Intestinal lymphocyte number, migration and antibody secretion in young and old rats

Effects of aging on urinary tract epithelial homeostasis and immunity

A global increase in older individuals creates an increasing demand to understand numerous healthcare challenges related to aging. This population is subject to changes in tissue physiology and the immune response network. Older individuals are particularly susceptible to infectious diseases, with one of the most common being urinary tract infections (UTIs). Postmenopausal and older women have the highest risk of recurrent UTIs (rUTIs); however, why rUTIs become more frequent after menopause and during old age is incompletely understood. This increased susceptibility and severity among older individuals may involve functional changes to the immune system with age. Aging also has substantial effects on the epithelium and the immune system that led to impaired protection against pathogens, yet heightened and prolonged inflammation. How the immune system and its responses to infection changes within the bladder mucosa during aging has largely remained poorly understood. In this review, we highlight our understanding of bladder innate and adaptive immunity and the impact of aging and hormones and hormone therapy on bladder epithelial homeostasis and immunity. In particular, we elaborate on how the cellular and molecular immune landscape within the bladder can be altered during aging as aged mice develop bladder tertiary lymphoid tissues (bTLT), which are absent in young mice leading to profound age-associated change to the immune landscape in bladders that might drive the significant increase in UTI susceptibility. Knowledge of host factors that prevent or promote infection can lead to targeted treatment and prevention regimens. This review also identifies unique host factors to consider in the older, female host for improving rUTI treatment and prevention by dissecting the age-associated alteration of the bladder mucosal immune system.

The impact of aging on intestinal mucosal immune function and clinical applications

Immune cells and immune molecules in the intestinal mucosa participate in innate and adaptive immunity to maintain local and systematic homeostasis. With aging, intestinal mucosal immune dysfunction will promote the emergence of age-associated diseases. Although there have been a number of studies on the impact of aging on systemic immunity, relatively fewer studies have been conducted on the impact of aging on the intestinal mucosal immune system. In this review, we will briefly introduce the impact of aging on the intestinal mucosal barrier, the impact of aging on intestinal immune cells as well as immune molecules, and the process of interaction between intestinal mucosal immunity and gut microbiota during aging. After that we will discuss potential strategies to slow down intestinal aging in the elderly.

Organotypic cultures as aging associated disease models

Aging remains a primary risk factor for a host of diseases, including leading causes of death. Aging and associated diseases are inherently multifactorial, with numerous contributing factors and phenotypes at the molecular, cellular, tissue, and organismal scales. Despite the complexity of aging phenomena, models currently used in aging research possess limitations. Frequently used in vivo models often have important physiological differences, age at different rates, or are genetically engineered to match late disease phenotypes rather than early causes. Conversely, routinely used in vitro models lack the complex tissue-scale and systemic cues that are disrupted in aging. To fill in gaps between in vivo and traditional in vitro models, researchers have increasingly been turning to organotypic models, which provide increased physiological relevance with the accessibility and control of in vitro context. While powerful tools, the development of these models is a field of its own, and many aging researchers may be unaware of recent progress in organotypic models, or hesitant to include these models in their own work. In this review, we describe recent progress in tissue engineering applied to organotypic models, highlighting examples explicitly linked to aging and associated disease, as well as examples of models that are relevant to aging. We specifically highlight progress made in skin, gut, and skeletal muscle, and describe how recently demonstrated models have been used for aging studies or similar phenotypes. Throughout, this review emphasizes the accessibility of these models and aims to provide a resource for researchers seeking to leverage these powerful tools.

The Aged Intestine: Performance and Rejuvenation

Owing to the growing elderly population, age-related problems are gaining increasing attention from the scientific community. With senescence, the intestine undergoes a spectrum of changes and infirmities that are likely the causes of overall aging. Therefore, identification of the aged intestine and the search for novel strategies to rescue it, are required. Although progress has been made in research on some components of the aged intestine, such as intestinal stem cells, the comprehensive understanding of intestinal aging is still limited, and this restricts the in-depth search for efficient strategies. In this concise review, we discuss several aspects of intestinal aging. More emphasis is placed on the appraisal of current and potential strategies to alleviate intestinal aging, as well as future targets to rejuvenate the aged intestine.

