Immunosenescence, aging, and systemic lupus erythematous

sCD163, sCD28, sCD80, and sCTLA-4 as soluble marker candidates for detecting immunosenescence

BACKGROUND

Inflammaging, the characteristics of immunosenescence, characterized by continuous chronic inflammation that could not be resolved. It is not only affect older people but can also occur in young individuals, especially those suffering from chronic inflammatory conditions such as autoimmune disease, malignancy, or chronic infection. This condition led to altered immune function and as consequent immune function is reduced. Detection of immunosenescence has been done by examining the immune risk profile (IRP), which uses flow cytometry. These tests are not always available in health facilities, especially in developing countries and require fresh whole blood samples. Therefore, it is necessary to find biomarkers that can be tested using stored serum to make it easier to refer to the examination. Here we proposed an insight for soluble biomarkers which represented immune cells activities and exhaustion, namely sCD163, sCD28, sCD80, and sCTLA-4. Those markers were reported to be elevated in chronic diseases that caused early aging and easily detected from serum samples using ELISA method, unlike IRP. Therefore, we conclude these soluble markers are beneficial to predict pathological condition of immunosenescence.

AIM

To identify soluble biomarkers that could replace IRP for detecting immunosenescence.

CONCLUSION

Soluble costimulatory molecule suchsCD163, sCD28, sCD80, and sCTLA-4 are potential biomarkers for detecting immunosenescence.

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.

Endogenous Retroviruses (ERVs): Does RLR (RIG-I-Like Receptors)-MAVS Pathway Directly Control Senescence and Aging as a Consequence of ERV De-Repression?

Bi-directional transcription of Human Endogenous Retroviruses (hERVs) is a common feature of autoimmunity, neurodegeneration and cancer. Higher rates of cancer incidence, neurodegeneration and autoimmunity but a lower prevalence of autoimmune diseases characterize elderly people. Although the re-expression of hERVs is commonly observed in different cellular models of senescence as a result of the loss of their epigenetic transcriptional silencing, the hERVs modulation during aging is more complex, with a peak of activation in the sixties and a decline in the nineties. What is clearly accepted, instead, is the impact of the re-activation of dormant hERV on the maintenance of stemness and tissue self-renewing properties. An innate cellular immunity system, based on the RLR-MAVS circuit, controls the degradation of dsRNAs arising from the transcription of hERV elements, similarly to what happens for the accumulation of cytoplasmic DNA leading to the activation of cGAS/STING pathway. While agonists and inhibitors of the cGAS-STING pathway are considered promising immunomodulatory molecules, the effect of the RLR-MAVS pathway on innate immunity is still largely based on correlations and not on causality. Here we review the most recent evidence regarding the activation of MDA5-RIG1-MAVS pathway as a result of hERV de-repression during aging, immunosenescence, cancer and autoimmunity. We will also deal with the epigenetic mechanisms controlling hERV repression and with the strategies that can be adopted to modulate hERV expression in a therapeutic perspective. Finally, we will discuss if the RLR-MAVS signalling pathway actively modulates physiological and pathological conditions or if it is passively activated by them.

Leukocyte Telomere Length and Childhood Onset of Systemic Lupus Erythematosus in the Black Women's Experiences Living with Lupus Study

Objective

The study objective was to compare leukocyte telomere length (LTL) among patients with systemic lupus erythematosus (SLE) diagnosed in childhood versus adulthood.

Methods

Data are from the Black Women's Experiences Living with Lupus (BeWELL) study. Multivariable linear regression analyses that examined childhood diagnosis of SLE (diagnosed before 18 years of age), age, and their interaction in relationship to LTL were conducted, adjusting for a range of demographic, socioeconomic, and health‐related covariates.

Results

The total analytic sample size was 415. Forty participants (9.6%) were diagnosed in childhood. There was no main effect of childhood diagnosis on LTL (b = 0.007; 95% confidence interval [CI]: −0.089 to 0.103). However, the interaction between age and childhood diagnosis was significant (b = −0.008; 95% CI: −0.016 to −0.001), indicating a steeper inverse association between age and LTL among those diagnosed in childhood compared with those diagnosed in adulthood. This interaction remained statistically significant (P = 0.024) after controlling for disease duration measured dichotomously (less than 10 years vs. 10 years or more); it was marginally significant (P = 0.083) when controlling for disease duration measured continuously.

