gamma-Interferon, interleukin-4 and interleukin-6 in vitro production in old subjects

Advanced Glycation End Products of Bovine Serum Albumin Suppressed Th1/Th2 Cytokine but Enhanced Monocyte IL-6 Gene Expression via MAPK-ERK and MyD88 Transduced NF-κB p50 Signaling Pathways

Advanced glycation end products (AGE), the most known aging biomarker, may cause “inflamm-aging” (i.e., chronic low-grade inflammation that develops with aging) in both aged and diabetes groups. However, the molecular bases of inflamm-aging remain obscure. We prepared AGE by incubating BSA (0.0746 mmol/L) + glucose (0.5 mol/L) at 37 °C in 5% CO₂–95% air for 1–180 days. The lysine glycation in BSA–AGE reached 77% on day 30 and 100% after day 130, whereas the glycation of arginine and cysteine was minimal. The N^ε-(carboxymethyl)-lysine content in BSA–AGE was also increased with increasing number of incubation days. The lectin-binding assay revealed that the glycation of BSA not only altered the conformational structure, but lost binding capacity with various lectins. An immunological functional assay showed that BSA–AGE > 8 μg/mL significantly suppressed normal human Th1 (IL-2 and IFN-γ) and Th2 (IL-10) mRNA expression, whereas AGE > 0.5 μg/mL enhanced monocyte IL-6 production irrelevant to cell apoptosis. The AGE-enhanced monocyte IL-6 production was via MAPK–ERK and MyD88-transduced NF-κBp50 signaling pathways. To elucidate the structure–function relationship of BSA–AGE-enhanced IL-6 production, we pre-preincubated BSA–AGE with different carbohydrate-degrading, protein-degrading, and glycoprotein-degrading enzymes. We found that trypsin and carboxypeptidase Y suppressed whereas β-galactosidase enhanced monocyte IL-6 production. In conclusion, BSA–AGE exerted both immunosuppressive and pro-inflammatory effects that are the molecular basis of inflamm-aging in aged and diabetes groups.

Toll-like Receptor function of murine macrophages, probed by cytokine induction, is biphasic and is not impaired globally with age

Aging is associated with a waning of normal immune function. This "immunosenescence" is characterized by a diverse repertoire of seemingly discreet and unbalanced immune alterations. A number of studies have suggested that aging-associated alterations in innate immune responsiveness, especially responsiveness dependent on Toll-like Receptor (TLR) engagement, are causally involved. We find, however, that the magnitude and dose-dependency of responsiveness to TLR engagement (assessed with respect to cytokine production) in distinct populations of murine macrophages are not altered generally with animal age or as a consequence of immunosenescence. Responses elicited with a wide array of TLR agonists were examined by extensive functional analyses, principally on the level of the individual cell. These studies reveal an intriguing "all-or-nothing" response behavior of macrophages, independent of animal age. Although reports to the contrary have been cited widely, aging-associated immune decline cannot be attributed to widespread alterations in the extents of TLR-dependent innate immune macrophage responses.

Age is not associated with hospital admission or uncontrolled symptoms of asthma if proper treatment is offered

BACKGROUND

Aging modifies immune response and respiratory physiology. Few studies evaluate the effect of age on asthma. The aim of our study was to evaluate whether age is associated with uncontrolled symptoms and hospital admissions due to asthma in a setting where patients were receiving proper treatment.

METHODS

We enrolled 401 patients with uncontrolled asthma who were inhaled corticosteroid-naive. The follow-up period was 1 year. They received medications for asthma, performed spirometry, a symptoms questionnaire, and all emergency room visits and hospital admissions due to asthma were reported. The primary end point was hospital admission during the follow-up period.

RESULTS

Baseline data demonstrated that subjects >55 years of age had a later onset of asthma and a longer duration of symptoms. Adjusted logistic regression models demonstrated that older age at enrollment did not predict asthma control in the follow-up: hospital admission due to asthma [odds ratio (OR) 1.7 and 95% confidence interval (CI) 0.6-4.7], symptoms score (OR 0.6 and 95% CI 0.3-1.1) and emergency room visits due to asthma (OR 0.9 and 95% CI 0.6-1.3). Older age was associated with worse lung function (OR 1.8 and 95% CI 1.1-3.3).

CONCLUSION

This study allows us to conclude that older age is associated with a later onset of asthma and a longer duration of symptoms. Age does not predict hospital admissions or poor control of asthma symptoms if proper treatment is offered. It does, however, predict worse lung function.

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

T cells are essential for defending hosts against microorganisms and malignancy as well as for regulating the development of immune-mediated inflammatory diseases like autoimmunity. Alterations in T-cell immunity occur with aging, affecting the function and proportions of T-cell subsets. Probably, the most noticeable age-associated change in T-cell immunity is an alteration in the frequency of naive and memory CD4+ and CD8+ T cells. In fact, the frequency of naive CD4+ and CD8+ T cells decreases with aging, whereas the frequency of memory CD4+ and CD8+ T cells increases. Also, changes in T-cell proliferation, cytokine production, memory response, and cytotoxicity as well as in regulatory T-cell number and function have been reported with aging. Such alterations could contribute to the development of infections, malignancies, and inflammatory diseases that rise with aging. Of interest, T cells are closely involved in the development of inflammatory airway and lung diseases including asthma and chronic obstructive pulmonary disease, which are prevalent in the elderly people. In addition, T cells play a major role in defending host against influenza virus infection, a serious medical problem with high morbidity and mortality in the elderly people. Thus, it is conceivable that altered T-cell immunity may account in part for the development of such respiratory problems with aging. Here, we will review the recent advances in T-cell immunity and its alteration with aging and discuss the potential effects of such changes on the lung.

Aging and asthma - changes in CD45RA, CD29 and CD95 T cells subsets

BACKGROUND

Aging is associated with thymus involution leading to a reduction in naive T cells and to an accumulation of effector-memory cells. Apoptosis is a key mechanism to clear the immune system from activated and harmful cells. In asthma the stimulation of T cells by environmental antigens can decrease naive cells and sustain activated cells. The aim of this work was to evaluate the imbalance between CD45RA and CD29 cells during the aging process and their changes in elderly asthma and to evaluate how elderly and chronic diseases like asthma can affect susceptibility to apoptosis.

METHODS

Elderly and young adult healthy volunteers and elderly asthmatic patients were submitted to skin prick tests, immunoglobulin determination and flow cytometry analyses of CD3, CD4, CD8, CD45RA, CD29, and CD95.

