T-cell biology in aging, with a focus on lung disease

Immune defects in the risk of infection and response to vaccination in monoclonal gammopathy of undetermined significance and multiple myeloma

The plasma cell proliferative disorders monoclonal gammopathy of undetermined significance (MGUS) and malignant multiple myeloma (MM) are characterized by an accumulation of transformed clonal plasma cells in the bone marrow and production of monoclonal immunoglobulin. They typically affect an older population, with median age of diagnosis of approximately 70 years. In both disorders, there is an increased risk of infection due to the immunosuppressive effects of disease and conjointly of therapy in MM, and response to vaccination to counter infection is compromised. The underlying factors in a weakened immune response in MGUS and MM are as yet not fully understood. A confounding factor is the onset of normal aging, which quantitatively and qualitatively hampers humoral immunity to affect response to infection and vaccination. In this review, we examine the status of immune alterations in MGUS and MM and set these against normal aging immune responses. We focus primarily on quantitative and functional aspects of B-cell immunity. Furthermore, we review the current knowledge relating to susceptibility to infectious disease in MGUS and MM, and how efficacy of conventional vaccination is affected by proliferative disease-related and therapy-related factors.

Human monocytes have increased IFN-γ-mediated IL-15 production with age alongside altered IFN-γ receptor signaling

IL-15 is involved in regulating host defense and inflammation. Monocytes produce the biologically active cell surface IL-15 in response to IFN-γ. Although aging can alter the immune system, little is known about whether and how aging affects IFN-γ-mediated IL-15 production in human monocytes. We showed that monocytes of healthy older adults (age ≥ 65) had increased cell surface IL-15 expression in response to IFN-γ compared to those of healthy young adults (age ≤ 40). This finding stems in part from increased IFN-γ receptor (R)1/2 expression on monocytes in older adults, leading to enhanced STAT1 activation and interferon regulatory factor 1 synthesis with increased IL15 gene expression. Our study suggests that with aging the IFN-γ-mediated IL-15 production pathway in human monocytes is uncompromised, but rather augmented, and could be considered as a therapeutic target point to modulate host defense and inflammation in older adults.

Premature CD4+ T cell aging and its contribution to lymphopenia-induced proliferation of memory cells in autoimmune-prone non-obese diabetic mice

Lymphopenia-induced proliferation (LIP), a mechanism to maintain a constant number of T cells in circulation, occurs in both normal aging and autoimmune disease. The incidence of most autoimmune diseases increases with age, and premature CD4(+) T cell aging has been reported in several autoimmune diseases. In this study, we tested the hypothesis that premature CD4(+) T cell aging can cause autoimmune disease by examining whether premature CD4(+) T cell aging exists and causes LIP in our mouse model. Non-obese diabetic (NOD) mice were used because, in addition to Treg defects, the LIP of T cells has been shown to plays a causative role in the development of insulin-dependent diabetes mellitus (IDDM) in these mice. We found that with advancing age, NOD mice exhibited an accelerated decrease in the number of CD4(+) T cells due to the loss of naïve cells. This was accompanied by an increase in the percentage of memory cells, leading to a reduced naïve/memory ratio. In addition, both the percentage of CD28(+) cells in CD4(+) T cells and IL-2 production decreased, while the percentage of FAS(+)CD44(+) increased, suggesting that NOD mice exhibit premature CD4(+) T cell aging. This process preferentially contributed to LIP of memory cells. Therefore, our results suggest that premature CD4(+) T cell aging underlies the development of IDDM in NOD mice. Given that CD28 and IL-2 play important roles in Treg function, the relationships between premature CD4(+) T cell aging and lymphopenia as well as Treg defects in autoimmune-prone NOD mice are proposed.

Influence of age on manifestation, VC and TLCO values, and bronchoalveolar lavage cell counts of sarcoidosis and extrinsic allergic alveolitis

INTRODUCTION

Immune response probably changes during human life, being influenced by cumulative exposure to environmental factors and individual genetic background.