Conclusion

This cross‐sectional analysis suggests that Black women with childhood‐onset SLE may undergo accelerated LTL shortening compared with their adult‐onset counterparts. This relationship persisted even after controlling for differences in SLE damage and disease duration. These findings inform research on immunosenescence mechanisms of SLE.

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

Objectives

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

Material and methods

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

Results

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

Conclusions

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

The Effect of Mango Mistletoes (Dendrophthoe pentandra) Leaves Extract on Percentage of CD4+CD28+, CD8+CD28+, and interleukin-2 Levels of Aged Balb/c Mice

BACKGROUND: Population aging is considered to be a global phenomenon today. Age-associated immune system dysfunction or “immunosenescence” is indicated by increased susceptibility to infections and chronic diseases, such as hypertension, diabetes mellitus, autoimmune diseases, heart disease, and atherosclerosis. One of the immunosenescence markers is a significant drop in CD28 and reduced proinflammatory cytokine interleukin-2 (IL-2). The mango mistletoes are deemed to have a better affinity for docking the CD28 and IL-2R receptors of α and β subunits than other plants. AIM: This study aims to determine the effect of ethanol extract of mango mistletoes on IL-2 levels, the percentage of CD4+CD28+, and the percentage of CD8+CD28+ in aged female mice. METHODS: The leaves of mango mistletoes were extracted using 96% ethanol solvent, and the extract was administered to aged female mice (18–20 months) orally with different doses for each group, namely 150, 300, and 600 mg/kg. Mango mistletoe leaves extract was administered once a day for 14 days. Then, the IL-2 levels of the mice were checked from their heart blood samples using Enzyme-Linked Immunosorbent Assay, while the percentages of CD4+CD28+ and CD8+CD28+ were examined from the spleen samples using flow cytometry. RESULTS: The ethanol extract of mango mistletoe leaves was able to increase the percentage of CD4+CD28+ significantly (p < 0.05) at doses of 300 and 600 mg/kg and increase the percentage of CD8+CD28+ significantly (p < 0.05) at a dose of 600 mg/kgBW, while other various doses had a strong enough correlation (r = 0.48) to increase IL-2 levels. CONCLUSION: The ethanol extract of mango mistletoe leaves has the good potential to inhibit the aging process in the immune system, as characterized by an increase in IL-2 levels and the percentage of CD4+CD28+ and CD8+CD28+.

An evaluation of the recognised systemic inflammatory biomarkers of chronic sub-optimal inflammation provides evidence for inflammageing (IFA) during multiple sclerosis (MS)

The pathogenesis of the human demyelinating disorder multiple sclerosis (MS) involves the loss of immune tolerance to self-neuroantigens. A deterioration in immune tolerance is linked to inherent immune ageing, or immunosenescence (ISC). Previous work by the author has confirmed the presence of ISC during MS. Moreover, evidence verified a prematurely aged immune system that may change the frequency and profile of MS through an altered decline in immune tolerance. Immune ageing is closely linked to a chronic systemic sub-optimal inflammation, termed inflammageing (IFA), which disrupts the efficiency of immune tolerance by varying the dynamics of ISC that includes accelerated changes to the immune system over time. Therefore, a shifting deterioration in immunological tolerance may evolve during MS through adversely-scheduled effects of IFA on ISC. However, there is, to date, no collective proof of ongoing IFA during MS. The Review addresses the constraint and provides a systematic critique of compelling evidence, through appraisal of IFA-related biomarker studies, to support the occurrence of a sub-optimal inflammation during MS. The findings justify further work to unequivocally demonstrate IFA in MS and provide additional insight into the complex pathology and developing epidemiology of the disease.

