Age-dependent changes in the expression of regulatory cell surface ligands in activated human T-cells

A silver bullet for ageing medicine?: clinical relevance of T-cell checkpoint receptors in normal human ageing

Immunosenescence describes dysregulation of the immune system with ageing manifested in both the innate and adaptive immunity, including changes in T-cell checkpoint signaling. Through complex and nuanced process, T-cells lose excitatory signaling pathways and upregulate their inhibitory signaling, leading to ineffective immune responses that contribute to the formation of the ageing phenotype. Here we expand on the expression, function, and clinical potential of targeting the T-cell checkpoint signaling in age and highlight interventions offering the most benefits to older adults' health. Notably, modifications in vaccination such as with mTOR inhibitors show immediate clinical relevance and good tolerability. Other proposed treatments, including therapies with monoclonal antibodies fail to show clinical efficacy or tolerability needed for implementation at present. Although T-cell co-signaling fits a valuable niche for translational scientists to manage immunosenescence, future study would benefit from the inclusion of older adults with multiple long-term conditions and polypharmacy, ensuring better applicability to actual patients seen in clinical settings.

Immunological features of ESRD patients undergoing hemodialysis of various ages

AIMS

To investigate the immunological characteristics of hemodialysis (HD) patients with end-stage renal disease (ESRD) of various ages, and the impact of age-related immune alterations on these patients, with a focus on peripheral T cells.

METHODS

From September 2016 to September 2019, HD patients were enrolled and followed prospectively for 3 years. Patients were divided into three groups based on their ages: < 45, 45 to 64, and ≥ 65. The distribution of T cell subsets in different age groups was investigated and compared. The effects of altered T cell subsets on overall survival were also investigated.

RESULTS

A total of 371 HD patients were enrolled. The reduced number of naive CD8+ T cells (P < 0.001) and increased number of EMRA CD8+ T cells (P = 0.024) were independently associated with the advanced age among all T cell subsets studied. Patient survival may be affected by numerical changes in naive CD8+ T cells. However, when HD patients were < 45 or ≥ 65 years, the reduction had no significant impact on survival. Only in HD patients aged 45 to 64 years, the number of naïve CD8+ T cells found to be insufficient but not deficient, identified as an independent predictor of poor survival.

CONCLUSIONS

The most significant age-related immune change in HD patients was a decrease in peripheral naive CD8+ T cells, which was an independent predictor of 3-year overall survival in HD patients aged 45 ~ 64 years.

Considerations and Approaches for Cancer Immunotherapy in the Aging Host

Advances in cancer immunotherapy are improving treatment successes in many distinct cancer types. Nonetheless, most tumors fail to respond. Age is the biggest risk for most cancers, and the median population age is rising worldwide. Advancing age is associated with manifold alterations in immune cell types, abundance, and functions, rather than simple declines in these metrics, the consequences of which remain incompletely defined. Our understanding of the effects of host age on immunotherapy mechanisms, efficacy, and adverse events remains incomplete. A deeper understanding of age effects in all these areas is required. Most cancer immunotherapy preclinical studies examine young subjects and fail to assess age contributions, a remarkable deficit given the known importance of age effects on immune cells and factors mediating cancer immune surveillance and immunotherapy efficacy. Notably, some cancer immunotherapies are more effective in aged versus young hosts, while others fail despite efficacy in the young. Here, we review our current understanding of age effects on immunity and associated nonimmune cells, the tumor microenvironment, cancer immunotherapy, and related adverse effects. We highlight important knowledge gaps and suggest areas for deeper enquiries, including in cancer immune surveillance, treatment response, adverse event outcomes, and their mitigation.

Expression of immune checkpoint on subset of monocytes in old patients

BACKGROUND

Immune checkpoints and their ligands are important actors of lymphocytes and monocytes activation's regulation. Their expression level within T cells changes with aging. Despite the major impact of aging on monocytes, there is no data about the expression of ICs on monocytes from old patients. The objective of our study is to describe the expression of ICs and their ligands on monocytes from young individuals compared to old patients.

METHODS

We included 18 old control (>75 years old), 10 young control (<55 years old) and 45 old patients with hip fracture (HF). Phenotypical and functional analyses were performed on cryopreserved PBMCs.

