVE

In the present study, we conducted a systematic review of patients recorded with NFKB1 and NFKB2 mutations, two of the most frequent monogenic IEIs.

METHODS

The search for relevant literature was conducted in databases including Web of Science, PubMed, and Scopus. Information encompassing demographic, clinical, immunological, and genetic data was extracted from cases reported with mutations in NFKB1 and NFKB2. The comprehensive features of manifestations in patients were described, and a comparative analysis of primary characteristics was conducted between individuals with NFKB1 loss of function (LOF) and NFKB2 (p52-LOF/IκBδ-gain of function (GOF)) variants.

RESULTS

A total of 397 patients were included in this study, 257 had NFKB1 mutations and 140 had NFKB2 mutations. There were 175 LOF cases in NFKB1 and 122 p52LOF/IκBδGOF cases in NFKB2 pivotal groups with confirmed functional implications. NFKB1LOF and p52LOF/IκBδGOF predominant cases (81.8% and 62.5% respectively) initially presented with a CVID-like phenotype. Patients with NFKB1LOF variants often experienced hematologic autoimmune disorders, whereas p52LOF/IκBδGOF patients were more susceptible to other autoimmune diseases. Viral infections were markedly higher in p52LOF/IκBδGOF cases compared to NFKB1LOF (P-value < 0.001). NFKB2 (p52LOF/IκBδGOF) patients exhibited a greater prevalence of ectodermal dysplasia and pituitary gland involvement than NFKB1LOF patients. Most NFKB1LOF and p52LOF/IκBδGOF cases showed low CD19 + B cells, with p52LOF/IκBδGOF having more cases of this type. Low memory B cells were more common in p52LOF/IκBδGOF patients.

CONCLUSIONS

Patients with NFKB2 mutations, particularly p52LOF/IκBδGOF, are at higher risk of viral infections, pituitary gland involvement, and ectodermal dysplasia compared to patients with NFKB1LOF mutations. Genetic testing is essential to resolve the initial complexity and confusion surrounding clinical and immunological features. Emphasizing the significance of functional assays in determining the probability of correlations between mutations and immunological and clinical characteristics of patients is crucial.

Exploring the Interplay between Cellular Senescence, Immunity, and Fibrosing Interstitial Lung Diseases: Challenges and Opportunities

Fibrosing interstitial lung diseases (ILDs) are characterized by the gradual and irreversible accumulation of scar tissue in the lung parenchyma. The role of the immune response in the pathogenesis of pulmonary fibrosis remains unclear. In recent years, substantial advancements have been made in our comprehension of the pathobiology driving fibrosing ILDs, particularly concerning various age-related cellular disturbances and immune mechanisms believed to contribute to an inadequate response to stress and increased susceptibility to lung fibrosis. Emerging studies emphasize cellular senescence as a key mechanism implicated in the pathobiology of age-related diseases, including pulmonary fibrosis. Cellular senescence, marked by antagonistic pleiotropy, and the complex interplay with immunity, are pivotal in comprehending many aspects of lung fibrosis. Here, we review progress in novel concepts in cellular senescence, its association with the dysregulation of the immune response, and the evidence underlining its detrimental role in fibrosing ILDs.

An updated immunosenescence exploration in healthy Chinese donors: circular elevated PD-1 on T cell and increased Ki67 on CD8+ T cell towards aging

Immunosenescence is a process of immune dysfunction that occurs along with aging. Many studies have focused on the changes of different lymphocyte subsets in diseases and immune aging. However, the fluctuation in the number and phenotype of lymphocyte subset caused by aging have not been comprehensively analyzed, especially the effects of new indicators such as PD-1 and Ki67 in peripheral blood have been rarely reported. We further investigated the humoral and cellular immune parameters of 150 healthy donors over 18 years old. Age was associated with decreased CD4+CD45RA+CD62L+ T cells, decreased CD4+CD45RA+CD31+ T cells, and increased memory CD4+ or CD8+ T cells, dominated by male CD8+ T cells. The loss of CD28 expression on T cells and the transverse trend of activated CD38 and HLA-DR were also related to the increased age. In addition, CD8+ T cells in men were more prominent in activation indicators, and the difference between the old and young groups was obvious. CD4+CD25+CD127- T cells percentage tended to decrease with age and did not differ significantly between gender. Interestingly, we found that age was positively associated with PD-1+ T cells and showed significant age-related variability in men. Similarly, the percentage of CD8+ki-67+ also showed an increasing trend, with significant differences between the young group and other elderly groups in males. Our findings can provide immunological clues for future aging research, offering new insights for clinical monitoring and prevention of certain diseases.

Biomarkers of Aging and Relevant Evaluation Techniques: A Comprehensive Review

The risk of developing chronic illnesses and disabilities is increasing with age. To predict and prevent aging, biomarkers relevant to the aging process must be identified. This paper reviews the known molecular, cellular, and physiological biomarkers of aging. Moreover, we discuss the currently available technologies for identifying these biomarkers, and their applications and potential in aging research. We hope that this review will stimulate further research and innovation in this emerging and fast-growing field.

Rebuilding and rebooting immunity with stem cells

Advances in modern medicine have enabled a rapid increase in lifespan and, consequently, have highlighted the immune system as a key driver of age-related disease. Immune regeneration therapies present exciting strategies to address age-related diseases by rebooting the host's primary lymphoid tissues or rebuilding the immune system directly via biomaterials or artificial tissue. Here, we identify important, unanswered questions regarding the safety and feasibility of these therapies. Further, we identify key design parameters that should be primary considerations guiding technology design, including timing of application, interaction with the host immune system, and functional characterization of the target patient population.

The Impact of Immune System Aging on Infectious Diseases

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

Human in vivo evidence of associations between herpes simplex virus and cerebral amyloid-beta load in normal aging

BACKGROUND

Mounting data suggests that herpes simplex virus type 1 (HSV-1) is involved in the pathogenesis of AD, possibly instigating amyloid-beta (Aβ) accumulation decades before the onset of clinical symptoms. However, human in vivo evidence linking HSV-1 infection to AD pathology is lacking in normal aging, which may contribute to the elucidation of the role of HSV-1 infection as a potential AD risk factor.

METHODS

To shed light into this question, serum anti-HSV IgG levels were correlated with 18F-Florbetaben-PET binding to Aβ deposits and blood markers of neurodegeneration (pTau181 and neurofilament light chain) in cognitively normal older adults. Additionally, we investigated whether associations between anti-HSV IgG and AD markers were more evident in APOE4 carriers.

RESULTS

We showed that increased anti-HSV IgG levels are associated with higher Aβ load in fronto-temporal regions of cognitively normal older adults. Remarkably, these cortical regions exhibited abnormal patterns of resting state-functional connectivity (rs-FC) only in those individuals showing the highest levels of anti-HSV IgG. We further found that positive relationships between anti-HSV IgG levels and Aβ load, particularly in the anterior cingulate cortex, are moderated by the APOE4 genotype, the strongest genetic risk factor for AD. Importantly, anti-HSV IgG levels were unrelated to either subclinical cognitive deficits or to blood markers of neurodegeneration.

