Stability of individual differences in cellular immune responses to acute psychological stress

What moderates salivary markers of inflammation reactivity to stress? A descriptive report and meta-regression

As the assessment of salivary markers of inflammation gains popularity in stress research, understanding factors that influence these markers' reactivity to stress is important. A recent meta-analysis synthesized literature on changes in salivary markers of inflammation in response to acute stressors in adults. As a supplement to this, we present pre-registered moderator analyses of salivary markers of inflammation responses to acute stress. Analyses included data from 27 studies (35 unique study samples). Outcomes were Cohen's d effect sizes for salivary biomarkers interleukin-1 beta (IL-1β), IL-6, IL-10, and tumor necrosis factor-alpha (TNF-α), from pre- to post-stress. Moderators included: college education levels of the study sample; percent of the study sample that identified as African-American; body mass index (BMI); use of a resting baseline saliva sample; and use of a social evaluative stressor. Descriptive results on saliva sample timing were also examined. Biomarkers peaked 0-60 minutes after the end of the stressor. Before removing influential outliers, no moderators of salivary inflammation reactivity emerged, though not all moderators could be tested due to missing data. After removing one influential outlier study, higher study sample average BMI was associated with greater salivary IL-1β reactivity to stress (b = 0.41, p=.007). For every 1-unit increase in study sample average BMI, effect sizes for IL-1β increased by 0.41 units. These findings suggest BMI may be important to examine when assessing salivary markers of inflammation in response to stress. As this field expands, it is important to replicate these results and consider the role of other moderators of salivary markers of inflammation reactivity to stress.

Sleep and Parasympathetic Activity During Rest and Stress in Healthy Adolescents and Adolescents With Bipolar Disorder

OBJECTIVE

Sleep disruption contributes to the pathophysiology of mental disorders, particularly bipolar illness, but the biobehavioral mechanisms of this relationship are insufficiently understood. This study evaluated sleep duration, timing, and variability as prospective predictors of parasympathetic nervous system activity during rest and social stress in adolescents with bipolar disorder, reflecting sleep-related interference in stress regulatory systems that may confer vulnerability to mood episodes.

METHOD

Participants were adolescents with bipolar disorder (n = 22) and healthy adolescents (n = 27). Sleep duration and timing were measured by actigraphy for 1 week before a laboratory social stress task, during which high-frequency heart rate variability (HF-HRV) was indexed using electrocardiography. Multilevel models were used to evaluate group, sleep characteristics, and their interactions as predictors of initial HF-HRV and change in HF-HRV during rest and stress.

RESULTS

Associations between group and changes in HF-HRV during stress were moderated by sleep duration mean (z = 2.24, p = .025) and variability (z = -2.78, p = .006). There were also main effects of mean sleep duration on initial HF-HRV during rest (z = -5.37, p < .001) and stress (z = -2.69, p = .007). Follow-up analyses indicated that, in bipolar adolescents during stress, shorter and longer sleep durations were associated with lower initial HF-HRV (z = -5.44, p < .001), and greater variability in sleep duration was associated with less change in HF-HRV (z = -2.18, p = .029).

CONCLUSIONS

Sleep durations that are relatively short or long, which are characteristic of mood episodes, are associated with parasympathetic vulnerability to social stress in adolescents with bipolar disorder. Obtaining regular sleep of moderate duration may favorably affect responses to stress in bipolar youth.

Acute psychological stress increases serum circulating cell-free mitochondrial DNA

Intrinsic biological mechanisms transduce psychological stress into physiological adaptation that requires energy, but the role of mitochondria and mitochondrial DNA (mtDNA) in this process has not been defined in humans. Here, we show that similar to physical injury, exposure to psychological stress increases serum circulating cell-free mtDNA (ccf-mtDNA) levels. Healthy midlife adults exposed on two separate occasions to a brief psychological challenge exhibited a 2-3-fold increase in ccf-mtDNA, with no change in ccf-nuclear DNA levels, establishing the magnitude and specificity for ccf-mtDNA reactivity. In cell-based studies, we show that glucocorticoid signaling - a consequence of psychological stress in humans - is sufficient to induce mtDNA extrusion in a time frame consistent with stress-induced ccf-mtDNA increase. Collectively, these findings provide evidence that acute psychological stress induces ccf-mtDNA and implicate neuroendocrine signaling as a potential trigger for ccf-mtDNA release. Further controlled work is needed to confirm that observed increases in ccf-mtDNA result from stress exposure and to determine the functional significance of this effect.

The interaction between positive schizotypy and high sensitivity C-reactive protein on response inhibition in female individuals

This study aimed to measure the associations between high sensitivity C-reactive protein (hsCRP), childhood maltreatment (CM), schizotypy and response inhibition, and to explore the interactions between hsCRP, CM and schizotypy on response inhibition. Two hundred and fourteen participants completed the Stop-Signal Task (SST), the Schizotypy Personality Questionnaire (SPQ) and the Childhood Trauma Questionnaire-Short Form (CTQ), which measured response inhibition, schizotypy and history of CM respectively. The level of hsCRP was also measured. The high schizotypy group (n = 114) had higher scores on SPQ and CTQ, higher hsCRP levels and longer SST reaction times (SSRTs) than the low schizotypy group (n = 100). In female participants, SSRT had a positive correlation with the SPQ positive factor and the disorganized SPQ factor and a positive correlation with physical neglect. HsCRP was positively correlated with the SPQ negative factor and positive SPQ factor. In male participants, SSRT was negatively correlated with emotional neglect and physical neglect. The majority of correlations between CTQ and SPQ variables were significant in both female and male participants. In female participants, hsCRP significantly predicted SSRT, and hsCRP significantly interacted with positive schizotypy in predicting SSRT.

Social stress response in adolescents with bipolar disorder

OBJECTIVE

Theoretical models posit that stressors contribute to the onset and maintenance of bipolar disorder in adolescence through disruptions in stress physiology, but physiological response to stressors has not been evaluated in adolescents with bipolar illness. The present study tests the hypothesis that adolescents with bipolar disorder will have greater reactivity to a laboratory social stress task than healthy adolescents.

METHOD

Adolescents with bipolar illness (n = 27) and healthy adolescents (n = 28) completed a modified version of the Trier Social Stress Task. Stress response was assessed using high frequency heart rate variability (HF-HRV), heart rate (HR), mean arterial blood pressure (MAP), salivary cortisol, and subjective stress. Multilevel models were used to test for group differences in resting-state physiology, and stress reactivity and recovery.

RESULTS

Adolescents with bipolar disorder had greater reactivity in HF-HRV (z = 3.32), but blunted reactivity in MAP (z = -3.08) and cortisol (z = -2.60), during the stressor compared to healthy adolescents. They also had lower resting HF-HRV (z = -3.49) and cortisol (z = -2.86), and higher resting HR (z = 3.56), than healthy adolescents.