RESULTS

There is a differential expression of immune checkpoints and their ligands within monocyte subtypes regardless of age at baseline. After stimulation, a differential expression of immune checkpoints in young subjects but not in old subjects was observed which would be in favor of a regulation defect in old subjects. We hypothesize that this lack of regulation could partially explain the excess production of pro-inflammatory cytokines by the stimulated monocytes in old subjects. In HF, we also observe a differential expression of immune checkpoints, especially in old patients with a poor prognosis.

CONCLUSION

Our results suggest that the immune regulation which should take place post-acute stress may be affected in old individuals.

The Impact of Microgravity on Immunological States

As we explore other planetary bodies, astronauts will face unique environmental and physiological challenges. The human immune system has evolved under Earth's gravitational force. Consequently, in the microgravity environment of space, immune function is altered. This can pose problematic consequences for astronauts on deep space missions where medical intervention will be limited. Studying the unique environment of microgravity has its challenges, yet current research has uncovered immunological states that are probable during exploration missions. As microgravity-induced immune states are uncovered, novel countermeasure developments and personalized mitigation programs can be designed to improve astronaut health. This can also benefit immune-related monitoring programs for disorders on Earth. This is a comprehensive review, including gaps in knowledge, of simulated and spaceflight microgravity studies in human and rodent models.

The impact of age-related syndromes on ICU process and outcomes in very old patients

In this narrative review, we describe the most important age-related "syndromes" found in the old ICU patients. The syndromes are frailty, comorbidity, cognitive decline, malnutrition, sarcopenia, loss of functional autonomy, immunosenescence and inflam-ageing. The underlying geriatric condition, together with the admission diagnosis and the acute severity contribute to the short-term, but also to the long-term prognosis. Besides mortality, functional status and quality of life are major outcome variables. The geriatric assessment is a key tool for long-term qualitative outcome, while immediate severity accounts for acute mortality. A poor functional baseline reduces the chances of a successful outcome following ICU. This review emphasises the importance of using a geriatric assessment and considering the older patient as a whole, rather than the acute illness in isolation, when making decisions regarding intensive care treatment.

Age Associations with Dry Eye Clinical Signs and Symptoms in the Dry Eye Assessment and Management (DREAM) Study

Purpose

To evaluate how increasing age is associated with dry eye disease (DED) signs and symptoms in the Dry Eye Assessment and Management (DREAM) study. This study was undertaken to better understand how DED signs and symptoms differ across decades of life with goals to help assess detection and treatment of DED.

Design

Secondary analysis of the DREAM study.

Subjects

One hundred twenty, 140, 185, and 90 participants aged < 50, 50 to 59, 60 to 69, and ≥ 70 years, respectively.

Methods

We performed a secondary analysis of data from the DREAM study, a multicenter randomized clinical trial, to evaluate the effect of omega-3 fatty acid supplementation for the treatment of DED. At baseline, 6 months, and 12 months follow-up, participants underwent an assessment of DED symptoms and signs using Ocular Surface Disease Index, Brief Pain Inventory, tear break-up time (TBUT) (in seconds), Schirmer test with anesthesia (mm/5 minutes), conjunctival staining, corneal staining, meibomian gland dysfunction evaluation, and tear osmolarity (mOsm/l). Multivariable generalized linear regression models were used to compare DED symptoms and signs across the 4 age groups among all participants and by sex.

Main Outcome Measures

Scores of DED symptoms, individual signs, and composite scores of DED signs.

Results

Among 535 patients with DED, increasing age was significantly associated with worse TBUT (P = 0.01), corneal staining (P < 0.001), a composite severity score of DED signs (P = 0.007), and tear osmolarity (P = 0.001). Similar significant differences were found across 4 age groups of 334 women in TBUT, corneal staining score, composite severity score of DED signs, and tear osmolarity (all P < 0.05) but not in men.

Conclusion

We found that corneal staining, TBUT, tear osmolarity, and a composite severity score of DED signs were significantly more severe with increasing age in women but not in men; worsening symptoms did not increase with increasing age.

