Characterization of the central nervous system innervation of the rat spleen using viral transneuronal tracing.

Splenic immune function is modulated by sympathetic innervation, which in turn is controlled by inputs from supraspinal regions. In the present study, the characterization of central circuits involved in the control of splenic function was accomplished by injecting pseudorabies virus (PRV), a retrograde transynaptic tracer, into the spleen and conducting a temporal analysis of the progression of the infection from 60 hours to 110 hours postinoculation. In addition, central noradrenergic cell groups involved in splenic innervation were characterized by dual immunohistochemical detection of dopamine-beta-hydroxylase and PRV. Infection in the CNS first appeared in the spinal cord. Splenic sympathetic preganglionic neurons, identified in rats injected with Fluoro-Gold i.p. prior to PRV inoculation of the spleen, were located in T(3)-T(12) bilaterally; numerous infected interneurons were also found in the thoracic spinal cord (T(1)-T(13)). Infected neurons in the brain were first observed in the A5 region, ventromedial medulla, rostral ventrolateral medulla, paraventricular hypothalamic nucleus, Barrington's nucleus, and caudal raphe. At intermediate survival times, the number of infected cells increased in previously infected areas, and infected neurons also appeared in lateral hypothalamus, A7 region, locus coeruleus, subcoeruleus region, nucleus of the solitary tract, and C3 cell group. At longer postinoculation intervals, infected neurons were found in additional hypothalamic areas, Edinger-Westphal nucleus, periaqueductal gray, pedunculopontine tegmental nucleus, caudal ventrolateral medulla, and area postrema. These results demonstrate that the sympathetic outflow to the spleen is controlled by a complex multisynaptic pathway that involves several brainstem and forebrain nuclei.

Identification of delta- and mu-type opioid receptors on human and murine dendritic cells.

The purpose of this study was to evaluate mu- and delta-opioid receptors (OR) on human and murine dendritic cells (DC). Expression of mu- and delta-OR mRNA on DC was demonstrated by RT-PCR. The immunocytochemical and Western blot analyses revealed the expression of OR protein in DC. Radioreceptor assay demonstrated the specific saturated temperature-dependent binding of [3H]-labeled opioid ligand on DC and B(max)=2.8+/-0.3 fmol/10(6) cells and K(D)=4.8+/-1.0 nM were calculated by a Scatchard analysis. Finally, OR ligands DADLE and DAGO dose-dependently modulated the capacity of DC to induce T cell proliferation in an MLR assay. Importantly, expression of functional OR on DC was significantly increased upon TNF-alpha-induced DC maturation. Thus, these data suggest a new mechanism of opioid-dependent neuroendocrine immunomodulation.

Associations between stress, trait negative affect, acute immune reactivity, and antibody response to hepatitis B injection in healthy young adults.

Eighty-four healthy graduate participants were administered the standard course of 3 hepatitis B vaccinations. Five months after the first dose (shortly after the second injection), each participant completed psychosocial measures, and a blood sample was drawn for determination of hepatitis B surface antibody titer. After completion of the vaccination series, participants performed an acute stress protocol, consisting of a 30-min adaptation period and a 5-min evaluative speech task. Blood was drawn at the end of the resting and task periods for assessment of cellular immune measures. Lower antibody response, as assessed after the second hepatitis B injection, was predicted independently by (a) high trait negative affect and (b) diminished T-cell proliferation in response to PHA. These data provide evidence that trait negative affect and the magnitude of stress-induced suppression of immune function may have clinical significance.

Psychological stress and antibody response to immunization: a critical review of the human literature.

OBJECTIVE: The objective of this review was to evaluate the evidence for the hypothesis that psychological stress influences antibody response to immunization in humans. METHODS: A critical review of the literature was conducted. RESULTS: The evidence supports an association between psychological stress and suppression of humoral immune (antibody) response to immunization. This association is convincing in the case of secondary immune response but weak for primary response. The lack of consistent evidence for a relation with primary response may be attributed to a failure to consider the critical points when stress needs to be elevated in the course of the production of antibody. Lower secondary antibody responses were found among patients with chronically high levels of stress (severe enduring problems or high levels of trait negative affect). These responses were found most consistently among older adults. Lower secondary responses were also found for those reporting acute stress or negative affect, but only in studies of secretory immunoglobulin A antibody in which psychological and antibody measures were linked very closely in time. Health practices did not mediate relations between stress and antibody responses; however, there were indications that elevated cortisol levels among stressed patients could play a role. Evidence also suggests the possible influences of dispositional stress-reactivity and low positive affect in the inhibition of antibody production. CONCLUSIONS: The literature supports a relationship between psychological stress and antibody responses to immunizations. The data are convincing in the case of secondary response but weak for primary response. More attention to the kinetics of stress and antibody response and their interrelations is needed in future research.

