Influence of aging on some specific and nonspecific mechanisms of the host defense system in 146 healthy subjects

Targeting Efferocytosis in Inflammaging

Rapid removal of apoptotic cells by phagocytes, a process known as efferocytosis, is key for the maintenance of tissue homeostasis, the resolution of inflammation, and tissue repair. However, impaired efferocytosis can result in the accumulation of apoptotic cells, subsequently triggering sterile inflammation through the release of endogenous factors such as DNA and nuclear proteins from membrane permeabilized dying cells. Here, we review the molecular basis of the three key phases of efferocytosis, that is, the detection, uptake, and degradation of apoptotic materials by phagocytes. We also discuss how defects in efferocytosis due to the alteration of phagocytes and dying cells can contribute to the low-grade chronic inflammation that occurs during aging, described as inflammaging. Lastly, we explore opportunities in targeting and harnessing the efferocytic machinery to limit aging-associated inflammatory diseases.

Immunosenescence as a convergence pathway in neurodegeneration

Immunity refers to the body's defense mechanism to protect itself against illness or to produce antibodies against pathogens. Senescence is a cellular phenomenon that integrates a sustainable growth restriction, other phenotypic abnormalities and including a pro-inflammatory secretome. It is highly involved in regulating developmental stages, tissue homeostasis, and tumor proliferation monitoring. Contemporary experimental reports imply that abolition of senescent cells employing evolved genetic and therapeutic approaches augment the chances of survival and boosts the health span of an individual. Immunosenescence is considered as a process in which dysfunction of the immune system occurs with aging and greatly includes remodeling of lymphoid organs. This in turn causes fluctuations in the immune function of the elderly that has strict relation with the expansion of autoimmune diseases, infections, malignant tumors and neurodegenerative disorders. The interaction of the nervous and immune systems during aging is marked by bi-directional influence and mutual correlation of variations. The enhanced systemic inflammatory condition in the elderly, and the neuronal immune cell activity can be modulated by inflamm-aging and peripheral immunosenescence resulting in chronic low-grade inflammatory processes in the central Nervous system known as neuro-inflammaging. For example, glia excitation by cytokines and glia pro-inflammatory productions contribute significantly to memory injury as well as in acute systemic inflammation, which is associated with high levels of Tumor necrosis factor -α and a rise in cognitive decline. In recent years its role in the pathology of Alzheimer's disease has caught research interest to a large extent. This article reviews the connection concerning the immune and nervous systems and highlights how immunosenescence and inflamm-aging can affect neurodegenerative disorders.

Cellular Mechanisms of Inflammaging and Periodontal Disease

Increased age is associated with an increased prevalence of chronic inflammatory diseases and conditions. The term inflammaging has been used to describe the age-related changes to the immune response that results in a chronic and elevated inflammatory state that contributes, in part, to the increased prevalence of disease in older adults. Periodontal disease is a chronic inflammatory condition that affects the periodontium and increases in prevalence with age. To better understand the mechanisms that drive inflammaging, a broad body of research has focused on the pathological age-related changes to key cellular regulators of the immune response. This review will focus on our current understanding of how certain immune cells (neutrophils, macrophages, T cells) change with age and how such changes contribute to inflammaging and more specifically to periodontal disease.

Frailty, aging, and periodontal disease: Basic biologic considerations

Aging is associated with the development of disease. Periodontal disease is one of the many diseases and conditions that increase in prevalence with age. In addition to the traditional focus on individual age-related conditions, there is now a greater recognition that multisystem conditions such as frailty play an important role in the health of older populations. Frailty is a clinical condition in older adults that increases the risk of adverse health outcomes. Both frailty and periodontal disease are common chronic conditions in older populations and share several risk factors. There is likely a bidirectional relationship between periodontal disease and frailty. Comorbid systemic diseases, poor physical functioning, and limited ability to self-care in frail older people have been implicated as underlying the association between frailty and periodontal disease. In addition, both frailty and periodontal disease also have strong associations with inflammatory dysregulation and other age-related pathophysiologic changes that may similarly underlie their development and progression. Investigating age-related changes in immune cells that regulate inflammation may lead to a better understanding of age-related disease and could lead to therapeutic targets for the improved management of frailty and periodontal disease.