CONCLUSIONS

All together, these results suggest that HSV infection is selectively related to cortical Aβ deposition in normal aging, supporting the inclusion of cognitively normal older adults in prospective trials of antimicrobial therapy aimed at decreasing the AD risk in the aging population.

Perimenopause in women with rheumatologic diseases: a spotlight on an under-addressed transition

Abundant research has been published describing the effects invoked during menopause across different organ systems. Changing levels of estrogen and progesterone result in bidirectional alterations of immune cell pathways. Overall, the net trend dampens immunoregulation and promotes inflammation. In paradigmatic rheumatologic diseases, the combined effect is far from predictable. While some features may abate during menopause, studies have shown a general increased frequency toward disease exacerbation. Similarly, while impossible to isolate the ramifications of menopause in women with fibromyalgia, a tendency toward enhanced symptoms is unquestionably apparent. Furthermore, the comorbidities accrued by increasing age and the consequences of long-term medication use may also confound this picture. Periodic rheumatologic visits are warranted, with clinical assessments directed toward a multi-disciplinary approach. Ultimately, while an arsenal of effective tools is available for caring for these women and their underlying conditions, more studies are needed to better clarify how the different stages surrounding perimenopause affect subpopulations with rheumatic diseases and fibromyalgia-related disorders so that clinical course can be predicted and addressed prior to the emergence of symptomatology.

Defective mitochondria remodelling in B cells leads to an aged immune response

The B cell response in the germinal centre (GC) reaction requires a unique bioenergetic supply. Although mitochondria are remodelled upon antigen-mediated B cell receptor stimulation, mitochondrial function in B cells is still poorly understood. To gain a better understanding of the role of mitochondria in B cell function, here we generate mice with B cell-specific deficiency in Tfam, a transcription factor necessary for mitochondrial biogenesis. Tfam conditional knock-out (KO) mice display a blockage of the GC reaction and a bias of B cell differentiation towards memory B cells and aged-related B cells, hallmarks of an aged immune response. Unexpectedly, blocked GC reaction in Tfam KO mice is not caused by defects in the bioenergetic supply but is associated with a defect in the remodelling of the lysosomal compartment in B cells. Our results may thus describe a mitochondrial function for lysosome regulation and the downstream antigen presentation in B cells during the GC reaction, the dysruption of which is manifested as an aged immune response.

Immune aging in annual killifish

Turquoise killifish (Nothobranchius furzeri) evolved a naturally short lifespan of about six months and exhibit aging hallmarks that affect multiple organs. These hallmarks include protein aggregation, telomere shortening, cellular senescence, and systemic inflammation. Turquoise killifish possess the full spectrum of vertebrate-specific innate and adaptive immune system. However, during their recent evolutionary history, they lost subsets of mucosal-specific antibody isoforms that are present in other teleosts. As they age, the immune system of turquoise killifish undergoes dramatic cellular and systemic changes. These changes involve increased inflammation, reduced antibody diversity, an increased prevalence of pathogenic microbes in the intestine, and extensive DNA damage in immune progenitor cell clusters. Collectively, the wide array of age-related changes occurring in turquoise killifish suggest that, despite an evolutionary separation spanning hundreds of millions of years, teleosts and mammals share common features of immune system aging. Hence, the spontaneous aging observed in the killifish immune system offers an excellent opportunity for discovering fundamental and conserved aspects associated with immune system aging across vertebrates. Additionally, the species' naturally short lifespan of only a few months, along with its experimental accessibility, offers a robust platform for testing interventions to improve age-related dysfunctions in the whole organism and potentially inform the development of immune-based therapies for human aging-related diseases.

Single-cell transcriptome analysis of aging mouse liver

Aging has a great impact on the liver, which causes a loss of physiological integrity and an increase in susceptibility to injury, but many of the underlying molecular and cellular processes remain unclear. Here, we performed a comprehensive single-cell transcriptional profiling of the liver during aging. Our data showed that aging affected the cellular composition of the liver. The increase in inflammatory cells including neutrophils and monocyte-derived macrophages, as well as in inflammatory cytokines, could indicate an inflammatory tissue microenvironment in aged livers. Moreover, aging drove a distinct transcriptional course in each cell type. The commonly significant up-regulated genes were S100a8, S100a9, and RNA-binding motif protein 3 across all cell types. Aging-related pathways such as biosynthesis, metabolism, and oxidative stress were up-regulated in aged livers. Additionally, key ligand-receptor pairs for intercellular communication, primarily linked to macrophage migration inhibitory factor, transforming growth factor-β, and complement signaling, were also elevated. Furthermore, hepatic stellate cells (HSCs) serve as the prominent hub for intrahepatic signaling. HSCs acquired an "activated" phenotype, which may be involved in the increased intrahepatic vascular tone and fibrosis with aging. Liver sinusoidal endothelial cells derived from aged livers were pseudocapillarized and procontractile, and exhibited down-regulation of genes involved in vascular development and homeostasis. Moreover, the aging-related changes in cellular composition and gene expression were reversed by caloric restriction. Collectively, the present study suggests liver aging is linked to a significant liver sinusoidal deregulation and a moderate pro-inflammatory state, providing a potential concept for understanding the mechanism of liver aging.

B Cells Dynamic in Aging and the Implications of Nutritional Regulation

Aging negatively affects B cell production, resulting in a decrease in B-1 and B-2 cells and impaired antibody responses. Age-related B cell subsets contribute to inflammation. Investigating age-related alterations in the B-cell pool and developing targeted therapies are crucial for combating autoimmune diseases in the elderly. Additionally, optimal nutrition, including carbohydrates, amino acids, vitamins, and especially lipids, play a vital role in supporting immune function and mitigating the age-related decline in B cell activity. Research on the influence of lipids on B cells shows promise for improving autoimmune diseases. Understanding the aging B-cell pool and considering nutritional interventions can inform strategies for promoting healthy aging and reducing the age-related disease burden.

Single-cell transcriptomics of Treg reveals hallmarks and trajectories of immunological aging

Age-related immunosenescence is characterized by progressive dysfunction of adaptive immune response and increased autoimmunity. Nevertheless, the impact of aging on CD4+ regulatory T cells that are master regulators of the immune system remains largely unclear. Here, we report cellular and molecular hallmarks of regulatory T cells derived from murine lymphoid and adipose tissues at 3, 18, and 24 mo of age, respectively, by analyzing their heterogeneity that displays dynamic changes in transcriptomic effector signatures at a single-cell resolution. Although the proportion of regulatory T cells among total Cd4+ T cells, as well as their expression levels of Foxp3, did not show any global change with time, we have identified 6 transcriptomically distinct clusters of regulatory T cells with cross-tissue conserved hallmarks of aging, including increased numbers of proinflammatory regulatory T cells, reduced precursor cells, increased immature and mature T follicular regulatory cells potentially supported by a metabolic switch from oxidative phosphorylation to glycolysis, a gradual loss of CD150hi regulatory T cells that support hematopoiesis, and increased adipose tissue-specific regulatory T cells that are associated with metabolic disease. To dissect the impact of immunosenescence on humoral immunity, we propose some potential mechanisms underlying T follicular regulatory cell-mediated dysfunction by interactome analysis on T follicular regulatory cells, T follicular helper cells, and B cells during aging. Lastly, spatiotemporal analysis further revealed trajectories of regulatory T-cell aging that demonstrate the most significant changes in marrow and adipose tissues that might contribute to the development of age-related immunosenescence and type 2 diabetes. Taken together, our findings could provide a better understanding of age-associated regulatory T-cell heterogeneity in lymphoid and adipose tissues, as well as regulatory T-cell hallmarks during progressive adaptation to aging that could be therapeutically targeted for rejuvenating the aging immune system in the future.