Gut microbiota alterations and health status in aging adults: From correlation to causation

The deterioration of tissue structure and decline in physiological function during aging are accompanied by alterations to the gut microbiota. The elderly has higher risks of various diseases and chronic diseases. However, inter-individual differences are more apparent in elderly than younger, and a proportion of individuals have a delayed onset or even avoid developing chronic diseases. This difference in health status is influenced by both heredity and Lifestyle and environmental factors. During the process of aging, the gut microbiota is also affected by the external environment, and provides a buffer to external challenge, and thus the gut microbiota reflects an individual's personal experience. Moreover, the immune system undergoes a series of changes with age, which are related to chronic inflammation in the elderly. The formation, maturation and senescence of the intestinal immune system is closely related to the gut microbiota. Additionally, changes in the gut microbiota of elderly individuals may modulate the immune system, which may in turn affect health status. Herein, we summarize the correlations between the gut microbiota with individual health status in the elderly and explore the related mechanisms, which may provide a basis to maintain or enhance the health of the elderly though interventions targeting the gut microbiota.

Age at Diagnosis Is Determinant for the Outcome of Inflammatory Bowel Disease: Is It a Myth?

INTRODUCTION

Patients with elderly-onset inflammatory bowel disease were previously associated with a less aggressive course of the disease. However, there are conflicting data that need further validation. We aimed to determine the association between age at diagnosis and the development of progressive disease in patients with Crohn's disease (CD) and ulcerative colitis (UC).

METHODS

This cohort study included patients with CD and UC followed in 6 secondary and tertiary care centers in mainland Portugal. Patients were divided into a derivation (80%) cohort and a validation (20%) cohort. The primary outcome was progressive disease. Logistic regression analysis, receiver operating characteristic curves, and the areas under the curve (AUC) were performed. Odds ratios with 95% confidence intervals (CIs) were estimated.

RESULTS

The derivation cohorts included 1245 patients with CD (68% with progressive disease) and 1210 patients with UC (37% with progressive disease), whereas the validation cohorts included 302 patients with CD and 271 patients with UC, respectively, with similar outcome proportions. In our final model, age at diagnosis older than 60 years was significantly associated with a lower risk of developing progressive disease (odds ratio 0.390, 95% CI 0.164-0.923, P = 0.032), with a high discriminative power (AUC 0.724, 95% CI 0.693-754) in patients with CD. However, according to this model, no significant associations were found between age at diagnosis and the risk of developing progressive disease in patients with UC. No differences were observed in the AUC values between the validation and the derivation cohorts.

DISCUSSION

Patients with elderly-onset CD, but not patients with UC, were associated with a less progressive course of the disease.

Single cell and tissue-transcriptomic analysis of murine bladders reveals age- and TNFα-dependent but microbiota-independent tertiary lymphoid tissue formation

Aging has multifaceted effects on the immune system, but how aging affects tissue-specific immunity is not well-defined. Bladder diseases characterized by chronic inflammation are highly prevalent in older women, but mechanisms by which aging promotes these pathologies remain unknown. Tissue transcriptomics of unperturbed, young and aged bladders identified a highly altered immune landscape as a fundamental feature of the aging female bladder. Detailed mapping of immune cells using single cell RNA-sequencing revealed novel subsets of macrophages and dendritic cells and unique changes to the immune repertoire in the aged bladder. B and T cells are highly enriched in aged bladders and spontaneously form organized bladder tertiary lymphoid tissues (bTLTs). Naïve, activated, and germinal center B cells and IgA⁺ plasma cells are found within bTLT and associated with increased urinary IgA concentrations. bTLTs form with increasing age and their formation is dependent on TNFα. Microbiota are not required to form bTLT, as aged germfree mice also harbor them. Thus, bTLTs require age-dependent TNFα but are independent of the microbiota. Our results indicate that chronic, age-associated inflammation underlies a fundamental alteration to the bladder and establishes a resource for further investigation of the bladder immune system in homeostasis, aging, and disease.

