Immunobiology of aging: evaluation of current status

Influence of surgical and chemical orchidectomy on weight and distribution of AChE-nerve fibres in thymuses of adult rats

The thymus is a crossroad between the immune and neuroendocrine systems. As such, it is innervated by acetylcholinesterase (AChE)-positive fibres of the vagus, the recurrent laryngeal and the phrenic nerves. It is well know, that the innervations density of the thymus increases with age. In our study, adult rats were orchidectomized (surgically and chemically by the application of a luteinizing hormone-releasing hormone). The density of AChE-positive nerve fibres in thymuses, as well as the weight of thymuses was examined. The authors found that both surgical and chemical orchidectomy result in macroscopic and microscopic regeneration of the atrophied thymuses. In regenerated rat’s thymuses after orchidectomy the density of AChE-positive nerve fibres was markedly higher in comparison with the control animals. The distribution, as well as the density of AChE-positive nerve fibres in regenerated thymuses after orchidectomy evokes the images of its innervations like in young animals before age-related involution. The authors also found a markedly higher weight of thymuses of orchidectomized rats in comparison with the control groups. In recent study the authors proved that after 8 weeks surgical orchidectomy leads to the regeneration of thymic AChE-positive innervation and chemical orchidectomy by administration of luteinizing hormone-releasing hormone after 4 weeks of adult rats.

Review: Age-related cataract: immunity and lens epithelium-derived growth factor (LEDGF)

This short review summarizes our recent work and relevant publications on autoimmunity and cataract. A complete review of this subject is beyond the scope of this paper. Age-related cataract (ARC) is the leading cause of world blindness. In spite of more than fifty years of basic and clinical research, there is no nonsurgical intervention to prevent or treat ARC, but there is a better understanding of the manifold complexities of this age-related condition. ARC is a multifactorial condition in which incidence and progress are modified by factors such as age, sex, radiation [visible, ultraviolet (UV), and X-ray], oxidation, physical trauma, diet, and medications. The lens contains at least three different cell types: central epithelial cells, dividing germinative epithelial cells, and fiber cells. The central epithelial cells covering the anterior axial part of the lens do not divide but survive throughout life. The bulk of the lens comprises anucleate fiber cells, differentiated germinative epithelial cells, which have undergone an apoptosis-like change "diffoptosis" to become elongated, crystallin-rich, organelle-deficient, cells. The epithelial cells and their active transport mechanisms maintain lens homeostasis and clarity. The survival mechanisms of the central lens epithelial cells (LECs) are unknown. In other cells, growth or survival factors, when present, enhance survival and, when absent or deficient, induce programmed cell death "apoptosis". Many developing mammalian cells produce signal proteins, or require signal proteins from other cells, to avoid apoptosis. Although much is known about the role of growth factors in the lens, less is known about how such signals are involved in the survival and death of LECs. We have hypothesized that LECs, like other mammalian cells, use signal proteins to regulate growth, survival, and apoptosis, and we have begun a search for such molecules. Furthermore, we have hypothesized that such factors, if found, may also be involved in the death of LECs, the consequent alteration of lens homeostasis and, eventually, certain types of ARC.

Host defense--a role for the amino acid taurine?

Taurine (2-aminoethane sulphonic acid), a ubiquitous beta-amino acid is conditionally essential in man. It is not utilized in protein synthesis but found free or in some simple peptides. Derived from methionine and cysteine metabolism, taurine is known to play a pivotal role in numerous physiological functions. Some of the roles with which taurine has been associated include osmoregulation, antioxidation, detoxification and stimulation of glycolysis and glycogenesis. Intracellular taurine is maintained at high concentrations in a variety of cell types and alteration of cell taurine levels is difficult. The role of taurine within the cell appears to be determined by the cell type. Recent research has determined a regulatory role for taurinechloramine, the product formed by the reaction between taurine and neutrophil derived hypochlorous acid on macrophage function. Plasma taurine levels are also high, although decreases are observed in response to surgical injury and numerous pathological conditions including cancer and sepsis. Supplementary taurine replenishes decreased plasma taurine. Although commonly used as a dietary supplement in the Far East, the potential advantages of dietary taurine supplementation have not as yet been fully recognized in the Western World; this is an area which could prove to be beneficial in the clinical arena.