Aberrant B-cell activation and B-cell subpopulations in rheumatoid arthritis: analysis by clinical activity, autoantibody seropositivity, and treatment

Few studies analyze the role of B-cell subpopulations in rheumatoid arthritis (RA) pathophysiology. Therefore, this study aimed to analyze the differences in B-cell subpopulations and B-cell activation according to disease activity, RA subtype, and absence of disease-modifying antirheumatic drugs (DMARDs) therapy. These subgroups were compared with control subjects (CS). One hundred and thirty-nine subjects were included, of which 114 were RA patients, and 25 were controls. Patients were divided into 99 with seropositive RA, 6 with seronegative RA, and 9 without DMARDs. The patients with seropositive RA were subclassified based on the DAS28 index. A seven-color multicolor flow cytometry panel was used to identify B-cell immunophenotypes and cell activation markers. There were no changes in total B-cell frequencies between RA patients and controls. However, a lower frequency of memory B cells and pre-plasmablasts was observed in seropositive RA compared to controls (P < 0.0001; P = 0.0043, respectively). In contrast, a higher frequency of mature B cells was observed in RA than in controls (P = 0.0002). Among patients with RA, those with moderate activity had a higher percentage of B cells (P = 0.0021). The CD69+ marker was increased (P < 0.0001) in RA compared to controls, while the CD40+ frequency was decreased in patients (P < 0.0001). Transitional, naïve, and double-negative B-cell subpopulations were higher in seronegative RA than in seropositive (P < 0.01). In conclusion, in seropositive and seronegative RA patients, there are alterations in B-cell activation and B-cell subpopulations, independently of clinical activity and DMARDs therapy.

From aging to long COVID: exploring the convergence of immunosenescence, inflammaging, and autoimmunity

The process of aging is accompanied by a dynamic restructuring of the immune response, a phenomenon known as immunosenescence. This mini-review navigates through the complex landscape of age-associated immune changes, chronic inflammation, age-related autoimmune tendencies, and their potential links with immunopathology of Long COVID. Immunosenescence serves as an introductory departure point, elucidating alterations in immune cell profiles and their functional dynamics, changes in T-cell receptor signaling, cytokine network dysregulation, and compromised regulatory T-cell function. Subsequent scrutiny of chronic inflammation, or "inflammaging," highlights its roles in age-related autoimmune susceptibilities and its potential as a mediator of the immune perturbations observed in Long COVID patients. The introduction of epigenetic facets further amplifies the potential interconnections. In this compact review, we consider the dynamic interactions between immunosenescence, inflammation, and autoimmunity. We aim to explore the multifaceted relationships that link these processes and shed light on the underlying mechanisms that drive their interconnectedness. With a focus on understanding the immunological changes in the context of aging, we seek to provide insights into how immunosenescence and inflammation contribute to the emergence and progression of autoimmune disorders in the elderly and may serve as potential mediator for Long COVID disturbances.

Non-Genomic Hallmarks of Aging-The Review

Aging is a natural, gradual, and inevitable process associated with a series of changes at the molecular, cellular, and tissue levels that can lead to an increased risk of many diseases, including cancer. The most significant changes at the genomic level (DNA damage, telomere shortening, epigenetic changes) and non-genomic changes are referred to as hallmarks of aging. The hallmarks of aging and cancer are intertwined. Many studies have focused on genomic hallmarks, but non-genomic hallmarks are also important and may additionally cause genomic damage and increase the expression of genomic hallmarks. Understanding the non-genomic hallmarks of aging and cancer, and how they are intertwined, may lead to the development of approaches that could influence these hallmarks and thus function not only to slow aging but also to prevent cancer. In this review, we focus on non-genomic changes. We discuss cell senescence, disruption of proteostasis, deregualation of nutrient sensing, dysregulation of immune system function, intercellular communication, mitochondrial dysfunction, stem cell exhaustion and dysbiosis.

Heterologous DNA-prime/protein-boost immunization with a monomeric SARS-CoV-2 spike antigen redundantizes the trimeric receptor-binding domain structure to induce neutralizing antibodies in old mice

A multitude of alterations in the old immune system impair its functional integrity. Closely related, older individuals show, for example, a reduced responsiveness to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) vaccines. However, systematic strategies to specifically improve the efficacy of vaccines in the old are missing or limited to simple approaches like increasing the antigen concentration or injection frequencies. We here asked whether the intrinsic, trimeric structure of the SARS-CoV-2 spike (S) antigen and/or a DNA- or protein-based antigen delivery platform affects priming of functional antibody responses particularly in old mice. The used S-antigens were primarily defined by the presence/absence of the membrane-anchoring TM domain and the closely interlinked formation/non-formation of a trimeric structure of the receptor binding domain (S-RBD). Among others, we generated vectors expressing prefusion-stabilized, cell-associated (TM+) trimeric "S2-P" or secreted (TM-) monomeric "S6-PΔTM" antigens. These proteins were produced from vector-transfected HEK-293T cells under mild conditions by Strep-tag purification, revealing that cell-associated but not secreted S proteins tightly bound Hsp73 and Grp78 chaperones. We showed that both, TM-deficient S6-PΔTM and full-length S2-P antigens elicited very similar S-RBD-specific antibody titers and pseudovirus neutralization activities in young (2-3 months) mice through homologous DNA-prime/DNA-boost or protein-prime/protein-boost vaccination. The trimeric S2-P antigen induced high S-RBD-specific antibody responses in old (23-24 months) mice through DNA-prime/DNA-boost vaccination. Unexpectedly, the monomeric S6-PΔTM antigen induced very low S-RBD-specific antibody titers in old mice through homologous DNA-prime/DNA-boost or protein-prime/protein-boost vaccination. However, old mice efficiently elicited an S-RBD-specific antibody response after heterologous DNA-prime/protein-boost immunization with the S6-PΔTM antigen, and antibody titers even reached similar levels and neutralizing activities as in young mice and also cross-reacted with different S-variants of concern. The old immune system thus distinguished between trimeric and monomeric S protein conformations: it remained antigen responsive to the trimeric S2-P antigen, and a simple change in the vaccine delivery regimen was sufficient to unleash its reactivity to the monomeric S6-PΔTM antigen. This clearly shows that both the antigen structure and the delivery platform are crucial to efficiently prime humoral immune responses in old mice and might be relevant for designing "age-adapted" vaccine strategies.