Association Between the Anti-Aging Gene Klotho and Selected Rheumatologic Autoimmune Diseases

Klotho long recognized for its role in anti-aging, is potentially implicated in the pathogenesis of rheumatoid arthritis, systemic lupus erythematosus, and systemic sclerosis. Aging of the immune system coincides with the inability of the body to recognize self-antigens, which often leads to autoimmune responses. The role of Klotho in these autoimmune diseases should be of high interest; however, few articles have been published exploring the role of Klotho in the pathogenesis, organ involvement, or clinical manifestation of rheumatoid arthritis, systemic lupus erythematosus, and systemic sclerosis. Herein, we discuss information gathered from peer-reviewed publications to describe the emerging role of Kl in these select rheumatologic autoimmune diseases.

Regulatory T Cells: Concept, Classification, Phenotype, and Biological Characteristics

Regulatory T cells (Treg) play an indispensable role in maintaining the body's immune nonresponse to self-antigens and suppressing the body's unwarranted and potentially harmful immune responses. Their absence, reduction, dysfunction, transformation, and instability can lead to numerous autoimmune diseases. There are several distinct subtypes of the Treg cells, although they share certain biological characteristics and have unique phenotypes with different regulatory functions, as well as mechanistic abilities. In this book chapter, we introduce the latest advances in Treg cell subtypes pertaining to classification, phenotype, biological characteristics, and mechanisms. We also highlight the relationship between Treg cells and various diseases, including autoimmune, infectious, as well as tumors and organ transplants.

Ectopic Lymphoid Follicles in Multiple Sclerosis: Centers for Disease Control?

While the contribution of autoreactive CD4⁺ T cells to the pathogenesis of Multiple Sclerosis (MS) is widely accepted, the advent of B cell-depleting monoclonal antibody (mAb) therapies has shed new light on the complex cellular mechanisms underlying MS pathogenesis. Evidence supports the involvement of B cells in both antibody-dependent and -independent capacities. T cell-dependent B cell responses originate and take shape in germinal centers (GCs), specialized microenvironments that regulate B cell activation and subsequent differentiation into antibody-secreting cells (ASCs) or memory B cells, a process for which CD4⁺ T cells, namely follicular T helper (T_FH) cells, are indispensable. ASCs carry out their effector function primarily via secreted Ig but also through the secretion of both pro- and anti-inflammatory cytokines. Memory B cells, in addition to being capable of rapidly differentiating into ASCs, can function as potent antigen-presenting cells (APCs) to cognate memory CD4⁺ T cells. Aberrant B cell responses are prevented, at least in part, by follicular regulatory T (T_FR) cells, which are key suppressors of GC-derived autoreactive B cell responses through the expression of inhibitory receptors and cytokines, such as CTLA4 and IL-10, respectively. Therefore, GCs represent a critical site of peripheral B cell tolerance, and their dysregulation has been implicated in the pathogenesis of several autoimmune diseases. In MS patients, the presence of GC-like leptomeningeal ectopic lymphoid follicles (eLFs) has prompted their investigation as potential sources of pathogenic B and T cell responses. This hypothesis is supported by elevated levels of CXCL13 and circulating T_FH cells in the cerebrospinal fluid (CSF) of MS patients, both of which are required to initiate and maintain GC reactions. Additionally, eLFs in post-mortem MS patient samples are notably devoid of T_FR cells. The ability of GCs to generate and perpetuate, but also regulate autoreactive B and T cell responses driving MS pathology makes them an attractive target for therapeutic intervention. In this review, we will summarize the evidence from both humans and animal models supporting B cells as drivers of MS, the role of GC-like eLFs in the pathogenesis of MS, and mechanisms controlling GC-derived autoreactive B cell responses in MS.

Molecular Mechanisms of Premature Aging in Hemodialysis: The Complex Interplay Between Innate and Adaptive Immune Dysfunction