Role of locus coeruleus in foot shock-evoked Fos expression in rat brain.

The robust activation of locus coeruleus neurons in response to a variety of stressors, in conjunction with the widespread outputs of the locus coeruleus, suggest that the locus coeruleus may be important in mediating responses to stress. Previous studies in rats have demonstrated that exposure to foot shock elicits Fos expression, a marker of neuronal activation, in the locus coeruleus and other brain sites. In order to evaluate the involvement of the locus coeruleus in foot shock-induced activation of other brain sites, shock-induced Fos expression was examined in the locus coeruleus and other brain areas known to be activated by foot shock, following direct inhibition of the locus coeruleus by local infusion of muscimol, a GABA agonist, prior to foot shock. Control rats received infusions of artificial cerebrospinal fluid into the locus coeruleus or muscimol into areas outside of locus coeruleus. Rats infused with artificial cerebrospinal fluid and then exposed to foot shock had significant increases in Fos expression in several brain areas, including locus coeruleus, nucleus O, several subdivisions of the hypothalamus, subnuclei of amygdala, bed nucleus of the stria terminalis and cingulate cortex. Inhibition of the locus coeruleus prior to foot shock significantly inhibited Fos expression in the locus coeruleus, nucleus O, some subdivisions of the hypothalamus including the magnocellular and medial parvicellular paraventricular hypothalamic nucleus, subnuclei of amygdala, and cingulate cortex. In contrast, inhibition of the locus coeruleus did not affect shock-induced Fos expression in other areas, including certain subdivisions of the hypothalamus and bed nucleus of the stria terminalis. We suggest that foot shock may activate multiple pathways, with activation of certain discrete nuclei requiring input from the locus coeruleus and activation of others occurring independently of locus coeruleus input.

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.

Personality and tonic cardiovascular, neuroendocrine, and immune parameters.

Although there is now abundant evidence that certain personality features constitute risk factors for negative health outcomes, personality measures have received little attention to date in the behavioral immunology literature. The present study assessed the relationship between major dimensions of personality and tonic cardiovascular, neuroendocrine, and immunologic parameters in 276 healthy adults. Participants who scored low in agreeableness tended to have higher levels of systolic blood pressure, diastolic blood pressure, and epinephrine. Low levels of extraversion were associated with higher blood pressure, epinephrine, norepinephrine, and natural killer cell cytotoxicity. Neuroticism was generally unrelated to physiologic outcomes. Personality was not associated with leukocyte subset counts. The magnitude of relationships between personality and physiology was modest, with personality measures accounting for 1 to 7% of the variance in selected physiological parameters. Health practices did not mediate associations between personality and physiologic outcomes. However, a substantial proportion of the relationship between extraversion and natural killer cell cytotoxicity was accounted for by their common association with epinephrine and to a lesser extent norepinephrine. These findings are consistent with the notion that personality contributes to basal physiology and provide a foundation for further research on the relationship between personality and natural killer cell cytotoxicity.

Relation between aerobic fitness level and stress induced alterations in neuroendocrine and immune function.

Alterations in neuroendocrine and immune function were examined in sedentary (n=15) (VO2peak; 31.4+/-0.7 ml x kg(-1) x min(-1); 24.4+/-1.2yr), moderately active (n=15) (VO2peak; 45.4+/-1.1 ml x kg(-1) x min(-1); 24.2+/-1.1 yr) and aerobically trained (n=15) (VO2peak; 58.8+/-0.9 ml x kg(-1) x min(-1); 24.3+/-1.0 yr) men following exposure to an acute mild psychological stressor. Subjects had 2 min to prepare, and 3 min to deliver a speech in front of 3 observers. Blood samples were drawn from an indwelling catheter before, during and 30 min following the speech task (ST). Self-reported measures of anxiety were obtained prior to and immediately following the stressor. The ST resulted in significant alterations in the number and function of immune cells, and in self-reported anxiety scores. Plasma levels of norepinephrine increased during the speech task. The neuroendocrine and immune response to the chosen stressor were independent of subject aerobic fitness level.

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.

Injection of corticotropin-releasing hormone into the locus coeruleus or foot shock increases neuronal Fos expression.