RESULTS

Serum IgE was increased in allergic patients (p=0.0001). Asthmatics presented an increase in CD4 cells (p<0.05). CD45RA was significantly decreased in elderly individuals (p<0.05) and this decrease was higher in asthmatics (p<0.05). CD29 was increased in elderly healthy individuals compared to the control young group (p=0.0001). A negative correlation between CD29 and CD45RA (p<0.05) was observed. CD95 lymphocytes increased in elderly (p=0.0001) and a positive correlation between age and CD95 (p<0.05) was found. Asthmatic patients showed significant decreases in CD95 (p=0. 0001).

CONCLUSIONS

Naive cells are key cells in the defence against infections and their decrease in the elderly and in asthma is a bad prognosis factor. The reduction of apoptosis markers can promote the persistence of activated cells involved in chronic conditions.

Gender specificity of altered human immune cytokine profiles in aging

Cytokine generation by T cells and monocytes was determined for 50 subjects aged 65 yr or older and concurrently studied young subjects individually matched to each old subject for sex, race, and national origin. Highly significant differences between cytokine levels of old and young subjects all were gender specific. For T cells stimulated with anti-CD3 plus anti-CD28 antibodies, mean ratios of IFN-gamma generation for healthy old to young subjects were 0.22 for men (P<0.001; n=15) and 3.35 for women (P<0.001; n=13), and those of IL-17 were 0.30 for men (P<0.001) and no difference for women. CD8 T cells were the source of high IFN-gamma in healthy old women. For old men with an inflammatory or immune disease (n=10), mean old to young ratios of T-cell-generated IFN-gamma and IL-17 increased with disease severity up to 5.78 and 2.97 (both P<0.01), respectively, without changes for old women with similar diseases (n=12). For differentiated LPS-stimulated monocytes, old to young ratios of TNF-alpha and IL-6 generation were high only in women with immune or inflammatory disease (2.38, P<0.05 and 1.62, P<0.01, respectively), whereas ratios of IFN-gamma-evoked IP-10 chemokine were low in all groups. Alterations in immune cytokine profiles with aging show significant gender specificity.

Cytomegalovirus infection- and age-dependent changes in human CD8+ T-cell cytokine expression patterns

T cells are strongly affected by immune aging, a phenomenon that leads to increased susceptibility to infections and decreased vaccination efficacy in elderly individuals. Cytomegalovirus (CMV) infection induces vigorous T-cell immune responses in humans and is thought to be a driving force of immune aging. In the present study we analyzed CMV-induced quantitative and qualitative differences in the cytokine-expressing T-cell repertoire from individuals of different age groups after in vitro stimulation. The CMV pp65 peptide pool and the superantigen Staphylococcus enterotoxin B (SEB) induced higher proportions of CD8+ effector T cells expressing gamma interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and granulocyte-macrophage colony-stimulating factor in the oldest study group, while only SEB induced increased responses in the middle-aged study group. Notably, CMV-specific multiple cytokine expression patterns revealed higher proportions of IFN-gamma- and TNF-alpha-coexpressing CD8+ T cells exclusively in the oldest study group. These qualitative differences were absent in SEB-induced CD8+ effector T cells, although quantitative differences were detected. We report age-dependent qualitative changes in CMV-specific CD8+ T-cell cytokine patterns which are biocandidate markers of immune exhaustion in elderly individuals.

Aging and the dendritic cell system: implications for cancer

The immune system shows a decline in responsiveness to antigens both with aging, as well as in the presence of tumors. The malfunction of the immune system with age can be attributed to developmental and functional alterations in several cell populations. Previous studies have shown defects in humoral responses and abnormalities in T cell function in aged individuals, but have not distinguished between abnormalities in antigen presentation and intrinsic T cell or B cell defects in aged individuals. Dendritic cells (DC) play a pivotal role in regulating immune responses by presenting antigens to naïve T lymphocytes, modulating Th1/Th2/Th3/Treg balance, producing numerous regulatory cytokines and chemokines, and modifying survival of immune effectors. DC are receiving increased attention due to their involvement in the immunobiology of tolerance and autoimmunity, as well as their potential role as biological adjuvants in tumor vaccines. Recent advances in the molecular and cell biology of different DC populations allow for addressing the issue of DC and aging both in rodents and humans. Since DC play a crucial role in initiating and regulating immune responses, it is reasonable to hypothesize that they are directly involved in altered antitumor immunity in aging. However, the results of studies focusing on DC in the elderly are conflicting. The present review summarizes the available human and experimental animal data on quantitative and qualitative alterations of DC in aging and discusses the potential role of the DC system in the increased incidence of cancer in the elderly.

Age-dependent modifications of Type 1 and Type 2 cytokines within virgin and memory CD4+ T cells in humans

Several alterations in immune function and a concomitant progressive increase in pro-inflammatory status are the major characteristics of ageing process. Cytokines play a key role during ageing acting both in regulatory communication among cells and in effector activity during an immune response. The impact of age on intracellular Type 1 (IFN-gamma and TNF-alpha) and Type 2 (IL-4) cytokines, after stimulation with PMA/ionomycin, was determined in three CD4+ T subsets, i.e. CD95- CD28+ (virgin), CD95+ CD28+ (activated/memory), and CD95+ CD28- (effector/memory) from 47 subjects aged between 21 and 99 years. The percentage of IFN-gamma positive cells significantly decreased in virgin CD4+ subset both in old and nonagenarian subjects, as well as in activated/memory T cells from old in comparison with young subjects. The percentage of TNF-alpha positive cells significantly decreased in activated/memory CD4+ subset from old people. Regarding Type 2 cytokines, IL-4 positive cells significantly increased in activated/memory CD4+ subset from nonagenarians. On the whole our data indicate that: (1) different Type 1 and Type 2 cytokine-positive CD4+ T subsets are differently affected by ageing process; (2) activated/memory T cells appear to be the most affected subset; (3) a shift towards an increased role of Type 2 cytokines and a diminished role of Type 1 cytokines emerges with ageing.

