Cellular and molecular aspects of immune system aging

Prevalence and clinical manifestations of dengue in older patients in Bangkok Hospital for Tropical Diseases, Thailand

BACKGROUND

The global incidence of dengue has increased with the ageing population. We examined the prevalence, clinical manifestations and risk factors associated with dengue severity among older patients.

METHODS

A retrospective cohort study was conducted at a hospital in Thailand from 2013 to 2018. Data were collected from patient records. Older patients were those aged ≥60 y, whereas adult patients were aged at least 18 y but younger than 60 y.

RESULTS

In total, 1822 patients were included in the study. The prevalence of older dengue was 7.96%. Older dengue patients were at a higher risk of developing dengue haemorrhagic fever (DHF) than adult dengue patients (40.69% vs 30.71%). Haematuria was significantly more frequent in older patients (24.82% vs 3.58%), whereas other clinical manifestations had similar frequencies between the groups. Multivariate logistic regression indicated that hypertension (adjusted OR [aOR]=3.549, 95% CI 1.498 to 8.407) and abdominal pain (aOR=10.904, 95% CI 1.037 to 114.710) were significantly associated with DHF among older patients.

CONCLUSIONS

Dengue is common in older adults, who also have a higher incidence of developing DHF. Older patients with dengue and comorbid hypertension and abdominal pain should be monitored for their increasing risk of DHF.

Predicting the mortality in geriatric patients with dengue fever

Geriatric patients have high mortality for dengue fever (DF); however, there is no adequate method to predict mortality in geriatric patients. Therefore, we conducted this study to develop a tool in an attempt to address this issue.We conducted a retrospective case-control study in a tertiary medical center during the DF outbreak in Taiwan in 2015. All the geriatric patients (aged ≥65 years) who visited the study hospital between September 1, 2015, and December 31, 2015, were recruited into this study. Variables included demographic data, vital signs, symptoms and signs, comorbidities, living status, laboratory data, and 30-day mortality. We investigated independent mortality predictors by univariate analysis and multivariate logistic regression analysis and then combined these predictors to predict the mortality.A total of 627 geriatric DF patients were recruited, with a mortality rate of 4.3% (27 deaths and 600 survivals). The following 4 independent mortality predictors were identified: severe coma [Glasgow Coma Scale: ≤8; adjusted odds ratio (AOR): 11.36; 95% confidence interval (CI): 1.89-68.19], bedridden (AOR: 10.46; 95% CI: 1.58-69.16), severe hepatitis (aspartate aminotransferase >1000 U/L; AOR: 96.08; 95% CI: 14.11-654.40), and renal failure (serum creatinine >2 mg/dL; AOR: 6.03; 95% CI: 1.50-24.24). When we combined the predictors, we found that the sensitivity, specificity, positive predictive value, and negative predictive value for patients with 1 or more predictors were 70.37%, 88.17%, 21.11%, and 98.51%, respectively. For patients with 2 or more predictors, the respective values were 33.33%, 99.44%, 57.14%, and 98.51%.We developed a new method to help decision making. Among geriatric patients with none of the predictors, the survival rate was 98.51%, and among those with 2 or more predictors, the mortality rate was 57.14%. This method is simple and useful, especially in an outbreak.

Characteristics of scrub typhus, murine typhus, and Q fever among elderly patients: Prolonged prothrombin time as a predictor for severity

BACKGROUND/PURPOSE

The clinical manifestations of scrub typhus, murine typhus and acute Q fever in the elderly are not clear.

METHODS

We conducted a retrospective study to identify the characteristics of the elderly aged ≥65 years with a comparison group aged 18-64 years among patients with scrub typhus, murine typhus, or acute Q fever who were serologically confirmed at three hospitals in Taiwan during 2002-2011.