Hemodialysis (HD) patient are known to be susceptible to a wide range of early and long-term complication such as chronic inflammation, infections, malnutrition, and cardiovascular disease that significantly affect the incidence of mortality. A large gap between the number of people with end-stage kidney disease (ESKD) and patients who received kidney transplantation has been identified. Therefore, there is a huge need to explore the underlying pathophysiology of HD complications in order to provide treatment guidelines. The immunological dysregulation, involving both the innate and adaptive response, plays a crucial role during the HD sessions and in chronic, maintenance treatments. Innate immune system mediators include the dysfunction of neutrophils, monocytes, and natural killer (NK) cells with signaling mediated by NOD-like receptor P3 (NLRP3) and Toll-like receptor 4 (TLR4); in addition, there is a significant activation of the complement system that is mediated by dialysis membrane-surfaces. These effectors induce a persistent, systemic, pro-inflammatory, and pro-coagulant milieu that has been described as inflammaging. The adaptive response, the imbalance in the CD4+/CD8+ T cell ratio, and the reduction of Th2 and regulatory T cells, together with an altered interaction with B lymphocyte by CD40/CD40L, have been mainly implicated in immune system dysfunction. Altogether, these observations suggest that intervention targeting the immune system in HD patients could improve morbidity and mortality. The purpose of this review is to expand our understanding on the role of immune dysfunction in both innate and adaptive response in patients undergoing hemodialysis treatment.

Molecular and Cellular Bases of Immunosenescence, Inflammation, and Cardiovascular Complications Mimicking "Inflammaging" in Patients with Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an archetype of systemic autoimmune disease, characterized by the presence of diverse autoantibodies and chronic inflammation. There are multiple factors involved in lupus pathogenesis, including genetic/epigenetic predisposition, sexual hormone imbalance, environmental stimulants, mental/psychological stresses, and undefined events. Recently, many authors noted that "inflammaging", consisting of immunosenescence and inflammation, is a common feature in aging people and patients with SLE. It is conceivable that chronic oxidative stresses originating from mitochondrial dysfunction, defective bioenergetics, abnormal immunometabolism, and premature telomere erosion may accelerate immune cell senescence in patients with SLE. The mitochondrial dysfunctions in SLE have been extensively investigated in recent years. The molecular basis of normoglycemic metabolic syndrome has been found to be relevant to the production of advanced glycosylated and nitrosative end products. Besides, immunosenescence, autoimmunity, endothelial cell damage, and decreased tissue regeneration could be the results of premature telomere erosion in patients with SLE. Herein, the molecular and cellular bases of inflammaging and cardiovascular complications in SLE patients will be extensively reviewed from the aspects of mitochondrial dysfunctions, abnormal bioenergetics/immunometabolism, and telomere/telomerase disequilibrium.

The Systemic Lupus Erythematosus Infection Predictive Index (LIPI): A Clinical-Immunological Tool to Predict Infections in Lupus Patients

Among autoimmune diseases, systemic lupus erythematosus (SLE) patients have a unique predisposition to develop infections, which represents one of their main causes of morbidity and mortality. Many infections occur at disease diagnosis in the absence of immunosuppressive therapy, suggesting that the immunological abnormalities in SLE patients might be fundamental for the development of this complication. The aim of this study was to address the main clinical and immunological features associated with the development of infection and to create and validate a compound clinical-immunological infection predictive index in a cohort of SLE patients. We included 55 SLE patients with < 5 years since diagnosis. The clinical and immunological features were evaluated periodically and patients were followed-up during 1 year, searching for the development of infection. Immunophenotyping was performed by multiparametric flow cytometry and neutrophil extracellular traps (NETs) were assessed by confocal microscopy. Eighteen patients (32.7%) presented 19 infectious events, 5 (26.3%) were severe. For the construction of the index, we performed a logistic regression analysis and the cutoff points were determined with ROC curves. Increased numbers of peripheral Th17 cells, B cell lymphopenia, and lower TLR2 expression in monocytes, as well as the use of cyclophosphamide were the major risk factors for the development of infection and thus were included in the index. Besides, patients that developed infection were characterized by increased numbers of low-density granulocytes (LDGs) and higher expression of LL-37 in NETs upon infection. Finally, we validated the index retrospectively in a nested case-control study. A score >1.5 points was able to predict infection in the following year (AUC = 0.97; LR- = 0.001, specificity 100%, P = 0.0003). Our index encompasses novel immunological features able to prospectively predict the risk of infection in SLE patients.