Intestinal epithelial barrier functions in ageing

The intestinal epithelial barrier protects the mucosa of the gastrointestinal (GI)-tract and plays a key role in maintaining the host homeostasis. It encompasses several elements that include the intestinal epithelium and biochemical and immunological products, such as the mucus layer, antimicrobial peptides (AMPs) and secretory immunologlobulin A (sIgA). These components are interlinked with the large microbial community inhabiting the gut to form a highly sophisticated biological system that plays an important role on many aspects of human health both locally and systemically. Like any other organ and tissue, the intestinal epithelial barrier is affected by the ageing process. New insights have surfaced showing that critical functions, including intestinal stem cell regeneration and regulation of the intestinal crypt homeostasis, barrier integrity, production of regulatory cytokines, and epithelial innate immunity to pathogenic antigens change across life. Here we review the age-associated changes of the various components of the intestinal epithelial barrier and we highlight the necessity to elucidate further the mechanisms underlying these changes. Expanding our knowledge in this area is a goal of high medical relevance and it will help to define intervention strategies to ameliorate the quality of life of the ever-expanding elderly population.

Rejuvenation of mucosal immunosenescence by adipose tissue-derived mesenchymal stem cells

Age-associated alterations in the mucosal immune system are generally termed mucosal immunosenescence. The major change seen in the aged mucosa is a failure to elicit an antigen-specific secretory IgA (SIgA) antibody response, which is a central player for host defense from various pathogens at mucosal surfaces. In this regard, it would be a first priority to compensate for mucosal dysregulation in the elderly in order to maintain their health in aging. We have successfully established antigen-specific SIgA antibody responses in aged (2 years old) mice, which provide protective immunity from Streptococcus pneumoniae and influenza virus infections, by using a new adjuvant system consisting of a plasmid encoding Flt3 ligand (pFL) and CpG ODN. In order to explore possible use of current mucosal vaccine strategies for the elderly, we have adoptively transferred adipose tissue-derived mesenchymal stem cells (AMSCs) to aged mice prior to mucosal vaccination. This immune therapy successfully resulted in protective antigen-specific antibody responses in the intestinal mucosa of aged mice that were comparable to those seen in young adult mice. In this regard, we postulate that adoptively transferred AMSCs could augment dendritic cell functions in aged mice. The potential cellular and molecular mechanisms whereby AMSCs restore mucosal immunity in immunosenescence are discussed in this short review. A stem cell transfer system could be an attractive and effective immunologic intervention strategy to reverse mucosal immunosenescence.

Allergic diseases in the elderly: biological characteristics and main immunological and non-immunological mechanisms

Life expectancy and the number of elderly people are progressively increasing around the world. Together with other pathologies, allergic diseases also show an increasing incidence in geriatric age. This is partly due to the growing emphasis on a more accurate and careful diagnosis of the molecular mechanisms that do not allow to ignore the real pathogenesis of many symptoms until now unknown, and partly to the fact that the allergic people from 20 years ago represent the elderly population now. Moreover, environmental pollution predisposes to the onset of allergic asthma and dermatitis which are the result of internal pathologies more than the expression of allergic manifestations. At the same time the food contamination permits the onset of allergic diseases related to food allergy. In this review we provide the state of the art on the physiological changes in the elderly responsible for allergic diseases, their biological characteristics and the major immunological and extra immunological mechanisms. Much emphasis is given to the management of several diseases in the elderly, including anaphylactic reactions. Moreover, some new features are discussed, such as management of asthma with the support of physical activity and the use of the AIT as prevention of respiratory diseases and for the purpose of a real and long lasting benefit. The mechanisms of adverse reactions to drugs are also discussed, due to their frequency in this age, especially in polytherapy regimens. Study of the modifications of the immune system is also of great importance, as regards to the distribution of the lymphocytes and also the presence of a chronic inflammatory disease related to the production of cytokines, especially in prevision of all the possible therapies to be adopted to allow an active and healthy aging.

