Rudy E. Ballieux

Cardiovascular and endocrine responses to experimental stress: Effects of mental effort and controllability

The objective of the study was to investigate the unique and interactive effects of the controllability of a task and mental effort required by that task on cardiovascular and endocrine reactivity, when both were manipulated independently. A 2 x 2 factorial design was used, with two levels of mental effort and two levels of control. Twenty-four healthy male subjects participated in each experimental condition. Heart rate, blood pressure, catecholamine and cortisol responses were determined. High effort lead to greater increases in heart rate, blood pressure and norepinephrine levels. Uncontrollability lead to higher cortisol, blood pressure and norepinephrine responses. In addition, there was an effort x control interaction effect on the diastolic blood pressure response. In conclusion, effort has clear sympathetic effects, whereas control influences both the sympathetic nervous system and the release of cortisol. Having control seems to be most beneficial in high effort situations, at least with respect to sympathetic reactivity.

β-Endorphin: Cytokine and neuropeptide

A decade of cytokine research has revealed that these mediators play a pivotal role in the functioning of many organ systems. The immune system is not the exclusive producer of cytokines. These mediators are also produced in, e.g., the brain, gastro-inlestinal tract and liver (Breder et al. 1988, Farrar et al. 1987, Dinarello 1984, Oppenheim & Gery 1982). In view of the fact that the immune system can react to cytokines produced by cell types other than leukocytes, immunologists had to accept that the immune system is not functioning autonomously, but that it is constantly communicating with other organ systems in order to maintain its homeostasis.

Influence of perceived psychological stress and distress on antibody response to low dose rDNA hepatitis B vaccine.

The present study focused on the relationship between psychological stress and immune reaction to a novel antigen. Participants completed questionnaires on daily hassles, psychoneurotic complaints, coping style, and loneliness, 2 and 6 months after the first of a series injections with a low dose recombinant DNA hepatitis B vaccine. Antibody response was determined 7 months after the first vaccination. Based on the psychological questionnaires two different stress measures were calculated: a Stress Index score-month-2 and a Stress Index score-month-6 indicating stress levels experienced at the beginning and at the end of the study respectively. Antibody levels were found to be negatively related with the Stress Index score-month-2. Although the influence of psychological stress reported on month 6 tended to be in the same direction, this effect was not significant. Coping styles and loneliness were not associated with antibody formation. These results suggest that antibody formation to rDNA hepatitis B vaccine is negatively influenced by psychological stress.

The effects of β‐adrenoceptor stimulation on adhesion of human natural killer cells to cultured endothelium

1 The circulation of natural killer (NK) cells in vivo is influenced by physical exercise, mental stress, and infusion of β‐adrenoceptor agonists. We have previously presented in vitro data, showing that β2‐adrenoceptor agonists induce detachment of NK cells from endothelial cells (EC), supporting the hypothesis that NK cells can be recruited from the marginating pool in blood vessels. 2 Because NK cells as well as EC express β2‐adrenoceptors, the present study was conducted to investigate whether stimulation of the β‐adrenoceptors on NK cells, EC or both cell types is required to induce detachment from EC. 3 Cells were pretreated (15min) with a selective β2‐adrenoceptor antagonist, GR81706, at various concentrations. The duration of β‐adrenoceptor blockade was tested by determining the adenosine 3′,5′‐cyclic monophosphate (cyclic AMP) production induced by terbutaline (a β2‐adrenoceptor specific agonist). This receptor‐mediated response was effectively inhibited for at least 4 h, whereas the cyclic AMP production in response to forskolin (a direct activator of adenylate‐cyclase) was not affected. 4 Functional adhesion assays were then performed to determine the role of β‐adrenoceptors on the different cell types involved (NK and EC) in catecholamine‐induced detachment. Peripheral blood mononuclear cells were allowed to adhere for 1 h to monolayers of unstimulated EC in the presence or absence of cyclic AMP inducing agents, and the percentage of NK cells in the adhering lymphocyte fraction was determined by flow cytometry. 5 Both adrenaline (10−5 m) and forskolin (10−5 m) caused detachment of NK cells from EC. After blockade of the β2‐adrenoceptors on NK cells by pretreatment with GR81706 (10−6 m), the effect of adrenaline on NK cells adhesion was pretented; after blockade of the β2‐adrenoceptors on EC, NK cell adhesion was still significantly reduced by adrenaline. In all cases, forskolin caused detachment of NK cells. 6 To establish further that stimulation of β‐adrenoceptors on NK cells is sufficient to cause detachment, we showed that adrenaline also reduced adhesion of NK cells to monolayers of Chinese hamster ovary cells, which do not express β‐adrenoceptors. 7 Together, these results show that stimulation of β2‐adrenoceptors on NK cells negatively influences their capacity to adhere to EC, and that β2‐adrenoceptors on EC play a negligible role in this phenomenon.