A Wrinkle in TIME: How Changes in the Aging ECM Drive the Remodeling of the Tumor Immune Microenvironment

SUMMARY

Cancer is an age-related disease, with the majority of patients receiving their diagnosis after the age of 60 and most mortality from cancer occurring after this age. The tumor microenvironment changes drastically with age, which in turn affects cancer progression and treatment efficacy. Age-related changes to individual components of the microenvironment have received well-deserved attention over the past few decades, but the effects of aging at the interface of two or more microenvironmental components have been vastly understudied. In this perspective, we discuss the relationship between the aging extracellular matrix and the aging immune system, how they affect the tumor microenvironment, and how these multidisciplinary studies may open avenues for new therapeutics. Cancer is a disease of aging. With a rapidly aging population, we need to better understand the age-related changes that drive tumor progression, ranging from secreted changes to biophysical and immune changes.

Epstein-Barr virus and genetic risk variants as determinants of T-bet+ B cell-driven autoimmune diseases

B cells expressing the transcription factor T-bet are found to have a protective role in viral infections, but are also considered major players in the onset of different types of autoimmune diseases. Currently, the exact mechanisms driving such 'atypical' memory B cells to contribute to protective immunity or autoimmunity are unclear. In addition to general autoimmune-related factors including sex and age, the ways T-bet+ B cells instigate autoimmune diseases may be determined by the close interplay between genetic risk variants and Epstein-Barr virus (EBV). The impact of EBV on T-bet+ B cells likely relies on the type of risk variants associated with each autoimmune disease, which may affect their differentiation, migratory routes and effector function. In this hypothesis-driven review, we discuss the lines of evidence pointing to such genetic and/or EBV-mediated influence on T-bet+ B cells in a range of autoimmune diseases, including systemic lupus erythematosus (SLE) and multiple sclerosis (MS). We provide examples of how genetic risk variants can be linked to certain signaling pathways and are differentially affected by EBV to shape T-bet+ B-cells. Finally, we propose options to improve current treatment of B cell-related autoimmune diseases by more selective targeting of pathways that are critical for pathogenic T-bet+ B-cell formation.

Severe COVID-19 patients exhibit elevated levels of autoantibodies targeting cardiolipin and platelet glycoprotein with age: a systems biology approach

Age is a significant risk factor for the coronavirus disease 2019 (COVID-19) severity due to immunosenescence and certain age-dependent medical conditions (e.g., obesity, cardiovascular disorder, and chronic respiratory disease). However, despite the well-known influence of age on autoantibody biology in health and disease, its impact on the risk of developing severe COVID-19 remains poorly explored. Here, we performed a cross-sectional study of autoantibodies directed against 58 targets associated with autoimmune diseases in 159 individuals with different COVID-19 severity (71 mild, 61 moderate, and 27 with severe symptoms) and 73 healthy controls. We found that the natural production of autoantibodies increases with age and is exacerbated by SARS-CoV-2 infection, mostly in severe COVID-19 patients. Multiple linear regression analysis showed that severe COVID-19 patients have a significant age-associated increase of autoantibody levels against 16 targets (e.g., amyloid β peptide, β catenin, cardiolipin, claudin, enteric nerve, fibulin, insulin receptor a, and platelet glycoprotein). Principal component analysis with spectrum decomposition and hierarchical clustering analysis based on these autoantibodies indicated an age-dependent stratification of severe COVID-19 patients. Random forest analysis ranked autoantibodies targeting cardiolipin, claudin, and platelet glycoprotein as the three most crucial autoantibodies for the stratification of severe COVID-19 patients ≥50 years of age. Follow-up analysis using binomial logistic regression found that anti-cardiolipin and anti-platelet glycoprotein autoantibodies significantly increased the likelihood of developing a severe COVID-19 phenotype with aging. These findings provide key insights to explain why aging increases the chance of developing more severe COVID-19 phenotypes.

Evaluation of Cell-Specific Epigenetic Age Acceleration in People With Multiple Sclerosis

BACKGROUND AND OBJECTIVES

In multiple sclerosis (MS), accelerated aging of the immune system (immunosenescence) may be associated with disease onset or drive progression. DNA methylation (DNAm) is an epigenetic factor that varies among lymphocyte subtypes, and cell-specific DNAm is associated with MS. DNAm varies across the life span and can be used to accurately estimate biological age acceleration, which has been linked to a range of morbidities. The objective of this study was to test for cell-specific epigenetic age acceleration (EAA) in people with MS.

METHODS

This was a case-control study of EAA using existing DNAm data from several independent previously published studies. Data were included if .idat files from Illumina 450K or EPIC arrays were available for both a case with MS and an age-matched and sex-matched control, from the same study. Multifactor statistical modeling was performed to assess the primary outcome of EAA. We explored the relationship of EAA and MS, including interaction terms to identify immune cell-specific effects. Cell-sorted DNA methylation data from 3 independent datasets were used to validate findings.

RESULTS

We used whole blood DNA methylation data from 583 cases with MS and 643 non-MS controls to calculate EAA using the GrimAge algorithm. The MS group exhibited an increased EAA compared with controls (approximately 9 mths, 95% CI 3.6-14.4), p = 0.001). Statistical deconvolution showed that EAA is associated with MS in a B cell-dependent manner (β int = 1.7, 95% CI 0.3-2.8), p = 0.002), irrespective of B-cell proportions. Validation analysis using 3 independent datasets enriched for B cells showed an EAA increase of 5.1 years in cases with MS compared with that in controls (95% CI 2.8-7.4, p = 5.5 × 10-5). By comparison, there was no EAA difference in MS in a T cell-enriched dataset. We found that EAA was attributed to the DNAm surrogates for Beta-2-microglobulin (difference = 47,546, 95% CI 10,067-85,026; p = 7.2 × 10-5), and smoking pack-years (difference = 8.1, 95% CI 1.9-14.2, p = 0.002).

DISCUSSION

This study provides compelling evidence that B cells exhibit marked EAA in MS and supports the hypothesis that premature B-cell immune senescence plays a role in MS. Future MS studies should focus on age-related molecular mechanisms in B cells.

Chronic inflammation and the hallmarks of aging

BACKGROUND

Recently, the hallmarks of aging were updated to include dysbiosis, disabled macroautophagy, and chronic inflammation. In particular, the low-grade chronic inflammation during aging, without overt infection, is defined as "inflammaging," which is associated with increased morbidity and mortality in the aging population. Emerging evidence suggests a bidirectional and cyclical relationship between chronic inflammation and the development of age-related conditions, such as cardiovascular diseases, neurodegeneration, cancer, and frailty. How the crosstalk between chronic inflammation and other hallmarks of aging underlies biological mechanisms of aging and age-related disease is thus of particular interest to the current geroscience research.