Aged marrow macrophages expand platelet-biased hematopoietic stem cells via Interleukin1B

The bone marrow microenvironment (BMME) contributes to the regulation of hematopoietic stem cell (HSC) function, though its role in age-associated lineage skewing is poorly understood. Here we show that dysfunction of aged marrow macrophages (Mφs) directs HSC platelet-bias. Mφs from the marrow of aged mice and humans exhibited an activated phenotype, with increased expression of inflammatory signals. Aged marrow Mφs also displayed decreased phagocytic function. Senescent neutrophils, typically cleared by marrow Mφs, were markedly increased in aged mice, consistent with functional defects in Mφ phagocytosis and efferocytosis. In aged mice, Interleukin 1B (IL1B) was elevated in the bone marrow and caspase 1 activity, which can process pro-IL1B, was increased in marrow Mφs and neutrophils. Mechanistically, IL1B signaling was necessary and sufficient to induce a platelet bias in HSCs. In young mice, depletion of phagocytic cell populations or loss of the efferocytic receptor Axl expanded platelet-biased HSCs. Our data support a model wherein increased inflammatory signals and decreased phagocytic function of aged marrow Mφs induce the acquisition of platelet bias in aged HSCs. This work highlights the instructive role of Mφs and IL1B in the age-associated lineage-skewing of HSCs, and reveals the therapeutic potential of their manipulation as antigeronic targets.

Ageing and the immune system: focus on macrophages

A fully functioning immune system is essential in order to maintain good health. However, the immune system deteriorates with advancing age, and this contributes to increased susceptibility to infection, autoimmunity, and cancer in the older population. Progress has been made in identifying age-related defects in the adaptive immune system. In contrast, relatively little research has been carried out on the impact of ageing on the innate immune response. This area requires further research as the innate immune system plays a crucial role in protection against infection and represents a first line of defence. Macrophages are central effector cells of the innate immune system and have many diverse functions. As a result, age-related impairments in macrophage function are likely to have important consequences for the health of the older population. It has been reported that ageing in macrophages impacts on many processes including toll-like receptor signalling, polarisation, phagocytosis, and wound repair. A detailed understanding of the impact of ageing on macrophages is required in order to develop therapeutics that will boost immune responses in the older population.

Aging impairs peritoneal but not bone marrow-derived macrophage phagocytosis

Aging results in deterioration of the immune system, which is associated with increased susceptibility to infection and impaired wound healing in the elderly. Phagocytosis is an essential process in both wound healing and immune defence. As such, age-related impairments in phagocytosis impact on the health of the elderly population. Phagocytic efficiency in peritoneal macrophages, bone marrow-derived macrophages and bone marrow monocytes from young and old mice was investigated. Aging significantly impaired phagocytosis by peritoneal macrophages, both in vitro and in vivo. However, bone marrow-derived macrophages and bone marrow monocytes did not exhibit age-related impairments in phagocytosis, suggesting no intrinsic defect in these cells. We sought to investigate underlying mechanisms in age-related impairments in phagocytosis by peritoneal macrophages. We hypothesized that microenvironmental factors in the peritoneum of old mice impaired macrophage phagocytosis. Indeed, macrophages from young mice injected into the peritoneum of old mice exhibited impaired phagocytosis. Proportions of peritoneal immune cells were characterized, and striking increases in numbers of T cells, B1 and B2 cells were observed in the peritoneum of old mice compared with young mice. In addition, B cell-derived IL-10 was increased in resting and LPS-activated peritoneal cell cultures from old mice. These data demonstrate that aging impairs phagocytosis by tissue-resident peritoneal macrophages, but not by bone marrow-derived macrophages/monocytes, and suggest that age-related defects in macrophage phagocytosis may be due to extrinsic factors in the tissue microenvironment. As such, defects may be reversible and macrophages could be targeted therapeutically in order to boost immune function in the elderly.

Macrophages from elders are more permissive to intracellular multiplication of Mycobacterium tuberculosis

The elderly account for a disproportionate share of all tuberculosis cases, and the population ageing may not fully explain this phenomenon. We have performed in vitro infection experiments to investigate whether there is an immunological basis for the apparent susceptibility of elders to tuberculosis. In our infection model, Mycobacterium tuberculosis induces a higher production of interleukin (IL)-6 and reactive oxygen species in macrophages from elders than from younger adults. This response did not prevent, however, an increased multiplication of M. tuberculosis in macrophages from elders as compared with the growth observed within cells from adults. By performing a factorial experiment, we have found that IFN-γ, but not IL-1β, IL-6 or TNF-α, stimulate the macrophages to restrict the multiplication of the bacterium in macrophages from elders. Although monocytes from elders seem to be in a higher level of activation, we present evidences that protein tyrosine phosphorylation response induced by M. tuberculosis is stronger in monocytes from adults than from elders. Using a protein array that detects 71 tyrosine phosphorylated kinases, we identified Pyk2 as the only kinase that displayed a difference of intensity larger than 50 % in adults than in elders. Furthermore, monocytes from elders that were incubated in the presence of tyrosine kinase inhibitors (genistein and PP2) allowed a higher level of bacterial multiplication. These observations may help to explain the susceptibility of elders to tuberculosis. An unexpected result was that both genistein and its negative control, daidzein, abundant soy isoflavones, promoted intracellular mycobacterial growth.