Financial Disclosures

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

T-cell senescence: A crucial player in autoimmune diseases

Senescent T cells are proliferative disabled lymphocytes that lack antigen-specific responses. The development of T-cell senescence in autoimmune diseases contributes to immunological disorders and disease progression. Senescent T cells lack costimulatory markers with the reduction of T cell receptor repertoire and the uptake of natural killer cell receptors. Senescent T cells exert cytotoxic effects through the expression of perforin, granzymes, tumor necrosis factor, and other molecules without the antigen-presenting process. DNA damage accumulation, telomere damage, and limited DNA repair capacity are important features of senescent T cells. Impaired mitochondrial function and accumulation of reactive oxygen species contribute to T cell senescence. Alleviation of T-cell senescence could provide potential targets for the treatment of autoimmune diseases.

Immune aging in multiple sclerosis is characterized by abnormal CD4 T cell activation and increased frequencies of cytotoxic CD4 T cells with advancing age

BACKGROUND

Immunosenescence (ISC) describes age-related changes in immune-system composition and function. Multiple sclerosis (MS) is a lifelong inflammatory condition involving effector and regulatory T-cell imbalance, yet little is known about T-cell ISC in MS. We examined age-associated changes in circulating T cells in MS compared to normal controls (NC).

METHODS

Forty untreated MS (Mean Age 43·3, Range 18-72) and 49 NC (Mean Age 48·6, Range 20-84) without inflammatory conditions were included in cross-sectional design. T-cell subsets were phenotypically and functionally characterized using validated multiparametric flow cytometry. Their aging trajectories, and differences between MS and NC, were determined using linear mixed-effects models.

FINDINGS

MS patients demonstrated early and persistent redistribution of naïve and memory CD4 T-cell compartments. While most CD4 and CD8 T-cell aging trajectories were similar between groups, MS patients exhibited abnormal age-associated increases of activated (HLA-DR+CD38+; (P = 0·013) and cytotoxic CD4 T cells, particularly in patients >60 (EOMES: P < 0·001). Aging MS patients also failed to upregulate CTLA-4 expression on both CD4 (P = 0·014) and CD8 (P = 0·009) T cells, coupled with abnormal age-associated increases in frequencies of B cells expressing costimulatory molecules.

INTERPRETATION

While many aspects of T-cell aging in MS are conserved, the older MS patients harbour abnormally increased frequencies of CD4 T cells with activated and cytotoxic effector profiles. Age-related decreased expression of T-cell co-inhibitory receptor CTLA-4, and increased B-cell costimulatory molecule expression, may provide a mechanism that drives aberrant activation of effector CD4 T cells that have been implicated in progressive disease.

FUNDING

Stated in Acknowledgements section of manuscript.

Reduced immune-regulatory molecule expression on human colonic memory CD4 T cells in older adults

BACKGROUND

The etiology of the low-level chronic inflammatory state associated with aging is likely multifactorial, but a number of animal and human studies have implicated a functional decline of the gastrointestinal immune system as a potential driver. Gut tissue-resident memory T cells play critical roles in mediating protective immunity and in maintaining gut homeostasis, yet few studies have investigated the effect of aging on human gut T cell immunity. To determine if aging impacted CD4 T cell immunity in the human large intestine, we utilized multi-color flow cytometry to measure colonic lamina propria (LP) CD4 T cell frequencies and immune-modulatory marker expression in younger (mean ± SEM: 38 ± 1.5 yrs) and older (77 ± 1.6 yrs) adults. To determine cellular specificity, we evaluated colon LP CD8 T cell frequency and phenotype in the same donors. To probe tissue specificity, we evaluated the same panel of markers in peripheral blood (PB) CD4 T cells in a separate cohort of similarly aged persons.

RESULTS

Frequencies of colonic CD4 T cells as a fraction of total LP mononuclear cells were higher in older persons whereas absolute numbers of colonic LP CD4 T cells per gram of tissue were similar in both age groups. LP CD4 T cells from older versus younger persons exhibited reduced CTLA-4, PD-1 and Ki67 expression. Levels of Bcl-2, CD57, CD25 and percentages of activated CD38+HLA-DR+ CD4 T cells were similar in both age groups. In memory PB CD4 T cells, older age was only associated with increased CD57 expression. Significant age effects for LP CD8 T cells were only observed for CTLA-4 expression, with lower levels of expression observed on cells from older adults.