RESULTS

Among 441 cases, including 187 cases of scrub typhus, 166 acute Q fever, and 88 murine typhus, 68 (15.4%) cases were elderly patients. The elderly had a higher severe complication rate (10.3% vs. 3.5%, p = 0.022), but did not have a significantly higher mortality rate (1.47% vs. 0.54%, p = 0.396). Compared with those without severe complications, we found the elderly (p = 0.022), dyspnea (p = 0.006), less relative bradycardia (p = 0.004), less febrile illness (p = 0.004), prolonged prothrombin time (PT) (p = 0.002), higher levels of initial C-reactive protein (p = 0.039), blood leukocyte counts (p = 0.01), and lower platelet counts (p = 0.012) are significantly associated with severe complications. Only prolonged prothrombin time was associated with severe complications in multivariate analysis (p = 0.018, CI 95% 0.01-0.66). Among clinical symptoms and laboratory data, multivariate analysis revealed chills was less frequently occurred in the elderly (p = 0.012, 95% confidence interval [CI]: 1.33-9.99).

CONCLUSION

The elderly cases with scrub typhus, murine typhus, or acute Q fever would be more likely to have severe complications, for which prothrombin time prolongation is an important predictor for severe complications.

Prevalence and clinical course of dengue infection in elderly patients with acute febrile illness in a tertiary care hospital in Cali, Colombia

INTRODUCTION

Little is known about the prevalence and clinical course of dengue infection in elderly patients living in endemic areas; it is presumed that there is a lower prevalence but higher severity, complications and mortality. 

OBJECTIVE

To describe the prevalence and clinical course of dengue infection in elderly patients who were admitted to a referral care center for infectious diseases in an endemic region. 

MATERIALS AND METHODS

We conducted an observational and descriptive study between 2011 and 2014, using a cohort of elderly patients with serological diagnosis of dengue. 

RESULTS

A total of 235 febrile elderly patients were assessed, of which 43 patients (18.3%) were found to have dengue. The median age was 71 years; 48.7% were female, and 89% of patients had at least one comorbid condition. According to the serological tests, 51.4% of cases were positive for NS1 Ag, 27% for IgM and 54.1% for IgG, while 64.8% were secondary infections. Dengue was diagnosed in 13 patients (35%), dengue with warning signs in 16 cases (43%), and severe dengue in 8 cases (22%). Nearly 56.7% of patients were admitted to hospital and 21.6%, to the intensive care unit. None died. 

CONCLUSION

We found dengue infection to be more frequent than expected in this sample of elderly patients, due to acute febrile syndrome. Elderly patients also required higher rate of hospitalization and had more complications, however there were no deaths due to good management.

The influence of hypercholesterolemia on some aspects of immune pattern in the elderly

In order to investigate if age related dislipidemia was associated with immunological changes in vivo, humoral, soluble and cellular immune parameters were evaluated both in elderly with and without hypercholesterolemia and in young adults. Significantly increased IgG and IgA values were found in hypercholesterolemic aged compared to the other groups. Increased plasma neopterin levels (a pteridine generally used as a marker of macrophage activity) were reported in healthy aged subjects, whereas a lesser degree of the activation of the macrophage system was found in the hypercholesterolemic aged subjects. Compared with the young controls, an increase of interleukin 2 receptor expressing cells and of the IL-2 soluble receptors was noticeable in healthy aged subjects, whereas in hypercholesterolemic aged subjects only a minor increase of the IL-2 membrane receptor was noticed. We suggest that hypercholesterolemia may play a role in immune function in aging.