Senescence and cytokines modulate the NK cell expression

We have been investigating senescence-related changes in human peripheral blood natural killer (NK2) cells. Data accumulated so far consistently and clearly show that both basal and cytokine (IL-2 and interferon alpha and gamma) induced antitumor MHC-unrestricted cytotoxic activity of NK cells are well-preserved in the healthy elderly. To investigate if the non-cytotoxic functions of NK cells are also spared from the influence of senescence, recombinant IL-2-inducible secretion of IFN-gamma, which serves as a first line of defense, was examined. The amount of IFN-gamma secreted by purified, 18 h activated NK cells from the elderly was only 25 percent of that released by the cells from the young. Thus, the type 1 cytokine-inducible cytotoxic and cytokine secretory functions appear to be dissociable properties of NK cells, at least in the elderly. However, this aging-related early phase secretory deficit could be overcome by chronic stimulation with IL-2 (7 day culture). Since different subsets could perform different functions, we analyzed the NK subsets by flow cytometry. A minor CD56bright subset and a major CD56dim subset could be distinguished based on the density of expression of the cell surface CD56 molecule (N-CAM). We inquired if immunosenescence is likely to impact the steady-state level of circulating NK subsets. A significant decrease (P < 0.01) in percent CD56bright among CD56+ cells was observed in the elderly with a relative sparing of the CD56dim subset. The CD56bright/CD56dim ratio, perhaps representing NK cell maturity status, declined with age. This maturation-related subset redistribution and partial loss during aging of high affinity IL-2 alpha beta gamma receptor bearing 'immature' CD56bright NK cells has not been reported before. It could be a consequence of the decline in the level of IL-2 during aging. It is concluded that post-adolescent age-associated modulations in human NK cells are not expressed uniformly; they are pronounced in some, subtle in others but negligible in yet other biological parameters.

Free radical theory of aging: history

Aging is the accumulation of changes responsible for the sequential alterations that accompany advancing age and the associated progressive increases in the chance of disease and death. These changes can be attributed to disease, environment, and the inborn aging process. The aging process is now the major risk factor for disease and death after about age 28. The free radical theory of aging arose in 1954 from a consideration of aging phenomenon from the premise that a single common process, modifiable by genetic and environmental factors, was responsible for the aging and death of all living things. The theory postulates that aging is caused by free radical reactions, i.e., these reactions may be involved in production of the aging changes associated with the environment, disease and the intrinsic aging process. The origination of the theory and its application to the problem of increasing the functional life span are discussed. Support for the free radical theory of aging has increased progressively and now includes: 1) studies on the origin of life and evolution, 2) studies on the effect of ionizing radiation on living things, 3) dietary manipulations of endogenous free radical reactions, 4) the plausible explanations it provides for aging phenomena, and 5) the growing numbers of studies that implicate free radical reactions in the pathogenesis of specific diseases. The rapidly growing number of scientists involved in studies on the role of free radical reactions in biological systems should assure future significant increases in the healthy, useful, life span of man.

Observations on biochemical and haematological parameters in healthy people above 80 years of age

Ninety-five apparently healthy people, aged 80 years or above, living in the Stockholm County Council of Sweden, participated in a pilot study in 1984. Reference values were obtained for routine haematological and biochemical analyses. Deviations from expected levels were confined to thyroid-stimulating hormone (TSH), vitamin B12 and calcium. It is noteworthy that a low-risk cholesterol level characterized this elderly population. It is suggested that in order to evaluate the influence of age, a dynamic aspect should be added using functional tests of various organs.

Physiological changes in ageing skin

The principal functions of the skin include protection, excretion, secretion, absorption, thermoregulation, pigmentogenesis, accumulation, sensory perception and regulation of immunological processes. These functions are all affected by the structural changes in the skin with ageing and, after middle age, most functions are reduced, some by as much as 50-60%. The physiological changes associated with these reductions include impairment of the barrier function, decreased turnover of epidermal cells, reduced numbers of keratinocytes and fibroblasts, and a reduced vascular network particularly around hair bulbs and glands. These changes result in fibrosis and atrophy, and decreases in hair and nail growth, vitamin D synthesis and the density of Langerhans cells. Production of epidermal thymocyte-activating factor, which enhances the T-cell response, is reduced leading to a decrease in the immune response; there is also a decreased functioning of Meissner's and Pacinian corpuscles. An increased generation of free radicals is observed. Certain environmental factors, particularly exposure to sun, accelerate the ageing of skin and are important in cutaneous carcinogenesis.

Sialic acid content and sialyltransferase activity in human lymphocytes with advancing age

Sialic acid and sialyltransferase activity were determined in lymphocytes obtained from the blood of 78 healthy male volunteers aged 20-80 years. When grouping was made in double decades, statistical evaluation using the Duncan procedure indicates that sialic acid did not show significant differences between groups, whereas the sialyltransferase activity was significantly higher in the group aged 41-60 years as compared to the group aged 20-40 years and the group aged 61-80 years, both at the 0.05 level.

Age-associated alterations in human natural killer cells. 2. Increased frequency of selective NK subsets