CONCLUSIONS

Greater age was associated with reduced expression of the co-inhibitory receptors CTLA-4 and PD-1 on LP CD4 T cells. Colonic LP CD8 T cells from older persons also displayed reduced CTLA-4 expression. These age-associated profiles were not observed in older PB memory CD4 T cells. The decline in co-inhibitory receptor expression on colonic LP T cells may contribute to local and systemic inflammation via a reduced ability to limit ongoing T cell responses to enteric microbial challenge.

Immunosenescence Study of T Cells: A Systematic Review

Background

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

Objective

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

Methods

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

Results

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

Conclusions

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

Aging and immunotherapies: New horizons for the golden ages

The life expectancy of the world’s elderly population (65 and older) continues to reach new milestones with older individuals currently comprising greater than 8.5% (617 million) of the world’s population. This percentage is predicted to approach 20% of the world’s population by 2050 (representing 1.6 billion people). Despite this amazing feat, many healthcare systems are not equipped to handle the multitude of diseases that commonly manifest with age, including most types of cancers. As the world’s aging population grows, cancer treatments continue to evolve. Immunotherapies are a new drug class that has revolutionized our ability to treat previously intractable cancers; however, their efficacy in patients with compromised immune systems remains unclear. In this review, we will discuss how aging-associated losses in immune homeostasis impact the efficacy and safety of immunotherapy treatment in preclinical models of aging. We will also discuss how these findings translate to elderly patients receiving immunotherapy treatment for refractory and relapsed cancers, as well as, strategies that could be explored to improve the efficacy of immunotherapies in aged patients.

Age-related alterations in human gut CD4 T cell phenotype, T helper cell frequencies, and functional responses to enteric bacteria

Intestinal lamina propria (LP) CD4 T cells play critical roles in maintaining intestinal homeostasis and in immune responses to enteric microbes, yet little is known regarding whether they contribute to age-associated intestinal immune dysfunction. In this study, we evaluated the direct ex vivo frequency, activation/inhibitory phenotype, death profiles, and in vitro functional responses of human jejunum LP CD4 T cells, including Th1, Th17, and Th22 subsets isolated from younger (<45 years) and older (>65years) persons. Expression of the co-inhibitory molecule CTLA-4 was significantly lower in older CD4 T cells, whereas expression of HLA-DR, CD38, CD57, and PD-1 were not significantly different between groups. Total CD4 T cell frequencies were similar between age groups, but lower frequencies and numbers of Th17 cells were observed directly ex vivo in older samples. Older Th17 and Th1 cells proliferated to a lesser degree following in vitro exposure to bacterial antigens vs. their younger counterparts. Levels of spontaneous cell death were increased in older CD4 T cells; however, cellular death profiles following activation did not differ based on age. Thus, small intestinal CD4 T cells from older persons have altered phenotypic and functional profiles including reduced expression of a co-inhibitory molecule, increased spontaneous cell death, and both reduced frequencies and altered functional responses of specific Th cell subsets. These changes may contribute to altered intestinal homeostasis and loss of protective gut immunity with aging.

Differential Levels of Regulatory T Cells and T-Helper-17 Cells in Women With Early and Advanced Endometriosis

CONTEXT

Regulatory T (Treg) cells and T-helper-17 (Th17) cells may be involved in endometriosis. Information on the pattern of change in the percentages of Treg and Th17 cells in the peripheral blood (PB) and peritoneal fluid (PF) of women with early and advanced endometriosis is unclear.

OBJECTIVE

To investigate the pattern of change in the percentages of Treg and Th17 cells in the PB and PF of women with early and advanced endometriosis.

METHODS

We recruited 31 women with laparoscopically and histologically confirmed, revised American Society of Reproductive Medicine stage I-II endometriosis, 39 women with stage III-IV endometriosis, and 36 control subjects without visible endometriosis. PB and PF samples were collected and T-cell subpopulations analyzed by flow cytometry using specific monoclonal antibodies recognizing CD4+, CD25+, FOXP3+, and IL-17A+ markers. PF concentrations of TGF-β and IL-17 were measured by ELISA.

RESULTS

The percentages of CD25+FOXP3+ Treg cells within the CD4+ T-cell population were significantly higher in the PF of women with advanced endometriosis than in either early endometriosis or in control subjects (P < 0.05 for both). A persistently lower percentage of CD4+IL-17A+ Th17 cells was found in both PB and PF of women with early and advanced endometriosis. Compared with IL-17 levels, PF levels of TGF-β were significantly higher in women with endometriosis (P = 0.01).