CONCLUSIONS

These results indicate that bipolar disorder is associated with disruptions in autonomic and endocrine response to stress during adolescence, including greater HF-HRV reactivity. Further research should evaluate whether these individual differences in stress physiology precede and predict the onset of mood episodes.

Early life socioeconomic status associates with interleukin-6 responses to acute laboratory stress in adulthood

It is proposed that environmental exposures in early life influence immune programming. Specifically, socioeconomic disadvantage is thought to program an immune phenotype that is prone to inflammation and associated with increased risk for inflammatory disease later in life. Existing literature shows an inverse association of early childhood socioeconomic status (SES) with adult levels of systemic inflammation. Here, we extend that literature to examine whether early childhood SES also relates to the magnitude of inflammatory response to acute psychological stress in adulthood. Healthy volunteers (N = 110; 40-58 years; 59% female; 90% white) performed a laboratory stress protocol, with blood samples drawn at the end of a 30-min baseline, a 5-min speech task, and a 30-min recovery to assess interleukin (IL)-6 stress responses. An early childhood SES index was derived from reports of parental home and vehicle ownership, and number of bedrooms per child in the home across ages 1-2, 3-4, and 5-6. Regressions adjusted for current age, sex, race, and BMI showed that lower SES at age 1-2 was associated with larger IL-6 stress responses in adulthood (ΔR² = 0.05, β = -0.24, p = .03). This association was independent of adult SES and task-evoked affective responses. No association was found between SES at ages 3-4 or 5-6 and IL-6 responses. These results provide initial evidence for a link between disadvantage in the first 2 years of life and heightened inflammatory response to stress in adulthood; this link may contribute to the increased disease risk that accompanies being raised in disadvantaged socioeconomic circumstances.

Sex differences in the association between stressor-evoked interleukin-6 reactivity and C-reactive protein

Individuals differ consistently in the magnitude of their inflammatory responses to acute stressors, with females often showing larger responses than males. While the clinical significance of these individual differences remains unclear, it may be that greater inflammatory responses relate to increased systemic inflammation and thereby risk for chronic inflammatory disease. Here, we examined whether acute stressor-evoked interleukin (IL)-6 responses associate with resting levels of C-reactive protein (CRP), a marker of systemic inflammation, and whether this association differs by sex. Subjects were 57 healthy midlife adults (30-51years; 33% female; 68% white). Blood was drawn before and 30-min after two mental stress tasks: a multisource interference task and a Stroop color word task. Hierarchical regressions controlling for age, sex, race, and BMI tested whether stressor-evoked IL-6 responses were associated with resting CRP and whether this association differed by sex. Results indicated that sex and stressor-evoked IL-6 responses interacted to predict CRP (ΔR²=0.08, B=-1.33, β=-0.39, p=0.02). In males, larger stressor-evoked IL-6 responses associated with higher CRP, whereas in females, stressor-evoked IL-6 responses showed a non-significant negative association with CRP. These findings indicate that inflammatory responses to acute stressors associate with resting levels of CRP; however, this association differs by sex. Previous literature suggests that there are sex differences in stressor-evoked IL-6 responses, but this is the first study to show sex differences in the relationship between acute inflammatory responses and systemic inflammation. The contribution of these sex differences to inflammatory disease risk warrants further investigation.

Resting heart rate, physiological stress and disadvantage in Aboriginal and Torres Strait Islander Australians: analysis from a cross-sectional study

Background

Lower socioeconomic status has been linked to long-term stress, which can manifest in individuals as physiological stress. The aim was to explore the relationship between low socioeconomic status and physiological stress in Aboriginal and Torres Strait Islander Australians.

Methods

Using data from the eGFR Study (a cross-sectional study of 634 Indigenous Australians in urban and remote areas of northern and central Australia), we examined associations between resting heart rate and demographic, socioeconomic, and biomedical factors. An elevated resting heart rate has been proposed as a measure of sustained stress activation and was used as a marker of physiological stress. Relationships were assessed between heart rate and the above variables using univariate and multiple regression analyses.

Results

We reported a mean resting heart rate of 74 beats/min in the cohort (mean age 45 years). On multiple regression analysis, higher heart rate was found to be independently associated with Aboriginal ethnicity, being a current smoker, having only primary level schooling, higher HbA1c and higher diastolic blood pressure (model R² 0.25).

Conclusions

Elevated resting heart rate was associated with lower socioeconomic status and poorer health profile in Aboriginal and Torres Strait Islander Australians. Higher resting heart rate may be an indicator of stress and disadvantage in this population at high risk of chronic diseases.

Electronic supplementary material

The online version of this article (doi:10.1186/s12872-016-0211-9) contains supplementary material, which is available to authorized users.

Cardiovascular reactivity to acute psychological stress following sleep deprivation

OBJECTIVE

Psychological stress and sleep disturbances are highly prevalent and are both implicated in the etiology of cardiovascular diseases. Given the common co-occurrence of psychological distress and sleep disturbances including short sleep duration, this study examined the combined effects of these two factors on blood pressure reactivity to immediate mental challenge tasks after well-rested and sleep-deprived experimental conditions.

METHODS

Participants (n = 20) were healthy young adults free from current or past sleep, psychiatric, or major medical disorders. Using a within-subjects crossover design, we examined acute stress reactivity under two experimental conditions: after a night of normal sleep in the laboratory and after a night of total sleep deprivation. Two standardized psychological stress tasks were administered, a Stroop color-word naming interference task and a speech task, which were preceded by a prestress baseline period and followed by a poststress recovery period. Each period was 10 minutes in duration, and blood pressure recordings were collected every 2.5 minutes throughout each period. Mean blood pressure responses during stress and recovery periods were examined with a mixed-effects analysis of covariance, controlling for baseline blood pressure.

RESULTS

There was a significant interaction between sleep deprivation and stress on systolic blood pressure (F(2,82.7) = 4.05, p = .02). Systolic blood pressure was higher in the sleep deprivation condition compared with the normal sleep condition during the speech task and during the two baseline periods.

CONCLUSIONS

Sleep deprivation amplified systolic blood pressure increases to psychological stress. Sleep loss may increase cardiovascular risk by dysregulating stress physiology.

Negative affective responses to a speech task predict changes in interleukin (IL)-6

Laboratory studies show that individuals differ appreciably in the magnitude of their inflammatory responses to acute psychological stress. These individual differences are poorly understood, yet may contribute to variation in stress-associated disease vulnerability. The present study examined the possibility that affective responses to acute stress contribute to these differences. For this purpose, 102 relatively-healthy community volunteers (mean age 50 years; 60% female; 91.2% white) performed an acute stress protocol and measures of affective state and serum levels of the proinflammatory cytokine, interleukin (IL)-6 were collected at the end of a 30-min resting baseline, a 5-min evaluative public speaking task, and a 30-min recovery period. Results of regression analyses, controlling for age, race, gender, menopausal status, and body mass index, revealed a positive association of task-related increases in anger and anxiety with increases in IL-6 (R² change = .08, p = .004; R² change = .08, p = .005, respectively). Further examination showed that these affective responses to the task were independent predictors of change in IL-6. Cardiovascular reactivity to the task did not explain the association. These results suggest that individuals who exhibit angry or anxious responses to acute challenge are more vulnerable to stress-related increases in markers of systemic inflammation, possibly rendering them more susceptible to inflammatory disease.