The inflammatory response to vaccination is altered in the elderly

To further explore whether immune function and acute phase response are altered during ageing, the response to a mild inflammatory stress (DT-Polio-Typhim vaccination) was studied in elderly and young subjects. Cytokine production (IFN-gamma, TNF-alpha, IL-6, IL-10) by whole blood cultures, circulating cytokines and acute phase proteins were analysed before and 2 days after vaccination. Prior to vaccination, only IFN-gamma production was lower in the elderly than in the young subjects due to a lower mononuclear cell number. In the same time, although in the normal range, several acute phase proteins were greater in elderly than in young subjects, suggesting a low-grade inflammatory state in the elderly. After vaccination, IFN-gamma production remained lower in the elderly than in the young, supporting an altered cell-mediated immunity with advancing age. TNF-alpha production was unaffected by either ageing or vaccination. IL-6 production was stimulated by vaccination in young subjects but not significantly in the elderly. IL-10 production was inhibited by vaccination in the elderly but not in the young. Acute phase proteins were less increased in elderly than in young subjects. Taken together, these results support a general lack of inflammatory response in the elderly exposed to an immune challenge and suggest that immune deficiency may concern both Th1 and Th2 responses. However, the interpretation must respect the limitation of small subjects number.

Inflamm-aging: autoimmunity, and the immune-risk phenotype

Aging of the immune system, or immunosenescence, is a complex subject best defined as a decline in cell-mediated immunity, particularly with respect to T cell function. Paradoxically with the decline in immune function is an increase in autoantibody frequency. It has been postulated that the accumulation of anamnestic cells over time and/or environmental/infectious mimics leads to the production of autoantibodies, sometimes accompanied by autoimmune disease. This specific phenotype has given rise to the concept of a specific cluster of cytokine profiles, coined an immune-risk phenotype (IRP). The IRP is likely dictated by not only cytokine production, but also defects in activation-induced cell death and also a shift in T cell subsets. These concepts are an important bridge between basic immune function and clinical immunology in the hopes for generation of effective reconstitution to improve immune function in the elderly.

Dysfunctional CMV-specific CD8+ T cells accumulate in the elderly

Large clonal expansions of peripheral CD8(+) T cells carrying receptors for single epitopes of CMV are common in the elderly and may be associated with an immune risk phenotype predicting mortality. To study the effect of ageing on the ability of CMV-specific CD8(+) T cells to produce type 1- and type 2-cytokines, interferon-gamma-and IL-10-producing, CD8(+) T cell responses in the presence of CMV peptide antigen were measured in CMV-seropositive old and young donors. We found that large expansions of A2/NLV-specific CD8(+) T lymphocytes in the elderly are accompanied by a partial loss of antigen responsiveness as reflected in a greatly decreased frequency of antigen-specific IFN-gamma-and IL-10-producing cells. Thus, despite carrying specific antigen receptors, the majority of the clonally expanded CMV-specific CD8(+) cells in the elderly was dysfunctional according to these criteria. Our data indicated a bias towards a more anti-inflammatory response in the elderly. The accumulation of dysfunctional CMV-specific cells might fill the 'immunological space' and decrease the available repertoire of T cells for novel antigens. This might account for the increased incidence of many infectious diseases in the elderly.

The effect of aging on immune responses

Although vaccine manufacturers make no specific recommendations regarding the vaccination of older horses and ponies, the similarities in age-induced immunologic changes between human beings and equids suggests that similar vaccination recommendations should be followed. The need for vaccination of the older horse depends, of course, on the relative risk of exposure for the individual horse. Particular care should be taken when using attenuated vaccine products because these live agents may pose a unique risk to the older individual. Immunization with inactivated agent vaccines is likely to be safer. In general, annual vaccination against equine influenza virus infection, tetanus, rabies, and encephalomyelitis viruses is warranted.

Anatomic site and immune function correlate with relative cytokine mRNA expression levels in lymphoid tissues of normal rhesus macaques

Reverse transcriptase real-time polymerase chain reaction was used to determine pro-inflammatory, anti-viral and immunoregulatory cytokine mRNA expression levels in peripheral blood mononuclear cells (PBMC) of healthy juvenile, adolescent and adult rhesus macaques. Few age-related changes in cytokine mRNA expression levels were observed. Expression of interleukin 2 and Mx, a type I interferon-inducible gene, decreased with age, whereas interleukin 4 and macrophage inflammatory protein 1 (MIP-1) alpha and beta mRNA levels increased in older monkeys. Independent of age, the pro-inflammatory cytokines [tumour necrosis factor alpha (TNF-alpha) and chemokines] were expressed at higher mRNA levels in PBMC than the immunoregulatory cytokines (interleukins 2, 4, 12). Pro-inflammatory cytokine mRNA expression levels were highest in lymphoid tissues draining mucosal surfaces. Thus, a correlation exists between cytokine mRNA levels in lymphoid tissues and the anatomical site.

Cytokine production by stimulated mononuclear cells did not change with aging in apparently healthy, well-nourished women

Aging is often associated with a dysregulation of the immune system. We examined mitogen-stimulated production of interleukin (IL)-2 and proinflammatory cytokines, IL-1beta and IL-6, in apparently healthy and generally well-nourished old versus young women. Subjects were screened for health using the SENIEUR protocol and a panel of laboratory tests for inflammation, as well as for the adequacy of nutritional status using criteria related to undernutrition, and protein, iron, vitamin B(12), and folate status. Young (n=26, age: 20-40 years) and old (n=44, age: 62-88 years) cohorts did not differ on the number of circulating monocytes, granulocytes, B (CD19+) cells, and T (CD3+, CD4+, and CD8+) cells. No differences (P>0.10) were seen between the two age groups in IL-2, IL-1beta and IL-6 levels in whole blood cultures at 48 h after stimulation with PHA (5 mg/l). Furthermore, no age-related differences were noted in the absolute amounts (pg) of IL-1beta and IL-6 after normalizing for circulating monocytes, B cells, or T cells (P>0.10). Similarly, no age-related decline in absolute amount of IL-2 (pg) after normalizing for circulating T cells was noted (P>0.10). Thus, contrary to most previous reports, our results do not support an increase in the production of proinflammatory cytokines IL-1beta and IL-6, and a reduced production of IL-2 with aging when health and nutritional status are maintained. These findings support our previous results of no change in monocyte function and few alterations in acquired immune response in a carefully selected group of healthy and well-nourished elderly women.