Enumeration of IFN-γ-producing human lymphocytes by spot-ELISA: A method to detect lymphokine-producing lymphocytes at the single-cell level

Abstract We present a method to detect and enumerate individual interferon (IFN)-producing human lymphocytes. The assay is based on the ELISA-plaque assay developed by Sedgwick and Holt (J. Exp. Med. (1983) 157, 2178; J. Immunol. Methods (1986) 87, 37). Mitogen-stimulated T cells are seeded in anti-IFN-γ-coated wells. After a 16 h incubation period, the cells are removed. Subsequently a rabbit anti-IFN-γ-antiserum followed by goat anti-rabbit antiserum conjugated to alkaline phosphatase are used to detect the IFN-γ spots. Application of the spot-ELISA in combination with the conventional ELISA reveals the amount of IFN-γ produced per cell. The spot-ELISA is a highly sensitive, easy to perform and rapid assay. Provided specific antisera are available, this method is suitable to detect production of other lymphokines at the single-cell level. To our knowledge, this is the first report of a single, well-defined T cell product measurement by the spot-ELISA.

Modulation of the immune response by emotional stress

The influence of mild, emotional stress was investigated for its effect on the immune system by subjecting rats to the one-trial-learning passive avoidance test. The reactivity of the immune system was tested by determining the proliferative response after mitogenic stimulation in vitro as well as the capacity to generate a primary antibody response in vivo after immunization with sheep red blood cells. Our results demonstrate that exposure of rats to a single electric footshock (learning trial) or habituation to the passive avoidance apparatus, induces an increase of the immune response in vitro and in vivo. Thus, emotional stimuli seem to facilitate immunological responsiveness. However, when the animal is confronted with a conflict situation, as tested by the retention of the avoidance response after a single learning trial, the initially enhanced reactivity of the immune system decreases. It is concluded that the immune system is capable of reacting specifically and immediately to distinct psychological stimuli.

Immune responses to experimental stress: effects of mental effort and uncontrollability.

OBJECTIVE Two important determinants of physiological stress responses have been identified, uncontrollability of the stressor and amount of effort involved in coping with the stressor. In the present experiment, we tried to identify the specific contributions of effort and uncontrollability to immune system responses to stress. METHODS In a 2 x 2 design, effort and uncontrollability were manipulated independently of each other. Subjects participated in one of four experimental conditions, and their endocrine, immune, and sympathetic nervous system responses to the task were assessed. RESULTS Effort had a stimulating effect on enumerative immunological parameters (CD8 and CD16+ cells) and on natural killer cell activity. The effect occurred immediately after the stressor and was transient. Regression models indicated that this effort effect may have been mediated by activation of the sympathetic nervous system. Uncontrollability influenced in vitro production of the cytokine interleukin-6, leading to decreased production 15 and 30 minutes after the stressor. Uncontrollability also led to an increased level of cortisol, but no evidence was found that the decrease in cytokine production was mediated by cortisol release. CONCLUSION The results suggest that two major stressor characteristics, effort and uncontrollability, may have differential effects on the immune system.

Modulation of immune response to rDNA hepatitis B vaccination by psychological stress

In a previous study it was shown that antibody formation after vaccination with a low-dose recombinant DNA (rDNA) hepatitis B vaccine was negatively influenced by psychological stress. The present study was designed to assess whether the same inverse relation between HBs-antibody levels and psychological stress could be observed, while administering the standard, and thus higher, dose of vaccine. Volunteers (n = 68) scoring extremely low or high on a combination of questionnaires measuring daily problems and psychoneurotic symptoms were selected for participation. Antibody levels were determined 2, 6, and 7 months after the first vaccination. Questionnaires were completed before entering the study and at month 6. In contrast to the previous study, psychological stress was not found to be related to the antibody levels at any timepoint. These results suggest that, under certain conditions, stress-induced immunomodulation in vivo might be dependent on antigen dose.

Differential effects of β-endorphin on cAMP levels in human peripheral blood mononuclear cells

Abstract In the present paper we demonstrate that one of the early effects of the opioid peptide β-endorphin on human peripheral blood mononuclear cells is the induction of a change in the intracellular cAMP level. However, the effect of β-endorphin on cAMP levels is not uniform; increases as well as decreases in cAMP level are observed. It appears that β-endorphin is a true modulator of intracellular cAMP level: the peptide will increase cAMP levels in cells with a low baseline level. In contrast, β-endorphin tends to decrease cAMP levels in cells with a high cAMP concentration. Moreover, β-endorphin modulates the rise in cAMP induced by β-adrenergic activation. The effect of β-endorphin on cAMP level correlates negatively with the magnitude of the change in cAMP level induced by β-adrenergic activation.

β-endorphin secretion by human peripheral blood mononuclear cells: Regulation by glucocorticoids

Corticotropin-releasing factor (CRF), a 41-aminoacid neuropeptide, can induce lymphocytes to production of beta-endorphin (beta E). Furthermore, the neuropeptide Arginine-Vasopressin (AVP) can enhance CRF-induced production of beta E. We have demonstrated that CRF acts by stimulating monocytes to production of the cytokine interleukin-1 (IL-1). IL-1 can in its turn activate the lymphocytes to secretion of beta E. Here we demonstrate that the glucocorticoid analogue dexamethasone is capable of modulating CRF-induced beta E secretion by lymphocytes. It appeared that dexamethasone can inhibit secretion of lymphocyte-derived beta E. The mechanism by which dexamethasone exerts its inhibitory activity is by blocking CRF-induced production of IL-1, thereby preventing induction of beta E secretion by B cells. These results support the concept that peptide hormones and glucocorticoids are mediating a reciprocal modulation of neuroendocrine and immunological activities.