SCOPE OF REVIEW

This review integrates the cellular and molecular mechanisms of age-associated chronic inflammation with the other eleven hallmarks of aging. Extra discussion is dedicated to the hallmark of "altered nutrient sensing," given the scope of Molecular Metabolism. The deregulation of hallmark processes during aging disrupts the delicate balance between pro-inflammatory and anti-inflammatory signaling, leading to a persistent inflammatory state. The resultant chronic inflammation, in turn, further aggravates the dysfunction of each hallmark, thereby driving the progression of aging and age-related diseases.

MAIN CONCLUSIONS

The crosstalk between chronic inflammation and other hallmarks of aging results in a vicious cycle that exacerbates the decline in cellular functions and promotes aging. Understanding this complex interplay will provide new insights into the mechanisms of aging and the development of potential anti-aging interventions. Given their interconnectedness and ability to accentuate the primary elements of aging, drivers of chronic inflammation may be an ideal target with high translational potential to address the pathological conditions associated with aging.

Bystanders or not? Microglia and lymphocytes in aging and stroke

As the average age of the world population increases, more people will face debilitating aging-associated conditions, including dementia and stroke. Not only does the incidence of these conditions increase with age, but the recovery afterward is often worse in older patients. Researchers and health professionals must unveil and understand the factors behind age-associated diseases to develop a therapy for older patients. Aging causes profound changes in the immune system including the activation of microglia in the brain. Activated microglia promote T lymphocyte transmigration leading to an increase in neuroinflammation, white matter damage, and cognitive impairment in both older humans and rodents. The presence of T and B lymphocytes is observed in the aged brain and correlates with worse stroke outcomes. Preclinical strategies in stroke target either microglia or the lymphocytes or the communications between them to promote functional recovery in aged subjects. In this review, we examine the role of the microglia and T and B lymphocytes in aging and how they contribute to cognitive impairment. Additionally, we provide an important update on the contribution of these cells and their interactions in preclinical aged stroke.

Inflammation and aging: signaling pathways and intervention therapies

Aging is characterized by systemic chronic inflammation, which is accompanied by cellular senescence, immunosenescence, organ dysfunction, and age-related diseases. Given the multidimensional complexity of aging, there is an urgent need for a systematic organization of inflammaging through dimensionality reduction. Factors secreted by senescent cells, known as the senescence-associated secretory phenotype (SASP), promote chronic inflammation and can induce senescence in normal cells. At the same time, chronic inflammation accelerates the senescence of immune cells, resulting in weakened immune function and an inability to clear senescent cells and inflammatory factors, which creates a vicious cycle of inflammation and senescence. Persistently elevated inflammation levels in organs such as the bone marrow, liver, and lungs cannot be eliminated in time, leading to organ damage and aging-related diseases. Therefore, inflammation has been recognized as an endogenous factor in aging, and the elimination of inflammation could be a potential strategy for anti-aging. Here we discuss inflammaging at the molecular, cellular, organ, and disease levels, and review current aging models, the implications of cutting-edge single cell technologies, as well as anti-aging strategies. Since preventing and alleviating aging-related diseases and improving the overall quality of life are the ultimate goals of aging research, our review highlights the critical features and potential mechanisms of inflammation and aging, along with the latest developments and future directions in aging research, providing a theoretical foundation for novel and practical anti-aging strategies.

Molecular Mechanisms for the Vicious Cycle between Insulin Resistance and the Inflammatory Response in Obesity

The comprehensive anabolic effects of insulin throughout the body, in addition to the control of glycemia, include ensuring lipid homeostasis and anti-inflammatory modulation, especially in adipose tissue (AT). The prevalence of obesity, defined as a body mass index (BMI) ≥ 30 kg/m², has been increasing worldwide on a pandemic scale with accompanying syndemic health problems, including glucose intolerance, insulin resistance (IR), and diabetes. Impaired tissue sensitivity to insulin or IR paradoxically leads to diseases with an inflammatory component despite hyperinsulinemia. Therefore, an excess of visceral AT in obesity initiates chronic low-grade inflammatory conditions that interfere with insulin signaling via insulin receptors (INSRs). Moreover, in response to IR, hyperglycemia itself stimulates a primarily defensive inflammatory response associated with the subsequent release of numerous inflammatory cytokines and a real threat of organ function deterioration. In this review, all components of this vicious cycle are characterized with particular emphasis on the interplay between insulin signaling and both the innate and adaptive immune responses related to obesity. Increased visceral AT accumulation in obesity should be considered the main environmental factor responsible for the disruption in the epigenetic regulatory mechanisms in the immune system, resulting in autoimmunity and inflammation.

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.

The Role of Viral Infections in the Onset of Autoimmune Diseases

Autoimmune diseases (AIDs) are the consequence of a breach in immune tolerance, leading to the inability to sufficiently differentiate between self and non-self. Immune reactions that are targeted towards self-antigens can ultimately lead to the destruction of the host's cells and the development of autoimmune diseases. Although autoimmune disorders are comparatively rare, the worldwide incidence and prevalence is increasing, and they have major adverse implications for mortality and morbidity. Genetic and environmental factors are thought to be the major factors contributing to the development of autoimmunity. Viral infections are one of the environmental triggers that can lead to autoimmunity. Current research suggests that several mechanisms, such as molecular mimicry, epitope spreading, and bystander activation, can cause viral-induced autoimmunity. Here we describe the latest insights into the pathomechanisms of viral-induced autoimmune diseases and discuss recent findings on COVID-19 infections and the development of AIDs.

Molecular Markers of Blood Cell Populations Can Help Estimate Aging of the Immune System

Aging of the immune system involves functional changes in individual cell populations, in hematopoietic tissues and at the systemic level. They are mediated by factors produced by circulating cells, niche cells, and at the systemic level. Age-related alterations in the microenvironment of the bone marrow and thymus cause a decrease in the production of naive immune cells and functional immunodeficiencies. Another result of aging and reduced tissue immune surveillance is the accumulation of senescent cells. Some viral infections deplete adaptive immune cells, increasing the risk of autoimmune and immunodeficiency conditions, leading to a general degradation in the specificity and effectiveness of the immune system in old age. During the COVID-19 pandemic, the state-of-the-art application of mass spectrometry, multichannel flow cytometry, and single-cell genetic analysis have provided vast data on the mechanisms of aging of the immune system. These data require systematic analysis and functional verification. In addition, the prediction of age-related complications is a priority task of modern medicine in the context of the increase in the aged population and the risk of premature death during epidemics. In this review, based on the latest data, we discuss the mechanisms of immune aging and highlight some cellular markers as indicators of age-related immune disbalance that increase the risk of senile diseases and infectious complications.