Intermittent fasting favored the resolution of Salmonella typhimurium infection in middle-aged BALB/c mice

Intermittent fasting (IF) reportedly increases resistance and intestinal IgA response to Salmonella typhimurium infection in mature mice. The aim of this study was to explore the effect of aging on the aforementioned improved immune response found with IF. Middle-aged male BALB/c mice were submitted to IF or ad libitum (AL) feeding for 40 weeks and then orally infected with S. typhimurium. Thereafter, infected animals were all fed AL (to maximize their viability) until sacrifice on day 7 or 14 post-infection. We evaluated body weight, bacterial load (in feces, Peyer's patches, spleen and liver), total and specific intestinal IgA, lamina propria IgA+ plasma cells, plasma corticosterone, and messenger RNA (mRNA) expression of α-chain, J-chain, and the polymeric immunoglobulin receptor (pIgR) in liver and intestinal mucosa. In comparison with the infected AL counterpart, the infected IF group (long-term IF followed by post-infection AL feeding) generally had lower intestinal and systemic bacterial loads as well as higher total IgA on both post-infection days. Both infected groups showed no differences in corticosterone levels, body weight, or food and caloric intake. The increase in intestinal IgA was associated with enhanced pIgR mRNA expression in the intestine (day 7) and liver. Thus, to maintain body weight and caloric intake, IF elicited metabolic signals that possibly induced the increased hepatic and intestinal pIgR mRNA expression found. The increase in IgA probably resulted from intestinal IgA transcytosis via pIgR. This IgA response along with phagocyte-induced killing of bacteria in systemic organs (not measured) may explain the resolution of the S. typhimurium infection.

Salivary Immunoglobulin A Secretion Rate Is Negatively Associated with Cancer Mortality: The West of Scotland Twenty-07 Study

Immunoglobulins are essential for combating infectious disease although very high levels can indicate underlying pathology. The present study examined associations between secretory immunoglobulin A (sIgA) in saliva and mortality rates in the general population. Participants were 639 adults from the eldest cohort of the West of Scotland Twenty-07 Study aged 63 years at the time of saliva sampling in 1995. From unstimulated 2-minute saliva samples, saliva volume and S-IgA concentration were measured, and S-IgA secretion rate determined as their product. Mortality data were tracked for 19 years. Cox proportional hazard models were applied to compute hazard ratios (HR) for all-cause mortality from sIgA secretion rate. Associations were adjusted for gender, assay batch, household occupational group, smoking, medication usage, and self-reported health. There was a negative association between log sIgA secretion rate and all-cause mortality, HR = 0.81, 95%CI = 0.73–0.91, p < .001. Further analysis of specific causes of mortality revealed that the all-cause association was due to an underlying association with cancer mortality and in particular with cancers other than lung cancer. The HR for non-lung cancer was 0.68 (95%CI = 0.54 to 0.85) implying a 32% reduction in mortality risk per standard deviation rise in log sIgA secretion rate. Effects were stronger for men than women. For deaths from respiratory diseases, sIgA secretion had a non-linear relationship with mortality risk whereby only the very lowest levels of secretion were associated with elevated risk. SIgA concentration revealed a similar but weaker pattern of association. In the present study, higher secretion rates of sIgA were associated with a decreased risk of death from cancer, specifically non-lung cancer, as well as from respiratory disease. Thus, it appears that sIgA plays a protective role among older adults, and could serve as a marker of mortality risk, specifically cancer mortality.

Compartmentalization of immunosenescence: a deeper look at the mucosa

Developments in medical care and living conditions led to an astonishing increase in life-span perspective and subsequently a rise in the old population. This can be seen as a success for public health policies but it also challenges society to adapt, in order to cope with the potentially overwhelming cost for the healthcare system. A fast-growing number of older people lose their ability to live independently because of diseases and disabilities, frailty or cognitive impairment. Many require long-term care, including home-based nursing, communities and hospital-based care. Immunosenescence, an age-related deterioration in immune functions, is considered a major contributory factor for the higher prevalence and severity of infectious diseases and the poor efficacy of vaccination in the elderly. When compared with systemic immunosenescence, alterations in the mucosal immune system with age are less well understood. For this reason, this area deserves more extensive and intensive research and support. In this article, we provide an overview of age-associated changes occurring in systemic immunity and discuss the distinct features of mucosal immunosenescence.