Anti-Inflammatory effects of antidepressants through suppression of the interferon-gamma/interleukin-10 production ratio

There is some evidence that major depression--in particular, treatment-resistant depression (TRD)--is accompanied by activation of the inflammatory response system and that proinflammatory cytokines may play a role in the etiology of depression. This study was carried out to examine the effects of antidepressive agents, i.e., imipramine, venlafaxine, L-5-hydroxytryptophan, and fluoxetine on the production of interferon-gamma (IFN-gamma), a proinflammatory cytokine, and interleukin-10 (IL-10), a negative immunoregulatory cytokine. Diluted whole blood of fluoxetine-treated patients with TRD (mean age, 50.6+/-3.9 years) and age-matched healthy controls (mean age, 51.6+/-1.7 years) and younger healthy volunteers (mean age, 35.4+/-9.6 years) was stimulated with phytohemagglutinin (1 microg/mL) and lipopolysaccharide (5 microg/mL) for 48 hours with and without incubation with the antidepressants at 10-6 M and 10(-5) M. IFN-gamma and IL-10 were quantified by means of enzyme-linked immunoassays. The ratio of IFN-gamma to IL-10 production by immunocytes was computed because this ratio is of critical importance in determining the capacity of immunocytes to activate or inhibit monocytic and T-lymphocytic functions. All four antidepressive drugs significantly increased the production of IL-10. Fluoxetine significantly decreased the production of IFN-gamma. All four antidepressants significantly reduced the IFN-gamma/IL-10 ratio. There were no significant differences in the antidepressant-induced changes in IFN-gamma or IL-10 between younger and older healthy volunteers and TRD patients. Tricyclic antidepressants, selective serotonin reuptake inhibitors, and serotonin-noradrenaline reuptake inhibitors, as well as the immediate precursor of serotonin, have a common, negative immunoregulatory effect by suppressing the IFN-gamma/IL-10 production ratio. It is suggested that the therapeutic efficacy of antidepressants may be related to their negative immunoregulatory effects.

Immunosenescence: a review

Aging involves the morphological and functional integrity of all organs, including the cellular and humoral immunological functions. The main alterations can be listed as follows: (i) Thymic involution resulting in the decreased number of lymphoid precursor T- and B-cells. (ii) Reduced proliferative capacity of T-cells; loss of lymphocyte subgroups as a consequence of the shortening of telomeres. (iii) Qualitative deficiency of B-lymphocytes with a reduced response to exogenous antigens. (iv) Compromised activity of the accessory cells, both directly by depressing the chemotactic and phagocytic responses, and indirectly by increasing the prostaglandin production which inhibit the proliferation of T-cells. (v) Alterations in the production and secretion of various cytokines. (vi) Other factors like the general physiological conditions, the nutritional state, psychological habit and various hormone levels.

Preliminary studies on the effect of dehydroepiandrosterone (DHEA) on both constitutive and phytohaemagglutinin (PHA)-inducible IL-6 and IL-2 mRNA expression and cytokine production in human spleen mononuclear cell suspensions in vitro

In order to gain further insight into the potential immunological benefits of oral administration of DHEA we have examined its effects on the constitutive and PHA-inducible expression by human spleen cell suspensions in vitro of IL-6 and IL-2. This was studied at both the mRNA and protein levels. The quantification of specific mRNA was undertaken using commercially available quantitative polymerase chain reaction kits. These studies, which were performed on suspensions from six individual spleens, revealed that 10(-5) M DHEA did not impair the expression of IL-6 at either the mRNA or protein level, but may have slightly enhanced the latter. In contrast, IL-2 mRNA levels were increased on most occasions, whilst IL-2 secretion was decreased, albeit slightly. Additional studies revealed that cyclosporin (approx. 10(-5) M) and dexamethasone (10(-7) M) readily inhibited these responses and the production of other cytokines, including interferon-gamma and tumour necrosis factor-alpha. These preliminary studies suggest that high doses of DHEA do not readily inhibit the production of IL-6, and indeed other cytokines, by PHA-stimulated secondary human lymphoid tissue suspensions in vitro. They may also partially explain the meagre immunomodulatory effects noted in some DHEA replacement studies in humans.

Reduced IFN-gamma production in elderly people following in vitro stimulation with influenza vaccine and endotoxin

Cytokine interferon gamma (IFN-gamma) is pivotal in the defence against viruses and intracellular pathogens and an age-related decreased IFN-gamma production may explain the increased infectious disease morbidity and mortality in the elderly. Therefore, we performed a series of clinical experiments evaluating the influence of age and health status on IFN-gamma production following in vitro stimulation with influenza vaccine or endotoxin. Both healthy and frail elderly people produced significantly lower amounts of IFN-gamma following ex vivo stimulation with influenza vaccine or endotoxin. We conclude that ageing is accompanied by a decreased capacity to produce IFN-gamma. This may explain the increased incidence and case-fatality caused by viruses and intracellular pathogens in the elderly.

Aging, immunity, and cancer

BACKGROUND

The prime function of the immune system is to protect the entire organism from a variety of insults and illnesses, including the development of cancer. The question of how age-related declines in immune function contribute to an increasing incidence of malignancies continues to be a focus of discussion and speculation.

METHODS

The recent literature from the National Library of Medicine database (1990 through the present) was searched for articles using the medical subject headings (MeSH terms) of aging, immunity, cancer, senescence, and apoptosis. Bibliographies of articles retrieved were also scanned.

RESULTS

Data from in vitro and in vivo animal and human studies demonstrate clear age-related alterations in both the cellular and humoral components of the immune system, but there is little evidence supporting direct causal links between immune senescence and most malignancies.

CONCLUSIONS

Senescent decline in immune surveillance leads to the accumulation of cellular and DNA mutations that could be a significant factor in the development of malignancy and programmed cell death or apoptosis observed in the elderly.

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.

In vitro treatment with interleukin-2 normalizes type-1 cytokine production by lymphocytes from elderly

The term immunosenescence is taken to mean the deterioration of immune function seen in elderly, which is manifested in increased susceptibility to infectious diseases, neoplasias, and autoimmune diseases. It is only recently that we have begun to understand the cellular and molecular changes involved. Of special interest in this regard are observations of a decline in synthesis of Type-1 cytokines which predisposes to diminished cell mediated immunity. We have evaluated the production of type 1 cytokines in old and young donors either in presence or in absence of recombinant interleukin-2 (rIL-2). Lymphocytes were stimulated with plastic bound anti-CD3 and after 48 h the supernatants were harvested and stored at -70 degrees C until assay. Type 1 cytokine, i.e. IL-12 and interferon-gamma (IFN-gamma) production by anti-CD3 stimulated lymphocytes from old subjects was significantly reduced when compared to that from young ones. This impaired production was reversed by adding rIL-2 in the culture medium. In previous studies on aged subjects, we have been able to demonstrate that in vitro treatment with rIL-2 completely restores proliferative responses and partially rescues the increased apoptosis of T cell cultures. Present and previous results suggest that rIL-2 completely restores Type 1 responses by overcoming the well known costimulation deficit of aged lymphocytes.