METHODS

Patients investigated for suspected interstitial lung disease were prospectively enrolled. After completing the diagnostic process, 121 patients were diagnosed extrinsic allergic alveolitis (EAA) and 136 sarcoidosis. Three groups according to age were established (<30 years, 30-60 years, >60 years), clinical manifestation, vital capacity (VC), forced expired volume in 1 s (FEV1 ), lung diffusing capacity for carbon monoxide-transfer factor (TLCO ) and bronchoalveolar lavage fluid (BALF) differential cell count were compared among the groups.

RESULTS

Age subgroups of EAA patients did not significantly differ in lung functions. In the group above 60 years, non-significantly higher neutrophils and eosinophils counts and CD4/CD8 ratio were observed. Sarcoidosis patients were significantly younger than EAA group and had significantly better lung functions (VC, FEV1 , TLCO ). Patients with sarcoidosis above 60 years of age had significantly higher percentages of neutrophils in BALF compared with younger patients. BALF percentage of neutrophils positively correlated with age.

CONCLUSIONS

Presented results may support the hypothesis that reactivity of immune system changes during the life, which may result in different manifestation of interstitial lung diseases according to age.

Human cytotoxic T lymphocytes directed to seasonal influenza A viruses cross-react with the newly emerging H7N9 virus

In February 2013, zoonotic transmission of a novel influenza A virus of the H7N9 subtype was reported in China. Although at present no sustained human-to-human transmission has been reported, a pandemic outbreak of this H7N9 virus is feared. Since neutralizing antibodies to the hemagglutinin (HA) globular head domain of the virus are virtually absent in the human population, there is interest in identifying other correlates of protection, such as cross-reactive CD8(+) T cells (cytotoxic T lymphocytes [CTLs]) elicited during seasonal influenza A virus infections. These virus-specific CD8(+) T cells are known to recognize conserved internal proteins of influenza A viruses predominantly, but it is unknown to what extent they cross-react with the newly emerging H7N9 virus. Here, we assessed the cross-reactivity of seasonal H3N2 and H1N1 and pandemic H1N1 influenza A virus-specific polyclonal CD8(+) T cells, obtained from HLA-typed study subjects, with the novel H7N9 virus. The cross-reactivity of CD8(+) T cells to H7N9 variants of known influenza A virus epitopes and H7N9 virus-infected cells was determined by their gamma interferon (IFN-γ) response and lytic activity. It was concluded that, apart from recognition of individual H7N9 variant epitopes, CD8(+) T cells to seasonal influenza viruses display considerable cross-reactivity with the novel H7N9 virus. The presence of these cross-reactive CD8(+) T cells may afford some protection against infection with the new virus.

Effects of aging on influenza virus infection dynamics

The consequences of influenza virus infection are generally more severe in individuals over 65 years of age (the elderly). Immunosenescence enhances the susceptibility to viral infections and renders vaccination less effective. Understanding age-related changes in the immune system is crucial in order to design prophylactic and immunomodulatory strategies to reduce morbidity and mortality in the elderly. Here, we propose different mathematical models to provide a quantitative understanding of the immune strategies in the course of influenza virus infection using experimental data from young and aged mice. Simulation results suggested a central role of CD8(+) T cells for adequate viral clearance kinetics in young and aged mice. Adding the removal of infected cells by natural killer cells did not improve the model fit in either young or aged animals. We separately examined the infection-resistant state of cells promoted by the cytokines alpha/beta interferon (IFN-α/β), IFN-γ, and tumor necrosis factor alpha (TNF-α). The combination of activated CD8(+) T cells with any of the cytokines provided the best fits in young and aged animals. During the first 3 days after infection, the basic reproductive number for aged mice was 1.5-fold lower than that for young mice (P < 0.05).

IMPORTANCE

The fits of our models to the experimental data suggest that the increased levels of IFN-α/β, IFN-γ, and TNF-α (the "inflammaging" state) promote slower viral growth in aged mice, which consequently limits the stimulation of immune cells and contributes to the reported impaired responses in the elderly. A quantitative understanding of influenza virus pathogenesis and its shift in the elderly is the key contribution of this work.