The Cutaneous Spectrum of Lupus Erythematosus

Systemic lupus erythematosus is a complex autoimmune disease with a wide spectrum of clinical and immunopathological features. Cutaneous and articular manifestations are the most common signs in patients with systemic lupus erythematosus. We here review the pathogenesis and the new classification of cutaneous lupus erythemathosus with a discussion of the significance of the various cutaneous signs. The lesions are classified according to the level of the cellular infiltrate and tissue damage in the epidermis, dermis, and/or subcutis. Furthermore, cutaneous lesions pointing to the presence of a thrombotic vasculopathy and those due to a distinct inflammatory, neutrophilic-mediated reaction pattern are highlighted. Particular attention will be given in describing the histology of skin manifestation. Treatment options for cutaneous lupus erythemathosus have increased with the introduction of new biological therapies. However, the majority of the patients still benefit from antimalarials, which remain the cornerstone of treatment. The evaluation and management of cutaneous lupus erythemathosus patients depend on the clinical findings and associated symptoms.

The interaction between environmental triggers and epigenetics in autoimmunity

Systemic lupus erythematosus flares when genetically predisposed people encounter environmental agents that cause oxidative stress, such as infections and sunlight. How these modify the immune system to initiate flares is unclear. Drug induced lupus models demonstrate that CD4+ T cells epigenetically altered with DNA methylation inhibitors cause lupus in animal models, and similar T cells are found in patients with active lupus. How infections and sun exposure inhibit T cell DNA methylation is unclear. DNA methylation patterns are replicated each time a cell divides in a process that requires DNA methyltransferase one (Dnmt1), which is upregulated as cells enter mitosis, as well as the methyl donor S-adenosylmethionine, created from dietary sources. Reactive oxygen species that inhibit Dnmt1 upregulation, and a diet poor in methyl donors, combine to cause lupus in animal models. Similar changes are found in patients with active lupus, indicating a mechanism contributing to lupus flares.

Continuous Dual Resetting of the Immune Repertoire as a Basic Principle of the Immune System Function

Idiopathic chronic inflammatory conditions (ICIC) such as allergy, asthma, chronic obstructive pulmonary disease, and various autoimmune conditions are a worldwide health problem. Understanding the pathogenesis of ICIC is essential for their successful therapy and prevention. However, efforts are hindered by the lack of comprehensive understanding of the human immune system function. In line with those efforts, described here is a concept of stochastic continuous dual resetting (CDR) of the immune repertoire as a basic principle that governs the function of immunity. The CDR functions as a consequence of system's thermodynamically determined intrinsic tendency to acquire new states of inner equilibrium and equilibrium against the environment. Consequently, immune repertoire undergoes continuous dual (two-way) resetting: against the physiologic continuous changes of self and against the continuously changing environment. The CDR-based dynamic concept of immunity describes mechanisms of self-regulation, tolerance, and immunosenescence, and emphasizes the significance of immune system's compartmentalization in the pathogenesis of ICIC. The CDR concept's relative simplicity and concomitantly documented congruency with empirical, clinical, and experimental data suggest it may represent a plausible theoretical framework to better understand the human immune system function.

The Telomere/Telomerase System in Chronic Inflammatory Diseases. Cause or Effect?

Telomeres are specialized nucleoprotein structures located at the end of linear chromosomes and telomerase is the enzyme responsible for telomere elongation. Telomerase activity is a key component of many cancer cells responsible for rapid cell division but it has also been found by many laboratories around the world that telomere/telomerase biology is dysfunctional in many other chronic conditions as well. These conditions are characterized by chronic inflammation, a situation mostly overlooked by physicians regarding patient treatment. Among others, these conditions include diabetes, renal failure, chronic obstructive pulmonary disease, etc. Since researchers have in many cases identified the association between telomerase and inflammation but there are still many missing links regarding this correlation, the latest findings about this phenomenon will be discussed by reviewing the literature. Our focus will be describing telomere/telomerase status in chronic diseases under the prism of inflammation, reporting molecular findings where available and proposing possible future approaches.