When is enough measurement, enough? Generalizability of primate immunity over time

A statistical generalizability analysis gauges the degree to which a single assessment of a parameter successfully estimates that measure over repeated assessments for that individual. The generalizability of enumerative and functional immune parameters was estimated for two species of macaque monkeys assessed every 3 months between 18 and 42 months of age. Subjects were cross-balanced by species (bonnet, Macaca radiata, n=22; pigtail, Macaca nemestrina, n=21), sex (male, n=21; female, n=22), and brief early maternal separation with reunion (control, n=21; separated, n=22). Cell subset analysis showed the best generalizability (35-69%). Natural cytotoxicity also performed well (44-70%), but when computed on a lysis per cell basis, removing the effect of cell phenotype, it was less stable (15-48%). For most immune parameters, at least 5 assessments would be necessary to establish conventionally reliable (0.80) characterizations of long-term, stable individual differences in immunity, and three for minimally reliable (0.60) characterizations. More reactive parameters, as well as more behaviorally reactive species, yielded more generalizable results. Cell subsets that are typically most sensitive to acute stress (CD8, CD16) were more stable than other subsets (CD4, CD20). Behaviorally reactive species (pigtail) yielded more stable natural cytotoxicity results than the less reactive species (bonnet). Sex and rearing condition (early, brief maternal separation) did not substantially affect generalizability, although females tended to generate more stable results than did males.

Mobilization of gammadelta T lymphocytes in response to psychological stress, exercise, and beta-agonist infusion

The mobilization of cytotoxic lymphocytes, such Natural Killer (NK) cells and CD8(+) T cells, during stress and exercise is well documented in humans. However, humans have another cytotoxic lymphocyte subset that has not been studied in this context: the Gamma Delta (gammadelta) T lymphocyte. These cells play key roles in immune processes including the elimination of bacterial infection, wound repair and delayed-type hypersensitivity reactions. The current study investigated the effects of stress, exercise, and beta-agonist infusion on the mobilization of gammadelta T lymphocytes. Three separate studies compared lymphocytosis in response to an acute speech stress task (n=29), high (85%W(max)) and low (35%W(max)) intensity concentric exercise (n=11), and isoproterenol infusion at 20 and 40 ng/kg/min (n=12). Flow cytometric analysis was used to examine lymphocyte subsets. gammadelta T lymphocytes were mobilized in response to all three tasks in a dose-dependent manner; the extent of mobilization during the speech task correlated with concomitant cardiac activation, and was greater during higher intensity exercise and increased dose of beta-agonist infusion. The mobilization of gammadelta T lymphocytes was greater (in terms of % change from baseline) than that of CD8(+) T lymphocytes and less than NK cells. This study is the first to demonstrate that gammadelta T cells are stress-responsive lymphocytes which are mobilized during psychological stress, exercise, and beta-agonist infusion. The mobilization of these versatile cytotoxic cells may provide protection in the context of situations in which antigen exposure is more likely to occur.

Stress and childhood asthma risk: overlapping evidence from animal studies and epidemiologic research

Rapidly expanding evidence increasingly strengthens the evidence linking psychological factors to asthma and allergy expression. Parallel studies in animals and humans demonstrating the influence of prenatal maternal stress and early caregiving experiences on the disrupted regulation of defensive biological systems [eg, sympathetic and adrenomedullary (SAM) system and the hypothalamicpituitary-adrenocortical (HPA) axis] provide strong proof of concept for this line of research. The consequent altered neuroimmune responses may influence the expression of immune-mediated disorders such as asthma as well as enhance an individual's susceptibility to other environmental factors that may also contribute to asthma risk.

Longitudinal analysis of pro- and anti-inflammatory cytokine production in severely fatigued adolescents

In the adolescent population, fatigue is associated with somatic complaints, unrefreshing sleep, cognitive disturbances and symptoms of depression and anxiety. This pattern of symptoms resembles the one described in chronic fatigue syndrome (CFS). Since immunological alterations have been reported in CFS patients, we wondered whether also severely fatigued girls from a healthy population would show comparable alterations in psychological and immunological parameters. We tested this hypothesis in a longitudinal design, allowing a reliable assessment of the participants' characteristic immune status. Groups of severely fatigued (N=67) and non-fatigued (N=61) participants were selected. Severely fatigued girls reported more depressive symptoms, anxiety, reduced sleep quality, and somatic and CFS-related symptoms than non-fatigued participants across three measurements during one year (T1: spring, T2: autumn, T3: spring). In contrast, no group differences in mitogen-induced cytokine production or T-cell proliferation in vitro or in leukocyte subset counts were observed. Although absolute cytokine production and cell counts were affected by seasonal variation, the within-subject values, relatively to the rest of the participants, were fairly stable. Data from a small group of CFS patients (N=11) showed similarities in self-reported complaints between CFS patients and fatigued participants. Interestingly, CFS patients showed a distinct immune profile when compared to the severely fatigued or non-fatigued participants, i.e. increased levels of anti-inflammatory cytokines (IL-10, decreased IFN-gamma/IL-10 ratio) and reduced levels of pro-inflammatory cytokines (IL-6, TNF-alpha) over all three time points analyzed. These results show that, although overlap in symptomatology between the general population and patients with CFS was observed, only CFS patients show a skewing of the cytokine balance towards an anti-inflammatory profile.

Prenatal maternal stress and early caregiving experiences: implications for childhood asthma risk

There is still much debate as to the pathways through which some children develop asthma and others do not. One possible mechanism outlined here concerns the way in which stress may influence the neuroendocrine system and thence the immune system. Supporting evidence from animal experiments suggests that maternal prenatal stress may be of importance, resulting in programming of the infant's HPA axis. In addition, social stressors during the early part of a child's life may also affect the HPA axis and thence dysregulation of immune system functioning with implications for the development of asthma.

Effects of footbathing on autonomic nerve and immune function

The purpose of this study was to investigate the effects of footbathing on autonomic nerve and immune function. Eleven healthy female volunteers (aged 22-24 years) undertook footbaths at 42 degrees C for 10 min, with or without additional mechanical stimulation (air bubbles and vibration). Autonomic responses were evaluated by electrocardiography and spectral analysis of heart rate variability, and by measurement of blood flow in the sural region. White blood cell (WBC) counts, ratios of lymphocyte subsets, and natural killer (NK) cell cytotoxicity were used as indicators of immune function. Footbathing with mechanical stimulation produced (1) significant changes in the measured autonomic responses, indicating a shift to increased parasympathetic and decreased sympathetic activity and (2) significant increases in WBC count and NK cell cytotoxicity, suggesting an improved immune status. Because these physiological changes are likely to be of benefit to health, our findings support the use of footbathing in nursing practice.