We have analyzed the peripheral blood lymphocytes from healthy volunteers (20 to 94 years) for the expression of natural killer (NK) cell surface markers, NK activity, and B-cell proliferative response. An increase (2- to 3.5-fold) in relative percentage and absolute number of lymphocytes expressing Leu-7 (HNK-1) or Leu-11a (CD 16) antigen was found in the elderly group (greater than 80 years) as compared to young adults (less than 40 years). A two-color immunofluorescence analysis revealed that the age-associated increment was both progressive and selective; the actual increase occurred in Leu-7+11a+ and Leu-7+11a- populations (subsets with variable and weak NK activity) but not in the Leu-7-11a+ (most active) subset. There is a corresponding decrease in the 7-11a- cells. The ratios of 7+11a+/7-11a+ and 7+11a-/7-11a+ cells doubled with advancing age. Linear regression analysis suggests that the 7-11a+ cells are highly preserved through human senescence and the ratio of 7+11a- cells to the most stable subset, 7-11a+, could expand nearly 100-fold from birth to old age. Further analysis of Leu-7+ cells for the coexpression of Leu-11c (an epitope of Leu-11a) confirmed a similar pattern of changes in 7+11c+ and 7+11c- NK subsets with advancing age. The frequency of Leu-11+ (epitopes 11a+ or 11c+), but not of the subsets of 7+ phenotype (7+11a- or 7+11c-), correlates well with the NK activity (spontaneous killing of K562 tumor cell line). The 7+11c+ cells may directly or indirectly be responsible for the increase in NK activity observed with a majority of aged donors. The inverse relationship observed between the mitogenic response of lymphocytes to pokeweed mitogen (PWM) and the initial frequency of 7+11a-, but not other phenotypes, raises a potential functional significance for the expansion of the 7+11a-(7+11c-) subset. These age-associated NK phenotypic changes provide a cellular basis for our observations on age-associated increase in NK activity and decrease in mitogenic response to PWM.

Age-associated alterations in human natural killer cells. 1. Increased activity as per conventional and kinetic analysis

We report a positive association between the human peripheral blood natural killer (NK) cell activity and the age (20-94 years) of 137 healthy volunteers. Irrespective of the methods of data representation, the elderly (greater than 80 years) express a statistically significant (at 0.001 level) higher (35-80.7%) mean NK activity when compared to younger adults (less than 40 years). Results of repeat assays and paired assays support a similar conclusion. This difference can be demonstrated at a wide range of effector or target cell concentrations or times of assay and is not influenced by in vivo lymphocyte count. Single-cell assay results suggest that an increase in the frequency of NK cells may be responsible for the higher NK activity in the elderly. These findings were confirmed by an enzyme-like kinetic analysis. Vmax, the maximum cytotoxic potential of the lymphocytes from the elderly, is nearly four times higher than that of younger adults. It is concluded that unlike the age-related general decline in T- and B-cell reactivity (as demonstrated here with concanavalin A and pokeweed mitogen), the NK cell system is highly active in a majority of the healthy elderly.

Reversal of age-associated decline in immune responsiveness by dietary glutathione supplementation in mice

The potential of dietary glutathione to alter immune response in aging mice was studied. Four (young), 17 (mature) and 24 (old) month old C57BL/6Nia male mice were fed semi-purified, nutritionally adequate diets containing 0 (control) to 1.0% of reduced glutathione (GSH) for 4 weeks. Concanavalin A (Con A) stimulated proliferation of splenocytes was assessed by [3H]thymidine incorporation. Delayed-type hypersensitivity (DTH) to dinitrofluorobenzene (DNFB) was measured by a radioisotopic method. Spleen GSH and splenocyte thiol (-SH) levels were determined by HPLC and N-ethyl[14C]maleimide binding, respectively. In the control fed group, mature and old mice showed 67% and 72% reductions (P less than 0.05) in Con A stimulated [3H]thymidine incorporation compared to young mice. Dietary GSH supplementation partially, but significantly (P less than 0.05) reversed this age-associated decline in mature and old mice. DTH assays revealed that the in vivo T-cell-mediated immune function is depressed with age and that dietary GSH supplementation reverses this depression. Spleens from control-fed mature and old mice contained 12 and 19% less GSH, respectively, than young mice (P less than 0.05). This decline was also reversed (P less than 0.05) by dietary GSH supplementation. Splenocyte -SH content after incubation with Con A and responsiveness to this mitogen were positively correlated in old mice and were greater (P less than 0.05) in GSH supplemented animals. Thus, dietary GSH supplementation improves the splenic status of this tripeptide and enhances T-cell mediated immune responses in aging mice.

Structural and functional changes of normal aging skin

Solar-induced cutaneous changes are more prevalent and profound in older persons and, thus, are often inappropriately attributed to the aging process, per se. Structural and functional alterations caused by intrinsic aging and independent of environmental insults are now recognized in the skin of elderly individuals. Structurally the aged epidermis likely becomes thinner, the corneocytes become less adherent to one another, and there is flattening of the dermoepidermal interface. The number of melanocytes and Langerhans cells is decreased. The dermis becomes atrophic and it is relatively acellular and avascular. Dermal collagen, elastin, and glycosaminoglycans are altered. The subcutaneous tissue is diminished in some areas, especially the face, shins, hands, and feet, while in others, particularly the abdomen in men and the thighs in women, it is increased. The number of eccrine glands is reduced and both the eccrine and apocrine glands undergo attenuation. Sebaceous glands tend to increase in size but paradoxically their secretory output is lessened. The nail plate is generally thinned, the surface ridged and lusterless, and the lunula decreased in size. There is a progressive reduction in the density of hair follicles per unit area on the face and scalp, independent of male-pattern alopecia. The hair shaft diameter is generally reduced but in some areas, especially the ears, nose, and eyebrows of men and the upper lip and chin in women, it is increased as vellus hairs convert to cosmetically compromising terminal hairs. Functional alterations noted in the skin of elderly persons include a decreased growth rate of the epidermis, hair, and nails, delayed wound healing, reduced dermal clearance of fluids and foreign materials, and compromised vascular responsiveness. Eccrine and apocrine secretions are diminished. The cutaneous immune and inflammatory responses are impaired, particularly cell-mediated immunity. Clinical correlates of these intrinsic aging changes of the skin include alopecia, pallor, xerosis, an increased number of benign and malignant epidermal neoplasms, increased susceptibility to blister formation, predisposition to injury of the dermis and underlying tissues, delayed onset and resolution of blisters and wheals, persistent contact dermatitis, impaired tanning response to ultraviolet light, increased risk for wound infections, prolongation of therapy necessary for onychomycosis, and thermoregulatory disturbances.