CD3(+)CD8(+)CD28(-) T Lymphocytes in Patients with Lupus Nephritis

The results of studies on the CD3⁺CD8⁺CD28⁻ cells in SLE are inconsistent since several analyses describe CD3⁺CD8⁺CD28⁻ as either immunosuppressive or cytotoxic. The aim of this study is to inquire whether the quantitative changes of CD3⁺CD8⁺CD28⁻ T lymphocytes subpopulation are related to the clinical status of patients with lupus nephritis. Evaluation of Foxp3 expression on CD3⁺CD8⁺CD28⁻ cells may shed some light on functional properties of these cells. 54 adult SLE patients and 19 sex and age matched healthy volunteers were enrolled in the study. There were 15 patients in inactive (SLEDAI ≤ 5) and 39 in active (SLEDAI > 5) phase of disease. We determined absolute count of CD3⁺CD8⁺CD28⁻ and CD3⁺CD8⁺CD28⁻Foxp3⁺ subpopulations by flow cytometry. We observed a statistically significant increase in absolute count and percentage of CD3⁺CD8⁺CD28⁻ in SLE patients compared to HC (p < 0.001). Moreover there was significant positive correlation between increasing absolute count of CD3⁺CD8⁺CD28⁻ cells and disease activity measured by SLEDAI (rs = 0.281, p = 0.038). Active LN patients had increased absolute count of CD3⁺CD8⁺CD28⁻ cells compared to HC. Positive correlation of CD3⁺CD8⁺CD28⁻ number with disease activity, and lack of Foxp3 expression on these cells, suggests that CD3⁺CD8⁺CD28⁻ lymphocytes might be responsible for an increased proinflammatory response in the exacerbation of SLE.

Thymus: the next (re)generation

As the primary site of T-cell development, the thymus plays a key role in the generation of a strong yet self-tolerant adaptive immune response, essential in the face of the potential threat from pathogens or neoplasia. As the importance of the role of the thymus has grown, so too has the understanding that it is extremely sensitive to both acute and chronic injury. The thymus undergoes rapid degeneration following a range of toxic insults, and also involutes as part of the aging process, albeit at a faster rate than many other tissues. The thymus is, however, capable of regenerating, restoring its function to a degree. Potential mechanisms for this endogenous thymic regeneration include keratinocyte growth factor (KGF) signaling, and a more recently described pathway in which innate lymphoid cells produce interleukin-22 (IL-22) in response to loss of double positive thymocytes and upregulation of IL-23 by dendritic cells. Endogenous repair is unable to fully restore the thymus, particularly in the aged population, and this paves the way toward the need for exogenous strategies to help regenerate or even replace thymic function. Therapies currently in clinical trials include KGF, use of the cytokines IL-7 and IL-22, and hormonal modulation including growth hormone administration and sex steroid inhibition. Further novel strategies are emerging in the preclinical setting, including the use of precursor T cells and thymus bioengineering. The use of such strategies offers hope that for many patients, the next regeneration of their thymus is a step closer.

Telomere length attrition and chronic periodontitis: an ARIC Study nested case-control study

AIM

This nested case-control study sought to determine whether an accelerated rate of leukocyte telomere length (LTL) shortening over 6 years was associated with chronic periodontitis.

MATERIALS AND METHODS

We sampled cases (n = 178) with severe chronic periodontitis and controls (n = 178) with no/mild chronic periodontitis from the Atherosclerosis Risk in Communities study. Controls were frequency-matched to cases by study site, age, sex and race. Age ranged from 53 to 73 years. Severe chronic periodontitis was defined using the CDC-AAP case classification. LTL was measured from DNA collected at two time points, 6 years apart, with quantitative polymerase chain reaction relative to a single-copy control gene. Multiple linear regression evaluated associations between LTL measured at baseline, follow-up and change scores with severe chronic periodontitis, adjusting for potential confounders.

RESULTS

Cases had shorter LTL than controls at baseline (p = 0.03) and follow-up (p = 0.04) after adjusting for confounding. Overall there was a net reduction in LTL over time (p = 0.02). The rate of LTL did not differ between cases and controls (p = 0.80).

CONCLUSIONS

Leukocyte telomere length shortening occurred at the same rate among adults with and without severe chronic periodontitis. This suggests that LTL shortening may have occurred earlier in the life course.