The effect of acute psychologic stress on systemic and rectal mucosal measures of inflammation in ulcerative colitis

BACKGROUND & AIMS

Recent studies suggest that life events and chronic stress increase the risk of relapse in inflammatory bowel disease. Our aim was to study the effects of acute psychologic stress on systemic and rectal mucosal inflammatory responses in patients with inactive ulcerative colitis (UC).

METHODS

Twenty-five patients with inactive UC and 11 healthy volunteers (HV) underwent an experimental stress test. Ten patients with UC and 11 HV underwent a control procedure. Before and after each procedure, systemic inflammatory response was assessed by serum interleukin (IL)-6 and IL-13 concentrations, tumor necrosis factor (TNF)-alpha and IL-6 production by lipopolysaccharide (LPS)-stimulated whole blood, leukocyte count, natural killer (NK) cell numbers, platelet activation, and platelet-leukocyte aggregate (PLA) formation. In patients with UC, rectal mucosal inflammation was assessed by TNF-alpha, IL-13, histamine and substance P release, reactive oxygen metabolite (ROM) production, mucosal blood flow (RMBF) and histology.

RESULTS

Stress increased pulse (P < .0001) and systolic BP (P < .0001). In UC, stress increased LPS-stimulated TNF-alpha and IL-6 production by 54% (P = .004) and 11% (P = .04), respectively, leukocyte count by 16% (P = .01), NK cell count by 18% (P = .0008), platelet activation by 65% (P < .0001), PLA formation by 25% (P = .004), mucosal TNF-alpha release by 102% (P = .03), and ROM production by 475% (P = .001) and reduced rectal mucosal blood flow by 22% (P = .05). The control protocol did not change any of the variables measured. There were no differences between the responses of the patients with UC and HV.

CONCLUSIONS

Acute psychologic stress induces systemic and mucosal proinflammatory responses, which could contribute to exacerbations of UC in ordinary life.

Does subjective burden of early breast cancer and its treatment affect immune measures during adjuvant therapy?

Psychosocial factors have been described as affecting cellular immune measures in healthy subjects. In patients with early breast cancer we explored bi-directional psycho-immune effects to determine whether subjective burden has an impact on immune measures, and vice versa. Patients (n = 239) operated for early breast cancer and randomized into International Breast Cancer Study Group (IBCSG) adjuvant clinical trials were assessed immediately before the beginning of adjuvant treatment (baseline) and 3 and 6 months thereafter, at the beginning of the corresponding treatment cycle. Cellular immune measures (leukocytes, lymphocytes, lymphocyte subset counts), markers of activation of the cellular immune system (beta2-microglobulin, soluble interleukin-2 receptor serum levels), and self-report subjective burden (global indicators of physical well-being, mood, coping effort) were assessed concurrently. The relationship between subjective burden and gradients of immune measures was investigated with regression analyses controlling for adjuvant treatment. There was a pattern of small negative associations between all variables assessing subjective burden before the beginning of adjuvant therapy with the gradients of the markers of activation of the cellular immune system and NK cell counts. In particular, better mood predicted a decline in the course of beta2-microglobulin and IL-2r at months 3 and 6. The gradient of beta2-microglobulin was associated with mood and coping effort at month 3. However, the effect sizes were very small. In conclusion, in this explorative investigation, there was an indication for subjective burden affecting and being affected by markers of activation of the cellular immune system during the first 3 and 6 months of adjuvant therapy. The question of clinical significance remains unanswered. These associations have to be investigated with refined assessment tools and schedules.

Alternative modalities for asthma that reduce stress and modify mood states: evidence for underlying psychobiologic mechanisms

OBJECTIVE

To review the evidence supporting a role for psychological interventions in the treatment of asthma, with particular emphasis on underlying psychobiological mechanisms.

DATA SOURCES

Independent literature searches on MEDLINE, PREMEDLINE, Cochrane Library, and PSYCHINFO from their respective inception to 2003 were performed. Separate searches were performed for psychological stress and asthma, psychoneuroimmunology and asthma, stress management, relaxation, asthma, complementary and alternative medicine and asthma, and immune function and psychological intervention. The search was not limited based on language of publication.

STUDY SELECTION

Supportive evidence from overlapping research was included based on the expert opinion of the author and through discussions with consultants in the field.

RESULTS

This review first discusses human and animal studies focused on psychological stress and the effects of stress on the neuroendocrine and immune system, emphasizing the implication of these effects on asthma. Second, studies that evaluated the influence of stress reduction modalities on neuroendocrine and immune function were examined. Existing evidence from human clinical studies that explored the role of psychological interventions for asthma is reexamined in this context.

CONCLUSIONS

A growing appreciation of the interactions among behavioral, neural, endocrine, and immune processes suggests possible mechanisms through which psychological interventions for asthma may be operating. This review provides a framework in which we can begin to see links among these systems that might provide new insights to guide future explorations.

Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry

The present report meta-analyzes more than 300 empirical articles describing a relationship between psychological stress and parameters of the immune system in human participants. Acute stressors (lasting minutes) were associated with potentially adaptive upregulation of some parameters of natural immunity and downregulation of some functions of specific immunity. Brief naturalistic stressors (such as exams) tended to suppress cellular immunity while preserving humoral immunity. Chronic stressors were associated with suppression of both cellular and humoral measures. Effects of event sequences varied according to the kind of event (trauma vs. loss). Subjective reports of stress generally did not associate with immune change. In some cases, physical vulnerability as a function of age or disease also increased vulnerability to immune change during stressors.

Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry

The present report meta-analyzes more than 300 empirical articles describing a relationship between psychological stress and parameters of the immune system in human participants. Acute stressors (lasting minutes) were associated with potentially adaptive upregulation of some parameters of natural immunity and downregulation of some functions of specific immunity. Brief naturalistic stressors (such as exams) tended to suppress cellular immunity while preserving humoral immunity. Chronic stressors were associated with suppression of both cellular and humoral measures. Effects of event sequences varied according to the kind of event (trauma vs. loss). Subjective reports of stress generally did not associate with immune change. In some cases, physical vulnerability as a function of age or disease also increased vulnerability to immune change during stressors.