Increased Th17 differentiation in aged mice is significantly associated with high IL-1β level and low IL-2 expression

OBJECTIVE

Aging has been reported to be associated with changes in immune function. Although frequent infection and the development of malignancy suggest the decline of immune function with aging, changes toward proinflammatory conditions also develop at the same time. Th17 cells are well known CD4(+) T cell subpopulation closely linked to chronic inflammation and autoimmunity. In this study, changes in the Th17 population were investigated to elucidate a possible mechanism for this response with aging.

METHODS

Splenocytes were isolated from 2-month-old (young) and 20-month-old (aged) mice. CD4(+)CD44(+) memory T cells and CD4(+)CD62L(+) naïve T cells were isolated and sorted using magnetic beads and flow cytometry. The frequency of IL-17-producing cells was measured using flow cytometry. The expression of IL-17 and Th17-related factors at the mRNA level was measured with RT-PCR. IL-17 and Il-1β expression in spleen tissues was additionally assessed using confocal microscopy.

RESULTS

The proportion of IL-17-producing CD4(+) T cells was higher in the splenocytes among the old mice than those of the young mice. When splenocytes were cultured in Th17 polarizing conditions, the proportion of IL-17 producing CD4(+) T cells was higher in aged mice as well. This was consistently observed when naïve and memory cells were isolated and differentiated into Th17 respectively. In addition, the expression of retinoic acid receptor-related orphan nuclear receptor gamma t (RORγt) and other Th17-related factors (AhR, CCR6, and CCL20) increased in the splenocytes of aged mice compared to the young mice. The expression of IL-1β, showing to promote Th17 differentiation, was higher in the aged mice. Likewise, CD4(+) T cell expression of IL-1R was higher in the aged mice, suggesting that the CD4(+) T cells of the aged mice are readily prepared to differentiate into Th17 cells in response to IL-1β. Confocal microscopy showed that cells positive for IL-1R or IL-1β were more frequent in the spleens of the aged mice. When an anti-IL-2 antibody was applied, the proportion of IL-17-producing cells increased more prominently in the young mice. We observed that IL-2 production and IL-2R expression were reduced in the aged mice, respectively, explaining the blunted response to the anti-IL-2 antibody treatment and the consequent minimal change in the Th17 population.

CONCLUSION

We demonstrated that the proportion of Th17 cells increased in the aged mice both in naïve and memory cell populations. Elevation of IL-1R and IL-1β expression and the reduction in IL-2 and IL-2R expression in aged mice seemed to promote Th17 differentiation. Our results suggest that enhanced Th17 differentiation in aging may have a pathogenic role in the development of Th17-mediated autoimmune diseases.

Premature lung aging and cellular senescence in the pathogenesis of idiopathic pulmonary fibrosis and COPD/emphysema

Different anatomic and physiological changes occur in the lung of aging people that can affect pulmonary functions, and different pulmonary diseases, including deadly diseases such as chronic obstructive pulmonary disease (COPD)/emphysema and idiopathic pulmonary fibrosis (IPF), can be related to an acceleration of the aging process. The individual genetic background, as well as exposure to a variety of toxic substances (cigarette smoke in primis) can contribute significantly to accelerating pulmonary senescence. Premature aging can impair lung function by different ways: by interfering specifically with tissue repair mechanisms after damage, thus perturbing the correct crosstalk between mesenchymal and epithelial components; by inducing systemic and/or local alteration of the immune system, thus impairing the complex mechanisms of lung defense against infections; and by stimulating a local and/or systemic inflammatory condition (inflammaging). According to recently proposed pathogenic models in COPD and IPF, premature cellular senescence likely affects distinct progenitors cells (mesenchymal stem cells in COPD, alveolar epithelial precursors in IPF), leading to stem cell exhaustion. In this review, the large amount of data supporting this pathogenic view are discussed, with emphasis on the possible molecular and cellular mechanisms leading to the severe parenchymal remodeling that characterizes, in different ways, these deadly diseases.