The influence of age and gender on serum dehydroepiandrosterone sulphate (DHEA-S), IL-6, IL-6 soluble receptor (IL-6 sR) and transforming growth factor beta 1 (TGF-beta1) levels in normal healthy blood donors

Dysregulation of IL-6 synthesis is thought to play a role in the development of a number of age-related conditions, such as rheumatoid arthritis, osteoporosis, atherosclerosis, Alzheimer's disease and B cell malignancies. Recently it has been suggested that the production of IL-6 is influenced by the adrenal hormone dehydroepiandrosterone (DHEA) and its sulphated derivative DHEA-S. In humans we investigated the relationship between DHEA-S, IL-6, IL-6 sR and TGF-beta1 in the serum of normal healthy male and female blood donors. Using immunoassay techniques we found that the serum levels of DHEA-S significantly (P = 0.0001) decreased with age in both males and females. Furthermore, mean DHEA-S levels in all age groups were significantly (P = 0.0001) higher in males. Such correlations were not apparent for IL-6 using a standard assay, but a high sensitivity assay revealed that serum IL-6 was significantly (P = 0.0018) positively correlated with age in males only. In addition, serum levels of DHEA-S were significantly (P = 0.048) negatively correlated with serum IL-6, again in male subjects only. In contrast, serum IL-6 sR and TGF-beta1 levels were not correlated with age in either males or females and were not significantly different between the sexes. However, a significant (P = 0.024) negative correlation between DHEA-S and IL-6 sR was found in males. These studies clearly highlight the complex nature of the relationship between these molecules in the ageing process in normal healthy blood donors and demonstrate the need to use high sensitivity assays when measuring IL-6 in apparently healthy individuals under the age of 70 years.

Age-related changes in the expression of CD95 (APO1/FAS) on blood lymphocytes

Aging is associated with alterations of the immune system, thought to be related to an increased susceptibility to infectious diseases, and possibly to cancer and autoimmunity in the elderly. In the present paper we report data obtained on freshly collected blood from 148 healthy subjects of different ages (from cord blood to 102 years old). The subjects were divided into seven age classes (cord blood, 3-11 years, 15-39 years, 41-60 years, 61-74 years, 75-84 years, 85-102 years) and their lymphocyte subsets and the expression of the apoptosis-related molecule CD95 were evaluated. In respect of lymphocyte subsets, the major differences were found in the cord-blood samples compared with the oldest old groups. In the cord-blood group, the absolute number of all the lymphocyte subsets was enhanced, but in the oldest group, an increase of CD16+ lymphocytes was observed, whereas CD19+ lymphocytes, which progressively decrease with age, continue to decrease further in the very old. The data show that the expression of CD95 increases until age 74 years, whereas in the oldest old it tends to decrease again. The trend of CD95 expression seems to be related to the change of expression of CD95 on CD4+ lymphocytes, because the CD8+/CD95+ population rose steadily throughout the entire age range. The evaluation of CD95+/CD45R0+ lymphocytes shows similar results to those observed analyzing CD95 on total lymphocytes. Furthermore, a constant increase of CD95+/CD28+ and a related decline of CD28+ lymphocytes was observed in all age groups. These data suggest that the expression of CD95 on the different subsets of lymphocytes can be considered a good marker for studies of immunosenescence, because it may be predictive of successful aging, and can partially explain the change in lymphocytes subsets in elderly.

T cell immunosenescence in vitro and in vivo

The term "immunosenescence" refers to an age-associated dysregulation of immune function which contributes to the increased susceptibility of the elderly to infectious disease. Although there are age-associated changes measurable in the innate immune system (Pawelec et al., 1998c), it is the adaptive, particularly T cell, system which is most susceptible to the deleterious effects of aging. In this minireview, characteristics of aging in long-term human T cell cultures will be summarized, and the parallels between the in vitro model and in vivo immunosenescence will be documented. The use of culture models to screen for ways of manipulating immunosenescence in vitro may provide a basis for intervention to ameliorate immunosenescence in vivo.

Aging and T-cell-mediated immunity

Changes in the T-lymphocyte compartment represent the most critical component of immunological aging. Recent studies have demonstrated that the age-related decline in T-cell-mediated immunity is a multifactorial phenomenon affecting T-cell subset composition as well as several proximal events such as protein tyrosine phosphorylation, generation of second messengers, calcium mobilization and translocation of protein kinase C, and distal events such as lymphocyte proliferation and cytokine production of the T-cell activation pathway. Age-related T-cell immune deficiency is preceded by thymic involution and is influenced by several intrinsic as well as extrinsic factors. Further, the role of monocytes and macrophages in T-cell activation changes with advancing age. This brief review will summarize the current knowledge of the cellular as well as molecular aspects of immunodeficiency of T cells due to aging, some of the paradoxes of aging as related to T-cell-mediated immunity, and possible factors which contribute to this paradox. Finally, experimental approaches will be suggested that might resolve these controversies and that might provide insights into the diverse and complex mechanisms that contribute to immunodeficiency of T cells. Ultimately these studies may suggest possible therapeutic interventions to enhance immune function in the elderly.

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.

Alterations in immune functions during normal aging and Alzheimer's disease

It is thought that aging induces immune changes, which are related to the pathophysiology of Alzheimer's disease (DAT). In this study, the total number of leukocytes, white blood cell differentiation, mitogen-induced lymphocytic proliferation, neutrophil phagocytosis and superoxide release, and prostaglandin E2 (PGE2) production by mitogen-stimulated whole blood cultures were comparatively investigated between healthy adults (range 22-45 years) and healthy elderly volunteers (range 70-91 years), and between DAT patients (range 56-94 years) and age-matched control subjects. Healthy elderly volunteers showed significantly lower phytohemagglutinin (PHA)-induced lymphocyte proliferation and percentage and absolute number of basophils than young volunteers. In normal volunteers, there were significant and negative correlations between age and the number of basophils. Patients with DAT showed a trend toward significantly higher PHA-induced lymphocyte proliferation and significantly decreased percentage and absolute number of large unstained cells than healthy volunteers. In DAT patients, the total number of leukocytes and the percentage and number of neutrophils were positively correlated with age. All other immune-inflammatory variables were not significantly altered either by the aging process or DAT. The present study suggests that aging and DAT may differently affect some immune variables.

