Stress-induced modulation of the immune response

SYNBIO® Probiotic and Antioxidant Dietary Supplementation: Clinical Trial Evaluation of Potential Effects on Airline Flight Crew Members’ Well-Being

The irregular lifestyle of airline crew members, wide/adverse job-related exposures, and the impact of temporary hypoxia on gut microbiota well-being have increased concern about the daily recommended dose of certain nutrients among flight crew. The aim of this study was to determine if daily consumption of a SYNBIO® probiotics–elderberry extract supplement (ACTIVE) may contribute to the well-being of flight attendants. Forty healthy crew members enrolled in a double-blind, randomized, placebo-controlled study consumed one ACTIVE capsule/day or placebo for 30 days. Bowel well-being, health-related quality of life, and gastrointestinal tolerance were assessed by validated questionnaires. Saliva and fecal samples were analyzed to determine secretory immunoglobulin-A (sIgA) levels and to characterize gut microbiota composition, respectively. ACTIVE subjects presented a physiological improvement and a statistically significant higher Psychological General Well-Being Index (PGWBI) global score compared to PLACEBO subjects. The ACTIVE subjects showed significantly increased levels of lactobacilli and bifidobacteria compared to the PLACEBO group, while a significant increase in lactobacilli and a significant reduction in Enterobacteriaceae were registered when compared with the beginning of supplementation, confirming the persistence of probiotics in the gastrointestinal tract and the direct antagonism and competitive exclusion effects. Additionally, sIgA levels were significantly higher in the ACTIVE group compared to the baseline and to the PLACEBO group at the end of supplementation. The ACTIVE supplementation might be beneficial to airline crew members, improving their physiological state, their immune defenses, and the strength and efficiency of their gastrointestinal tract when responding to stressful conditions.

Exercise and adrenergic regulation of immunity

Exercise training has a profound impact on immunity, exerting a multitude of positive effects in indications such as immunosenescence, cancer, viral infections and inflammatory diseases. The immune, endocrine and central nervous systems work in a highly synergistic manner and it has become apparent that catecholamine signaling through leukocyte β-adrenergic receptors (β-ARs) is a key mechanism by which exercise mediates improvements in immune function to help mitigate numerous disease conditions. Central to this is the preferential mobilization and redistribution of effector lymphocytes with potent anti-viral and anti-tumor activity, their interaction with muscle-derived cytokines, and the effects of catecholamine signaling on mitochondrial biogenesis, immunometabolism and the resulting inflammatory response. Here, we review the impact of acute and chronic exercise on adrenergic regulation of immunity in the context of aging, cancer, viral infections and inflammatory disease. We also put forth our contention that exercise interventions designed to improve immunity, prevent disease and reduce inflammation should consider the catecholamine-AR signaling axis as a therapeutic target and ask whether or not the adrenergic signaling machinery can be 'trained' to improve immune responses to stress, disease or during the normal physiological process of aging. Finally, we discuss potential strategies to augment leukocyte catecholamine signaling to boost the effects of exercise on immunity in individuals with desensitized β-ARs or limited exercise tolerance.

Exploratory RNA-seq analysis in healthy subjects reveals vulnerability to viral infections during a 12- month period of isolation and confinement

Exposure to stressful environments weakens immunity evidenced by a detectable reactivation of dormant viruses. The mechanism behind this observation remains unclear. We performed next generation sequencing from RNA extracted from blood samples of 8 male subjects collected before, during and after a 12-month stay at the Antarctic station Concordia. RNA-seq data analysis was done using QIAGEN Ingenuity Pathway Analysis (IPA) software. Data revealed the inactivation of key immune functions such as chemotaxis and leukocyte recruitment which persisted after return. Next to the activation of the stress response eIF2 pathway, interferon signaling was predicted inactivated due to a downregulation of 14 downstream genes involved in antiviral immunity. Among them, the interferon stimulated genes (ISGs) IFITM2 and 3 as well as IFIT3 exhibited the strongest fold changes and IFIT3 remained downregulated even after return. Impairment of antiviral immunity in winter-over crew can be explained by the downregulation of a battery of ISGs.