Increases in lipids and immune cells in response to exercise and mental stress in patients with suspected coronary artery disease: effects of adjustment for shifts in plasma volume

This study examined the role of shifts in plasma volume on lipid and immune reactions to stress. Lipid, immune, rheological, and cardiovascular reactions to exercise and mental stress in 51 patients with suspected coronary artery disease were determined. Blood pressure and heart rate were measured during and blood samples taken at the end of each rest and task. Lipids (total cholesterol, triglycerides, HDL, LDL) and immune cells (lymphocytes, monocytes, granulocytes) increased with exercise, whereas cholesterol, LDL, and lymphocytes increased with mental stress. Plasma volume decreased by 1 and 5% following mental and exercise stress, respectively. The task-induced increases in lipids were no longer statistically significant following adjustment for changes in plasma volume, whereas the increases in immune cell numbers survived such correction. This study provides evidence that, in coronary artery disease patients, exercise and mental stress-induced increases in lipids but not immune cells can be largely accounted for by shifts in plasma volume.

Long-term immune-endocrine effects of bereavement: relationships with anxiety levels and mood

Psychological, endocrine and immune parameters were measured over a 6-month period in 14 healthy subjects who underwent an unpredictable acute emotional stress (e.g. sudden death of a loved one) compared with 14 controls who did not. Probands were profoundly stressed as assessed 10 days after bereavement by their scores on the Hamilton Rating Scales of Anxiety and Depression, adrenocorticotropin and cortisol plasma concentrations, and non-suppression in response to dexamethasone. Functional alterations of immune parameters, such as responsiveness of peripheral blood lymphocytes to mitogens, were found 40 days after bereavement. Despite a normal number of circulating lymphocyte subsets, the functional activity of natural killer (NK) cells was markedly reduced at day 40. Changes in the intracellular concentration of beta-endorphin in peripheral blood mononuclear cells correlated with anxiety and depression scores. Controls showed no changes in psychometric, endocrine and immune measures during the 6-month study. Cluster analysis revealed two groups of bereaved subjects with different patterns of immune and endocrine changes: (1) Five subjects, characterized by harm-avoidant temperament and long-lasting dysphoric mood, showed reduced responsiveness of peripheral blood lymphocytes to mitogens, decreased NK cell activity and non-suppression in response to dexamethasone that persisted for 6 months. (2) Nine subjects showed significant changes only during the early phase after bereavement. Our data suggest that the immunological consequences of stress do not simply overlap with psychological and endocrine alterations, and are particularly severe and long-lasting in a subgroup of subjects, indicating the importance of individual variability in the capacity to cope with stress.

Stable individual differences in physiological response to stressors: implications for stress-elicited changes in immune related health

Stress reactivity refers to a stable individual difference in response to stressors. This article addresses three questions about reactivity: (1) Are cardiovascular, endocrine, and immune responses to acute laboratory stressors stable over time and across stressor tasks? (2) Are cardiovascular, endocrine, and immune reactors the same people? and (3) Are reactive people more vulnerable to stressor-induced effects on susceptibility to infectious disease? We conclude that for many individual indicators of physiological responsiveness to stressors there is moderate stability over time and across stressor tasks indicating the possible existence of underlying dispositional characteristics; the commonality of immune and cardiovascular and hormonal responses to stress depend on the nature of regulation of the immune response being assessed; reactivity appears to have implications for vulnerability to stressor-associated disease risk (stress-by-reactivity interaction) in the natural environment, but the exact nature of this vulnerability is not as yet entirely clear.

The effects of acute psychological stress on lymphocyte adhesion molecule expression and density in cardiac versus vascular reactors

This study examined the effects of acute psychological stress on lymphocyte subsets and their differential changes according to their cell adhesion molecule expression in cardiac versus vascular reactors. We classified 49 subjects into cardiac or vascular reactors based on the participants' cardiac output or total peripheral resistance reactivity to a speech presentation task. Analysis demonstrated that there were no significant differences in lymphocyte counts or adhesion molecule expression between cardiac and vascular reactors at rest. Cardiac reactors showed a significant decrease of surface density of CD62L on mixed lymphocytes (p <.001) as well as on CD4 (p <.01) and CD8 T-cells (p <.001). There was also a disproportionate increase in the number of CD62L(-) T cells compared to CD62L(+) T cells only in cardiac reactors (p <.001). There were no significant effects of the stressor observed in vascular responders. The findings replicate previous studies demonstrating associations between cardiovascular and immune responses to acute stress and extends those findings by suggesting that the relationship is more significant in individuals who increase their blood pressure primarily through a cardiac mechanism.

Stress-related immune changes in middle-aged and older women: 1-year consistency of individual differences

This study reviews prior research and reports longer-term consistency of stress-related immune variables in middle-aged and older women who performed mental math and speech tasks 2 times 1 year apart. Leukocyte subsets, mitogen-induced lymphocyte proliferation, and natural killer cell activity were measured at baseline, after tasks, and after 30-min recovery. Epstein-Barr virus (EBV) antibody titers were assessed at baseline. Pearson coefficients and standardized maximum-likelihood estimates of year-to-year covariances for leukocyte subsets and EBV titers showed moderately high to high baseline and posttask consistency and lower recovery consistency; consistency for other functional immune assays and reactivity scores for all variables was moderate to low. Results support longitudinal study of psychosocial context effects on tonic immune function and posttask scores.

Temporal stability of acute stress-induced changes in leukocyte subsets and cellular adhesion molecules in older adults

This study investigated the temporal stability of enumerative immune and catecholamine responses to acute psychosocial stress in 67 Alzheimer's caregivers ages 56-82 years (45 women and 22 men) who were required to prepare and deliver two 3-min speeches on three occasions at 2-week and 6-week intervals. All leukocyte subsets and adhesion molecules (CD62L and CD11a) changed significantly from rest to postspeak at each of the three testing sessions (p's <.0005). Responses showed moderate to high temporal stability across baseline and absolute task values (r's =.65-.96). Reliability was predictably lower for both forms of change scores (r's = -.16-.64). The level of temporal stability achieved is comparable to that seen previously in younger adults, indicating that acute psychosocial stress produces reliable changes in circulating leukocytes and cell adhesion molecules in older adults.

Reactivity and vulnerability to stress-associated risk for upper respiratory illness

OBJECTIVE

We tested the hypothesis that the greater a person's laboratory stress-elicited elevation in cortisol, the greater the life stress-related risk for upper respiratory infection (URI). We also tested the prediction that the greater the laboratory stress-elicited rise in natural killer cell (NK) cytotoxicity, the smaller the life stress-related URI risk. Finally, we explored whether sympathetic nervous system (SNS) and enumerative immune reactivities to laboratory stress moderate the relation between life stress and URI.

METHODS

At baseline, 115 healthy subjects were administered a negative stressful life events checklist and were tested to assess their SNS (blood pressure, heart rate, and catecholamines), HPA (cortisol), and immune (NK cell cytotoxicity and lymphocyte subsets) reactivities to laboratory speech tasks administered 2 weeks apart. Responses were averaged across the two laboratory assessments to create reactivity scores. After these assessments were completed, participants were followed weekly for 12 consecutive weeks. At each follow-up they completed a measure of perceived stress experienced over the last week. They were also instructed to contact the study coordinator if they had a cold or flu at any time during follow-up. A health care worker verified reported illnesses.