Studies on the age-related decline in the response of lymphoid cells to mitogens: measurements of concanavalin A binding and stimulation of calcium and sugar uptake in thymocytes from rats of varying ages

We have previously demonstrated that mitogenic response of rat thymocytes to concanavalin A (Con A) declines with age (Segal, Troen and Ingbar, Thymus, in press). To elucidate the mechanism underlying this process, we have examined the effect of age on Con A binding and stimulation of calcium and sugar uptake in thymocytes from rats varying in age from 10 to 360 days. Binding of Con A by thymocytes remained unchanged with advancing age. Basal uptake of the glucose analogue 2-[3H]deoxyglucose (2-DG) by rat thymocytes declined with age, becoming significantly lower than maximal values (26 days) at 4 months of age. While the proportionate increase in thymocyte 2-DG uptake produced by Con A remained essentially unchanged. However, because of the decline in basal 2-DG uptake, total uptake of 2-DG in the presence of Con A decreased with age becoming significantly lower than maximal values at 4 months. Basal calcium-45 uptake by thymocytes was practically the same in all the age-groups studied, except at 21 days, where, as with basal 2-DG uptake, it was markedly smaller, But the stimulatory effect of Con A on 45Ca uptake declined progressively with age and was nil at 360 days. From these observations I suggest that the age-related decline in the responsiveness of rat thymocytes to Con A does not result from a change in the binding of Con A by the lymphoid cell, but from, at least in part, a decrease in its cellular stimulation of calcium and sugar uptake.

Human B-lymphocyte colony responses: suboptimal colony responsiveness in aged humans associated with defective function of B cells and monocytes

The abilities of human B cells from young and aged subjects to form colonies in semisolid cultures stimulated with Staphylococcus protein A were investigated. Approximately three-fourths of aged adults had significantly diminished colony responses compared to young adults. In 55% of these aged adults, the in vitro blocking of monocyte prostaglandin synthesis lead to a 1.5-fold or greater augmentation of the depressed colony responses. Other experiments showed that the improvement with indomethacin could not be explained by the greater sensitivity of aged versus young B-cell colony precursors to prostaglandin suppression. However, indomethacin failed to improve the depressed colony responses of the remaining aged adults. This failure could not be attributed to deficient interleukin 1 production, detectable alterations in accessory cell subsets of monocytes, or the lack of potential colony precursors bearing sIgD/M. Instead, the B cells from these aged subjects demonstrated a substantial decrease in the capping of sIgD/M compared to the B cells of aged subjects which displayed improved colony responses with indomethacin and compared to the B cells from young adults. Thus, these data indicate that the diminished B-cell colony responses of aged humans represent aberrancies within both the B-cell and monocyte lineages which might coexist.

Carbohydrate metabolism in transforming lymphocytes from the aged

There is an age-related decline in immune capacity which has been linked to a decreased response of lymphocytes to mitogens in vitro. During transformation, lymphocytes require a marked increase in energy production and biosynthesis which is supplied primarily by glycolysis. In the elderly, the glycolytic enzymes increase significantly in transforming lymphocytes at least 24 hr later than in the young and then at significantly reduced levels. Glucose utilization is also impaired in stimulated lymphocytes from the elderly but follows the impairment of glycolysis. In stimulated cells from the young, increases in glycolytic enzyme activity levels accompany sharp increases in blastogenesis while a delayed increase in glycolytic enzyme activity in the elderly is accompanied by a delay in blastogenesis. Maximal glycolytic enzyme activity levels are significantly reduced in transformed lymphocytes from the elderly though the number of transformed cells is also significantly reduced. However, glycolytic enzyme activity levels are significantly lower in the elderly than in the young even on a per transformed cell basis. Thus, this reduction cannot be attributed to the lower number of transformed cells that are present in the elderly. This defect in the increase of glycolysis in stimulated cells from the elderly suggests an intracellular mechanism which could be related to the impaired lymphocyte stimulation in vitro in the aged.