Interleukin-5 production by mononuclear cells from aged individuals: implication for autoimmunity

It is well known that in the elderly a deterioration of immune functions may occur. Particularly, stimulation of T cells from aged individuals leads to different kind and/or size of responses if compared with the responses obtained from T cells from young individuals. At the same time, an increase in prevalence of autoantibodies occurs in elderly. The altered production of certain cytokines might explain this paradox of decreased responsiveness to foreign antigens in the face of an increased response to self-antigens. We and others have suggested that this kind of immune response might depend on an age-associated impairment of Th-1 type function that selectively affects production of cytokines involved in the control of cellular responses. In contrast, Th-2 type function is seemingly not affected in elderly, as suggested by normal in vitro production of cytokines involved in humoral responses. To strengthen this hypothesis, in this study we have analysed the influence of age on the ability of mitogen-stimulated cultures of peripheral blood mononuclear cells from human beings to produce another Th-2 type cytokine, i.e. interleukin-5 (IL-5). IL-5 content of both 24- and 48-h stimulated cultures from old individuals was greater than that of young ones, although this difference attained significance only at 48 h. We suggest that the decreased production of Th-1 type cytokines in the presence of a normal or even increased production of Th-2 type cytokines might account for the pattern of immune response which may be observed in elderly, i.e. a normal or increased humoral response, including an autoimmune one, in the face of a low cell mediated immune response.

Effect of age on cytokine production in humans

Aging is accompanied by many changes in immune response, with the most consistent and dramatic alterations occurring within the T cell compartment. Since cytokines are central to immune cell communications, age-associated changes in cytokine production may contribute to these alterations. While data from murine studies suggest a switch from a Th1 (IL-2, IFNγ) to a Th2 (IL-4, IL-6, IL-10) cytokine response, this model has not been as clearly established in humans. In addition, this current review of over 50 studies in humans suggests that age-associated changes in cytokine production are not consistent.

Perioperative cytokine release during coronary artery bypass grafting in patients of different ages

Surgical interventions and cardiopulmonary bypass (CPB) induce a systemic inflammatory response with cytokine release. Ageing is perceived as a process of impaired immune functions: IL-1beta, IL-6 and tumour necrosis factor-alpha (TNF-alpha) secretion are increased while IL-2 release is reduced in advanced age. At present, little information is available about perioperative immune reactions at different stages of ageing. The aim of the present study was to compare IL-6, IL-1beta, TNF-alpha, IL-10 and soluble IL-2 receptor (sIL-2R) in younger and older patients undergoing cardiac surgery. Male patients (n = 14) undergoing elective coronary artery bypass grafting (CABG) surgery employing CPB with moderate hypothermia were divided into two groups according to their age: group 1 included seven patients < 50 years old, group 2 included seven patients > 65 years old. All patients received general anaesthesia using a balanced technique with sufentanil, isoflurane and midazolam. Blood samples were collected pre-operatively (T1); intra-operatively during CPB (T2); post-operatively on the day of surgery (T3); on the first post-operative day (T4). Blood concentrations of IL-6, IL-1beta, IL-10, TNF-alpha and sIL-2R were measured using commercially available ELISA kits and corrected for plasma cell volume. Statistical analysis was performed by non-parametric analysis of variance and Mann-Whitney U-test. Significance level was set to P<0.05. There were no statistically significant differences in the perioperative release of TNF-alpha, IL-6, IL-1beta, IL-10 and sIL-2R among the two groups. We conclude that the perioperative course of cytokine release in patients undergoing CABG surgery with CPB and comparable perioperative management does not significantly differ in the two age groups.

Interleukin-12 release by mitogen-stimulated mononuclear cells in the elderly

Defects involving cellular expression of activation molecules, cell mediated immune response and natural killer (NK) activity are commonly observed in the elderly. Herein, data are reported on the evaluation of IL-12 production by old subjects. IL-12 is, actually, considered the key molecule for the induction of a T helper 1 (Th1) -type and NK response. IL-12 production from old subjects peripheral blood mononuclear cells (PBMNC) was evaluated using T-independent (bacterial lipopolysaccharide, LPS) or -dependent (phytoemagglutinin, PHA; immobilized anti-CD3 monoclonal antibodies, anti-CD3) mitogens. The IL-12 production after LPS stimulation was not reduced in cultures from old subjects when compared to that from young ones. On the contrary, IL-12 production by PHA or anti-CD3 stimulated PBMNC from old subjects was decreased. Furthermore, we have demonstrated a reduced CD40 and CD40 ligand (CD40L) expression on PBMNC from old subjects. This finding fits very well with the reduced cytokine production observed in the T-dependent stimulation systems, being the CD40-CD40L interaction mandatory for an efficient IL-12 production. All together, these results seem to suggest that defects in cell expression of activation molecules can affect the IL-12 secretion and in consequence other Th1-type cytokines.

Apoptosis and ageing

Stimulation of T cells from aged individuals leads to different kinds and/or size of responses if compared with the responses of T cells obtained from young individuals. In fact elderly is associated with a progressive decline of immune response besides an increasing incidence of autoimmune phenomena. These differences might be the result of modified cellular mechanisms controlling the immune system in the course of ageing. The apoptotic deletion of activated T cells has been proposed as the key mechanism to maintain T cell homeostasis, and in this respect CD95 (Fas antigen) seems to play a major role in this course of events. In this study we show that just collected lymphocytes from old subjects displayed an increased expression of the apoptosis molecule CD95. The expression of CD95 and the spontaneous apoptosis showed the same trend. In fact the percentage of apoptotic cells in blood collected from old subjects was enhanced too. The lymphocyte subpopulation analysis by flow cytometry did not show significant changes in T subset percentages between old and young subjects. Moreover mononuclear cells obtained from aged individuals underwent apoptosis in culture in response to a single stimulation with mitogen or anti-CD3, more than mononuclear cells from young controls. To gain insight into mechanisms of this increased apoptosis, experiments were performed to evaluate the behaviors of lymphocytes from old and young donors in respect of interleukin-2 (IL-2) rescue from apoptosis. Results show that IL-2 rescued only a little fraction of cells of old donors from apoptosis when activated by anti-CD3 and that this effect was not related to a different expression of CD95. Thus, during the course of ageing the different regulation of T cell homeostasis might be also explained by the modified proneness of lymphocytes to undergo apoptosis. The contemporaneous demonstration of a reduced Ca2+ influx in lymphoid cells of these subjects allows to suppose that multiple defects play a role in the pathogenesis of immunosenescence.

CD4+ and CD8+ cell cytokine profiles in neonates, older children, and adults: increasing T helper type 1 and T cytotoxic type 1 cell populations with age

The growing body of evidence suggestive of T helper types 1 and 2 (Th1/Th2) including their counterparts T cytotoxic types 1 and 2 (Tc1/Tc2) cell responses during various human disease states necessitates determination of normal T cell subsets' cytokine profiles. We show here, using intracellular cytokine staining and flow cytometry, that in healthy subjects interferon (IFN)-gamma producing CD4+ (Th1) and CD8+ (Tc1) cell populations progressively increase with age with strong correlation to CD45RO surface antigen expression. Meanwhile populations of cells capable of producing IL-4 (Th2 and Tc2) are comparably minimal across all age groups. Collectively, these results may reflect the maturation and expansion of Th1 and Tc1 cell populations from the neonatal period to adulthood, most probably dependent on antigen exposure.