RESULTS

In a traditional prospective analysis, high cortisol reactors with high levels of life events had a greater incidence of verified URI than did high reactors with low levels of life events and low reactors irrespective of their life event scores. Using hierarchical linear modeling, CD8(+) number, Natural Killer (NK) cell number, and NK cell cytotoxicity, each interacted with weekly perceived stress levels in predicting concurrent occurrences of self-reported URIs. For these outcomes, low immune reactors were more likely to experience an URI during high stress than low stress weeks. High immune reactors did not exhibit differences in weekly URIs as a function of weekly stress level. The SNS reactivity markers did not moderate the association of stress and URI incidence in either analysis.

CONCLUSIONS

Acute HPA and immune responses to laboratory stressors are markers of how vulnerable people are to the increased risk for URI associated with stressors in the natural environment.

Psychoneuroimmunology and psychosomatic medicine: back to the future

OBJECTIVE

Although psychological modulation of immune function is now a well-established phenomenon, much of the relevant literature has been published within the last decade. This article speculates on future directions for psychoneuroimmunology research, after reviewing the history of the field.

METHODS

This review focuses on human psychoneuroimmunology studies published since 1939, particularly those that have appeared in Psychosomatic Medicine. Studies were clustered according to key themes, including stressor duration and characteristics (laboratory stressors, time-limited naturalistic stressors, or chronic stress), as well as the influences of psychopathology, personality, and interpersonal relationships; the responsiveness of the immune system to behavioral interventions is also addressed. Additionally, we describe trends in populations studied and the changing nature of immunological assessments. The final section focuses on health outcomes and future directions for the field.

RESULTS

There are now sufficient data to conclude that immune modulation by psychosocial stressors or interventions can lead to actual health changes, with the strongest direct evidence to date in infectious disease and wound healing. Furthermore, recent medical literature has highlighted a spectrum of diseases whose onset and course may be influenced by proinflammatory cytokines, from cardiovascular disease to frailty and functional decline; proinflammatory cytokine production can be directly stimulated by negative emotions and stressful experiences and indirectly stimulated by chronic or recurring infections. Accordingly, distress-related immune dysregulation may be one core mechanism behind a diverse set of health risks associated with negative emotions.

CONCLUSIONS

We suggest that psychoneuroimmunology may have broad implications for the basic biological sciences and medicine.

Cortisol mediates redistribution of CD8+ but not of CD56+ cells after the psychological stress of public speaking

The present study investigated the question if a pharmacological blockade of cortisol release with stress affects lymphocyte redistribution in healthy volunteers. It was expected that the well known increases in the number of CD8+ (T-suppressor/cytotoxic cells) and CD56+ (natural killer cells) after stress would not be downregulated in the absence of an appropriate cortisol response, since redistribution is markedly influenced by glucocorticoids. In a double blind design, forty healthy male volunteers were exposed to a brief psychological stressor (public speaking) and received a single oral dose of dexamethasone [DEX] (N=20) or placebo (N=20) the evening before the main experiment. Ratings on emotional states and blood samples for determination of hormones, CD8+, and CD56+ cell counts were obtained at different time points during the experiment. Stress of public speaking led to highly significant increases in catecholamine and cortisol concentrations, to subjective discomfort and, most pronounced, to high increases in the number of CD8+ and CD56+ cells. DEX neither influenced baseline levels of mood, catecholamines and cell numbers nor stress induced responses of mood and catecholamines. However, during the whole experiment cortisol concentrations were suppressed in the DEX-condition and the number of CD8+, but not CD56+, cells remained elevated at the end of the session, while in the placebo condition the numbers of these cells were decreased to baseline levels. The data demonstrate that cortisol seems to play an important role in stress induced redistribution patterns of CD8+ but not CD56+ cells. This, however, can be explained by different migration processes between those cells (e.g. different targets of migration) and, therefore, different glucocorticoid influences on target tissues.

The relationship of depression and stressors to immunological assays: a meta-analytic review

This is a broad meta-analysis of the relations of both depression and stressors to immunological assays. The number of study samples (greater than 180) and measures (greater than 40) is much more extensive than any so far. Analyses are done by both fixed and random effects. By a fixed-effects analysis, both major depression and naturally occurring acute stressors are associated with (1) an overall leukocytosis, (2) mild reductions in absolute NK-cell counts and relative T-cell proportions, (3) marginal increases in CD4/CD8 ratios, and (4) moderate decreases in T- and NK-cell function. However, the degree of heterogeneity of the studies' results raises questions about their robustness. Therefore, we also did the first random effects analysis to estimate what is likely to appear in future studies. For depression, the analysis showed the immunological correlates included (1) an overall leukocytosis, manifesting as a relative neutrophilia and lymphoenia; (2) increased CD4/CD8 ratios; (3) increased circulating haptoglobin, PGE(2), and IL-6 levels; (4) reduced NK-cell cytotoxicity; and (5) reduced lymphocyte proliferative response to mitogen. For stressors, the random effects analysis showed that future studies are likely to find the following effects: (1) an overall leukocytosis, manifesting as an absolute lymphocytosis; (2) alterations in cytotoxic lymphocyte levels, CD4/CD8 ratios, and natural killer cell cytotoxicity with the direction of change depending on the chronicity of the stressor; (3) a relative reduction of T-cell levels; (3) increased EBV antibody titers; (4) reduced lymphocyte proliferative response and proportion of IL-2r bearing cells following mitogenic stimulation; and (5) increased leukocyte adhesiveness. The random-effects analysis revealed that for both major depression and naturally occurring stressors the following effects are shared: leukocytosis, increased CD4/CD8 ratios, reduced proliferative response to mitogen, and reduced NK cell cytotoxicity. The implications for these findings for disease susceptibility and the pathophysiology of these conditions is discussed.

The stability of and intercorrelations among cardiovascular, immune, endocrine, and psychological reactivity

One hundred fifteen college students were exposed to an evaluative speech task twice, separated by 2 weeks. At both sessions, we assessed cardiovascular, endocrine, immune, and psychological response at baseline and during the task. We found stability across sessions for stress-induced increases in anxiety and task engagement, heart rate, blood pressure, norepinephrine (but not epinephrine), cortisol, natural killer cell cytotoxicity, and numbers of circulating CD3+, CD8+, and CD56+ (but not CD4+ or CD19+) lymphocytes. The stable cardiovascular, immune, and endocrine reactivities were intercorrelated, providing evidence of a unified physiological stress response across these outcomes. Although stable stress-induced increases in task engagement were associated with the physiological stress responses, stress-induced anxiety was not.