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Whole blood transcriptome analysis during 12-months of isolation in the Antarctic.

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Data show an inactivation of key immune functions and pathways without recovery.

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The IFN pathway is most affected showing a downregulation of 14 downstream genes.

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The results suggest impairment of antiviral immunity and vulnerability to infection.

Prospective pilot trial with combination of propranolol with chemotherapy in patients with epithelial ovarian cancer and evaluation on circulating immune cell gene expression

OBJECTIVE

To determine the feasibility of pharmacologic beta-adrenergic blockade in women with newly diagnosed stage II-IV epithelial ovarian cancer (EOC) throughout primary treatment.

METHODS

Patients initiated propranolol prior to beginning chemotherapy or surgery. Feasibility was assessed as proportion able to complete 6 chemotherapy cycles while on adrenergic suppression. Descriptive statistics summarized surveys, and paired changes were analyzed using signed rank tests. Random-intercept Tobit models examined immune response.

RESULTS

Median age was 59.9; 88.5% were stage IIIC/IV; and 38.5% underwent primary debulking. Thirty-two patients were enrolled; 3 excluded because they never took propranolol; an additional 3 didn't meet inclusion criteria, leaving 26 evaluable. Eighteen of 26 (69%), 90% credible interval (CI) of 53-81%, completed 6 chemotherapy cycles plus propranolol (an 82% posterior probability that the true proportion of success is ≥60%). Among the 23 patients with baseline and six month follow up data, overall QOL, anxiety, and depression improved (P < 0.05) and leukocyte expression of pro-inflammatory genes declined (P = 0.03) after completion of therapy. Decrease from baseline of serum IL-6 and IL-8 preceded response to chemotherapy (P < 0.0014). Change from baseline IL-10 preceded complete response.

CONCLUSION

Use of propranolol during primary treatment of EOC is feasible and treatment resulted in decrease in markers of adrenergic stress response. In combination with chemotherapy, propranolol potentially results in improved QOL over baseline.

Beta blocker use correlates with better overall survival in metastatic melanoma patients and improves the efficacy of immunotherapies in mice

Immunotherapy has expanded treatment options for cancers with historically poor outcomes, yet a significant proportion of patients still fail to achieve durable clinical benefit. We defined the contribution of β-adrenergic receptor (βAR) signaling, a component of the stress response, on success of immunotherapy for melanoma since the use of antagonists (β-blockers) is associated with improved clinical outcomes in some cancers. We show that metastatic melanoma patients who received immunotherapy had improved overall survival if they also received pan β-blockers. This retrospective analysis is reinforced by results showing that βAR blockade enhances the control of murine melanoma growth by anti-(α)PD-1 checkpoint blockade. However, this effect was most significant when β-blocker was combined with dual αPD-1 + high dose interleukin-2 therapy and was reproduced by selective blockade of β₂ARs. These results identify a novel strategy that can be quickly introduced to potentially increase the number of patients who benefit from immune-based therapies.

The Salient Stressor Impact Questionnaire (SSIQ)

High stress is known to affect health, but stress impact, determined by events and responses to them, has not been studied systematically. For the Salient Stressor Impact Questionnaire (SSIQ), the impact of events was assumed to depend on their salience and chronicity and the impact of responses on their chronicity and intensity with greater unfavorable appraisal associated with greater response. The SSIQ assessed a person’s two most salient stressors. Chronicity items discriminated between clinically stressed and nonclinical participants and measured the chronicity of stressful feelings (distress) and the event. The remaining items measured the degree of distress and unfavorable appraisal. The SSIQ showed good test-retest and internal consistency reliability, concurrent validity, and stability across diverse populations. Exploratory analyses grouped items into distress, chronicity, and appraisal elements, and confirmatory analysis revealed a good fit to the hypothesized model. Preliminary data suggest that the SSIQ will be useful for studying relationships between stress and health.