The influence of age and sex on phagocyte chemiluminescence

The process of ageing is associated with increased susceptibility to infection. Phagocytes form the primary defence mechanism against infecting microorganisms, but the influence of ageing on phagocyte function remains controversial. In this study we have applied a microtitre plate phagocyte chemiluminescence (CL) assay suitable for clinical use to compare phagocyte oxidative metabolism in younger healthy subjects (age 20-60 years) and healthy older (60-70 years) subjects. Polymorphonuclear leukocytes (PMNL) and monocytes were stimulated using phorbol myristate acetate (PMA), serum opsonized zymosan (SOZ), and non-opsonized zymosan (ZYM) in the presence of both lucigenin and luminol. Monocytes showed a higher luminol-enhanced CL response to PMA in males compared with females in the younger age group. No PMNL differences were observed between the sexes. Although no differences were found in relation to age when cells were stimulated with PMA and SOZ, significantly lower background (unstimulated) CL was obtained from PMNL with luminol. PMNL luminol-enhanced CL responses were also lower in response to ZYM. The findings suggest a reduced response of PMNL from older subjects to minimal stimulation. This could be related to abnormalities in the triggering of the respiratory burst or myeloperoxidase release due to ageing. The influence of age and sex should be taken into account in clinical studies of phagocyte CL.

Selective inhibition by alcohol and cortisol of natural killer cell activity of lymphocytes from cord blood

1. The immunosuppressive effects of drugs such as alcohol or hormones such as cortisol may be age-related. To test this hypothesis, the authors investigated the in vitro effects of ethanol (EtOH) and cortisol on Natural Killer (NK) cell activity of lymphocytes from normal cord blood in comparison with that of lymphocytes from normal adult peripheral blood. 2. K562, an erythroleukemia cell line, was used as a target in a 4 hr 51Cr release assay. 3. Ethanol at 0.3% (V/V) and cortisol at 0.05, 0.1 and 0.2 microgram/ml concentrations, added directly to a mixture of effector and target cells significantly suppressed the NK activity of cord blood lymphocytes in a dose dependent fashion, whereas similar concentrations of either EtOH or cortisol did not manifest significant immunoregulatory effects on NK cell activity of normal adult lymphocytes. 4. Pre-treatment of the target with either EtOH or cortisol for 4 hours did not affect cytotoxicity. Inhibition of cytotoxicity was also not due to direct toxicity of effector cells because lymphocytes treated with either EtOH or cortisol showed normal 51Cr release and their viability was comparable to that of untreated control cells. 5. This suggests a selective inhibitory effect of EtOH and cortisol on NK activity of neonatal lymphocytes that may be of clinical significance.

Elevated interleukin-6 secretion levels by mononuclear cells of Alzheimer's patients

It has been suggested in recent research that interleukin-1 (IL-1) and interleukin-6 (IL-6) play a role in the pathogenesis of Alzheimer's disease (AD). Production of IL-1, by lipopolysaccharide (LPS)-stimulated monocytes, and IL-6, by phytohaemagglutinin (PHA)-stimulated mononuclear cells, was assessed in patients with AD divided into two groups--mild and moderately severe--according to severity of disease, and elderly controls. No differences in IL-1 production were found among AD patients and controls. However, significant elevation in IL-6 secretion levels was observed in both the mild and moderately severe AD patients. Our results suggest that peripheral IL-6 secretion levels may be responsible for acute-phase proteins observed in the serum of AD patients.

Cost-benefit of granulocyte colony-stimulating factor administration in older patients with non-Hodgkin's lymphoma treated with combination chemotherapy

BACKGROUND

Older patients with non-Hodgkin's lymphoma (NHL) display a poorer response to chemotherapy and a significantly higher treatment-associated toxicity than do younger individuals. We investigated the potential clinical benefits and the cost-effectiveness of accelerated granulocyte recovery induced by recombinant granulocyte colony-stimulating factor (G-CSF) in patients with aggressive NHLs, aged 60-70 years, during treatment with a second-generation combination chemotherapy.

PATIENTS AND METHODS

12 consecutive patients (median age 66 years) treated with six to eight courses of CHVmP/VB plus subcutaneous G-CSF (5 micrograms/kg/day) were compared with 11 consecutive subjects (median age 65 years) who received the same chemotherapy regimen without growth factor support. The two groups of patients were fully comparable as to the clinicopathologic features. A comparative analysis of treatment costs (including hospitalization, antimicrobial prophylaxis and therapy, supportive and diagnostic procedures, and G-CSF) was also performed.