Partners in crime: Autoantibodies complicit in COVID-19 pathogenesis

Autoantibodies (AABs) play a critical role in the pathogenesis of autoimmune diseases (AIDs) and serve as a diagnostic and prognostic tool in assessing these complex disorders. Viral infections have long been recognized as a principal environmental factor affecting the production of AABs and the development of autoimmunity. COVID-19 has primarily been considered a hyperinflammatory syndrome triggered by a cytokine storm. In the following, the role of maladaptive B cell response and AABs became more apparent in COVID-19 pathogenesis. The current review will primarily focus on the role of extrafollicular B cell response, Toll-like receptor-7 (TLR-7) activation, and neutrophil extracellular traps (NETs) formation in the development of AABs following SARS-CoV-2 infection. In the following, this review will clarify how these AABs dysregulate immune response to SARS-CoV-2 by disrupting cytokine function and triggering neutrophil hyper-reactivity. Finally, the pathologic effects of these AABs will be further described in COVID-19 associate clinical manifestations, including venous and arterial thrombosis, a multisystem inflammatory syndrome in children (MIS-C), acute respiratory distress syndrome (ARDS), and recently described post-acute sequelae of COVID-19 (PASC) or long-COVID.

COVID-19: A Comprehensive Review on Cardiovascular Alterations, Immunity, and Therapeutics in Older Adults

Here, we present a review focusing on three relevant issues related to COVID-19 and its impact in older adults (60 years and older). SARS-CoV-2 infection starts in the respiratory system, but the development of systemic diseases accompanied by severe clinical manifestations has also been reported, with cardiovascular and immune system dysfunction being the major ones. Additionally, the presence of comorbidities and aging represent major risk factors for the severity and poor prognosis of the disease. Since aging-associated decline has been largely related to immune and cardiovascular alterations, we sought to investigate the consequences and the underlying mechanisms of these pathologies to understand the severity of the illness in this population. Understanding the effects of COVID-19 on both systems should translate into comprehensive and improved medical care for elderly COVID-19 patients, preventing cardiovascular as well as immunological alterations in this population. Approved therapies that contribute to the improvement of symptoms and a reduction in mortality, as well as new therapies in development, constitute an approach to managing these disorders. Among them, we describe antivirals, cytokine antagonists, cytokine signaling pathway inhibitors, and vaccines.

Senescent-like Blood Lymphocytes and Disease Progression in Amyotrophic Lateral Sclerosis

BACKGROUND AND OBJECTIVES

Aging is known to exacerbate neuroinflammation, and in the neurodegenerative disorder amyotrophic lateral sclerosis (ALS), an older age is associated with a worse prognosis. We have previously shown the activation of cell senescence pathways in the proteome of peripheral blood mononuclear cells and the increase of proinflammatory cytokines in blood from individuals living with ALS. In this single-center, retrospective study, we investigated the expression of senescent-like blood mononuclear cells in ALS.

METHODS

We first applied multidimensional cytometry by time-of-flight (CyTOF) to study the senescent immunophenotype of blood mononuclear cells from 21 patients with ALS and 10 healthy controls (HCs). We then used targeted flow cytometry (FC) to investigate frequencies of senescent blood lymphocytes in 40 patients with ALS and 20 HCs. Longitudinal analysis included 2 additional time points in 17 patients with ALS. Frequencies of senescent-like lymphocytes were analyzed in relation to survival.

RESULTS

Unsupervised clustering of CyTOF data showed higher frequencies of senescent CD4+CD27-CD57+ T cells in patients with ALS compared with those in HCs (p = 0.0017, false discovery (FDR)-adjusted p = 0.029). Moderate to strong negative correlations were identified between CD4 T central memory-cell frequencies and survival (R = -061, p = 0.01; FDR-adjusted p < 0.1) and between CD95 CD8 cells and ALS functional rating scale revised at baseline (R = -0.72, p = 0.001; FDR-adjusted p < 0.1).Targeted FC analysis showed higher memory T regulatory cells (p = 0.0052) and memory CD8+ T cell (M-Tc; p = 0.0006) in bulbar ALS (A-B) compared with those in limb ALS (A-L), while late memory B cells (LM-B) were also elevated in A-B and fast-progressing ALS (p = 0.0059). Higher M-Tc levels separated A-B from A-L (AUC: 0.887; p < 0.0001). A linear regression model with prespecified clinical independent variables and neurofilament light chain plasma concentration showed that higher frequencies of LM-B predicted a shorter survival (hazard ratio: 1.094, CI: 1.026-1.167; p = 0.006).

DISCUSSION

Our data suggest that a systemic elevation of senescent and late memory T and B lymphocytes is a feature of faster progressing ALS and of ALS individuals with bulbar involvement. Lymphocyte senescence and their memory state may be central to the immune dysregulation known to drive disease progression in ALS and a target for biomarkers and therapeutics discovery.

Immune system modulation in aging: Molecular mechanisms and therapeutic targets

The function of the immune system declines during aging, compromising its response against pathogens, a phenomenon termed as "immunosenescence." Alterations of the immune system undergone by aged individuals include thymic involution, defective memory T cells, impaired activation of naïve T cells, and weak memory response. Age-linked alterations of the innate immunity comprise perturbed chemotactic, phagocytic, and natural killing functions, as well as impaired antigen presentation. Overall, these alterations result in chronic low-grade inflammation (inflammaging) that negatively impacts health of elderly people. In this review, we address the most relevant molecules and mechanisms that regulate the relationship between immunosenescence and inflammaging and provide an updated description of the therapeutic strategies aimed to improve immunity in aged individuals.

Altered transcriptional responses in the lungs of aged mice after influenza infection

Background

Influenza causes a serious infection in older individuals who are at the highest risk for mortality from this virus. Changes in the immune system with age are well known. This study used transcriptomic analysis to evaluate how aging specifically affects the functional host response to influenza in the lung. Adult (12–16 weeks) and aged (72–76 weeks) mice were infected with influenza and lungs were processed for RNA analysis.

Results

Older mice demonstrated a delayed anti-viral response on the level of transcription compared to adults, similar to the immunologic responses measured in prior work. The transcriptional differences, however, were evident days before observable differences in the protein responses described previously. The transcriptome response to influenza in aged mice was dominated by immunoglobulin genes and B cell markers compared to adult animals, suggesting immune dysregulation. Despite these differences, both groups of mice had highly similar transcriptional responses involving non-immune genes one day after inoculation and T cell genes during resolution.

Conclusions

These results define a delayed and dysregulated immune response in the lungs of aged mice infected with influenza. The findings implicate B cells and immunoglobulins as markers or mechanisms of immune aging. In addition to discovering new therapeutic targets, the findings underscore the value of transcription studies and network analysis to characterize complex biological processes, and serve as a model to analyze the susceptibility of the elderly to infectious agents.

Supplementary information

The online version contains supplementary material available at 10.1186/s12979-022-00286-9.