Norepinephrine preferentially modulates memory CD8 T cell function inducing inflammatory cytokine production and reducing proliferation in response to activation

BACKGROUND

Norepinephrine (NE) is one of the primary catecholamines of the sympathetic nervous system released during a stress response and plays an important role in modulating immune function. NE binds to the adrenergic receptors on immune cells, including T cells, resulting in either suppressed or enhanced function depending on the type of cell, activation status of the cell, duration of NE exposure and concentration of NE. Here, we aim to analyze the effects of NE on the functionality of naïve (Tn), central memory (Tcm) and effector memory (Tem) CD8 T cells.

METHODS

We isolated CD8 T cell subsets from healthy human adults and treated cells in vitro with NE (1×10(-6)M) for 16h; we then stimulated NE treated and untreated CD8 T cell subsets with antibodies for CD3 and CD28 for 24 and 72h. We assessed the level of beta-2 adrenergic receptor (ADRB2) expression in these cells as well as global gene expression changes in NE treated Tcm cells by microarray analysis. Altered expressed genes after NE treatment were identified and further confirmed by RT-qPCR, and by ELISA for protein changes. We further determined whether the observed NE effects on memory CD8 T cells are mediated by ADRB2 using specific adrenergic receptor agonist and antagonists. Finally, we examined the levels of mRNA and protein of the NE-induced genes in healthy adults with high serum levels of NE (>150pg/mL) compared to low levels (<150pg/mL).

RESULTS

We found that memory (Tcm and Tem) CD8 T cells expressed a significantly higher level of ADRB2 compared to naïve cells. Consequently, memory CD8 T cells were significantly more sensitive than naïve cells to NE induced changes in gene expressions in vitro. Global gene expression analysis revealed that NE induced an elevated expression of inflammatory cytokines and chemokines in resting and activated memory CD8 T cells in addition to a reduced expression of growth-related cytokines. The effects of NE on memory CD8 T cells were primarily mediated by ADRB2 as confirmed by the adrenergic receptor agonist and antagonist assays. Finally, individuals with high serum levels of NE had similar elevated gene expressions observed in vitro compared to the low NE group.

CONCLUSIONS

Our results demonstrate that NE preferentially modulates the functions of memory CD8 T cells by inducing inflammatory cytokine production and reducing activation-induced memory CD8 T cell expansion.

Annual research review: The neuroinflammation hypothesis for stress and psychopathology in children--developmental psychoneuroimmunology

Experimental animal and adult human data suggest that stress exposure is associated with alterations in immune system function that may underlie increased susceptibility to disease and behavioral disorders. The implications of these data for child psychology and psychiatry are not yet clear. The current review seeks to distil and translate the relevant animal and adult human work to children to advance a developmental model of psychoneuroimmunology. In addition to reviewing key specific findings, we consider biological/conceptual models and technical aspects of psychoneuroimmunology work in pediatric populations, and outline the rationales and advantages of integrating hypotheses concerning neuroinflammation in developmental studies of psychopathology.

Serum levels of immunoglobulins (IgG, IgA, IgM) in Antarctic summer expeditioners and their relationship with seasickness

The Antarctic continent is full of environmental extremes like isolation, cold, UV exposure, and blizzards etc. The present study was conducted to analyze the effect of ship borne journey and the impact of Antarctic harsh environment on serum immunoglobulin (IgG, IgM, IgA) levels and their relationship with seasickness in Indian expeditioners. It was observed that one month onboard ship journey induced an increase in serum IgA levels and decrease in IgG levels while after being one month off board at the Indian research station Maitri, decreased levels of IgG and increased levels of IgA were found. IgM levels were not altered in comparison to the base line control. Moreover, serum IgG level showed a positive correlation while IgA level showed a negative correlation with seasickness. The stimulation of human peripheral blood mononuclear cells (PBMCs) with serum of expeditioner at different places showed that IgA at lower dose induces the release of pro-inflammatory IL-1β, and IL-6 cytokines from PBMCs while higher dose of IgA decreases proinflammatory cytokine production. The release of anti-inflammatory cytokines TGF-β1 and IL-10 was not significantly altered. Thus, the present study concluded that ship borne journey and Antarctic environment lead to increased serum IgA levels while decreased IgG levels. It also suggests that serum IgA level could be a possible biomarker for environmental stress.