RESULTS

Both the overall response rate and the percentage of complete remissions were comparable in the two treatment groups. In the control group, 32.5% of chemotherapy courses were delayed, as opposed to 19% in the G-CSF group (p = 0.05). The mean duration of delay for patients receiving or not receiving G-CSF was 10.1 and 25.9 days, respectively (p = 0.02). Grade 3 and 4 granulocytopenia complicated 27.7% of chemotherapy courses in control patients and only 4.8% in subjects receiving G-CSF (p < 0.001). Similarly, severe infections and mucositis were significantly higher in patients receiving chemotherapy alone (15.6% and 3.6%, respectively) compared to the G-CSF group (4.8%, p = 0.01; p = 0.04, respectively). A mean of 1.1 days/course of hospitalization was required in the control group, as opposed to 0.2 days/course in patients receiving G-CSF (p = 0.05). Although overall treatment costs were higher in the control group, single cost of the recombinant growth factor exceeded by far all the other expenses in the G-CSF group, reaching a statistical relevance (p = 0.01).

CONCLUSIONS

The inclusion of prophylactic G-CSF in the treatment plan for aggressive NHL in older patients appears safe and cost-effective in view of the peculiar clinical features of aged subjects and the possibility of delivering effective doses of antineoplastic drugs on an outpatient setting.

Gender differences in age-related decline in DNA double-strand break damage and repair in lymphocytes

DNA repair capacity has been suggested to be a genetic mechanism which influences the rate of ageing and length of life. We recently reported an age-related decline in DNA double-strand break (DSB) repair in unstimulated human lymphocytes (Mayer, Lange, Bradley, and Nichols 1989, 1990). In that work peripheral lymphocytes isolated from whole blood donated by 20 normal, healthy subjects aged 23-78 years, were X-irradiated (30 Gy) on ice and incubated at 37 degrees C for repair times of 15, 30, and 120 min, and neutral filter elution was used to assay DSB induction and completeness of DSB rejoining. Further analysis reveals that the decrease in DSB rejoining appears to be more pronounced in older women than in older men (and may begin after age 65 years). Moreover the reported age-related decline in DSB induction occurs more rapidly (by a factor of ca. 2) in women than in men. We had previously demonstrated that, independently of in vivo age, cells with lower radiosensitivity (i.e. lesser DSB induction) appear to be less repair-proficient (Mayer et al. 1990). The present analysis reveals a gender-specific pattern in this correlation between extent of DSBs induced and percentage of DSBs rejoined: at comparable levels of DSB induction, cells from men rejoin a higher percentage of DSBs than do cells from women. This preliminary study suggests the following hypothesis: age-related DSB effects (i.e. induction and rejoining) are due to changes in chromatin structure and males are less sensitive than females to the influence which age-related alterations in chromatin exert on DSB effects.

Changing pattern of CD5+ CD20+ double positive lymphocytes with ageing and cytotoxic chemotherapy