The immunopathology of B lymphocytes during stroke-induced injury and repair

B cells, also known as B lymphocytes or lymphoid lineage cells, are a historically understudied cell population with regard to brain-related injuries and diseases. However, an increasing number of publications have begun to elucidate the different phenotypes and roles B cells can undertake during central nervous system (CNS) pathology, including following ischemic and hemorrhagic stroke. B cell phenotype is intrinsically linked to function following stroke, as they may be beneficial or detrimental depending on the subset, timing, and microenvironment. Factors such as age, sex, and presence of co-morbidity also influence the behavior of post-stroke B cells. The following review will briefly describe B cells from origination to senescence, explore B cell function by integrating decades of stroke research, differentiate between the known B cell subtypes and their respective activity, discuss some of the physiological influences on B cells as well as the influence of B cells on certain physiological functions, and highlight the differences between B cells in healthy and disease states with particular emphasis in the context of ischemic stroke.

Sex bias in lymphocytes: Implications for autoimmune diseases

Autoimmune diseases are characterized by a significant sex dimorphism, with women showing increased susceptibility to disease. This is, at least in part, due to sex-dependent differences in the immune system that are influenced by the complex interplay between sex hormones and sex chromosomes, with contribution from sociological factors, diet and gut microbiota. Sex differences are evident in the number and function of lymphocyte populations. Women mount a stronger pro-inflammatory response than males, with increased lymphocyte proliferation, activation and pro-inflammatory cytokine production, whereas men display expanded regulatory cell subsets. Ageing alters the immune landscape of men and women in differing ways, resulting in changes in autoimmune disease susceptibility. Here we review the current literature on sex differences in lymphocyte function, the factors that influence this, and the implications for autoimmune disease. We propose that improved understanding of sex bias in lymphocyte function can provide sex-specific tailoring of treatment strategies for better management of autoimmune diseases.

PEGylated Gold Nanoparticles Target Age-Associated B Cells In Vivo

Engineered gold nanoparticles (GNPs) have become a useful tool in various therapeutic and diagnostic applications. Uncertainty remains regarding the possible impact of GNPs on the immune system. In this regard, we investigated the interactions of polymer-coated GNPs with B cells and their functions in mice. Surprisingly, we observed that polymer-coated GNPs mainly interact with the recently identified subpopulation of B lymphocytes named age-associated B cells (ABCs). Importantly, we also showed that GNPs did not affect cell viability or the percentages of other B cell populations in different organs. Furthermore, GNPs did not activate B cell innate-like immune responses in any of the tested conditions, nor did they impair adaptive B cell responses in immunized mice. Together, these data provide an important contribution to the otherwise limited knowledge about GNP interference with B cell immune function, and demonstrate that GNPs represent a safe tool to target ABCs in vivo for potential clinical applications.

Aging and Mesenchymal Stem Cells: Basic Concepts, Challenges and Strategies

Aging and frailty are complex processes implicating multifactorial mechanisms, such as replicative senescence, oxidative stress, mitochondrial dysfunction, or autophagy disorder. All of these mechanisms drive dramatic changes in the tissue environment, such as senescence-associated secretory phenotype factors and inflamm-aging. Thus, there is a demand for new therapeutic strategies against the devastating effects of the aging and associated diseases. Mesenchymal stem cells (MSC) participate in a "galaxy" of tissue signals (proliferative, anti-inflammatory, and antioxidative stress, and proangiogenic, antitumor, antifibrotic, and antimicrobial effects) contributing to tissue homeostasis. However, MSC are also not immune to aging. Three strategies based on MSC have been proposed: remove, rejuvenate, or replace the senescent MSC. These strategies include the use of senolytic drugs, antioxidant agents and genetic engineering, or transplantation of younger MSC. Nevertheless, these strategies may have the drawback of the adverse effects of prolonged use of the different drugs used or, where appropriate, those of cell therapy. In this review, we propose the new strategy of "Exogenous Restitution of Intercellular Signalling of Stem Cells" (ERISSC). This concept is based on the potential use of secretome from MSC, which are composed of molecules such as growth factors, cytokines, and extracellular vesicles and have the same biological effects as their parent cells. To face this cell-free regenerative therapy challenge, we have to clarify key strategy aspects, such as establishing tools that allow us a more precise diagnosis of aging frailty in order to identify the therapeutic requirements adapted to each case, identify the ideal type of MSC in the context of the functional heterogeneity of these cellular populations, to optimize the mass production and standardization of the primary materials (cells) and their secretome-derived products, to establish the appropriate methods to validate the anti-aging effects and to determine the most appropriate route of administration for each case.

Ageing and Low-Level Chronic Inflammation: The Role of the Biological Clock

Ageing is a multifactorial physiological manifestation that occurs inexorably and gradually in all forms of life. This process is linked to the decay of homeostasis due to the progressive decrease in the reparative and regenerative capacity of tissues and organs, with reduced physiological reserve in response to stress. Ageing is closely related to oxidative damage and involves immunosenescence and tissue impairment or metabolic imbalances that trigger inflammation and inflammasome formation. One of the main ageing-related alterations is the dysregulation of the immune response, which results in chronic low-level, systemic inflammation, termed "inflammaging". Genetic and epigenetic changes, as well as environmental factors, promote and/or modulate the mechanisms of ageing at the molecular, cellular, organ, and system levels. Most of these mechanisms are characterized by time-dependent patterns of variation driven by the biological clock. In this review, we describe the involvement of ageing-related processes with inflammation in relation to the functioning of the biological clock and the mechanisms operating this intricate interaction.

Aging, inflammaging and immunosenescence as risk factors of severe COVID-19

Coronavirus disease 2019 (COVID-19) is a respiratory infectious disease caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 is characterized by having a heterogeneous disease course, ranging from asymptomatic and mild symptoms to more severe and critical cases. In most cases the severity of COVID-19 is related to host factors, especially deregulation of the immune response in patients. Even if COVID-19 indiscriminately affects individuals of different age group, ethnicity and economic status; most severe cases and disproportional mortality occur in elderly individuals. This point out that aging is one risk factor for unfavourable clinical outcomes among COVID-19 patients. The biology of aging is a complex process; Aging can alter the structure and function of cells, tissues, and organs resulting in impaired response to stress. Alongside with other systems, the immune system is also affected with the aging process. Immunosenescence is an age associated change in the immune system that affects the overall response to immunological challenges in the elderly. Similarly, apart from the normal inflammatory process, aging is associated with a low grade, sterile, chronic inflammation which is termed as inflammaging. We hypothesized that inflammaging and immunosenescence could play an important role in SARS-CoV-2 pathogenesis and poor recovery from COVID-19 in elderly individuals. This review summarizes the changes in the immune system with age and how these changes play part in the pathogenesis of SARS-CoV-2 and clinical outcome of COVID-19 which could add to the understanding of age associated targeted immunotherapy in the elderly.

Immunosenescence in Neurological Diseases-Is There Enough Evidence?