Relationship between systemic inflammation and delayed-type hypersensitivity response to Candida antigen in older adults

Research has shown that aging is associated with increased systemic inflammation as well as a reduction in the strength of immune responses. However, little evidence exists linking the decrease in cell-mediated immunity in older adults with other health parameters. We sought to examine the relationship between cell-mediated immunity as measured in vivo by the delayed-type hypersensitivity (DTH) response to candida antigen and demographic and physiological variables in older (65–80 y.o.) adults. Candida antigen response was not related to gender or obesity, or to a number of other physiological variables including fitness and body composition. However, positive responders had significantly lower serum C-reactive protein levels (CRP, p<0.05) vs. non-responders. Furthermore, subjects with CRP<4.75 mg•L⁻¹ had greater odds of developing a positive response compared to those with CRP>4.75 mg•L⁻¹. Therefore, positive responses to candida antigen in older adults appears to be related to lower levels of systemic inflammation.

Aging is associated with circulating cytokine dysregulation

PURPOSE

Aging is accompanied by a progressive increase in pro-inflammatory cytokine status. However, little is known about the development of age-dependent modifications in other circulating cytokines. The aim of this study was to investigate in vivo the influence of age on circulating cytokine production in healthy subjects (HC).

METHODS

Circulating cytokines were measured by CBA and ELISA in 73 HC. Intracellular cytokine production was assessed in CD3+ and CD14+ cells by flow cytometry. Production of cytokines in cell culture supernatants was also studied after polyclonal stimulation.

RESULTS

Subjects were divided into three different groups according to age: 28 young HC (<30 years, 26.2 ± 2.4), 24 middle age HC (30-60 years, 44.7 ± 8.4) and 21 elderly HC (>60 years, 70.6 ± 7.9). Age was positively correlated with the circulating levels of IL-12p70, IL-1β, TNFα, IL-6, and IL-10. Age had a negative correlation with circulating levels of IL-17. Besides, age was positively correlated with spontaneous intracellular expression of proinflammatory cytokines in circulating monocytes. No correlation was found with other intracellular cytokine expression or with the production of cytokines in cell culture supernatants after in vitro stimulation. Gender had a marginal effect on the circulating cytokine profile.

CONCLUSION

Aging has a significant impact on the production of circulating cytokines in healthy individuals. The circulating cytokine milieu may contribute to the development of age-restricted conditions.

Intake of a milk-based wolfberry formulation enhances the immune response of young-adult and aged mice

Aging is associated with alterations of immune responses. Wolfberry, a popular Chinese functional ingredient, is prized for its anti-aging properties; however, little is known about the immunological effect of wolfberry intake. The purpose of this study was to examine the effect of dietary intake of a milk-based formulation of wolfberry, named Lacto-Wolfberry, on in vivo and ex vivo parameters of adaptive immunity in young-adult and aged mice. Over 44 days, young-adult (2 months) and aged (21 months) C57BL/6J mice were fed ad libitum with a controlled diet and received drinking water supplemented or not with 0.5% (wt/vol) Lacto-Wolfberry. All mice were immunized on day 15 and challenged on day 22 with a T cell- dependent antigen, keyhole limpet hemocyanin (KLH). Lacto-Wolfberry supplementation significantly increased in vivo systemic immune markers that are known to decline with aging. Indeed, both antigen-(KLH) specific humoral response and cell-mediated immune responses in young-adult and aged mice were enhanced when compared to their respective controls. No significant effect of Lacto-Wolfberry supplementation was observed on ex vivo spleen cells proliferative response to mitogens and on splenocyte T cell subsets. In conclusion, dietary intake of Lacto-Wolfberry may favorably modulate the poor responsiveness to antigenic challenge observed with aging.

Human innate immunosenescence: causes and consequences for immunity in old age

The past decade has seen an explosion in research focusing on innate immunity. Through a wide range of mechanisms including phagocytosis, intracellular killing and activation of proinflammatory or antiviral cytokine production, the cells of the innate immune system initiate and support adaptive immunity. The effects of aging on innate immune responses remain incompletely understood, particularly in humans. Here we review advances in the study of human immunosenescence in the diverse cells of the innate immune system, including neutrophils, monocytes, macrophages, natural killer and natural killer T (NKT) cells and dendritic cells-with a focus on consequences for the response to infection or vaccination in old age.

Pharmacodynamics in older adults: a review

BACKGROUND

Older individuals experience physiologic changes in organ function related to aging or to specific disease processes. These changes can affect drug pharmacodynamics in older adults.

OBJECTIVE

The goal of this article was to review age-related changes in pharmacodynamics and their clinical relevance.

METHODS

PubMed and International Pharmaceutical Abstracts were searched (January 1980-June 2006) for the following combination of terms: pharmacodynamic and elderly, geriatric or aged. References cited in other reviews were also evaluated. The current review focused on age-related pharmacodynamic changes in agents affecting the central nervous system (CNS), cardiovascular, and endocrine functions.