Aging and the mucosal immune system in the intestine

Bacterial and viral infections of the gastrointestinal tract are more common in the elderly and represent a major cause of morbidity and mortality. The mucosal immune system provides the first line of defence against pathogens acquired by ingestion and inhalation, but its function is adversely affected in the elderly. This aging-related decline in the immune function is termed immunosenescence and is associated with diminished abilities to generate protective immunity, reduced vaccine efficacy, increased incidence of cancer, inflammation and autoimmunity, and the impaired ability to generate tolerance to harmless antigens. In this review we describe our current understanding of the effects immunosenescence has on the innate and adaptive arms of the mucosal immune system in the intestine. Current estimates suggest that by the year 2050 up to 40% of the UK population will be over 65 years old, bringing with it important health challenges. A thorough understanding of the mechanisms that contribute to the development of immunosenescence is therefore crucial to help identify novel approaches to improve mucosal immunity in the elderly.

IBD across the age spectrum: is it the same disease?

IBD is a chronic disorder with disease onset ranging from early childhood to beyond the sixth decade of life. The factors that determine the age of onset currently remain unexplained. Is timing of occurrence a random event or is it indicative of different pathophysiological pathways leading to different phenotypes across the age spectrum? Over the past decade, several studies have suggested that the characteristics and natural history of IBD seem to be different according to age of onset. This heterogeneity suggests that the respective contributions of genetics, host immune system and environment to the aetiology and phenotype of Crohn's disease and ulcerative colitis are different across ages. Critical reviews that focus on differences characterizing IBD between age groups are scarce. Therefore, this Review updates the knowledge of the differences in epidemiology, clinical characteristics, and natural history of paediatric, adult and elderly-onset IBD. In addition, potential differences in host-gene-microbial interactions according to age are highlighted.

Mucosal adjuvants for vaccines to control upper respiratory infections in the elderly

Influenza virus and Streptococcus pneumoniae are two major pathogens that lead to significant morbidity and mortality in the elderly. Since both pathogens enter the host via the mucosa, especially the upper respiratory tract (URT), it is essential to elicit pathogen-specific secretory IgA (SIgA) antibody (Ab) responses at mucosal surfaces for defense of the elderly. However, as aging occurs, alterations in the mucosal immune system of older individuals result in a failure to induce SIgA Abs for protection from these infections. To overcome mucosal immunosenescence, we have developed a mucosal dendritic cell targeting, novel double adjuvant system which we show to be an attractive and effective immunological modulator. This system induces a more balanced Th1- and Th2-type cytokine response which supports both mucosal SIgA and systemic IgG1 and IgG2a Ab responses. Thus, adaptation of this adjuvant system to nasal vaccines for influenza virus and S. pneumoniae could successfully provide protection by supporting pathogen-specific SIgA Ab responses in the URT in the mouse model of aging. In summary, a double adjuvant system is considered to be an attractive and potentially important strategy for the future development of mucosal vaccines for the elderly.

Allergic diseases in the elderly

Demographic distribution of the population is progressively changing with the proportion of elderly persons increasing in most societies. This entails that there is a need to evaluate the impact of common diseases, such as asthma and other allergic conditions, in this age segment. Frailty, comorbidities and polymedication are some of the factors that condition management in geriatric patients. The objective of this review is to highlight the characteristics of allergic diseases in older age groups, from the influence of immunosenescence, to particular clinical implications and management issues, such as drug interactions or age-related side effects.

Aging impacts isolated lymphoid follicle development and function

BACKGROUND

Immunosenescence is the age-related decline and dysfunction of protective immunity leading to a marked increase in the risk of infections, autoimmune disease, and cancer. The majority of studies have focused on immunosenescence in the systemic immune system; information concerning the effect of aging on intestinal immunity is limited. Isolated lymphoid follicles (ILFs) are newly appreciated dynamic intestinal lymphoid structures that arise from nascent lymphoid tissues, or cryptopatches (CP), in response to local inflammatory stimuli. ILFs promote "homeostatic" responses including the production of antigen-specific IgA, thus playing a key role in mucosal immune protection. ILF dysfunction with aging could contribute to immunosenescence of the mucosal system, and accordingly we examined phenotypic and functional aspects of ILFs from young (2 month old) and aged (2 year old) mice.