Leukocyte glucocorticoid receptor expression and immunoregulation in veterans with and without post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is associated with a dysregulation of the hypothalamus-pituitary-adrenal axis (HPA axis). In addition, there is evidence for altered glucocorticoid receptor (GR) expression and function in peripheral blood mononuclear cells. The aim of the present study was to differentiate between the effect of trauma exposure and PTSD on leukocyte GR expression and glucocorticoid immune regulation. Leukocyte GR binding characteristics and glucocorticoid sensitivity of immune activity, determined as the effect of dexamethasone (DEX) on in vitro cytokine release and T-cell proliferation, were compared between veterans with PTSD, traumatized veterans without PTSD and healthy controls. Leukocyte GR density was significantly lower in veterans with and without PTSD compared to healthy controls. DEX-induced inhibition of T-cell proliferation was significantly lower in PTSD compared to trauma and healthy controls. DEX-induced increase in lipopolysaccharide-stimulated interleukin-10 was less pronounced in traumatized veterans with and without PTSD compared to healthy controls. No group differences were observed in the effect of DEX on other cytokines or in baseline immune activity, except for lower tumor necrosis factor-alpha production in PTSD patients compared to healthy controls. The results suggest that trauma exposure is sufficient to induce changes in GR binding characteristics, whereas resistance of T-cell proliferation to DEX only occurs in PTSD. DEX resistance of in vitro immune activity was not a general phenomenon, but was restricted to specific immune functions.

Cytokines in coagulation and thrombosis: a preclinical and clinical review

The cytokine network is a complex and dynamic system, involved in numerous biological responses in the human body. This review of the current literature describes the role of cytokines and their interaction with the coagulation system, specifically in the maintenance of the thrombo-hemorrhagic balance in vivo in human subjects and in animals. In general, cytokines are thrombogenic, but they are amenable to therapeutic manipulations and hence are a potentially attractive tool in the clinician's armamentarium. Studies of the effects of cytokines in vivo are difficult because cytokines act in a very finite microenvironment and, although their actions are significant, they are transient. Most of the available clinical data related to interactions between cytokines and the coagulation system focuses on the role of tumor necrosis factor-alpha and interleukin-1 in septicemia and septic shock. However, several other cytokines and related proteins, such as platelet activating factor and plasminogen activator inhibitor, are also known to influence coagulation and thrombosis. These factors interact closely with cytokines, and have been included in this review for a better understanding of their interactions with traditional cytokines. Studies that utilize cell culture systems do not accurately model the in vivo status of this complex system and, hence, this review has excluded such studies. The role of the cytokine network in coronary artery disease, angiogenesis, or neoplasia has been addressed elsewhere by other workers and is not discussed here. By emphasizing important in vivo interactions, the intention of this review is to serve as an impetus to further translational research, both clinical and in the laboratory.

'Sensitivity syndromes' related to radiation exposures

The primary health effects of radiation are traditionally believed to result from cellular genetic damage. These effects are believed to result in a statistically detectable increase in the induction of cancer in exposed populations. A significant number of residents of areas affected by the Chernobyl disaster and workers involved in the clean-up ('liquidators') have reported debilitating physical illnesses that cannot be easily explained by a genetic effect. This paper presents results of a literature search that strongly suggests that a previously unrecognized neural pathway may be responsible for the induction of these debilities. In addition, a common link between radiation and chemical sensitivity syndromes may now be identified.