RESULTS

Older adults frequently demonstrate an exaggerated response to CNS-active drugs. This is in part due to an underlying age-related decline in CNS function and in part due to increased pharmacodynamic sensitivity for some benzodiazepines, anesthetics, and opioids. The most important pharmacodynamic differences with age for cardiovascular agents are the decrease in effect for beta-adrenergic agents. This decline in response in vascular, cardiac, and pulmonary tissue may be due to a decrease in Gs protein interactions. Most studies indicate there is no decrease in cx-receptor sensitivity with age. Angiotensin-converting enzyme inhibitors do not show age-related differences in elderly patients. With the dihydropyridine calcium channel blockers, there was a slight increase in effect for older adults, but this was only for treatment-naive patients and was transient. Nondihydropyridines did not show an age- associated change in pharmacodynamic effect; however, in the elderly, there appeared to be a decrease in the PR interval prolongation normally seen with these agents. Studies of diuretics indicated that the changes in diuretic and natriuretic effects seen in the elderly were associated with pharmacokinetic changes and were not pharmacodynamic in nature. There was a lack of consistent evidence regarding whether sulfonylureas show age-related changes in pharmacodynamic effect.

CONCLUSIONS

There is a general trend of greater pharmacodynamic sensitivity in the elderly; however, this is not universal, and these age-related changes must be investigated agent-by-agent until further research yields greater understanding of the molecular mechanisms underlying the aging process.

Markers to measure immunomodulation in human nutrition intervention studies

Normal functioning of the immune system is crucial to the health of man, and diet is one of the major exogenous factors modulating individual immunocompetence. Recently, nutrition research has focused on the role of foods or specific food components in enhancing immune system responsiveness to challenges and thereby improving health and reducing disease risks. Assessing diet-induced changes of immune function, however, requires a thorough methodological approach targeting a large spectrum of immune system parameters. Currently, no single marker is available to predict the outcome of a dietary intervention on the resistance to infection or to other immune system-related diseases. The present review summarises the immune function assays commonly used as markers in human intervention studies and evaluates their biological relevance (e.g. known correlation with clinically relevant endpoints), sensitivity (e.g. within- and between-subject variation), and practical feasibility. Based on these criteria markers were classified into three categories with high, medium or low suitability. Vaccine-specific serum antibody production, delayed-type hypersensitivity response, vaccine-specific or total secretory IgA in saliva and the response to attenuated pathogens, were classified as markers with high suitability. Markers with medium suitability include natural killer cell cytotoxicity, oxidative burst of phagocytes, lymphocyte proliferation and the cytokine pattern produced by activated immune cells. Since no single marker allows conclusions to be drawn about the modulation of the whole immune system, except for the clinical outcome of infection itself, combining markers with high and medium suitability is currently the best approach to measure immunomodulation in human nutrition intervention studies. It would be valuable to include several immune markers in addition to clinical outcome in future clinical trials in this area, as there is too little evidence that correlates markers with global health improvement.

Declining cell-mediated immunity and increased chronic disease burden

BACKGROUND

The effects of chronic disease have been proposed as an explanation for conflicting results in studies of age effects on cell-mediated immunity.

OBJECTIVE

To examine the hypothesis that declining cell-mediated immunity is more closely linked to chronic disease burden than to chronological age.

METHODS

Fifty-eight elderly individuals were tested for delayed-type hypersensitivity (DTH) responses to Candida and tetanus antigens. Disease burden was quantified using the Cumulative Illness Rating Scale (CIRS). Higher CIRS scores reflect greater disease burden. Mean DTH response by age group (<71, 71-78, and >78 years) was compared with mean DTH response by CIRS score (<11, 11-15, >15). Total serum IgE levels were measured and similarly stratified by age and CIRS score.

RESULTS

Mean Candida DTH responsiveness declined progressively with increasing disease burden (increasing CIRS score). Mean DTH responses were 7.78, 3.05, and 0.0 mm for CIRS scores less than 11, 11 to 15, and greater than 15, respectively. Candida DTH responses showed no progressive decline with advancing age. Mean DTH responses were 4.7, 3.5, and 5.0 mm in participants younger than 71, 71 to 78, and older than 78 years, respectively. Total serum IgE levels increased with advancing age. Mean total IgE levels were 182, 249, and 342 IU/mL in participants younger than 71, 71 to 78, and older than 78 years, respectively. No correlation was observed between mean total IgE levels and CIRS scores.

CONCLUSIONS

An inverse relationship between Candida DTH response and CIRS score suggests that increased chronic disease burden is associated with diminished cell-mediated immune response. Advancing age did not predict a diminished DTH response in our patients. No relationship was observed between chronic disease burden and total serum IgE level.