RESULTS

We observed that aged mice have increased numbers of ILFs and increased numbers of structures corresponding to an early stage of CPs transforming into ILFs. The cellular composition of ILFs in aged mice is altered with a smaller B-lymphocyte population and an increased T-lymphocyte population. The ILF T-lymphocyte population is notable by the presence of CD4+ CD8αα+ T-lymphocytes, which are absent from the systemic compartment. The smaller B-lymphocyte population in ILFs from aged mice is directly correlated with decreased mRNA and protein expression of CCL20 and CXCL13, two chemokines that play crucial roles in recruiting B-lymphocytes into ILFs. Aged mice had elevated levels of serum and fecal immunoglobulins and despite the decreased B-lymphocyte population, ILFs from aged mice displayed increased IgA production. The immunoglobulin repertoire was skewed in aged mice, and ILFs demonstrated a repertoire usage similar to that of the systemic pool in both young and aged mice.

CONCLUSIONS

Here we observed that ILF development, cellular composition, and immunoglobulin production are altered with aging suggesting that ILF dysfunction contributes to mucosal immunosenescence.

Food allergy: only a pediatric disease?

Epidemiologic studies report an increase in food allergies in industrialized countries, but mainly focus on children and young adults. This leads to the impression that food allergies do not occur in the older population. However, age-related changes dramatically affect both the innate as well as the adaptive immune system - a phenomenon known as immunosenescence. Deficiencies in micronutrients, especially zinc and iron, as well as vitamin D, in the elderly may also contribute to the development of allergies. A further risk factor of the elderly in developing food allergies could also be the decreased digestive ability of the stomach due to atrophic gastritis or anti-ulcer medication. In these settings, undigested proteins may persist and become allergenic. In fact, mouse models indicate that these pharmaceuticals support the induction of Th2 responses not only in young adult, but also in aged animals. Previous reports have already suggested that allergies are underdiagnosed among the elderly. Based on our own recent study conducted in a geriatric nursing home, we also suggest that food allergies may be underestimated.

Aged B lymphocytes retain their ability to express surface markers but are dysfunctional in their proliferative capability during early activation events

Background

Ageing is associated with dysfunction in the humoral response leading to decreased protection against infectious diseases. Defects in T cell function due to age have been well characterized but it is unclear if dysfunctions in antibody responses are due to deficiencies in a helper environment or intrinsic B cell defects. Previous studies from our laboratory have shown that aged B lymphocytes are able to differentiate into high affinity antibody-secreting cells at a frequency similar to their young counterparts. However, expansion of B cells in vivo was reduced in aged animals when compared to young.

Methods

To further investigate the cause of this reduced expansion, we have now examined early activation events of aged B cells in response to anti-CD40 monoclonal antibody (mAb) and lipopolysaccharide (LPS) stimulation in vitro. To do this spleen cells were harvested from young, middle-aged and aged quasi-monoclonal (QM) mice and cultured in complete RPMI for 24 and 48 hours. Cultures contained either LPS or anti-CD40 mAb and murine IL-4. Cells were collected and analyzed using flow cytometry. To examine the proliferative capacity of aged B cells spleen cells were collected as before and cultured in 96 well microtiter plates with either LPS or anti-CD40 mAb and murine IL-4 for 24 hours. Tritiated thymidine ([3H]-Tdr) was added to each well and incubated for another 24 hours after which cells were collected and analyzed using a scintillation counter.

Results

Resting aged B cells exhibited similar levels of CD40 expression when compared to young cells and efficiently up-regulated CD86 and CD69 and also down-regulated CD38 upon stimulation. However, aged B cells proliferated less than young B cells and showed a consistent, but not statistically significant, reduction in their ability to form blast cells.

Conclusion

Aged B cells exhibited a reduced response in some early activation events but produced at least a partial response in all cases. Thus, therapeutic intervention may be possible, despite intrinsically different responses in aged B cells.