The aging of the immune system has recently attracted a lot of attention. Immune senescence describes changes that the immune system undergoes over time. The importance of immune senescence in neurological diseases is increasingly discussed. For this review, we considered studies that investigated cellular changes in the aging immune system and in neurological disease. Twenty-six studies were included in our analysis (for the following diseases: multiple sclerosis, stroke, Parkinson's disease, and dementia). The studies differed considerably in terms of the patient groups included and the cell types studied. Evidence for immunosenescence in neurological diseases is currently very limited. Prospective studies in well-defined patient groups with appropriate control groups, as well as comprehensive methodology and reporting, are essential prerequisites to generate clear insights into immunosenescence in neurological diseases.

Immunoglobulin G glycans - Biomarkers and molecular effectors of aging

Immunoglobulin G (IgG) antibodies are post-translationally modified by the addition of complex carbohydrate molecules - glycans, which have profound effects on the IgG function, most significantly as modulators of its inflammatory capacity. Therefore, it is not surprising that the changes in IgG glycosylation pattern are associated with various physiological states and diseases, including aging and age-related diseases. Importantly, within the inflammaging concept, IgG glycans are considered not only biomarkers but one of the molecular effectors of the aging process. The exact mechanism by which they exert their function, however, remains unknown. In this review, we list and comment on, to our knowledge, all studies that examined changes in IgG glycosylation during aging in humans. We focus on the information obtained from studies on general population, but we also cover the insights obtained from studies of long-lived individuals and people with age-related diseases. We summarize the current knowledge on how levels of different IgG glycans change with age (i.e., the extent and direction of the change with age) and discuss the potential mechanisms and possible functional roles of changes in IgG glycopattern that accompany aging.

Correlation between Type I Interferon Associated Factors and COVID-19 Severity

Antiviral type I interferons (IFN) produced in the early phase of viral infections effectively inhibit viral replication, prevent virus-mediated tissue damages and promote innate and adaptive immune responses that are all essential to the successful elimination of viruses. As professional type I IFN producing cells, plasmacytoid dendritic cells (pDC) have the ability to rapidly produce waste amounts of type I IFNs. Therefore, their low frequency, dysfunction or decreased capacity to produce type I IFNs might increase the risk of severe viral infections. In accordance with that, declined pDC numbers and delayed or inadequate type I IFN responses could be observed in patients with severe coronavirus disease (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as compared to individuals with mild or no symptoms. Thus, besides chronic diseases, all those conditions, which negatively affect the antiviral IFN responses lengthen the list of risk factors for severe COVID-19. In the current review, we would like to briefly discuss the role and dysregulation of pDC/type I IFN axis in COVID-19, and introduce those type I IFN-dependent factors, which account for an increased risk of COVID-19 severity and thus are responsible for the different magnitude of individual immune responses to SARS-CoV-2.

A gut-centric view of aging: Do intestinal epithelial cells contribute to age-associated microbiota changes, inflammaging, and immunosenescence?

Intestinal epithelial cells (IECs) serve as both a physical and an antimicrobial barrier against the microbiota, as well as a conduit for signaling between the microbiota and systemic host immunity. As individuals age, the balance between these systems undergoes a myriad of changes due to age-associated changes to the microbiota, IECs themselves, immunosenescence, and inflammaging. In this review, we discuss emerging data related to age-associated loss of intestinal barrier integrity and posit that IEC dysfunction may play a central role in propagating age-associated alterations in microbiota composition and immune homeostasis.

The Role of B Lymphocyte Subsets in Adipose Tissue Development, Metabolism, and Aging

Adipose tissue contains resident B lymphocytes (B cells) with varying immune functions and mechanisms, depending on the adipose depot type and location. The heterogeneity of B cells and their functions affect the immunometabolism of the adipose tissue in aging and age-associated metabolic disorders. B cells exist in categorizations of subsets that have developmental or phenotypic differences with varying functionalities. Subsets can be categorized as either protective or pathogenic depending on their secretion profile or involvement in metabolic maintenance. In this article, we summarized recent finding on the B cell heterogeneity and discuss how we can utilize our current knowledge of adipose resident B lymphocytes for potential treatment for age-associated metabolic disorders. © 2022 American Physiological Society. Compr Physiol 12: 1-13, 2022.

CD11bhigh B Cells Increase after Stroke and Regulate Microglia

Recent studies have highlighted the deleterious contributions of B cells to post-stroke recovery and cognitive decline. Different B cell subsets have been proposed on the basis of expression levels of transcription factors (e.g., T-bet) as well as specific surface proteins. CD11b (α-chain of integrin) is expressed by several immune cell types and is involved in regulation of cell motility, phagocytosis, and other essential functions of host immunity. Although B cells express CD11b, the CD11b^high subset of B cells has not been well characterized, especially in immune dysregulation seen with aging and after stroke. Here, we investigate the role of CD11b^high B cells in immune responses after stroke in young and aged mice. We evaluated the ability of CD11b^high B cells to influence pro- and anti-inflammatory phenotypes of young and aged microglia (MG). We hypothesized that CD11b^high B cells accumulate in the brain and contribute to neuroinflammation in aging and after stroke. We found that CD11b^high B cells are a heterogeneous subpopulation of B cells predominantly present in naive aged mice. Their frequency increases in the brain after stroke in young and aged mice. Importantly, CD11b^high B cells regulate MG phenotype and increase MG phagocytosis in both ex vivo and in vivo settings, likely by production of regulatory cytokines (e.g., TNF-α). As both APCs and adaptive immune cells with long-term memory function, B cells are uniquely positioned to regulate acute and chronic phases of the post-stroke immune response, and their influence is subset specific.

Immunosenescence in Childhood Cancer Survivors and in Elderly: A Comparison and Implication for Risk Stratification

The population of childhood cancer survivors (CCS) has grown rapidly in recent decades. Although cured of their original malignancy, these individuals are at increased risk of serious late effects, including age-associated complications. An impaired immune system has been linked to the emergence of these conditions in the elderly and CCS, likely due to senescent immune cell phenotypes accompanied by low-grade inflammation, which in the elderly is known as "inflammaging." Whether these observations in the elderly and CCS are underpinned by similar mechanisms is unclear. If so, existing knowledge on immunosenescent phenotypes and inflammaging might potentially serve to benefit CCS. We summarize recent findings on the immune changes in CCS and the elderly, and highlight the similarities and identify areas for future research. Improving our understanding of the underlying mechanisms and immunosenescent markers of accelerated immune aging might help us to identify individuals at increased risk of serious health complications.

Aging Affects the Role of Myeloid-Derived Suppressor Cells in Alloimmunity

Myeloid-derived suppressor cells (MDSC) are defined as a group of myeloid cells with potent immunoregulatory functions that have been shown to be involved in a variety of immune-related diseases including infections, autoimmune disorders, and cancer. In organ transplantation, MDSC promote tolerance by modifying adaptive immune responses. With aging, however, substantial changes occur that affect immune functions and impact alloimmunity. Since the vast majority of transplant patients are elderly, age-specific modifications of MDSC are of relevance. Furthermore, understanding age-associated changes in MDSC may lead to improved therapeutic strategies. Here, we provide a comprehensive update on the effects of aging on MDSC and discuss potential consequences on alloimmunity.