Influence of age and physical activity on the primary in vivo antibody and T cell-mediated responses in men

The aging immune system is characterized by the progressive decline in the antibody and T cell-mediated responses to antigen. Little is known, however, about the benefits of exercise in aging on the generation of a primary immune response to antigen and the subsequent antibody and memory T cell-mediated response. Most in vivo immune research to date has utilized vaccines or recall antigens to elicit an immune response. Therefore, the purpose of this experiment was to examine the association of aging and physical activity on the primary antibody and T cell response to the novel protein antigen keyhole-limpet hemocyanin (KLH). Forty-six physically active and sedentary, young (20-35 yr) and older (60-79 yr) men were recruited. Subjects were intramuscularly immunized with 100 microg of KLH, and blood samples were collected at days 0, 7, 14, 21, and 28. Samples were measured for anti-KLH IgM, IgG, IgG1, and IgG2 by ELISA. On day 21 after intramuscular KLH administration, subjects received an intradermal injection with 1 microg of KLH of inflammation recorded at 24, 48, 72, 96, and 120 h to assess anti-KLH delayed-type hypersensitivity response. There was a significant reduction in all anti-KLH measures with aging except for anti-KLH IgG2. The physically active older group had significantly higher anti-KLH IgM, IgG, IgG1, and delayed-type hypersensitivity responses, but not IgG2 compared with the sedentary older group. In conclusion, regular physical activity in older men is associated with a more robust immune response to novel antigenic challenge.

Peritoneal macrophages function modulation by L-carnitine in aging rats

BACKGROUND AND AIMS

The aging process is associated with a progressive decline in physiological functions involving immune response in most species. The aim of the present study was to determine the effect of L-carnitine on impaired macrophages function in aged rats.

METHODS

Superoxide anion production, chemotaxis and phagocytic activity were studied in peritoneal macrophages obtained from young (2 months old) and aged (24 months old) rats. L-carnitine (50 mg/kg bw) or control vehicle was orally gavaged into young and aged rats for 30 consecutive days.

RESULTS

The peritoneal macrophages of the aged rats exhibited an increase in superoxide anion generation and a decline in chemotaxis and phagocytic index by comparison with the young rats. Superoxide anion production in aged rats was significantly reduced by L-carnitine treatment, as accompanied by a significant enhancement of chemotactic activity, which was restored to control levels observed in young rats. The age-related reduction in phagocytic index was only slightly, but not significantly, restored by L-carnitine administration, however.

CONCLUSION

The findings suggest that L-carnitine administration may be useful in reversing some age-related changes.

Influence of age, sex, and hepatitis C virus infection on peripheral blood lymphocyte subsets in stable kidney transplantation

BACKGROUND

Young age and hepatitis C virus infection (HCVI) are believed to be risk factors in kidney transplantation recipients. The first group is treated empirically with an intensive immunosuppressive regimen, because it is considered to have high immune alloreactivity. The other cohort usually receives a less intensive regimen to avoid excessive immunosuppressive effects. Our aim was to investigate the influence of age, sex, and HCVI on immune status in stable kidney transplant recipients through measurement of peripheral blood lymphocyte subsets.

METHODS

Absolute CD3+, CD3+, CD4+, CD3+, CD8+, CD19+, CD16+ CD3- lymphocyte counts and CD4/CD8 ratios were assessed at five time points in 65 stable kidney allograft patients over 12 months. The subsets were compared according to age, sex, and HCVI of the recipients.

RESULTS

An inverse association was observed between recipient age and absolute CD19+ and CD3+ CD4+ lymphocyte counts, which was significant at all time points with respect to CD19+ counts, and at three time points with respect to CD3+ CD4+ counts. A significant positive association was observed between recipient age and absolute CD3- CD16+ lymphocyte counts at three time points. Female recipients showed significantly lower CD3+ CD8+ counts and significantly higher CD4/CD8 ratios than male recipients at four time points. HCVI recipients showed significantly lower CD16+ CD3- counts at four time points.

CONCLUSIONS

We observed links between immune status and age, sex and HCVI in stable kidney transplant recipients that could offer new insights into recommendations for maintenance immunosuppression.

Specific and nonspecific immune responses to fasting and refeeding differ in healthy young adult and elderly persons

BACKGROUND

Undernutrition is a main cause of immunodeficiency. Many confounding factors limit the interpretation of immune function in hospitalized elderly patients.

OBJECTIVE

We compared the effects of short-term fasting and refeeding on lymphocyte subset distribution and neutrophil function in healthy subjects.

DESIGN

Seven young adult (x +/- SE age: 24 +/- 2 y) and 8 elderly (71 +/- 3 y) subjects were fed standardized diets (1.6 x predicted resting energy expenditure; 16% protein) for 7 d. They then fasted for 36 h and were refed for 4 h (42 kJ/kg). Lymphocyte subsets were quantified by using fluorochrome-conjugated monoclonal antibodies. Neutrophil chemotactic migration was evaluated by using a 2-compartment chamber. Neutrophil reactive oxygen species production was measured by using a luminol-amplified chemiluminescence assay and oxidation of 2'7'-dichlorofluorescein diacetate.