Previous research suggests that corticotropin-releasing hormone can act in the locus coeruleus to increase the firing of locus coeruleus neurons and elicit physiological responses resembling those associated with stress. The present study used immunocytochemical detection of Fos as a measure of neuronal activation to identify brain areas that were activated by bilateral injections of corticotropin-releasing hormone into the locus coeruleus of rats. Injection of corticotropin-releasing hormone into the locus coeruleus increased the expression of Fos in the locus coeruleus as compared with injection of vehicle into the locus coeruleus or injection of corticotropin-releasing hormone into neighbouring pontine sites. The pattern of Fos expression throughout the brain after injections of corticotropin-releasing hormone into the locus coeruleus was generally consistent with the anatomical organization of efferent projections arising from the locus coeruleus; increased Fos expression was observed in many brain areas including the ventral lateral septum, septohypothalamic nucleus, bed nucleus of the stria terminalis, the central amygdaloid nucleus, the dorsomedial nuclei of the hypothalamus, and the thalamic paraventricular and rhomboid nuclei. Foot shock also increased Fos expression in the locus coeruleus and the other brain regions that expressed Fos after corticotropin-releasing hormone injections into the locus coeruleus. A few brain regions, most notably the hypothalamic paraventricular nucleus, expressed Fos in response to foot shock but not corticotropin-releasing hormone. These results indicate that local injection of corticotropin-releasing hormone into the locus coeruleus stimulates the activity of the locus coeruleus neurons. However, the pattern of Fos expression throughout the brain evoked by injection of corticotropin-releasing hormone into the locus coeruleus does not fully replicate the effects of foot shock.

Types of stressors that increase susceptibility to the common cold in healthy adults.

Two-hundred seventy-six volunteers completed a life stressor interview and psychological questionnaires and provided blood and urine samples. They were then inoculated with common cold viruses and monitored for the onset of disease. Although severe acute stressful life events (less than 1 month long) were not associated with developing colds, severe chronic stressors (1 month or longer) were associated with a substantial increase in risk of disease. This relation was attributable primarily to under- or unemployment and to enduring interpersonal difficulties with family or friends. The association between chronic stressors and susceptibility to colds could not be fully explained by differences among stressed and nonstressed persons in social network characteristics, personality, health practices, or prechallenge endocrine or immune measures.

Immune system differences in men with hypo- or hypercholesterolemia.

Substantial epidemiologic evidence indicates that relative hypocholesterolemia in apparently healthy individuals is associated with increased subsequent mortality from cancer and other nonatherosclerotic causes of death. To test a hypothesis potentially underlying these unexplained associations, we evaluated whether individuals with hypo- and hypercholesterolemia differ in various enumerative and functional indices of the immune system. Nineteen healthy adult men with a mean age of 46 years and a mean total cholesterol concentration of 151 mg/dl constituted a low cholesterol group and were compared with 39 men of a similar age whose total cholesterol averaged 261 mg/dl. Relative to the high cholesterol group, hypocholesterolemic men had significantly fewer circulating lymphocytes, fewer total T cells, and fewer CD8+ cells (P's < 0.05). Trends toward fewer CD4+ cells and less IL-2 release in response to PHA were also noted in the low, compared to the high, cholesterol group. The low and high cholesterol groups did not differ in number of B lymphocytes, level of PHA-induced proliferation, number of natural killer (NK) cells, or degree of NK cytotoxicity. These data provide preliminary evidence of immune system differences in healthy individuals with hypo- and hypercholesterolemia.

Social ties and susceptibility to the common cold.

OBJECTIVE: To examine the hypothesis that diverse ties to friends, family, work, and community are associated with increased host resistance to infection. DESIGN: After reporting the extent of participation in 12 types of social ties (eg, spouse, parent, friend, workmate, member of social group), subjects were given nasal drops containing 1 of 2 rhinoviruses and monitored for the development of a common cold. SETTING: Quarantine. PARTICIPANTS: A total of 276 healthy volunteers, aged 18 to 55 years, neither seropositive for human immunodeficiency virus nor pregnant. OUTCOME MEASURES: Colds (illness in the presence of a verified infection), mucus production, mucociliary clearance function, and amount of viral replication. RESULTS: In response to both viruses, those with more types of social ties were less susceptible to common colds, produced less mucus, were more effective in ciliary clearance of their nasal passages, and shed less virus. These relationships were unaltered by statistical controls for prechallenge virus-specific antibody, virus type, age, sex, season, body mass index, education, and race. Susceptibility to colds decreased in a dose-response manner with increased diversity of the social network. There was an adjusted relative risk of 4.2 comparing persons with fewest (1 to 3) to those with most (6 or more) types of social ties. Although smoking, poor sleep quality, alcohol abstinence, low dietary intake of vitamin C, elevated catecholamine levels, and being introverted were all associated with greater susceptibility to colds, they could only partially account for the relation between social network diversity and incidence of colds. CONCLUSIONS: More diverse social networks were associated with greater resistance to upper respiratory illness.