Mucosal immunity and tolerance in the elderly

Age-associated dysregulation of the immune system of the gastrointestinal (GI) tract has been well documented for both secretory (S)-IgA immunity and oral tolerance. Thus, impaired antigen-specific Ab responses in aged animals and the elderly have been reported. Further, it has been shown that gut-associated lymphoreticular tissue (GALT) mediated immune responses are more susceptible to aging than are lymphoid tissues involved in peripheral immunity. Aging also impairs oral tolerance, which may be of central importance for maintaining GI homeostasis. Thus, as early as 6-8-month-old mice failed to establish systemic unresponsiveness to orally introduced antigens. Despite these studies, the precise mechanisms for impaired GI tract immune system responses remain unclear. The evidence of reduced sizes of Peyer's patches through aging suggests that age-associated mucosal dysregulation may be the result of mucosal inductive tissue dysfunction. Indeed, the frequencies of naive CD4+ T cells and dendritic cells (DCs) in Peyer's patches of aged mice were reduced and this led to a lack of essential cytokine synthesis for the induction of either S-IgA immunity or oral tolerance.

Senescence-associated decline of lymphocyte migration in gut-associated lymphoid tissues of rat small intestine

Scenescence-induced changes in gut-associated lymphoid tissues may contribute largely to the impaired immune responses during aging. Age-related changes in lymphocyte recirculations were investigated in Peyer's patches of rat small intestine. Cell dynamics of labeled T lymphocytes were observed under an intravital fluorescence microscope and compared between young and aged rats. Lymphocyte transport through intestinal lymph was decreased in aged rats. The lymphocyte rolling and adherence in postcapillary venules (PCV) of Peyer's patches was also significantly impaired in aged rats, with decreased expression of L-selectin on lymphocyte surfaces. Immunohistochemical analysis revealed a significant decrease in the CD8-positive cell population in Peyer's patches of the aged group, although mucosal addressin cell adhesion molecule-1 (MAdCAM-1) expression in postcapillary venules was unaltered. Lymphocyte adoptive-transfer studies indicated that although both the donor and recipient factors influence the adherence of T cells, the former may play a predominant role in the age-related change. This study clearly demonstrated in situ that T cell migration into Peyer's patches is significantly decreased in the aged intestine, which may reflect the impaired immune responses in the aging process.

Mucosal and systemic immunity to intestinal reovirus infection in aged mice

Systemic immunity is progressively impaired in aging, predisposing to morbidity and mortality from neoplasia and infectious disease. However, the effect of aging on mucosal immunity is controversial. To assess intestinal immunity in aging, young and aged mice were orally exposed to reovirus or cholera toxin (CT) and specific antibody and reovirus-specific cytotoxic T-cell (CTL) responses were assessed. As previously reported, aged mice immunized orally with CT mounted diminished intestinal IgA responses to CT compared to young mice. In contrast, aged mice yielded two to three-fold more reovirus-specific IgA-producing cells in the Peyers's patches (PP) compared to young mice, and higher titers of reovirus-specific IgA in fragment culture supernatants. Cytotoxicity and CTL frequencies from aged mice were not different from those of young mice. Together, these results suggest a diminished potential for systemic and intestinal immunity to orally applied protein antigens in aging, but an intact ability to respond to intestinal virus infection. Infection with a replicating virus may induce inflammatory mediators and innate immune factors that potentiate the priming of mucosal immunity; overcoming aging related deficits otherwise observed following oral immunization with non-replicating antigens, and suggests the importance of antigen replication to antigen-specific immunotherapy strategies in the elderly.

Expression of lymphocyte homing receptors alpha4beta7 and MAdCAM-l in young and old rats

The elderly constitute the most rapidly growing subpopulation in the United States. This age group represents a significant burden on the healthcare system due, in part, to increases in morbidity and mortality associated with an increase in the incidence of intestinal infectious diseases. Our previous studies suggest that impaired homing of IgA immunoblasts from the Peyer's patches to the intestinal lamina propria contributes to the diminished intestinal immune response in the elderly. The present study employs flow cytometry and quantitative immunohistochemistry to assess age-related changes in the numbers of peripheral blood mononuclear cells expressing the homing integrin alpha4beta7 and vascular endothelial cells in the intestine expressing its specific receptor, the address in MAdCAM-1, in inbred Fischer 344 rats. The proportion of alpha4beta7-positive mononuclear cells in young rats is significantly greater than that measured in the blood of senescent animals. Although the density of intestinal lamina propria blood vessels with MAdCAM-1-positive endothelium was greater in young adult rats in comparison to old animals, this difference achieved only borderline statistical significance. This is the first study to examine the expression of these two critical lymphocyte homing molecules as a function of age.