Individual differences in peripheral blood immunological and hormonal measures in adult male rhesus macaques (Macaca mulatta): evidence for temporal and situational consistency

A growing body of research has indicated that consistent individual differences exist in physiological systems with which the immune system interacts. Few data have been reported that demonstrate stable individual differences in immunological measures, however. In the present study, enumerative measures of immune system activity were examined in 36 adult male rhesus macaques over a 13 month period under baseline conditions as well as under conditions of pharmacological and physical challenge. Blood samples were assayed for plasma concentrations of ACTH and cortisol, as well as neutrophil, total lymphocyte, CD4+ and CD8+ lymphocyte numbers, and the CD4/CD8 ratio. Analyses revealed that individual differences in the CD4/CD8 ratio and, to a lesser extent, plasma ACTH and cortisol concentrations, and neutrophil and CD4+ lymphocyte numbers were consistent across situations and times, despite changes in mean values during the various blood sampling sessions. The results suggest that the CD4/CD8 ratio might be considered trait-like and a useful immunological measure of biobehavioral organization.

A prospective study of neuroendocrine and immune alterations associated with the stress of an oral academic examination among graduate students

Stressful experiences may influence neuroendocrine, immune and cytokine functioning, as well as physical and psychological well being. The present prospective investigation assessed physiological and behavioral variations in anticipation of a critical oral academic examination among graduate students (i.e. related to a dissertation or comprehensive defense). Relative to matched control subjects, plasma cortisol levels were elevated among graduate students, especially females, 1 h prior to the oral examination, but not 6-8 weeks earlier (at about the time of the submission of the written document). In contrast, mitogen-stimulated (Con-A) lymphocyte proliferation was only reduced 6-8 weeks before the examination. Neither adrenocorticotrophic hormone (ACTH), prolactin, serum interleukin-1beta (IL-1beta) nor mitogen stimulated IL-1beta production was influenced at any time. Although, graduate students did not differ from controls with respect to perceived stress and feelings of mastery, they reported more frequent malaise (e.g. headaches, sore throat, fatigue) than did controls. The present findings suggest that during the course of lengthy anticipatory periods preceding a scheduled stressor, different stress-sensitive, situation-dependent biological processes may be engendered. It is further suggested that cortisol release is most closely aligned with immediate threats, while the immune alterations are sensitive to more distal events, or are subject to adaptation in response to a protracted stressor.

Modulation of secretory immunoglobulin A in saliva; response to manipulation of mood

Secretory immunoglobulin A (sIgA) measured in saliva, an index of mucosal immunity, has repeatedly been shown to be sensitive to psychological variables. Chronic stress is downregulatory whereas an acute psychological challenge induces mobilisation. We examined whether an acute manipulation of mood to induce negative hedonic tone would be downregulatory, as in the chronic stress paradigm and further, whether induction of positive mood might have opposite effects. Two separate experiments were conducted. In the first, mood manipulation was by mental recall and in the second by music. For both sIgA concentration and sIgA secretion rate there was a significant elevation in response to the mood manipulation by recall regardless of hedonic tone. There was some evidence that for sIgA secretion rate the response was more pronounced for positive mood. Mood induction by music also resulted in significant elevations in sIgA concentration and secretion rate and responses were not distinguished by mood valence. None of the mood induction procedures was associated with changes in free cortisol. In these studies, we found no evidence that transient lowering of mood was downregulatory for salivary sIgA. The predominant finding was of sIgA mobilisation.

Negative emotions and acute physiological responses to stress

One pathway through which stressors are thought to influence physiology is through their effects on emotion. We used meta-analytic statistical techniques with data from nine studies to test the effects of acute laboratory stressors (speech, star mirror-image tracing, handgrip) on emotional (undifferentiated negative emotion, anger, anxiety) and cardiovascular (CV) response. In all of the studies, participants responded to stressors with both increased CV response and increased negative emotion. Increases in negative emotion were associated with increases in CV response across tasks, however, these associations were small. The range of variance accounted for was between 2% and 12%. Thus, the contribution of negative emotion, as assessed in these studies, to physiological responses to acute laboratory stressors was limited. Although these results raise questions about the role of emotion in mediating stress-elicited physiological responses, the nature of the acute laboratory stress paradigm may contribute to the lack of a strong association.

Modification of the plasma cortisol response to stress in rainbow trout by selective breeding

Male and female rainbow trout were segregated into high- and low-responding individuals (HR, LR) on the basis of their plasma cortisol response to a 3-h period of confinement imposed at monthly intervals for 5 months. Consistent divergence was obtained in the responsiveness of the two groups, although the difference between LR and HR groups was greater in female fish (56 c.f. 116 ng ml(-1)) than in males (45 c.f. 69 ng ml(-1)). Progeny groups (full-sib families) were obtained from the pairing of HR males and females and LR males and females. A third progeny group (US) was obtained by random pairing of parents which were not selected as HR or LR. Poststress plasma cortisol levels in the progeny were first tested at 6 months after hatch and were significantly correlated with the response of the corresponding parental groups, HR > US > LR (178, 126, 81 ng ml(-1), respectively). The difference in responsiveness between LR and HR groups was demonstrated in all four subsequent tests over a 12-month period. There were no significant differences in baseline plasma cortisol levels in LR and HR groups prior to confinement. During a 4-h period of confinement, the differences in plasma cortisol levels between LR and HR fish were sustained throughout, indicating that the trait upon which the fish were selected was related to absolute maximum levels of circulating cortisol and not to the rate of change of cortisol levels during exposure to a stressor. A moderately high heritability (h(2)) for confinement-induced plasma cortisol of 0.41 was obtained by a parent-progeny regression. Manipulation of stress responsiveness in fish by selective breeding offers scope for optimizing performance under intensive rearing conditions but also provides a useful research tool for investigating the operation of the endocrine stress response.

Review of psychosocial stress and asthma: an integrated biopsychosocial approach

Environmental stressors may impact asthma morbidity through neuroimmunological mechanisms which are adversely impacted and/or buffered y social networks, social support, and psychological functioning. In addition, life stress may impact on health beliefs and behaviours that may affect asthma management. Whereas earlier psychosomatic models have supported a role for psychological stress in contributing to variable asthma morbidity among those with existing disease, a growing appreciation of the interactions between behavioural, neural, endocrine, and immune processes suggest a role for these psychosocial factors in the genesis of asthma as well. While a causal link between stress and asthma has not bee established, this review provides a framework in which we can begin to see links between these systems that might provide new insights to guide future explorations. The complexity of these interactions underscore the need for a multidisciplinary approach which combines the idea that the origin of asthma is purely psychogenic in nature with the antithetical consideration that the biological aspects are all important. These distinctions are artificial, and future research that synthesizes biological, psychological, sociocultural, and family parameters is urgently needed to further our understanding of the rising burden of asthma.