Genes, immunity, and senescence: looking for a link

Aging is under the control of a small number of regulatory genes. Mice genetically selected for high immune responses, in most cases, exhibit longer life span and lower lymphoma incidence than do mice selected for low responses. The link between immunity and aging is further evidenced by the age-related alterations of the immune system, mostly of the T-cell population, in terms of replacement of virgin by memory cells, accumulation of cells with signal transduction defects, and changes in the profile of Th1 and Th2 type cytokines. Also, B cells exhibit intrinsic defects, and natural killer (NK) cell activity is profoundly depressed by aging. In vitro experiments indicate that IL-2, IFN-gamma, and IL-4 production by mouse spleen cells changes with aging and may be upregulated by recombinant cytokines. These findings suggest possible cytokine interventions to prevent or treat age-related immune disorders, as they may affect the duration and the biological quality of life.

Defective expression of CD95 (FAS/APO-1) molecule suggests apoptosis impairment of T and B cells in HLA-B8, DR3-positive individuals

Activation-induced apoptosis is one of the primary control mechanisms for the negative selection of an immune response, leading to maintenance of immune homeostasis and selective T cell deletion. The interaction between the surface molecule Fas and its ligand (FasL) has been proposed as a primary mechanism initiating T cell apoptosis. The T cell receptor modulates the expression and function of these molecules. Defects in the Fas/FasL apoptosis pathway have been shown to result in autoimmune disease in humans and in murine models. Because subjects carrying the HLA-B8, DR3 haplotype show a number of immune dysfunctions, including membrano-proliferative glomerulonephritis, systemic lupus erythematosus, Graves' disease, and others, we investigated Fas expression on T and B cells, and sensitivity to Fas-mediated apoptosis of activated T cells, to determine whether abnormalities of the Fas pathway might be associated with the development of autoimmune diseases in this group of individuals. Our findings show that B cells and resting T cells from HLA-B8+, DR3+ subjects express markedly reduced levels of Fas compared with those isolated from HLA-B8-, DR3+ individuals. Reduced levels of Fas were also evident on the surface of T cells from HLA-B8+, DR3+ subjects activated in vitro by stimulation with OKT3 and phytohemoagglutinin. Cycling T cells from these subjects, evaluated for apoptotic nuclei by flow cytometry after incubation with a cytolytic anti-Fas mAb, showed a significantly lower percentage of Fas-mediated apoptosis than did those from HLA-B8-, DR3- individuals. Normal levels of apoptosis were restored after exposure to a synthetic ceramide analog (C2). Further elucidation of the interaction of these molecules in autoimmune diseases may lead to better understanding of the pathogenesis of these disorders.

Does the secretion of cytokines in the periphery reflect their role in bone metabolic diseases?

Much interest has been focused on the role of the immune system in bone remodeling. Here, we compare the production of Interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) by peripheral blood mononuclear cells (PBMC) in elderly Paget's patients, elderly osteoporotic patients and in normal elderly subjects. We studied Paget's patients (71.00 +/- 3.74 years), 7 osteoporotic patients (71.86 +/- 3.23 years), age and sex matched, and 5 elderly healthy control subjects (74.20 +/- 4.10 years) An ELISA test was used to quantify IL-1 beta and IL-6 in the supernatant culture of PBMC stimulated by phytohemagglutinin (PHA). IL-1 beta and IL-6 production from Paget's patients (IL-1 beta, 651.43 +/- 95.92 pg/ml; IL-6, 1402.85 +/- 148.11 pg/ml) was not statistically different from the production observed in the osteoporotic patients (IL-1 beta, 552.57 +/- 79.04 pg/ml; IL-6, 1458.85 +/- 118.35 pg/ml) and in the healthy elderly group (IL-1 beta, 717.60 +/- 131.34 pg/ml; IL-6, 1502.40 +/- 211.90 pg/ml). Although IL-1 and IL-6 can be involved in the bone remodeling process, we did not find any difference when we compared their production by PBMC in elderly normal, elderly osteoporotic and elderly Paget's patients.

Prevalence of organ-specific and non organ-specific autoantibodies in healthy centenarians

In the present study we have investigated the prevalence of organ-specific and non organ-specific autoantibodies in 26 healthy centenarians (6 men, 20 women; age range 101-106 years), using as controls 54 healthy old (33 men and 21 women, age range 71-93) and 56 young subjects (29 men and 27 women, age range 26-60). We assayed sera of each group for the following organ-specific autoantibodies, anti-gastric mucosa (anti-PCA), anti-thyroglobulin (anti-Tg) and non organ-specific autoantibodies, anti-cardiolipin (anti-APA IgG and IgM), anti-nuclear antigens (anti-ANA), anti-double strand DNA (anti-ds-DNA), anti-extractable nuclear antigens (anti-ENA). Finally, natural anti-alpha-galactosyl (anti-alpha-GAL) antibodies were also analyzed. As expected, in the old subjects there was a significant increase of prevalence of anti-Tg and anti-PCA autoantibodies. By contrast, in centenarians the prevalence of organ specific anti-Tg and anti-PCA antibodies was not significantly different from that observed in controls aged less than 60 years. The prevalence of non organ-specific autoantibodies anti-APA (IgG), anti-APA (IgM), anti-ANA, was significantly increased both in the elderly and centenarians when compared with the prevalence observed in sera from the young. Anti-ENA and anti-dsDNA antibodies were not detected in all groups studied. Finally, the prevalence of natural anti-alpha-GAL antibodies significantly increases with age, including centenarians. In conclusion, we confirm and extend the results previously obtained by other authors. In fact, as already described, the prevalence of organ-specific autoantibodies in the elderly is not seen after the tenth decade of life. Interestingly, the prevalence of non organ-specific autoantibodies is instead increased in these subjects, suggesting that different mechanisms are involved in the pathogenesis of these autoantibodies. Particularly, these autoantibodies could be the expression of a damaged tissue process rather than of an autoimmune one, as suggested by data concerning natural antibodies.