In this cross-sectional clinical study, it was found that two subtypes of CD5+ B-lymphocytes existed either with CD5-high and CD20-low or CD5-low and CD20-high expression, as determined by dual fluorescence analysis with fluorochrome-labeled monoclonal antibodies on a FACScan flowcytometer. In the normal healthy subjects (n = 20), the CD20 positive cells could be broken down into 3 subsets: CD5(2+) CD20+, 25.4 +/- 3.0% (mean +/- S.E.M.), CD5+ CD20(2+), 18.4 +/- 2.4% and CD5- CD20(2+), 56.2 +/- 2.7%. Similar values were observed in a group of patients (n = 29) suffering from a wide variety of benign or untreated malignant disorders. The CD5(2+) CD20+ subset was typically related to age (Spearman coefficient of correlation rho = 0.77, P less than 0.001 in healthy subjects and rho = 0.46, P = 0.02 in pathological cases). The CD5+ CD20(2+) subpopulation was a salient feature of newborns and little infants (n = 6, 75.4 +/- 2.4%, P less than 0.01). The CD5- CD20(2+) subset was characteristically depressed in patients treated with cytotoxics (n = 21, 41.2 +/- 3.6%, P = 0.001). As far as cytotoxic chemotherapy may represent a model of accelerated ageing, it is worth noting that, in patients treated with cytotoxics, the CD5 CD20 pattern was frequently disturbed in a hyperyoung or hyperaged picture. That age and cytotoxics can affect CD5 expression on CD20+ lymphocytes, suggests some specific B-dysregulation and should be put together with the known emergence of autoantibodies, paraproteinemias and lympho-plasmocytic tumors with age and chemotherapy.

Cellular immunosenescence: an overview

Recent studies on space flights suggest that certain T cell immunologic activities are vulnerable to microgravitation. It would be desirable to know the extent to which these changes can be prevented or reversed. Since the changes observed are analogous to the effects of aging on immunity, a brief overview is presented of our current knowledge of age-related changes in immune cells and of the various interventional methods which have been used successfully in preventing the decline with age and in elevating the levels of immune functions of old individuals.

Serum levels of antibodies against Actinobacillus actinomycetemcomitans in various forms of human periodontitis

Serum levels of IgG, IgA, and IgM antibodies against extracts from Bacteroides gingivalis PER8, Actinobacillus actinomycetemcomitans Y4, and Bacteroides fragilis NCTC 9343 were determined in three categories of periodontitis patients by means of enzyme-linked immunosorbent assay. The test groups comprised 10 patients with juvenile periodontitis (JP), 18 young patients with severe periodontitis (YP), and 31 patients with adult periodontitis (AP). Nine subjects with healthy periodontium (HP) served as a reference group. Increased frequencies of patients with significantly elevated IgG and IgA antibody values against B. gingivalis and A. actinomycetemcomitans were found in the three periodontitis groups as compared with the HP group. The AP group, however, showed lower IgM values than the other groups. The results support the contention that A. actinomycetemcomitans may play a contributory role in adult periodontitis and that B. gingivalis is a suspected periopathogenic bacterium in juvenile periodontitis. The clinical YP classification was not supported by the present serologic findings.

Age-dependent decline in rejoining of X-ray-induced DNA double-strand breaks in normal human lymphocytes

Unstimulated human peripheral blood lymphocytes (HPBL), separated by density centrifugation from anticoagulated whole blood, were X-irradiated (30 Gy) on ice and incubated in medium at 37 degrees C for repair times of 15, 30, and 120 min. Blood donors were 18 normotensive, non-smoking Caucasians aged 23-78, free from overt pathology and not taking any medications. Neutral filter elution was used to assay DNA double-strand break (DSB) induction and completeness of DSB rejoining (plus rejoining of any X-ray-induced alkali-labile sites converted to DSBs in vitro at pH 9.6). After 30 or 120 min repair incubation, the percentage of DSBs rejoined by cells from older donors (aged 66-78 years) was less than half the percentage of DSBs rejoined by cells from younger donors (aged 23-39 and 42-57). When data from the 3 age groups were pooled, the age-related decline in percent DSBs rejoined was significant for repair times 30 min (r = -0.63, p less than 0.005) and 120 min (r = -0.64, p less than 0.005) but not for 15 min (r = -0.04). These age-related declines were observed even though DNA from older donors sustained fewer strand breaks as demonstrated by the negative correlation between donor age and DSB induction (r = -0.65, p less than 0.005). These results suggest that the efficacy of X-ray-induced DSB repair diminishes with in vivo age in unstimulated HPBL.