RESULTS

Baseline total and cytotoxic T lymphocyte subpopulations were lower in elderly than in adult subjects (P < 0.01). Nutritional state had a significant effect (P < 0.05) on total, helper, and cytotoxic T and B lymphocyte counts in all subjects, and the response of lymphocyte subpopulations to nutritional fluctuations was significantly affected by age. The chemotactic index was lowered by fasting in both groups (P < 0.05 compared with basal values). After refeeding, neutrophil migration was restored in adult but not elderly subjects. The superoxide anion production rate increased with fasting and reverted to prefasting values with refeeding in both groups (P < 0.05). Fasting induced a significant decrease in hydrogen peroxide production in stimulated neutrophils that was reversed by refeeding in adult but not elderly subjects.

CONCLUSION

The lack of response of lymphocyte subpopulation counts and neutrophil function to nutritional changes may help to explain the proneness of elderly persons to infection.

Age-related responses of the microcirculation to ischemia-reperfusion and inflammation

Aging is a major risk factor for a variety of ischemic disorders including ischemic heart disease and stroke. Intense research over the past decade into ischemia-reperfusion (I/R) injury has implicated a general mechanism whereby reactive oxygen species produced at the onset of reperfusion overwhelm endogenous antioxidants, resulting in a cascade of events including mast cell degranulation, recruitment of neutrophils to the endothelial wall, arteriolar constriction that limits tissue perfusion, and increased vascular permeability that leads to inflammation and edema. Much of our knowledge regarding I/R injury comes from animal models; however, despite the fact that I/R disproportionately affects older individuals, young animals are usually chosen in models of I/R injury due to their greater availability, lower cost, and fewer health problems. Results obtained from young animals demonstrate a central role for both neutrophils and mast cells in I/R-induced increases in microvascular permeability and arteriolar constriction; however, it is not clear that a role for neutrophils is extended to older animals. A growing body of evidence indicates that neutrophils isolated from elderly individuals exhibit attenuated chemotaxis, oxidant release, and phagocytosis, and it has been suggested that these deficiencies are related to an age-associated increase in glucocorticoid production and oxidative stress. Therefore, neutrophils may have a limited capacity to influence microcirculatory tissue in the elderly compared to in the young. In support of this hypothesis, I/R-induced increases in microvascular permeability and decreases in vascular perfusion have been found to occur in older rats despite the absence of a significant increase in leukocyte-endothelial cell adhesion. Furthermore, elimination of circulating neutrophils attenuates I/R-induced mesenteric permeability only in young rats. Therefore, it appears that neutrophil-independent mechanisms of inflammation may be responsible for much of the microvascular dysfunction initiated by I/R in older animals.

Performance of antigens used in detecting delayed-type hypersensitivity in adolescents infected with the human immunodeficiency virus

We examined the performance of delayed-type hypersensitivity (DTH) antigens employing a new Candida albicans product in a human immunodeficiency virus (HIV)-infected and nonanergic adolescent population. Diameters of induration (in millimeters) for three intradermally applied antigens (C. albicans, tetanus toxoid, and mumps) were compared in a population of HIV-infected 12 to 18 year olds at study entry in a national multicenter study of HIV disease progression. CD4+ T-cell counts were measured in quality-controlled laboratories. The influence of past immunization, gender, and clinical status on antigen reactivity was evaluated with contingency table comparisons and relative risk estimation. Nearly one-half of the 123 eligible subjects were untreated, and almost three-quarters were early in HIV disease by clinical indicators. There was no statistically significant difference in reactivity by past immunization status. Candida antigen (CASTA; Greer Laboratories) evoked DTH response in a significantly higher number of males and females at every level of induration (largest P value, 0.049 for male comparisons; all P values, <0.001 for females) and in subjects with early and intermediate HIV disease at every level of induration (all P values, <0.0001) than either tetanus or mumps antigens. No two-antigen combination was as useful as all three antigens across either gender or clinical categories, although candida and tetanus was the most useful two-antigen combination at indurations of <3 mm. The superior performance of a new C. albicans antigen may extend the utility of DTH assessment in monitoring immune function.

The prevalence of anergy in human immunodeficiency virus-infected adolescents and the association of delayed-type hypersensitivity with subject characteristics

PURPOSE

To examine the prevalence of anergy in HIV-infected adolescents and factors associated with its occurrence.

METHODS

Anergy was defined as less than 2mm induration to each of three intradermally applied antigens (Candida albicans, tetanus toxoid, and mumps) between 24 and 96 hours in a population of HIV-infected adolescents aged 12-18 at entry in a national multicenter study of HIV disease progression. CD4(+) T-cell counts and plasma HIV-1 RNA were measured in quality controlled laboratories. Factors associated with the probability of anergy were examined with contingency table comparisons, tree-structured classification, and logistic regression analyses.