CONCLUSION

Our findings reconfirmed the current speculation that endometriosis is related to alteration of Treg and Th17 cells in the pelvis causing survival and implantation of ectopic endometrial lesions.

CD48 is a key molecule of immunomodulation affecting prognosis in glioma

Purpose: Glioma is a refractory disease associated with immune cell infiltration, and the effectiveness of checkpoint blockade remains suboptimal. As an adhesion and costimulatory molecule, CD48 plays a significant role in immunomodulation. As such, studying CD48 may provide additional understanding of the immune and inflammation response of glioma. Methods: Using R language and GraphPad Prism 7, RNA sequencing data of 946 patients from Chinese Glioma Genome Atlas and The Cancer Genome Atlas cohorts were analyzed. Results: CD48 was highly expressed in the malignant progression of glioma. As an independent risk factor, high-CD48 patients were associated with poor prognosis. CD48 influenced glioma purity and the local immune cell subpopulation. CD48 was closely related to immune function in glioma. Patients with an enhanced immune phenotype, high CD48, were associated with immune suppressive molecules and checkpoints. In addition, CD48 correlated with the immune and inflammatory response. A checkpoint risk score including CD48, SLAMF8 and PD-L1 was used to assess the role of checkpoints. Risk score was particularly high in a malignant subtype of glioma and was an independent predictive indicator of unfavorable outcome. Additionally, age, IDH subtype and MGMT promoter status influenced the predictive significance of checkpoint risk score. Conclusion: CD48 exhibits a crucial role in reduced survival and immunomodulation in glioma. In addition, we found that checkpoints play a greater role in patients older than 40 years old with IDH wild-type and MGMT methylated status. These findings suggest that combining CD48 blockade with PD-L1 may be a promising approach to glioma immunotherapy for specific subpopulations of patients.

Immune Checkpoint Blockade for Advanced NSCLC: A New Landscape for Elderly Patients

The therapeutic scenario for elderly patients with advanced NSCLC has been limited to radiotherapy and chemotherapy. Recently, a novel therapeutic approach based on targeting the immune-checkpoints has showed noteworthy results in advanced NSCLC. PD1/PD-L1 pathway is co-opted by tumor cells through the expression of PD-L1 on the tumor cell surface and on cells within the microenvironment, leading to suppression of anti-tumor cytolytic T-cell activity by the tumor. The success of immune-checkpoints inhibitors in clinical trials led to rapid approval by the FDA and EMA. Currently, data regarding efficacy and safety of ICIs in older subjects is limited by the poor number of elderly recruited in clinical trials. Careful assessment and management of comorbidities is essential to achieve better outcomes and limit the immune related adverse events in elderly NSCLC patients.

Erosive Pustular Dermatosis: A Manifestation of Immunosenescence A Report of 8 Cases

Erosive pustular dermatosis (EPD) is a rare condition of the scalp and legs that is marked by crusted erosions or superficial ulcerations that may result in scarring alopecia and chronic wounds. The condition predominantly affects elderly female as compared to male patients. Its pathogenesis remains poorly understood. The majority of the cases in the literature are from the United Kingdom and continental Europe. In this series, we present 8 North American patients with EPD of the scalp, one of whom also had involvement of the legs and another with the involvement of the face. All our patients were advanced in age and had a predisposition to chronic actinic damage, which are common characteristics of EPD previously reported in the literature. We hypothesize that immunosenescence leads to an aberrant immune response to wound healing and, along with other factors such as a loss of the normal epidermal barrier, ultraviolet damage, and hormonal factors, may contribute to the development of this condition.

An overview of the toxicities of checkpoint inhibitors in older patients with cancer

Checkpoint inhibitors offer an exciting new option for treatment of a wide variety of cancers. By binding to surface receptors or their associated ligands on T cells, this class of drugs enhances immune activation and response to cancer cells. In available studies, the drugs are well tolerated, although toxicity involving skin, gastrointestinal tract, liver, lungs, and endocrine organs has been observed. Unfortunately, few studies to date have included patients older than 70 years of age. Since aging has been linked to changes in immune function, there are theoretical concerns that this patient population might experience a different profile of adverse events. This article reviews the tolerability of checkpoint inhibitors in older patients with cancer in clinical practice.