Perspectives on vaccine development for the elderly

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

Aging leads to prolonged duration of inflammation-induced depression-like behavior caused by Bacillus Calmette-Guérin

Geriatric depression is a costly health issue, but little is known about its physiological underpinnings. Systemic inflammation sensitizes the innate immune system of aged animals and humans, but it is unknown if chronic, low-grade infections affect the duration of depressive-like behaviors. In this report, we infected adult (4-6 months) and aged (20-24 months) Balb/c mice with an attenuated strain of Mycobacterium bovis, Bacillus Calmette-Guérin (BCG), to induce a chronic infection. We then measured depression-like behaviors that have construct, face and predictive validity for human inflammation-associated clinical depression. Exposure to BCG caused acute sickness responses in both adult and aged mice. However, sickness behavior was prolonged in aged mice, as assessed by both locomotor and rearing activity. Two measures of depression-like behavior, which were tests involving sucrose preference and tail suspension, both showed that adult mice displayed depression-like behaviors at one day and seven days after exposure to BCG. However, aged mice continued to express both of these depression-like behaviors at three weeks following infection. Infection with BCG caused an increase in tryptophan catabolism, as evidenced by a significant rise in the plasma kynurenine/tryptophan ratio that peaked at 7 days post-infection. In aged mice, greater tryptophan catabolism persisted longer and remained elevated at 21 days post-infection. This finding is consistent with the prolonged duration of depression-like behaviors in aged mice. These are the first data using a chronic infection model to establish that recovery from inflammation-induced depression-like behavior and tryptophan catabolism are prolonged in aged animals.

Reactivation of immune responses against Mycobacterium tuberculosis by boosting with the CpG oligomer in aged mice primarily vaccinated with Mycobacterium bovis BCG

BACKGROUND

Mycobacterium bovis bacillus Calmette Guérin (BCG) vaccine, which has been inoculated to more than one billion people world-wide, has significant effect in preventing tuberculous meningitis and miliary tuberculosis (TB) in neonate and early childhood. However, BCG fails to adequately protect against pulmonary TB and reactivation of latent infections in adults. To overcome this problem, adequate booster is urgently desired in adult who received prior BCG vaccination, and appropriate animal models that substitute human cases would be highly valuable for further experimentation.

FINDINGS

The booster effect of the synthesized CpG oligomer (Oligo-B) on aged mice which had been primarily vaccinated with BCG at the age of 4-week old. The specific Th1 type reaction, production of interferon-γ, in response to TB antigens, purified protein derivatives (PPD) and protection against challenge with Mycobacterium tuberculosis (MTB) H37Rv decreased with increasing age and were not observed in 89-week old mice. In order to rejuvenate the Th1 type response against PPD and protection activity against MTB infection, Oligo-B, which is known to augment Th1 responses, was administered as a booster to 81-90-week old mice (late 50's in human equivalent) vaccinated with BCG at 4-week old. The boosting with Oligo-B increased the number of CD4+ CD44high CD62Lhigh, central memory type T cell. Furthermore, the Oligo-B boosting rejuvenated the ability of mice to protect against infection with MTB H37Rv.

CONCLUSIONS

Th1-adjuvant CpG oligo DNA, such as Oligo-B, may be a promising booster when coupled with BCG priming.

The influence of ageing on the development and management of rheumatoid arthritis

The population of elderly individuals with rheumatoid arthritis (RA) is expanding, due mainly to increasing life expectancy. A variety of theories have been proposed to explain the ageing process, including accumulation of DNA damage and resultant changes in biological processes. Such changes can influence the development and/or course of disease. Furthermore, alterations in biological function determine the biological age-as opposed to chronological age-of an individual, which strongly influences their ability to cope with disease. Moreover, comorbidities are more frequent in elderly individuals. Together, these factors complicate treatment of disease and necessitate careful patient management. Indeed, although evidence from clinical trials suggests that DMARDs and biologic agents have good efficacy and are well tolerated in elderly patients with RA, such individuals are often undertreated and inadequately managed. Unfortunately, insufficient data are available for the development of evidence-based guidelines for this population, as elderly patients are often excluded from clinical trials owing to age restrictions or comorbidities. Thus, additional clinical studies in elderly patients are warranted, with treatment regimens tailored according to vitality or frailty parameters. This Review focuses on the pathophysiological aspects of ageing and their implications for the management of RA in elderly patients.