Age-dependent changes in the expression of dopamine receptor subtypes in human peripheral blood lymphocytes

The pharmacological profile and the density of dopamine D3 and D5 receptor subtypes expressed by human peripheral blood lymphocytes of subjects of different ages (ranging from 20 to 75 years) were assessed using radioligand binding techniques. Dopamine D3 receptor was assayed with [3H]7-hydroxy-N,N-di-n-propyl-2-aminotetraline ([3H]7-OH-DPAT) as a ligand. Dopamine D5 receptor was assayed using [3HIR]-(+)-(-chloro-2,3,4,5, tetrahydro-5-phenyl-1H-3-benzazepin-al-hemimaleate) ([3H]SCH 23390) as a ligand. The affinity and the pharmacological profile of [3H]7-OH-DPAT and [3H]SCH 23390 at dopamine D3 and D5 receptor, respectively, were similar in subjects of different ages. The density of dopamine D3 receptor binding sites was slightly decreased in subjects of 30-39 years in comparison with younger individuals. A remarkable loss of dopamine D3 receptor was then found between 40 and 49 years of age in comparison with younger subjects. A further slight decrease was noticeable between 50 and 59 years of age. The number of [3H]7-OH-DPAT binding sites was then stabilized after 60 years of age. The density of dopamine D5 receptor binding sites did not show age-dependent changes. The above findings indicate the occurrence of a decline in the density of lymphocyte dopamine D3 but not D5 receptor between adult and mature subjects. The possibility that dopamine D3 receptor assay in peripheral blood lymphocytes may represent a tool for investigating dopamine receptor function in aging and age-related neurological disorders is discussed.

In vitro T cell activation in elderly individuals: failure in CD69 and CD71 expression

A large number of T cell dysfunctions have been observed in the elderly. The most widely observed is the inability of these cells to proliferate at a level comparable to T cells from young individuals after stimulation by mitogens. To better characterize T cell impairment, we have focused on the in vitro T cell activation, analyzing by flow cytometry the activation molecules CD69 and CD71 on mitogen-stimulated lymphocytes from young and elderly subjects. The results show that the percentages of CD69+ and CD71 + T cells were significantly decreased in cultures from elderly subjects when compared to values obtained culturing cells from young individuals. The differences observed seem not due to differences in CD4 and CD8 rates in the "old' cells that underwent activation, since, following activation, the pattern of CD4 and CD8 phenotypes was the same in both groups of subjects. Signals from CD69 are relevant in controlling cytokine gene expression because its stimulation leads to interleukin-2 production and increases its receptor expression. The interaction of this cytokine with its cellular receptor is an essential requirement for T lymphocytes to express CD71 and to start proliferation. Thus, a key role in the age-associated impairment of T cell activation could be played by an ineffective modulation of CD69 expression suggesting a defect in the signal transduction pathway of the T cell receptor-CD3 complex in elderly.

Cytokine production pathway in the elderly

It is well known that aging is associated with various alterations in lymphoid cell functions, particularly with a progressive decline in immune responsiveness to exogenous antigens and increasing incidence of autoimmune phenomena. Many studies have been focused on the mechanisms of the immunologic features of aging. this review describes our results of studies performed to determine the influence of age on the capacity to produce interleukin-2 (IL-2), interferon-gamma (IFN-gamma), interleukin-4 (IL-4), interleukin-t (IL-5), interleukin-6 (IL-6) and tumor necrosis factor (TNF). Mitogen-stimulated cultures of mononuclear cells (MNC) from human beings were assessed for cytokine-producing capacity. A significant decrease in IFN-gamma and IL-2 production by MNC cultures from elderly individuals was observed. No significant difference was instead observed between cultures from elderly individuals and those from young ones as regards TNF-alpha, IL-4 and IL-6 production. Mitogen or antigen-stimulated cultures of MNC from aged mice also displayed a significant decrease in IFN-gamma and IL-2 production as well as TNF-beta. Instead IL-4 and IL-5 production significantly increased in these cultures. We suggest that this imbalanced cytokine production may well account for the pattern of immune response which may be observed in the elderly, i.e. a normal or increased humoral response (including autoimmune responses) in face of a low T cell immune responsiveness.

In vitro impairment of interleukin-5 production in HLA-B8, DR3-positive individuals implications for immunoglobulin A synthesis dysfunction

Healthy subjects carrying the HLA-B8,DR3 haplotype may show a large number of immune dysfunctions. Concerning T-cell dysfunctions, the most intriguing is a defect of the early phases of T-cell activation, responsible for the impairment of in vitro mitogen-stimulated cytokine production. Regarding B-cell dysfunctions, one the most fascinating topics is the association between this haplotype and IgA deficiency in healthy blood donors. Accordingly, HLA-B8,DR3-positive healthy subjects show significantly lower values of serum IgA than HLA-B8,DR3-negative ones. Because IL-5 is a stimulating factor for the secretion of IgA by committed B cells, we have analyzed the in vitro mitogen-stimulated IL-5 production by MNCs from healthy HLA-B8,DR3-positive individuals to study whether they display an impaired production of IL-5. The results clearly demonstrate that MNCs from HLA-B8,DR3-positive individuals display significant reduction of IL-5 production, suggesting that IgA synthesis dysregulation observed in HLA-B8,DR3-positive subjects could be due to an impairment of IL-5 production.

In vitro cytokine production by HLA-B8,DR3 positive subjects

It is well known that healthy subjects carrying the HLA-B8,DR3 haplotype may show an impairment of immune system, the T cells being the most affected. To gain insight into the mechanism(s) of the impairment displayed by these subjects, efforts have been centered on the study of in vitro cytokine production because of the pivotal role played by these mediators in the activation and control of several immune functions. The available results indicate that the ability to several immune functions. The available results indicate that the ability to produce interleukin-1 (IL-1), IL-2 and the soluble form of its receptor (sIL-2R) is impaired in HLA-B8,DR3 positive healthy subjects. To better characterize the cytokine production capacity of HLA-B8,DR3 positive subjects, we have investigated the pattern of in vitro production of IL-2, sIL-2R, IL-4. IL-6 and gamma-interferon (gamma-IFN) by mononuclear cells from HLA-B8, DR3 positive subjects after phytohaemoagglutinin stimulation. A significant decrease of IL-2, sIL-2R and gamma-IFN production by HLA-B8,DR3 positive subjects was observed. No significant difference was instead found between the HLA-B8,DR3 positive subjects and the negative ones as regards IL-4 and IL-6 production. We suggest that this imbalanced cytokine production may well account for the pattern of immune response that may observed in HLA-B8,DR3 positive subjects, i.e. a normal or increased humoral response in face of a low T cell immune responsiveness.