Natural killer (NK) cell activity and NK cell subsets in workers with a tendency of burnout

The involvement of cellular immunity in the burnout syndrome remains to be elucidated. We assessed three components of burnout of the Maslach Burnout Inventory: emotional exhaustion; depersonalization (DP); and personal accomplishment, as well as natural killer cell activity (NKCA) and NK cell subsets in 42 male workers. Workers with a higher DP score showed a lower NKCA and a lower proportionality of CD57+CD16+ to total lymphocytes. There were no differences in any of the health behaviors (e.g., smoking, alcohol, or obesity) between workers showing higher burnout and those showing lower burnout. A stepwise multiple regressions analysis demonstrated that NKCA was closely correlated with DP, independent of other variables, including a stress index. These results suggest that the relationship between reduced cellular immunity and DP is not due to traditional work stress or health behavioral problems. Further studies on DP as a psychosomatic disorder as well as an occupational health problem should be performed in the future.

Glucocorticoid-induced type 1/type 2 cytokine alterations in humans: a model for stress-related immune dysfunction

Increased psychologic and physiologic stressors can have profound effects on the immune system. Previously believed to be immunosuppressive, there is mounting evidence that stress may actually induce a shift in the type 1/type 2 cytokine balance toward a type 2 cytokine response. Cortisol is elevated in response to stress and has been reported to alter cytokine production in murine and human peripheral blood mononuclear cells (PBMC). The current investigation examined the effects of dexamethasone (DEX) mimicking basal, stress, and supraphysiologic levels of cortisol on production of interferon-gamma (IFN-gamma) (type-1), interleukin (IL)-12p40 (type 1), IL-10 (type 2), and IL-4 (type 2) by human PBMC. Both supraphysiologic and stress levels of DEX decreased production of type 1 cytokines and either increased or maintained production of type 2 cytokines PBMC stimulated with phytohemagglutinin (PHA), immobilized anti-CD3, lipopolysaccharide (LPS) or tetanus. Although preincubation with DEX was sufficient to induce a type 2 switch in short-term mitogen cultures, PBMC cultures for extended periods of time required DEX at the initiation and throughout the duration of culture. Mifepristone, a glucocorticoid receptor antagonist, blocked the DEX-induced shift in the type 1/type 2 cytokine balance. These data demonstrated the ability of the glucocorticoid dexamethasone, to induce a shift in the type 1/type 2 cytokine balance toward a type 2 cytokine response and simulate the type 1/type 2 cytokine alterations observed in in vivo stress models. This model will allow detailed investigation of the cellular and molecular mechanisms of stress-induced immune alterations in humans.

Inhibitory effect of pregnancy on stress-induced immunosuppression through corticotropin releasing hormone (CRH) and dopaminergic systems

To clarify the involvement of pregnancy in the response of the neuroendocrine-immune system to stress, we examined splenic natural killer-cell-activity-(NKCA) and its relevant central and blood parameters in female virgin and pregnant rats (10 to 11 days gestation) exposed to forced water-immersion stress with durations of 90 min and 180 min. Decreases in splenic NKCA, corticotropin releasing hormone (CRH) in the hypothalamus, and increases in progesterone (P), beta-endorphin (beta EP), and dopamine (DA) metabolic ratios in the frontal cortex and nucleus accumbens produced by stress were recognized in the virgin rats, but not in the pregnant rats. Pregnancy reduced splenic NKCA in rats without stress, but elevated it in the rats exposed to stress with a duration of 180 min. These findings suggest inhibitory effects of pregnancy on stress-induced immunosuppression and neuroendocrine changes, thereby promoting homeostasis in the neuroendocrine-immune system against stress. Such enhanced homeostasis associated with pregnancy seemed to be mediated by the activation of placental P and placental or pituitary beta EP in cooperation with mesocortical and mesolimbic DA systems and hypothalamic CRH.

Plasma catecholamine and lymphocyte beta 2-adrenergic receptor alterations in elderly Alzheimer caregivers under stress

OBJECTIVE

The purpose of this study was to determine the effects of chronic stress on beta-adrenergic physiology in elderly spousal caregivers to Alzheimer patients.

METHODS

Thirty-seven elderly spousal caregivers and matched noncaregiver controls (mean age 73 years, SD = 6) were studied. Life stress categorization (presence of marked threat) covering the previous 6 months was determined using a semistructured interview based on the Psychiatric Epidemiological Research Inventory and the Life Events and Difficulties Schedule. beta 2-adrenergic receptor sensitivity (isoproterenol-stimulated cyclic AMP accumulation) and density were determined in lymphocytes.