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-related changes in the proliferative kinetics of phytohemagglutinin-stimulated lymphocytes. Analysis by uptake of tritiated precursors of DNA, RNA and proteins, and by flow cytometry

We have examined the age-related changes in the kinetics of lymphocyte proliferative responses to phytohemagglutinin by flow cytometry and by the uptake of tritiated thymidine, uridine and leucine. The lymphocyte suspensions used in these experiments were obtained by umbilical cord blood samples of full-term normal newborns and from the peripheral blood of young (under 30-year-old) or aged (more than 70-year-old) healthy donors. The results indicate that the cord blood lymphocytes were activated by phytohemagglutinin to incorporate tritiated precursors of proteins, RNA and DNA at a more rapid rate than the lymphocytes from young or old donors in the first 3 days of in vitro culture. Flow cytometry confirmed higher percentages of activated cycling cells in umbilical cord blood after 24 h of culture. The lymphocytes from old donors incorporated significantly lower amounts of tritiated precursors of DNA and RNA than lymphocytes from young donors at the third day of culture. The uptake of tritiated leucine by lymphocytes from old donors was significantly reduced up to the sixth day of culture. On the contrary, at the eight day of culture, lymphocytes from old donors incorporated significantly higher amounts of labeled DNA, RNA and protein precursors. In agreement with these findings, flow cytometry demonstrated a trend towards higher percentages of cycling cells in the lymphocyte cultures from old donors after 6 and 8 days. These results indicate an age-related decline in the rate of lymphocyte blastogenesis after in vitro PHA stimulation and suggest that after a delayed PHA-induced activation, the lymphocytes from aged donors have a near-normal ability to proliferate.

AL721, a novel membrane fluidizer

AL721, which is a novel lipid mixture extracted from egg yolks, is believed to be a therapeutic pharmacologic agent. AL721 interacts with membranes of various types of cells with a common mode of action. AL721 modifies cellular membrane composition and fluidity through passive extraction and/or exchange of cholesterol. Physiologically diminished cell function due to rigidification of its membrane is reversible both in vitro and in vivo by AL721. Fluidization of aged membranes with AL721 has been shown to restore brain serotonin receptor function both in vitro and in vivo. AL721 can also successfully restore deficient immune responsiveness of lymphocytes to mitogen stimulation in aged subjects. Drug tolerance to morphine and ethanol develops upon elevation of the viscosity of neuronal cell membranes in order to counteract the fluidization effect of the drug. Treatment of rigidified cellular membranes with AL721 in vivo can markedly reduce withdrawal symptoms. The virucidal effect of AL721 on the human immunodeficiency virus is believed to operate by lowering of viral membrane cholesterol thus interfering with the binding of the viral antigen to the host cell. Non-toxicity of AL721 is clearly demonstrated in animal and human safety studies.

Analysis of fluorescent low density lipoprotein uptake by lymphocytes. Paradoxical increase in the elderly

Uptake of dioctadecylindocarbocyanine (DiI)-labelled low density lipoproteins (LDL) by peripheral blood lymphocytes (PBL) from young healthy donors has been characterized by flow cytometric analysis. The receptor positive cells were primarily (greater than 70%) T cells. Saturation and competition studies were performed with freshly isolated PBL as well as after a 2-3-day incubation in cholesterol-free medium. In both cases uptake was specific for LDL and not high density lipoprotein. It was also abrogated by chemical modification of apo B, and was not shown by PBL from a patient with familial hypercholesterolemia. DiI-LDL-uptake by cells from elderly donors was compared with that of PBL from young donors. There was a clear increase in uptake by freshly isolated PBL from aged donors which was shown not to stem from underlying "sickness". In contrast, uptake by pre-incubated cells was very variable, in terms of percentage receptor-positive cells and the level of uptake by those cells. However, LDL rescued mevinolin-suppressed mitogen responses from both old and young donors indicating that there is no impairment of uptake or degradation of LDL by PBL from the elderly.