Immunological aspects of aging: early changes in thymic activity

Age related changes in immune function are preceded by changes in thymic function. One index of thymic function is the ability of the thymus to induce the differentiation of bone marrow pre-T cells into active T cells. Movement of precursors of PHA-responsive T cells into the thymus ceases prior to adolescence in long-lived, autoimmune disease resistant mice as determined by studies utilizing chromosome markers in parabiotic mice. The cause for this age-dependent, cell traffic phenomenon is not known, but it would appear that an extrathymic regulatory mechanism may be operating, since these precursor T cells have the capacity to migrate into the thymus, and even a grafted, involuting thymus is capable of accepting precursor T cells, under extraordinary conditions. Results indicate that shortly after adolescence, immature T cell precursors of PHA-responsive cells in the thymus, and perhaps the periphery, are the sole source of PHA-responsive T cells. T cell migration and maturation is discussed in relation to thymic hormones and the thymic-neuroendocrine regulatory axis.

Effect of dietary 2-mercaptoethanol on the life span, immune system, tumor incidence and lipid peroxidation damage in spleen lymphocytes of aging BC3F1 mice

The age-related decline in immune function, which is thought to be responsible for the increased incidence with age of certain diseases, including cancer, has been attributed primarily to a loss of T-lymphocyte function. As free radical reactions may contribute to cellular deterioration and loss of cell function with age, we investigated the effect of adding an immunopotentiating antioxidant, 2-mercaptoethanol (2-ME), to the diet of BC3F1 mice in a longitudinal study. For the study, young mice were divided into two groups, one of which received the 2-ME-supplemented diet. Approximately every 3 months for 2.5 years, mice from each group were sacrificed and the spleen lymphocytes assessed for immune function (proliferative response to concanavalin A, phytohemagglutinin, and lipopolysaccharide and the humoral response to sheep red blood cells). The accumulation of fluorescent products indicative of free radical damage was measured in the spleen lymphocytes and the cytochrome P-450 content and activity assessed in the liver. The effect of the 2-ME-supplemented diet on the mean and maximum life span and tumor incidence was also determined. The results showed that the animals fed the 2-ME diet had an increased mean and maximum life span and a postponed onset and decreased incidence of tumors. In general the T-cell-dependent immune responses were higher in the 2-ME-fed mice compared to the controls when the animals were young. No difference was observed between the two groups during mid-life. The responses declined in both groups during the latter half of the life span, but the responses of the 2-ME-fed animals declined to a lesser extent. The accumulation of fluorescent products of lipid peroxidation damage was also delayed in the lymphocytes of the 2-ME-fed mice. Cytochrome P-450 content and activity in the liver was not different in the two groups. The results suggest that the antioxidant activity of 2-ME delayed the accumulation of free radical damage in spleen lymphocytes, which resulted in a delay in the decline of immune function and was associated with the decreased tumor incidence and increased life span.

Immune manipulations and brain-reactive antibody formation in aging mice

Previous studies have demonstrated an increase in brain-reactive antibodies (BRA) in sera of various mammals as a function of age. The present study attempts to obtain a better understanding of the mode of formation of BRA by using various immunologic manipulations in young and old C57BL/6 mice. The mean BRA levels were significantly higher in older mice than in the young ones. Mixtures of bone marrow cells and spleen cells from old donors were able to adoptively transfer high BRA levels in young irradiated mice and this was not altered by pretreatment of the cells with anti-Thy-1.2 or anti-Ig serum plus complement. Transfer of young cells to old irradiated hosts did not lower the high BRA levels in the hosts. However, when the old hosts were also thymectomized and grafted with neonatal thymuses, BRA levels were significantly lowered. The studies tend to indicate that thymic involution or loss of thymic function in aging plays an important role in BRA formation in sera of aged mice.

Autologous mixed lymphocyte reaction in health and disease states in man

In this review are discussed the nature of T cell subsets, defined with monoclonal antibodies, responding in T-non-T and T-T autologous mixed-lymphocyte reactions (AMLR) and antigens stimulating in AMLR, soluble products of AMLR and generation of suppressor, helper and cytotoxic functions. On the basis of these data a model of immunoregulation in vivo can be proposed. We believe that AMLR is a real-phenomenon and not an artefact and perhaps represents a mechanism by which various immune functions are regulated, including feedback regulation of AMLR. The significance of AMLR is further supported by studies in various human and animal diseases.