RESULTS

Caregivers with high life stress had higher plasma norepinephrine levels (p < .04) but no change in plasma cortisol. For beta-receptor sensitivity, 30% of the variance was accounted for by high life stress rating, increased age, being male, and lower norepinephrine (p = .018); 17% of the variance in beta-receptor density was accounted for by plasma norepinephrine (p = .03).

CONCLUSIONS

The findings demonstrate that chronic high stress may be associated with changes in adrenergic physiology and may provide a mechanism through which chronic stress alters cellular immunity.

Evaluation of stress induced by flight activity by measuring the hormonal response

The aim of the present study was to quantitatively investigate the different levels of adaptation to flight and to evaluate the hormonal response to flight activity as a possible reliable tool to quantify the level of stress induced by flight. The hormonal response of growth hormone (GH), cortisol, and prolactin (PRL) to flight activity was evaluated in a group of student pilots (n = 11; all male; age 20 +/- 2 years) and flight instructors (n = 11; all male; age 27 +/- 2 years) of an Italian Air Force flight school. Blood samples were obtained immediately before and after a training flight session. Hormonal determination by RIA technique after flight showed a significant increase of plasma hormonal levels of GH, PRL, and cortisol in the students. Conversely, in the instructors only GH showed a significant increase versus preflight values, whereas PRL and cortisol did not show significant differences. Moreover, preflight hormonal levels of GH and PRL were significantly higher for student pilots compared to the same values for flight instructors. The data lead to establishing a close correlation between the hormonal response to flight activity and the level of tolerance and adaptation to flight-induced stress.

Psychogenic stress induces chromosomal and DNA damage

In this investigation, rats subjected to swim stress showed within 24 hours significant increases in both the level of chromosome aberrations and Sister Chromatid Exchanges (SCEs) in bone marrow cells. The generality of cytogenetic damage by behavioral stressors was demonstrated by exposing rats to both cold-and warm-water forced swims, to white noise, and to continuous or intermittent inescapable foot shock stress (IFS). The induction of chromosome aberrations and SCEs, to differing degrees, by stressors that differ both quantitatively and qualitatively, demonstrates that this is a general phenomenon of stress. The use of an additional measure, unscheduled DNA Synthesis (UDS) showed that stress-induced genotoxic damage can occur in a second cell type and on a molecular as well as chromosomal level. These results indicate that there may be a cellular genetic basis for some of the effects of stress.

Demonstration of the "anti-stress" activity of an extract of Ginkgo biloba (EGb 761) using a discrimination learning task

1. Young (4-month-old) and old (20-month-old) rats, maintained under water restriction, were trained to discriminate to obtain a small amount of drinking water as a reward. Each animal had to learn to press a lever corresponding to a light that was randomly distributed on the left or right. 2. Introduction of an auditory perturbation ("stress") during the discriminative phase of learning modified the capacity and rate of acquisition in both young and old animals, changes that were correlated with increases in plasma concentrations of epinephrine, norepinephrine and corticosterone. 3. Stress-induced detrimental changes in both discrimination learning and plasma hormones were suppressed by 20 days of oral treatment with an extract of Ginkgo biloba leaves (EGb 761; 50 or 100 mg/kg/day) in both young and old rats, effects that became statistically significant by the third day of learning (time of maximal acquisition rate). 4. EGb 761 treatment was less effective in increasing the percentage of efficient lever presses in old than in young rats, but more effective in decreasing the number of inefficient lever presses and reaction time in the older animals. 5. These results indicate that EGb 761 can facilitate behavioral adaptation despite adverse environmental influences, a property that supports its clinical use in treating cognitive impairment, especially in elderly patients.