Age-related RNA polymerase I activity in isolated nuclei of PHA stimulated human lymphocytes

In order to extend to the immune system previous findings that there is an age-related loss of hybridizability of the genes for ribosomal RNA (rRNA) in several tissues of mice, dogs and humans, we have investigated the function of the genes for rRNA in human T lymphocytes. These cells were chosen because they show a substantial decline in function with age, greater than that of other components of the immune system. rRNA synthesis was determined by measuring tritiated-UTP incorporation into acid precipitable counts as a result of the action of RNA polymerase I in nuclei isolated from phytohemagglutinin (PHA) stimulated peripheral-blood lymphocytes from 24 young adult and old human donors. The number of PHA-responsive cells from each donor was determined by counting grains in autoradiographs after a pulse of tritiated-uridine had been administered to them. The aggregate PHA induced synthesis of rRNA in the cultures decreased as a function of the age of the donor. However, the number of PHA-responsive cells also dropped with age. When the data are normalized for the number of PHA-responsive cells in each culture, it appears that rRNA synthesis per PHA-responding cell does not significantly decline with age, even though there is a suggestion of a decrease after corrections are made. On the average, differences between individuals of the same age group were as great or greater than age-related differences.

Do immature T cells accumulate in advanced age?

The hypothesis that decreased T cell function in the elderly involves an increased number of less differentiated T cells was examined. Three markers known to change during thymocyte development were analyzed; ratio of adenosine deaminase (ADA) to purine nucleoside phosphorylase (PNP), lactate dehydrogenase (LD) H/M subunit ratios and the T cell associated antigens, T3, T4, T8 and T10. Cells tested were from 10 old (greater than 75 years) and 10 young (less than 35 years) persons with equal numbers of males and females in each group. Before analysis, cells were purified into three groups; unfractionated, and monocyte depleted T cell and B cell enriched populations. Results for ADA/PNP ratios showed no significant differences between old and young in any of the fractions analyzed. H/M ratios however, were significantly reduced in all three fractions from old donors when compared with young. Surface marker distribution pattern as illustrated by the T3 - (T4 + T8) difference was lower in samples from old donors but not significantly so. There was a very significant reduction in percent cells positive for T3 in all three fractions from old persons. Although some of the changes seen in these markers could be due to a failure of normal differentiation, they could also be caused by the general phenomenon of altered gene expression known to occur with advanced age in a variety of non-lymphoid cells. The absence of any difference in the ADA/PNP ratio suggests that T cell dysfunction in the elderly may not be due to increased numbers of less differentiated cells as a result of thymic involution.

Lack of correlation between serum cholesterol levels, lymphocyte plasma membrane fluidity and mitogen responsiveness in young and aged chickens

Chickens were studied in an attempt to demonstrate correlations between serum lipid levels and peripheral blood lymphocyte (PBL) plasma membrane fluidity and mitogen responsiveness: (a) in the laying hen; (b) during aging; and (c) following dietary manipulation of serum cholesterol of young and aged chickens. The membrane fluidity of PBL from laying hens was significantly greater than that of immature birds. However, no direct correlation was found between serum lipid levels, nor the serum free cholesterol/phospholipid (FC/Pl) mole composition and PBL membrane fluidity in any of the age-groups tested. Likewise, no correlation was found either between serum FC/Pl mole ratio or membrane fluidity and mitogen responsiveness of PBL from birds up to 5 years of age nor was there any evidence for a decline in mitogen responsiveness up to this age. Supplementation of diets with 1% cholesterol induced hypercholesterolemia, mainly in the very low density lipoprotein (VLDL) fraction, but membrane fluidity and mitogen responsiveness remained unaffected.