Immunobiologic staging of patients with carcinoma of the head and neck

For decades immunologic deficiencies have been documented in patients with carcinoma, and many investigators have attempted to utilize this information in determining prognosis more accurately. Determining prognosis more accurately would be most helpful with Stage III patients, since at present there are no useful guidelines as to which Stage III patients would benefit from aggressive surgery and/or radiation therapy and which would not. Assays of cellular immunity--such as skin testing, determining peripheral T-lymphocyte counts, and assessing lymphocyte reactivity--have achieved extremely limited clinical application. These assays are too expensive and/or too difficult to perform in the routine clinical setting. Total lymphocyte counts, however, are readily available in the clinical setting and can be helpful in determining prognosis. Other readily available clinical information, such as age and pretreatment serum immunoglobulin levels, can also be of value in determining prognosis. In this study, logistic regression was utilized to determine the prognostic implications of stage, age, and pretreatment total lymphocyte counts in 132 patients with carcinoma of the head and neck. Although each variable determined prognosis accurately less than 70% of the time, the stage, age, lymphocyte prognostic index (SALPI) accurately predicted outcome at 3 year follow-up 80% of the time (Pr. less than .0001). Discriminant function analysis was utilized to determine the prognostic implications of pretreatment serum immunoglobulins in 243 patients with head and neck carcinoma. A serum immunoglobulin prognostic index (SIPI) was derived which was based on the observations that elevated levels of immunoglobulin A (IgA) indicated a poor prognosis, while elevated levels of immunoglobulin E (IgE) and immunoglobulin D (IgD) indicated a favorable prognosis (Pr. less than .009). The SIPI was not as accurate as the SALPI in determining prognosis; however, when the indices were used simultaneously, concurring indices predicted the outcome of Stage III patients correctly 86% of the time.

Cellular immunosenescence in F344 rats: decline in responsiveness to phytohemagglutinin involves changes in both T cells and macrophages

Spleen cells from F344 male rats showed decreased DNA synthetic responsiveness [( 3H]thymidine incorporation) with age to the T cell mitogen phytohemagglutinin (PHA). Decreased proliferative responses were associated with decreased production of interleukin-2 (IL-2) and could be partially restored by providing exogenous IL-2. Responses of spleen cells from aged rats could also be enhanced by removal of Sephadex G-10 adherent cells. Furthermore, co-culture of adherent cell-containing spleen cells from aged rats with nonadherent spleen cells from young rats resulted in suppression of responses. Purified peritoneal exudate macrophages (PEM) from aged rats showed potent regulatory effects on PHA responses of young and old nonadherent spleen cells resulting in suppression above 2.5% macrophage/nonadherent spleen cell ratios. PEM from young rats enhanced the response of young T cells but failed to affect the response of aged T cells. T cell proliferation in the presence of prostaglandin (PGE1) showed age-dependent differences in regulation such that at 10(-6) to 10(-7) M young responses were enhanced and old responses were suppressed. These results suggest that decreased responsiveness of T cells to PHA with age is a complex phenomenon involving changes in both production of regulatory mediators by T cells (IL-2) and macrophages (PGE) as well as changes in T cell responsiveness to these signals.

Aging of natural and acquired immunity of mice. I. Decreased natural killer cell function and hybrid resistance

Two "natural resistance" functions, natural killer (NK) cell activity against YAC-1 lymphoma cells and rejection by irradiated mice of parental-strain or H-2 allogeneic bone marrow cell grafts (hybrid or allogeneic resistance) were compared in mice at ages between 10 weeks and 26 months. NK cell numbers, as assessed by target-binding cells, decreased to one-half that of young mouse spleen cells, whereas NK lytic function was much more depressed. Hybrid, but not allogeneic, resistance to marrow grafts was weakened by 17 months of age. The immunogenicity of marrow stem cells of old Fl hybrid mice had not changed. The interferon inducer polyinosinic:polycytidylic acid (pI:pC) restored hybrid resistance to marrow grafts but only weakly boosted NK cell function in old mice. Incubation of spleen cells of old mice with beta interferon resulted in a weak boosting of NK cell activity. No cells capable of inhibiting NK cell function were detected in the spleens of old mice. These findings in old mice were similar to findings in young mice treated with 89Sr, with the exceptions that both hybrid and allogeneic resistance to marrow grafts are defective in 89Sr-treated mice and pI:pC failed to restore hybrid resistance in mice treated with 89Sr. This loss of "natural resistance" by aged mice, perhaps mediated by marrow-dependent effector cells, can partially explain the increased incidence of tumors in aging populations.

Lymphocyte subpopulation changes by aging

Peripheral blood lymphocyte suspensions of healthy young and aged subjects were tested for the percentage of (1) E-rosetting cells by three different modifications of the rosette technique; (2) alpha-naphthylacetate esterase positive cells of different staining patterns; (3) IgG-Fc receptor positive cells; (4) C3 receptor positive cells; (5) labile and stable bound surface immunoglobulin positive cells; and (6) cells bearing different classes of immunoglobulins on their surface or intracytoplasmically. Age dependent changes were registered both within the T-cell and the B-cell subpopulations, some of which may be due to in vivo activation of lymphocytes. Attention is called to some technical aspects of lymphocyte subpopulation determinations and to the significance of quantitative changes in the proportions of lymphocyte subpopulations in respect to the age dependent functional changes of lymphocytes.