RESULTS

Overall prevalence of anergy in this clinic-based population of 167 was 11% [7% in males and 12% in females (p = 0.57)]. The sole significant predictor of anergy was decreased CD4(+) T-cell count (p = 0.005).

CONCLUSION

The prevalence of anergy is low in this HIV-infected population compared to older infected cohorts. The occurrence of differential rates of anergy in particular age and sex groupings that may be related to intrinsic immunologic differences requires further study.

Increase of reactive oxygen (ROS) and nitrogen (RNS) species generated by phagocyting granulocytes related to age

In this present paper the age-induced effect on reactive oxidizing species generated by oxygen (ROS) and nitrogen (RNS) was studied using human phagocyting granulocytes. The ROS and RNS were quantified, respectively, in a chemiluminescence assay and by the measurement of nitrite production. The age-induced reactive oxidizing species generation was studied in healthy subjects ranging from 20 to 80 years old, divided into six age groups: group I, 20-29 years old; group II, 30-39 years old; group III, 40-49 years old; group IV, 50-59 years old; group V, 60-69 years old; and group VI, 70-80 years old. Our results demonstrate a parallelism between generation of the ROS and RNS induced by the age. A significant increase of ROS production was observed from 40 years old (age groups III, IV, V and VI while for RNS this increase was observed only from 50 years old (groups IV, V and VI). These data suggest an increase of oxidizing species generation (ROS/RNS) related to age. The increased generation of ROS (40-49 years old) was induced before the increasing of RNS (50-59 years old) and it may have consequences on inflammation and host defences.

Age-associated changes in interferon-gamma and interleukin-4 secretion by purified human CD4+ and CD8+ T cells

Aging is associated with a decline in immune function. Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4), two important immune deviation-related cytokines, are mainly produced by type 1 and type 2 T cells, respectively. To investigate the age-associated changes in the secretion of these two cytokines, 20 elderly and 20 young subjects fulfilling the SENIEUR protocol were enrolled. The ratios of CD4+ to CD8+ T cells were not different between the two age groups. The CD4+ and CD8+ T cells were purified by a magnetic cell sorting system, and then activated by concurrent anti-CD3 and anti-CD28 stimulation. The released cytokines were determined by ELISA. Both the CD4+ and the CD8+ T cells of the elderly individuals secreted a significantly larger amount of IFN-gamma after activation. Profound IL-4 production by CD8+ T cells was observed in the older subjects compared with that of the young subjects. These data suggested that age-associated decrease in immunity may be related to an imbalance in the secretion of immune deviation cytokines. The number of IL-4-secreting CD8+ T cells (T cytotoxic 2) rose significantly in the older individuals. Our design also provided a useful way to differentiate the T cell subsets secreting the same cytokine, such as IFN-gamma-producing T helper 1 and T cytotoxic 1 cells.

Immune function did not decline with aging in apparently healthy, well-nourished women

Nutrition plays a crucial role in immune function. Most studies on age-associated changes in immunocompetence in healthy adults did not examine the nutritional status of participants extensively. Inadequate nutritional status may confound the relationship of aging and immune response. The purpose of this study was to examine age-related changes in parameters of acquired and innate immunity in healthy and generally well-nourished older (62-88 years) versus younger (20-40 years) women. Subjects were screened for participation using the health criteria of the SENIEUR protocol as well as a number of nutrition criteria related to undernutrition, and protein, iron, vitamin B12, and folate status. Young and old women did not differ in total T (CD3+), T-helper (CD4+), or T-cytotoxic (CD8+) cell number. However, older women tended to have lower T-cell proliferation response to concanavalin A (P < 0.10) and significantly reduced response to phytohemagglutinin (P < 0.05). No age-related changes were noted in natural killer cell number or cytotoxicity. Phagocytosis and subsequent oxidative burst activity also did not differ between young and old women. Most immune parameters were not compromised with aging in this cohort of apparently healthy, well-nourished women. These findings highlight the importance of simultaneous examination of health and nutritional status in studies of immune function with aging.

The vanishing importance of age in renal transplantation

BACKGROUND

The growing number of patients awaiting a kidney transplant raises questions about allocation of kidneys to the elderly and about the use of elderly donors. In all reported studies analyzing the influence of age on the outcome after renal transplantation, age is investigated as a categorical variable.

METHODS

We studied age both as a categorical (Kaplan-Meier) and as a continuous (Cox) variable in a total of 509 cyclosporine-treated recipients of a primary cadaveric kidney graft who underwent transplantation between July 1983 and July 1997. For the Kaplan-Meier analysis, the population was divided into three comparably sized age groups: 17-43 years (n=171), 44-55 years (n=169), and 56-75 years (n=169).