Differential effects of age on mitotically active and inactive bone marrow stem cells and splenic T cells in mice

Young and old BALB/c mice and thymectomized young mice were subjected to continuous exposure of 6-thioguanine (6-TG), and the numbers of their bone marrow spleen colony-forming units (CFU-S) and in vitro culture colony-forming units (CFU-C) and the number and mitogen-induced proliferative activity of their splenic T cells were determined at various time intervals. The results indicated that (a) old mice have seven times more 6-TG-resistant (6-TGr) CFU-S than young mice, (b) the mitogen-induced proliferative activity of 6-TGr T cells is comparable to that of 6-TG-sensitive (6-TGs) T cells of both young and old mice, and (c) 6-TGr CFU-S and T cells are resistant to 6-TG because they are mitotically inactive and not because they are drug-resistant mutants.

The immune status of healthy centenarians

The immune status of 17 healthy individuals 100-103 years of age (centenarians) was investigated. Qualitative values for immunoglobulins IgG, IgM, IgA, and IgE were within normal ranges for subjects more than 60 years of age with the exception of elevated IgM in one individual. Cell marker studies employing a panel of 27 monoclonal antibodies delineating T and B lymphocytes, monocytes, natural killer cells, granulocytes, and functional and developmental subsets of each were performed to phenotype the peripheral blood leukocytes. Although the total lymphocyte count was normal in every subject, the numbers of T4-positive helper-inducer T lymphocytes were profoundly depressed, as were responses to the mitogen phytohemagglutinin and interleukin-2 production. Activated immature T lymphocytes and the number of cells bearing the phenotype of natural killer cells were increased, but natural killer cell activity was normal. Early B lymphocytes were also increased. The relative concentration of monocytes was normal. Taken together these findings indicate that the immune system in centenarians is similar to that in younger but still elderly individuals, i.e., discriminating T-lymphoid functions are reduced in association with an apparent failure of some T, B, and natural killer cells to differentiate to functional maturity.

Aggressive chemotherapy for diffuse histiocytic lymphoma in the elderly: increased complications with advancing age

Twenty patients greater than or equal to 70 years of age were included in a study of the treatment of diffuse histiocytic lymphoma utilizing cyclophosphamide, adriamycin, vincristine, and prednisone. These patients ranged in age from 70 to 94 years (median 75 years). There were also 55 younger patients (age range 33 to 69 years) in the treatment trial. There were no dose adjustments for age. The complete remission rate in the elderly patients (45 per cent) was not different from that in the younger patients (53 per cent). The overall survival in the elderly patients (median 13 months) was somewhat shorter than that in the younger patients (medians 22 months for patients 56-69 years of age and 41 months for patients 33-55 years of age), but not significantly different. Death during the first two treatment cycles from causes other than lymphoma occurred in 25 per cent of the patients greater than or equal to 70 years of age versus 2 per cent of younger patients (P less than 0.01). In addition, three other patients aged 79, 65, and 59 years died in the fourth or fifth cycles of treatment from causes other than lymphoma. Thus, 30 per cent of patients greater than or equal to 70 years of age died during therapy from causes other than lymphoma, versus 5 per cent of younger patients (P less than 0.01). Whether this altered ability to tolerate therapy in the older patients reflected decreased marrow function, altered drug metabolism, other effects of aging, or a combination of these factors is not clear. It might be appropriate to alter drug doses when treating elderly patients, and particular attention to supportive measures seems appropriate.

Stability of E-rosettes in aged humans: effect of cytochalasin B and colchicine

A greater stability of E-rosettes and a reduced rate of capping of sheep erythrocytes are observed in elderly people. The lack of qualitative changes in the sensitivity of these processes to colchicine and cytochalasin B suggests that the function of the microfilaments and the microtubules is not primarily affected by ageing. The density and the affinity of the lymphocytes for sheep erythrocytes do not decrease in aged subjects. So the defective rearrangement of the E-receptors cannot be accounted for by some receptor alteration but points to a possible hindrance of their cross-linking in the membrane or their submembrane connection to the cytoskeleton.