Inhibition of murine splenic T lymphocyte proliferation by 2-deoxy-D-glucose-induced metabolic stress

Female Swiss-Webster mice were injected with the glucose analogue 2-deoxy-D-glucose (2-DG), which when administered to rodents induces acute periods of metabolic stress. A single or multiple injections of 2-DG invoked a stress response, as evidenced by increases in serum corticosterone levels. The influence of this metabolic stressor on the blastogenic potential of splenic T lymphocytes was then examined. It was found that one, two, or three injections of 2-DG resulted in depressed T cell proliferative responses, with an attenuation of the effect occurring by the fifth injection. The 2-DG-induced inhibition of T cell proliferation was not attributable to 2-DG-induced cytolysis, as in vitro incubation of naive T cells with varying concentrations of 2-DG did not result in a reduction in cell number or viability, and flow cytometric analysis demonstrated that percentages of CD3, CD4, and CD8 splenic T cells were not altered as a result of 2-DG-induced stress. Incubating naive T cells in varying concentrations of 2-DG resulted in a dose-dependent inhibition of T cell blastogenic potential. Following in vivo exposure to 2-DG, T cell proliferation did not return to normal levels until 3 days after the cessation of 2-DG injections. Administering the beta-adrenergic receptor antagonist propranolol did not reverse the inhibited lymphoproliferation in 2-DG-treated mice. The inhibition in T cell proliferation was not observed, however, in mice that had been adrenalectomized or hypophysectomized and injected with 2-DG.(ABSTRACT TRUNCATED AT 250 WORDS)

Social separation and reunion affects immune system in juvenile rhesus monkeys

Removal of juvenile rhesus monkeys from their natal social group to indoor individual caging resulted in increased basal cortisol secretion and significant decrements in the frequency of lymphoid subpopulations. Fourteen juvenile rhesus monkeys, which had never been removed from the group, were studied. Baseline immune and cortisol measurements were obtained before seven of the subjects were removed from social housing to standard individual cages. The remaining seven subjects, matched for age, sex, weight, and rank, remained in the social group throughout the study serving as controls. Blood samples were taken 24 hours after removal of the test subjects from the group and at specific intervals thereafter through 11 weeks. At 24 hours after the separation test subjects showed a significant increase in basal cortisol levels (40%) and a significant decrease in several immune parameters, with absolute numbers of total T cells declining 72 +/- 12%. Significant group differences in immune parameters persisted through 11 weeks. Eighteen weeks following removal, the test subjects were returned to the group which produced a cortisol rise in both test and controls at the 24-hour postreturn sample. Although there were no group differences in the frequency of lymphoid subsets 24 hours after return, some test subjects showed marked decrements which were inversely related to cortisol and were predicted by behavioral events. These data demonstrate that the removal of naive juvenile rhesus monkeys from their natal social group to individual indoor caging is a potent psychosocial stressor and that the behavioral interactions which characterize the return of the individual subjects to the natal group may predict physiological response.

Formation of a new social group of unfamiliar female rhesus monkeys affects the immune and pituitary adrenocortical systems

Social stress associated with the formation of a new group of rhesus monkeys resulted in increased basal cortisol secretion and significant decreases in immunological parameters. Eight adult female rhesus monkeys, all of which had been raised in social groups, but with no common social history, were simultaneously introduced into an outdoor enclosure along with an adult male. Behavioral data were collected during the introduction and over 9 weeks thereafter. Blood samples were collected prior to and at intervals for 9 weeks following formation. The establishment of a dominance hierarchy, apparent within 48 h, was accomplished with no serious fighting and a complete absence of wounding or trauma. Overall, the group showed a significant increase in cortisol and a significant decrease in the absolute number of total lymphocytes and CD4+ and CD8+ T cells at 24 h postformation, but not thereafter. However, when partitioned into high and low dominance rank, differences in CD4+ and CD8+ T cells were evident for up to 9 weeks with low ranking subjects showing significantly lower values. The housing condition of the subjects immediately prior to introduction, either indoors in individual caging or outdoors in social groups, may have influenced behavior, rank acquisition, and possibly differences in immune parameters. These data demonstrate that social group formation is a potent psychosocial stressor in primates, since stress-sensitive changes were observed in the absence of serious aggression and wounding.