RESULTS

Patient survival was better and graft survival censored for death was worse in the younger patients. Overall graft survival (end point was death or graft failure) was not significantly influenced by age. In the Cox proportional hazards analysis, transplantation year turned out to be an important, independent variable influencing all end points. Because the influence was not linear, three periods were defined in which the relative risk remained stable: 1983-1990, 1991-1993, and 1994-1997. In the second period, the relative risk for transplant failure or death was 49% of that in the first period. In the third period, the relative risk had decreased to 22% of that in the first period. Recipient age and donor age were significant predictors of overall transplant failure. There was no interaction between these variables and transplantation year. Within each transplantation period, an increase in recipient age by 1 year increased the relative risk for overall graft failure by only 1.44%. The influence of donor age followed a J-shaped curve with a minimum at 30 years. The influence of increasing either recipient or donor age was counteracted by the improving results over time.

CONCLUSION

Considering the improving results over time, there are, at this moment, no arguments for an age restriction for kidney transplant recipients or donors.

Host defenses in the aged: evaluation of the balance between oxidizing species generation and reducing power in phagocyting human granulocytes

The respiratory burst reaction has been studied in human granulocytes from normal subjects divided in four age groups: (I) 20-29, (II) 30-39, (III) 40-49, and (IV) 50-59 years old. Zimosan opsonized particles (OZ) were used to evaluate, simultaneously, the reducing power and the oxidizing species generation. Our results showed a strong parallelism and a direct correlation between oxidizing species generation and reducing power in the groups (I) and (II), in presence or in the absence of opsonized zimosan. However, the age groups (III) and (IV) showed an increase in the free radicals generation and a significant decrease in the cellular reducing power. This inverse correlation observed between oxidizing/reducing power in the (III) and (IV) age groups may suggest a metabolic cellular disequilibrium.

Proinflammatory cytokine deficiency and pathogenesis of Pseudomonas aeruginosa keratitis in aged mice

Corneal clarity in young adult Swiss (HSD:ICR) mice is restored after Pseudomonas aeruginosa infection. Previous data showed that this response involves a rapid up-regulation of constitutive intercellular cell adhesion molecule-1 (ICAM-1) and migration of inflammatory cells into the cornea. In contrast, in aged mice, there is no up-regulation of corneal ICAM-1, inflammatory cell infiltration into the cornea is delayed, and the cornea perforates. Therefore, the aim of this study was to test whether specific cytokines which up-regulate ICAM-1 expression differ in young and aged mice. Corneas of young (6- to 8-week-old) and aged (1- to 2-year-old) mice were scarified and inoculated with P. aeruginosa. The eyes were graded for pathologic changes (score 0 to +4); at 6, 12, 24, and 48 h postinfection (p.i.), six mice from each age group were sacrificed. Three corneas from each respective group were excised for quantitation of interleukin-1beta (IL-1beta), tumor necrosis factor alpha, and gamma interferon (IFN-gamma) by enzyme-linked immunosorbent assay. The remaining three corneas from each age group were harvested for quantitation of viable bacteria by direct plate count determination and for infiltrating polymorphonuclear leukocytes (PMNs) by a myeloperoxidase (MPO) assay. Compared to those of young mice, the corneas of infected aged mice had less IL-1beta at 6 h p.i. (P < or = 0.04) and less IFN-gamma at 12 to 48 h p.i. (P < or = 0.05). Also, compared to those of young mice, corneas of aged mice had fewer PMNs (P < or = 0.008) by the MPO assay at 6 h p.i. and more viable bacteria (P < or = 0.01) per cornea by plate count determination at 24 h p.i. These data suggest that the lack of up-regulation of ocular ICAM-1 in aged mice may reflect a reduction in both IL-1beta and IFN-gamma levels in the infected cornea. Consequently, a sufficient number of PMNs and other inflammatory cells fail to rapidly migrate into the infected corneas of aged mice, the bacterial load is initially greater than that in young mice, and the cornea perforates.

Leukocyte migration inhibition studies and neutrophil cell function during aging in Nigerians

In this study, in vitro cell-mediated immune response was analysed in 150 healthy Nigerians between 6 and 95 years old by the leukocyte migration inhibitory factor (L-MIF) test. Lymphocytes were activated with the mitogen concanavalin A and candida, measles virus and mycobacterial antigens. Nonspecific cellular immune capacity was studied by the Nitroblue tetrazolium (NBT) test. Numerical estimates of leukocytes and lymphocyte subpopulations were done. Mean L-MIF activity obtained with the four lymphocyte activators decreased with rising age indicating a progressive decline in cellular immune function with age. There was no significant age-related change in formazan positivity rate for both unstimulated and stimulated NBT tests. No age-related change in number was observed for any of the leucocyte and lymphocyte subpopulations. These results show that cell-mediaging response in Nigerians immunity declines, but phagocyte function is unchanged during aging. Lymphocyte depletion or numerical alteration in resting T cell subsets could not be demonstrated to be responsible for depressed cell-mediated immunity in aging Nigerians.