Repressive/defensive coping, endogenous opioids and health: how a life so perfect can make you sick

Hyperactivity of endogenous opioid systems has been postulated to mediate the associations between defensive/repressive coping styles, enhanced stress responsivity, and reduced immunocompetence. Study 1 examined whether repressive/defensive coping would be associated with greater sensitivity to opioid antagonism. Judgments of the painfulness of ascending series of electrocutaneous stimulation applied to the forearm were determined before and after the administration of naloxone and placebo in 38 men and 42 women. All subjects were healthy with a mean age of 32.9 years. Naloxone (10 mg i.v.) and placebo were administered in double-blind fashion and counterbalanced. Subjects were classified as High- and Low-defensive and repressive copers on the basis of scores on the Marlowe-Crowne Social Desirability Scale and the Balanced Inventory of Desirable Responding, respectively. High Self-Deception was associated with naloxone-induced hyperalgesia, whereas no effects of naloxone on pain ratings were observed in low-Self-Deceptive subjects. In Study 2, resting plasma beta-endorphin levels were found to be positively correlated with defensiveness in men (n = 26), but not women (n = 44). Study 3 examined 82 healthy subjects (mean age = 28.7 years). Beta-endorphin/defensiveness correlations were found to be greater following, compared to prior to, electrical nociceptive stimulation in men (n = 49), but unrelated in women (n = 33). These findings are consistent with the hypothesized endorphinergic dysregulation associated with repressive/defensive coping styles and are discussed in terms of the immuno-regulatory implications of such a dysregulation.

Stressor-induced alteration of cytokine production in multiple sclerosis patients and controls

OBJECTIVE

We administered an acute psychological stressor to multiple sclerosis (MS) patients and normal controls to determine whether differences in subjective and physiological responses to stress may underlie the susceptibility of MS patients to stress-related exacerbations.

METHOD

Twenty-five MS patients (18 female, 7 male) and 25 age- and gender-matched controls participated in the study. They were asked to give a 5-minute videotaped speech defending themselves in a hypothetical scenario in which they were wrongly accused of stealing. Subjective and autonomic responses were monitored, and blood was sampled at baseline, 5, 20, and 60 minutes after the stressor to assess mitogen-stimulated production of interleukin-1beta(IL-1beta), interleukin-4 (IL-4), tumor necrosis factor-alpha (TNF-alpha), and interferon-gamma (IFN-gamma).

RESULTS

MS patients and controls demonstrated similar subjective and physiological responses to the stressor that were independent of gender, mood, and disability status. The macrophage-derived cytokines IL-1beta and TNF-alpha were increased during the stressor, and remained elevated through 60 minutes. Th1 lymphocyte-derived IFN-gamma production also was increased at 5 and 60 minutes relative to baseline; however, there was no change in the Th2 lymphocyte-derived cytokine IL-4.

CONCLUSIONS

These results favor the hypothesis that MS patients do not differ in stress response from normal controls; however, psychological stress may enhance cellular immune responses that would be potentially harmful to MS patients.

Selective reduction in CD2 expression on CD2bright/CD8+ lymphocytes from cynomolgus monkeys (Macaca fascicularis) in response to acute stress

Numerous reports have demonstrated a link between stressful stimuli and immune suppression. However, the cellular mechanisms by which stress impairs immune function are largely unknown. We have examined the effects of an acute stressor on the T cell population, specifically, the number and phenotype of T cells in a nonhuman primate model. In nonstressed adult monkeys, we found differences in the level of expression of CD2 on T cells, revealing two distinct subsets of T cells, CD2dim and CD2bright cells, with CD2bright cells predominately coexpressing CD8. In response to acute stress, we observed a significant loss in the number and percent of CD2bright/CD8+ cells, with percent of CD2bright cells returning to pre-stress values within 24 h.

Neuroendocrine measures and lymphocyte subsets in depressive illness: influence of a clinical interview concerning life experiences

The effects of a clinical interview concerning either positive or negative day-to-day events on lymphocyte subpopulations, and on plasma cortisol, ACTH and norepinephrine, were determined in depressive patients (major depressive and dysthymic) and in normal controls. Irrespective of its content, the interview provoked an elevation of circulating natural killer (NK) cells, suggesting that this effect was related to either a change in mood state (regardless of its valence) or to the stress associated with the interview procedure. Since the interview did not influence plasma cortisol, ACTH or norepinephrine, it is likely that the NK cell variations were independent of these endocrines. Although basal NK cells were elevated in the depressive group relative to controls, the extent of the NK cell increase provoked by the interview was comparable in depressive and control subjects. The failure to detect differences between these populations could not be attributed to ceiling effects precluding more pronounced alterations in the depressed subjects. Indeed, variations of circulating cell subtypes were found to be exquisitely sensitive to differences in stressor intensity. In a subset of control subjects, a more potent stressor (anticipation of an academic examination) increased the plasma endocrine levels, increased circulating NK cell number beyond that associated with the interview stress, and provoked an increase of several T cell subsets (CD3, CD4 and CD8). Evidently, while a clinical interview may be sufficiently stressful to influence circulating NK cells, the stress of such a procedure seems no greater in depressed than in control subjects. It is suggested that although depressed patients may exhibit higher basal NK levels, this effect is likely not related to increased reactivity to stressors.

Variations of lymphocyte subsets associated with stress in depressive populations

Major depression and dysthymia have been associated with increased perception of day-to-day stressors, greater reliance on emotion-focused coping efforts, and reduced perception of uplifting events. Moreover, it has been observed that levels of circulating natural killer (NK) cells were elevated in depressed patients. Given that mild stressors may increase circulating NK cells, it is conceivable that the elevated NK cells in depression may be secondary to the increased stress perception associated with the illness. In the present investigation a laboratory stressor, comprising a mathematical challenge, increased circulating NK cells; however, the extent of the increase was comparable in depressive, dysthymic and control subjects. Moreover, the increased NK cells induced by the stressor procedure appeared to be independent of variations of plasma cortisol, ACTH or norepinephrine. Interestingly, although the NK changes were not differentially influenced by stressors in the subject populations, in the major depressive patients correspondence existed between NK cell levels and emotion-focused coping styles. Likewise, the response to a laboratory stressor was directly related to the severity of depression and to the use of coping styles involving cognitive restructuring or problem solving.

Immunologic response to acute psychological stress in MS patients and controls

To determine whether MS patients differ from healthy subjects in stress-related immune changes, we examined immunologic alterations following a public speaking task in 25 MS patients and 25 healthy controls. Both groups demonstrated similar autonomic, neuroendocrine and immunologic responses to acute stress. Neutrophils, monocytes, CD8+ suppressor/cytotoxic T-lymphocytes and NK-cells transiently increased, with parallel changes in NK-cell activity. T-cell proliferation declined at 20 min, followed by increased reactivity at 60 min relative to baseline. This data suggests that stress-induced immune alterations remain intact in MS patients, and may contribute to immune changes associated with disease exacerbation.