Brain tumors and the geriatric patient

The prognosis, site of occurrence, and histologic type of primary brain tumors are age-dependent phenomena. In general, the incidence of meningiomas, acoustic Schwannomas, and glioblastomas increases with advancing age until the end of the eighth decade. Of 99 patients consecutively admitted to an aggressive multimodality treatment program for glioblastoma multiforme, 18 per cent were in the 61-70 age group and 4 per cent in the 71-80 group; the oldest was 85. The operative mortality was only 4 per cent. In 16 patients over 65, the 6- and 12-month calculated survival probabilities were 0.65 and 0.31, respectively. The Kaplan-Meier survival curve for these patients was significantly different from that for 26 patients under the age of 40. Grade 4 astrocytomas were present in 62 per cent of patients under 40 but in 83 per cent of patients over 61. In all glioblastoma populations, age is the most significant prognostic variable. The incidence of metastic brain tumors also increases with age, and all of the usual primary sites are represented. The prognosis for elderly patients with metastatic brain tumor is uniformly worse than that for younger patients, even though modern diagnostic and operative techniques carry virtually the same morbidity and mortality rates in older patients as in younger ones. It is vitally important, therefore, that the clinical effects of treatable intracranial tumors in the elderly are not ascribed to dementia, the aging process, the systemic effects of cancer, or the side effects of cancer therapy, without suitable diagnostic investigation.

Acquired immunological tolerance in aged mice. I. The dose-response relationship

Immunoresponsiveness declines with advancing age. In addition, there is an increase in specific and nonspecific suppressor cell activity. In view of these observations it might be predicted that aged mice would be easier to render immunologically tolerant. However, we show here that aged C57B1/6 mice are markedly more resistant to tolerance induction so that 100 times more tolerogen is required to induce unresponsiveness in 24-month-old than in 2-month-old animals. With age the variability between individuals for spleen size and sensitivity to antigen and tolerogen increases in C57B1/6 and Balb/c mice. On the other hand, the duration of tolerance is very little affected by age. The relationships between tolerance, aging and autoimmunity are discussed.

Impaired T-cell functions in aged guinea-pigs restored by thymostimulin (TS)

The age-related changes of different T-cell activities in guinea pigs and the effect of Thymostimulin (TS), a thymus extract, on the immunocompetence of these cells was studied. Mitogen-induced proliferation of peripheral blood lymphocytes was increased by TS in vitro. The intraperitoneal administration of TS (5 mg/kg) to aged animals restored the helper function of T lymphocytes and enhanced the reactivity to mitogens of both peripheral blood lymphocytes and spleen lymphocytes. The data obtained suggest that as in other species, there is an age-associated decline of immunological response, in guinea pigs too, probably due to a deficiency of thymic hormone(s) and that TS could correct this deficiency.

Nutritional implications of the free-radical theory of aging

Aging is the progressive accumulation of changes with time associated with and/or responsible for the ever-increasing susceptibility to disease and death. These time-related changes are attributed to the aging process. This process may be due in part to free radical reactions, largely those involving oxygen, going on continuously throughout the cells and tissues. Dietary manipulations expected to lower the rate of production of free-radical reaction damage have been shown to 1) increase the life span of mice, rats, fruit flies, nematodes, and rotifers, as well as the life span of neurospora, 2) inhibit development of some forms of cancer, 3) enhance humoral and cell-mediated immune responses, and 4) slow development of amyloidosis and the autoimmune disorders of NZB mice. Free-radical reactions may also play a significant role in the deterioration of the cardiovascular and central nervous systems with age. It is reasonable to expect, on the basis of present data, that the healthy life span can be increased by five or more years by keeping body weight down, at a level compatible with a sense of well-being, while ingesting diets adequate in essential nutrients but designed to minimize random free-radical reactions in the body.

Restoration of impaired immune functions in aging animals. VI. Differential potentiating effect of 2-mercaptoethanol on young and old murine spleen cells

The differential effect of 2-mercaptoethanol (2-ME) on spleen and bone marrow cells of young and old mice was determined in vitro. Both the ability of spleen cells to proliferate and to generate Ig-secreting cells and the capacity of bone marrow cells to generate myeloid colonies were assessed. All three activities assessed in both young and old mice were enhanced by the presence of 2-ME, but a differential effect with respect to age was noted in only one. This was the polyclonal activating antibody response to bacterial lipopolysaccharide (LPS) in which 2-ME enhanced young spleen cells to a greater extent than old spleen cells, although their mitogenic responses to LPS were enhanced to the same extent. The ability of 2-ME to enhance old spleen B cells to proliferate but not differentiate in their response to LPS would suggest that aging alters certain subpopulations of spleen cells, some of which are sensitive and others insensitive to the potentiation effects of 2-ME. The enhancing action of 2-ME on the proliferative activity of LPS-stimulated young spleen cells was reduced drastically by decreasing the number of T cells by prior treatment of spleen cells with anti-T cell reagent. The proliferative activity was then brought back to normal pretreatment level by adding enriched T cells. Therefore it would appear that regulatory T cells are the target of the enhancing action of 2-ME. The failure of old spleen cells to respond vigorously to the polyclonal activating action of LPS and 2-ME individually and in combination would indicate that age-related alterations may be taking place in the B cells and/or the regulatory cells. Young-old spleen cell mixture study indicates that there are regulatory cells in old spleen cells which can inhibit B cell differentiation but not B cell proliferation.