An altered relationship of influenza vaccine-specific IgG responses with T cell immunity occurs with aging in humans

Alterations in T cell immunity occur with aging. Influenza causes significant morbidity and mortality in the elderly. We investigated the relationship of serum IgG responses with hemagglutinin inhibition (HI) antibody titers and the frequency of distinct T cell subsets in young and elderly people who received the inactivated influenza vaccine. Influenza vaccine-specific IgG responses correlated with the increase of HI antibody titers and the frequency of CD4(+) T cells producing IFN-γ and IL-17 in young, but not elderly, people. Also, only in young people, such IgG responses correlated with the frequency of memory T cells, especially central memory cells, CD45RA(-) effector memory CD8(+) T cells and IL-7 receptor alpha high effector memory CD8(+) T cells with potent survival and proliferative capacity. These findings suggest that aging alters the association of influenza-vaccine specific IgG responses with HI antibody titers, cytokine-producing capacity and proportions of memory T cells in humans.

Geroprotectors as a novel therapeutic strategy for COPD, an accelerating aging disease

Chronic obstructive pulmonary disease (COPD) progresses very slowly and the majority of patients are therefore elderly. COPD is characterized by an abnormal persistent inflammatory response to noxious environmental stimuli and there are increasing evidences for a close relationship between premature aging and chronic inflammatory diseases. Thus, COPD is considered to be a disease of an accelerating aging. In this review, we collected the evidence for roles of aging on pathogenesis of COPD and considered future therapeutic strategy for COPD based on this senescence hypothesis. Since calorie restriction has been proved to extend lifespan, many efforts were made to clarify the molecular mechanism of aging. Aging is defined as the progressive decline of homeostasis that occurs after the reproductive phase of life is complete, leading to an increasing risk of disease or death due to impaired DNA repair after damage by oxidative stress or telomere shortening as a result of repeated cell division. During aging, pulmonary function progressively deteriorates; innate immunity is impaired and pulmonary inflammation increases, accompanied by structural changes, such as an enlargement of airspaces. Noxious environmental gases, such as cigarette smoke, may worsen these aging-related events in the lung or accelerate aging of the lung due to reduction in anti-aging molecules and/or stimulation of aging molecules. Aging signaling are complex but conserved in divert species, such as worm, fruit fry, rodent and humans. Especially the insulin like growth factor (IGF-1) signaling was well documented. Geroprotectors are therapeutics that affect the root cause of aging and age-related diseases, and thus prolong the life-span of animals. Most of geroprotectors such as melatonin, metformin, rapamycin and resveratrol are anti-oxidant or anti-aging molecule regulators. Therefore, geroprotection for the lung might be an attractive approach for the treatment of COPD by preventing premature aging of lung.

Effects of ionizing radiation on the immune system with special emphasis on the interaction of dendritic and T cells

Dendritic cells (DCs), as professional antigen-presenting cells, are members of the innate immune system and function as key players during the induction phase of adaptive immune responses. Uptake, processing, and presentation of antigens direct the outcome toward either tolerance or immunity. The cells of the immune system are among the most highly radiosensitive cells in the body. For high doses of ionizing radiation (HD-IR) both immune-suppressive effects after whole body irradiation and possible immune activation during tumor therapy were observed. On the other hand, the effects of low doses of ionizing radiation (LD-IR) on the immune system are controversial and seem to show high variability among different individuals and species. There are reports revealing that protracted LD-IR can result in radioresistance. But immune-suppressive effects of chronic LD-IR are also reported, including the killing or sensitizing of certain cell types. This article shall review the current knowledge of radiation-induced effects on the immune system, paying special attention to the interaction of DCs and T cells.