Inflammatory bowel disease

Although inflammatory bowel disease (IBD) usually presents in adolescents and young adults, both ulcerative colitis and Crohn's disease can also present in older adults. The diagnosis of IBD in the elderly is often difficult and can easily be confused with diverticulitis or ischaemic colitis. The symptoms and complications of IBD in the elderly are similar to those found in younger patients. However, when IBD presents later in life the disease is often less extensive and milder. Older IBD patients are treated with the same medications as younger patients, although the risk for drug toxicity is greater, especially with corticosteroid therapy. Comorbid illness in older patients often has a significant impact on the outcome of medical and surgical therapy for IBD but, in the absence of significant co-morbid disease, most elderly IBD patients can expect a good response to therapy.

Intestinal mucosal immunosenescence in rats

The elderly are characterized by systemic immunosenescence and high rates of morbidity and mortality associated with infectious diseases of the intestinal tract. Despite the consensus that the mucosal immune compartment is largely unaffected by aging, there are marked deficits in the intestinal mucosal immune responses of old animals and elderly humans. However, little is known about the mechanism(s) whereby aging disrupts intestinal immunity. Events in the generation of an intestinal immune response may be susceptible to the insults of aging. The first step involves the uptake of antigens by specialized follicular epithelial cells (M cells). There have been no studies on the efficacy of antigen uptake by M cells as a function of age. Little is known about the next step, i.e. antigen presentation by dendritic cells and subsequent isotype switching. The third event is the differentiation of putative immunolobulin A (IgA) plasma cells and their homing from the Peyer's patches (inductive site) to the lamina propria of the small intestine (effector site). Quantitative immunohistochemical and flow cytometry analyses suggest that the homing of IgA immunoblasts may be compromised in old rats and monkeys. Local antibody production/secretion by mature IgA plasma cells in the intestinal wall constitutes the fourth step. In vitro anti-cholera toxin IgA antibody secretion by intestinal lamina propria lymphocytes is equivalent in cells isolated from young adult and senescent rats. The final event in the mucosal immune response is the transport of IgA antibodies across the mucosal epithelial cells and their secretion onto the mucosal surface, i.e. receptor-mediated vesicular translocation of IgA by the intestinal epithelial cells. Binding assays did not detect age-associated declines in either the number or binding affinity of the polymeric immunoglobulin receptor expressed on rodent and monkey intestinal epithelial cells.

Aging impairs intestinal immunity

The elderly are characterized by immunosenescence accompanied by high rates of morbidity and mortality associated with infectious diseases. Despite suggestions that the mucosal immune compartment is relatively unaffected by aging, there are marked deficits in the intestinal mucosal immune responses of old animals and elderly humans. Little is known about the mechanism(s) whereby aging disrupts intestinal immunity. However, several events in the genesis of the intestinal immune response may be perturbed during aging. The first step is the uptake of antigens by specialized epithelial cells (M cells) that overlie the domes of Peyer's patches. We are unaware of any studies on the efficacy of antigen uptake in the intestine as a function of age. The effects of aging on the next step, antigen presentation by dendritic cells and lymphocyte isotype switching, have not been resolved. The third event is the maturation of immunoglobulin A (IgA) immunoblasts and their migration from the Peyer's patches to the intestinal mucosa. Quantitative immunohistochemical analyses suggest that the migration of these putative plasma cells to the intestinal effector site is compromised in old animals. Local antibody production by mature IgA plasma cells in the intestinal mucosa constitutes the fourth step. We recently reported that in vitro IgA antibody secretion by intestinal lamina propria lymphocytes from young and senescent rats is equivalent. The last event is the transport of IgA antibodies across the epithelial cells via receptor-mediated vesicular translocation onto the mucosal surface of the intestine. Receptor-binding assays did not detect age-associated declines in receptor number or binding affinity in either rodent or primate enterocytes as a function of donor age. Efforts to identify the mechanism(s) responsible for the age-related decline in intestinal mucosal immune responsiveness may benefit by focusing on the homing of IgA immunoblasts to the effector site.