Considerations for successful cancer immunotherapy in aged hosts

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

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

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

Considerations for successful cancer immunotherapy in aged hosts

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

Glutamate Receptor Interacting Protein 1 Regulates CD4(+) CTLA-4 Expression and Transplant Rejection

PDZ domains are common 80- to 90-amino-acid regions named after the first three proteins discovered to share these domains: postsynaptic density 95, discs large, and zonula occludens. PDZ domain-containing proteins typically interact with the C-terminus of membrane receptors. Glutamate receptor interacting protein 1 (GRIP1), a seven-PDZ domain protein scaffold, regulates glutamate receptor surface expression and trafficking in neurons. We have found that human and mouse T cells also express GRIP1. T cell-specific GRIP1(-/-) mice >11 weeks old had prolonged cardiac allograft survival. Compared with wild-type T cells, in vitro stimulated GRIP1(-/-) T cells had decreased expression of activation markers and increased apoptotic surface marker expression. Surface expression of the strong T cell inhibitory molecule cytotoxic T lymphocyte antigen-4 (CTLA-4) was increased on GRIP1(-/-) T cells from mice >11 weeks old. CTLA-4 increases with T cell stimulation and its surface expression on GRIP1(-/-) T cells remained high after stimulation was removed, indicating a possible internalization defect in GRIP1-deficient T cells. CTLA-4-blocking antibody treatment following heart transplantation led to complete rejection in T cell GRIP1(-/-) mice, indicating that increased CTLA-4 surface expression contributed to the extended graft survival. Our data indicate that GRIP1 regulates T cell activation by regulating CTLA-4 surface expression.

As we age: Does slippage of quality control in the immune system lead to collateral damage?

The vertebrate adaptive immune system is remarkable for its possession of a very broad range of antigen receptors imbuing the system with exquisite specificity, in addition to the phagocytic and inflammatory cells of the innate system shared with invertebrates. This system requires strict control both at the level of the generation the cells carrying these receptors and at the level of their activation and effector function mediation in order to avoid autoimmunity and mitigate immune pathology. Thus, quality control checkpoints are built into the system at multiple nodes in the response, relying on clonal selection and regulatory networks to maximize pathogen-directed effects and minimize collateral tissue damage. However, these checkpoints are compromised with age, resulting in poorer immune control manifesting as tissue-damaging autoimmune and inflammatory phenomena which can cause widespread systemic disease, paradoxically compounding the problems associated with increased susceptibility to infectious disease and possibly cancer in the elderly. Better understanding the reasons for slippage of immune control will pave the way for developing rational strategies for interventions to maintain appropriate immunity while reducing immunopathology.

Global analyses revealed age-related alterations in innate immune responses after stimulation of pathogen recognition receptors

Aging leads to dysregulation of multiple components of the immune system that results in increased susceptibility to infections and poor response to vaccines in the aging population. The dysfunctions of adaptive B and T cells are well documented, but the effect of aging on innate immunity remains incompletely understood. Using a heterogeneous population of peripheral blood mononuclear cells (PBMCs), we first undertook transcriptional profiling and found that PBMCs isolated from old individuals (≥ 65 years) exhibited a delayed and altered response to stimulation with TLR4, TLR7/8, and RIG-I agonists compared to cells obtained from adults (≤ 40 years). This delayed response to innate immune agonists resulted in the reduced production of pro-inflammatory and antiviral cytokines and chemokines including TNFα, IL-6, IL-1β, IFNα, IFNγ, CCL2, and CCL7. While the major monocyte and dendritic cell subsets did not change numerically with aging, activation of specific cell types was altered. PBMCs from old subjects also had a lower frequency of CD40+ monocytes, impaired up-regulation of PD-L1 on monocytes and T cells, and increased expression of PD-L2 and B7-H4 on B cells. The defective immune response to innate agonists adversely affected adaptive immunity as TLR-stimulated PBMCs (minus CD3 T cells) from old subjects elicited significantly lower levels of adult T-cell proliferation than those from adult subjects in an allogeneic mixed lymphocyte reaction (MLR). Collectively, these age-associated changes in cytokine, chemokine and interferon production, as well as co-stimulatory protein expression could contribute to the blunted memory B- and T-cell immune responses to vaccines and infections.