Aging and serum immunoglobulin E levels, immediate skin tests, RAST

The changes of the serum IgE levels, specific immediate skin-test responses, and RAST measurements with age were evaluated. A total of 331 unrelated individuals were studied, consisting of 166 subjects with ragweed allergic rhinitis and/or asthma, 67 with idiopathic (intrinsic) asthma, and 98 who appeared in good health with no clinical evidence of atopic diseases. All subjects were evaluated by history and physical examination, intradermal skin testing to the common aeroallergens, measurements of IgE antibody to common aeroallergens with the RAST, and serum IgE levels. Results demonstrated a significant decrease in serum IgE levels with aging in atopic individuals. This decline was exponential in character. In addition, a tendency for RAST and immediate type skin-test responses for selected antigens and histamine to decrease with age was observed.

Natural killing and antibody-dependent cytotoxicity by lymphocyte subpopulations in young and aging humans

Natural killer (NK) and antibody-dependent cellular cytotoxicity (ADCC) were examined in the peripheral blood lymphocytes and their major subpopulations from young and aging subjects. Monocyte-depleted unseparated lymphocyte-mediated NK activity (against cells of K-562) and ADCC (against IgG-coated chicken erythrocytes) were comparable between young and aging subjects. Similarly no significant difference was observed in T cell-mediated NK and ADCC and non-T cell-mediated ADCC between young and aging subjects. Non-T cell-mediated NK activity, however, was significantly (P less than 0.025) greater in aging humans compared to that of young subjects. When the data were analyzed according to gender, T cell-mediated ADCC in aging males was significantly (P less than 0.05) greater than that found in young males. No significant difference was observed between T-cell ADCC among young and aging females. T cell-mediated NK was comparable among young and aging males and young and aging females. Non-T cell-mediated NK as well as ADCC activity was significantly (P[ less than 0.025 or less than 0.05) greater in aging males compared to that in young males. Both non-T-cell NK and ADCC were comparable among young and aging females. This study demonstrates an increase in NK and ADCC activity in aging subjects that is primarily shared by males and not by females. No correlation was observed between the proportion of T gamma cells and T-cell NK or ADCC activity.

Brain-reactive antibodies in sera of aging non-human primates

Previous studies in our laboratory demonstrated an age-related increase in the brain-reactive antibodies in sera of aging mice. The present paper deals with the study of brain-reactive antibodies in sera of non-human primates (Macaca nemestrina) of three age groups (4, 10 and 20 years) by an indirect immunofluorescence method. The results indicated a progressive increase in the serum levels of these antibodies with advancing age. Since all three age groups examined demonstrated brain-reactive antibodies in sera, the age of onset of these antibodies could not be determined in these animals. It has been suggested that the formation of these antibodies could be evidence of autoimmune reactions which might play a significant role in neuronal degeneration during aging.

Body temperature in normal and endotoxin-treated mice of different ages

Elderly people contract more gram-negative infections than does the younger population and, thus, are exposed to larger amounts of bacterial endotoxins. The differential effects of bacterial lipopolysaccharides (LPS) in aging have been investigated here. LPS have increased toxicity for aged mice (12 and 24 months) compared to that in 2-month-old mice in that two-thirds of both 24-month-old Balb/c and C57Bl/6 male mice were killed by an intravenous dose of 50 microgram of LPS. Body temperatures were also affected by aging. Both C57Bl/6 and Balb/c mice showed a maximum body temperature at 12 months of age; 24-month-old mice had mean body temperatures of at least 2 C less than 12-month-old animals. LPS induced hypothermia in young mice as described by others, but in 24-month-old mice there was a marked hyperthermia following LPS injection. Increased sensitivity to LPS with age may result from differences in the effects of LPS on target cells or differences in responsiveness to secondary mediators. In addition, LPS have profound effects on the immune system which may be changed with age.

Decrease of the lymphoproliferative response to varicella-zoster virus antigen in the aged

Humoral antibodies and specific cellular immune reactions (proliferative immune response in the lymphocyte transformation test) to varicella-zoster virus antigen were measured in children, young adults, and elderly people. In children and young adults, the humoral varicella-zoster-specific antibodies and the virus-specific cellular immune response generally coincided. In the over-60 age group, however, a discrepancy was often observed between these parameters. Ninety percent of the elderly subjects showed humoral antibodies, but only 64% still had a measurable varicella-zoster-specific immune response. There was no correlation between the magnitude of the virus antigen-specific immune response and the mitogen-induced lymphoproliferative response (phytohemagglutinin stimulation). One in three elderly people, therefore, showed no cellular immune response to the varicella-zoster virus antigen, and this person could probably be regarded as a potential herpes zoster patient.

The older living renal donor: prognosis for the donor and recipient

Results after 46 renal transplants from living donors more than 50 years old are presented. There were no complications after transperitoneal nephrectomy and renal function remained stable in all donors. The mean followup for transplant recipients was 6.2 years. The 2-year patient and graft survival rates were 76.1 and 60.9 per cent, respectively, while the corresponding 5-year rates were 60.5 and 46.5 per cent, respectively. These results suggest that age per se should not eliminate living related kidney donation.