Chronic social stress, social status, and susceptibility to upper respiratory infections in nonhuman primates.

OBJECTIVE: The objective of the study was to assess the roles of social stress and social status in susceptibility to upper respiratory infection. METHOD: Sixty male cynomolgus monkeys were randomly assigned to stable or unstable social conditions for 15 months. Two markers of social status, social rank and percent of behaviors that were submissive, were assessed at independent observation periods. Endocrine, immune, and behavioral responses were each assessed (at 3-month intervals) during the 9th through 14th months of the study. At the beginning of the 15th month, all animals were exposed to a virus (adenovirus) that causes a common-cold-like illness. The primary outcome was whether or not an animal developed an infection (shed virus) after viral exposure. RESULTS: Although the social instability manipulation was associated with increased agonistic behavior as indicated by minor injuries and elevated norepinephrine responses to social reorganizations, the manipulation did not influence the probability of being infected by the virus. However, low social status (as assessed by either marker) was associated with a substantially greater probability of being infected. It was also associated with less body weight, greater elevated cortisol responses to social reorganizations, and less aggressive behavior. However, none of these characteristics could account for the relation between social status and infection. CONCLUSIONS: Social stress was not associated with susceptibility to infection. However, animals with lower social status were at higher risk than high social status animals.

Lactation alters the effects of conditioned stress on immune function.

During lactation, endocrine function is altered and stress responses are dampened. Stress effects on immune function are partially determined by endocrine factors; therefore, we assessed whether stress similarly alters immune function during lactation. Sprague-Dawley rats were conditioned by exposure to a tone paired with foot shock (2 sessions, 16 shocks each) prior to breeding or were left undisturbed. Lactating (day 10) (Lac) and nonlactating diestrous virgin controls (C) were killed immediately after reexposure to the tone or removal from their home cage. Plasma corticosterone stress responses were dampened in Lac relative to C animals. Peripheral blood lymphocyte proliferation to T cell receptor antibody stimulation was reduced to a similar extent in both experimental groups. Conditioned stress reduced splenocyte proliferation and increased nitrite accumulation in C animals, but not in Lac animals. Mesenteric lymph node lymphocyte proliferation was significantly increased after stress in Lac compared with C animals. Both plasma interleukin-6 (IL-6) and phytohemagglutinin-stimulated splenic IL-6 production were increased in Lac animals compared with C animals after stress exposure. These data indicate that stress-induced alterations may be determined by different regulatory mechanisms within immune compartments and that these effects depend on the physiological state of the organism.

Lymphocyte function and cytokine production during incremental exercise in active and sedentary males and females.

This study examined the effects of acute continuous incremental exercise on lymphocyte mitogenic function and cytokine production in physically active and sedentary males and females. Physically active (n = 32) and sedentary (N = 32) male and female subjects were randomly assigned to an exercise or control condition. Exercise involved a continuous incremental protocol consisting of cycling for 3 periods of 6 min at workrates corresponding to 55%, 70% and 85% VO2peak. Blood samples were drawn from a venous catheter at baseline, 6 min, 12 min and 18 min, and 2 h following completion of exercise. Relative to baseline and control condition the percentage of T (CD3+) and B cells (CD19+) significantly decreased, and the percentage of NK cells (CD3-CD16+CD56+) increased (p < 0.001) during each stage of the incremental exercise test. The proliferative response to ConA was suppressed, enhanced, or unchanged using 1.25 micrograms/ml, 2.5 micrograms/ml and 5.0 micrograms/ml ConA, respectively. The in-vitro production of IL-1 and IFN-gamma increased during each workload. In contrast IL-4 production did not change during exercise. The resting and exercise induced alterations in lymphocyte function and cytokine production were independent of gender and fitness level, and returned to baseline 2 h into recovery. The in-vitro production of IFN-gamma and IL-4 suggests that physical activity may alter the balance of TH1 and TH2 lymphocytes.

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.