Attack stress and IgE antibody production in rats

Role of the hypothalamo-pituitary-adrenal axis in the modulation of pollinosis induced by pollen antigens

BACKGROUND

To clarify the mechanism of stress-induced modification of allergic diseases, we studied the effect of restraint stress on plasma levels of cytokines and the symptoms of pollinosis in mice.

METHODS

The effects of restraint stress and the role of the hypothalamo-pituitary-adrenal axis (HPA-axis) in the development of pollen antigen-induced pollinosis were studied in control, hypophysectomized, adrenalectomized or ACTH-administered mice. Twenty days after sensitization, animals were subjected to mild restraint stress for 3 hours, and plasma levels of IFN-gamma, IL-10, and IgE were measured. We analyzed the incidence of sneezing and nasal rubbing in the sensitized animals.

RESULTS

Plasma levels of IL-10 and IgE increased in the sensitized animals with a concomitant increase in the incidence of sneezing and nasal rubbing. The increases in plasma IgE, IL-10 and the incidence of sneezing and nasal rubbing were suppressed by restraint stress. Adrenalectomy increased IFN-gamma, inhibited the increase in plasma IL-10 and IgE, and suppressed the incidence of sneezing. In contrast, hypophysectomy increased plasma levels of IL-10, IFN-gamma, and IgE and the incidence of sneezing. Intraperitoneal administration of ACTH decreased IL-10 in plasma but increased IFN-gamma and suppressed the incidence of nasal rubbing.

CONCLUSIONS

The present findings show that the HPA-axis and ACTH play important roles in the regulation of plasma cytokines and IgE thereby modulating symptoms of pollinosis. The results also suggest that a mild restraint stress suppresses the increase in Th2-dependent cytokines and IgE to reduce the symptoms of pollinosis.

Effect of acute pain on splenic NK cell activity, lymphocyte proliferation and cytokine production activities

Various types of physical and physiological stress in animals have been shown to affect their humoral and cell-mediated immune responses. The present study was designed to investigate the possible influence of acute pain on the immune system. BALB/c mice were exposed to an increasing number of heat shocks using a Tail Flick apparatus; an equal number of control mice received no shock treatments. After each of the regimens was completed, the spleen of each mouse was recovered and various cell populations isolated to assess: the proliferative response to phytohemagglutinin by lymphocytes; cytotoxic activities of natural killer (NK) cells; and, the production of select important cytokines by splenic lymphocytes. The results indicated that NK cell activity and proliferation of lymphocytes were significantly (p < 0.001) increased due to the shock regimens after only a single day's rounds of stimulation (i.e., 3 rounds of approximately 12 equally time-spaced shocks/hr with 30-45 min gap between rounds). After 2 and 3 days' rounds of stimulations, no significant changes were detected in the proliferative response of isolated lymphocytes; conversely, the activity of NK cells remained significantly elevated compared to the controls hosts' cells, even on the second day of stimulation but not on the third. Regarding effects on cytokines, no significant changes were detected in the amount of Interferon-gamma (IFNgamma) and Interlukin-10 (IL-10) produced by lymphocytes obtained from the spleens of any of the shocked mice. These results could suggest that certain acute stressors might actually strengthen a host's immunological reactivity and, possibly, result in an enhanced capacity to resist pathogens that might infect the body.

Immunosuppressive effect of restraint stress on the initiation of allergic rhinitis in mice

BACKGROUND

Exposure to acute stressors modulates both innate and acquired immune function. However, little is known about whether stress has the potential to modulate the pathogenesis of allergic rhinitis.

OBJECTIVES

To determine the effects of acute restraint stress on the initiation of allergic rhinitis in a murine model.

METHODS

CBA/J mice were repeatedly intranasally sensitized with phospholipase A2 (PLA2) from honeybee venom without adjuvant. Restraint stress was applied using uniform cylinders once a week for a continuous 8-hour period, on five occasions in total. Production of PLA2-specific antibodies and degree of nasal and blood eosinophilia were compared between stressed and control mice.

RESULTS

Repeated intranasal sensitization with PLA2 induced PLA2-specific IgE and marked eosinophilia in both the nose and blood in CBA/J mice. Exposure to restraint stress significantly inhibited production of PLA2-specific IgE, IgG1 and IgG2a. Conversely, the stress exerted no significant effect on eosinophilia.

CONCLUSIONS

Exposure to acute restraint stress inhibits antigen-specific antibody production, but not local or systemic eosinophilia. The results of this study suggest that acute stress has the potential to modulate the initiation of allergic rhinitis.

Social stress affects migration of blood T cells into lymphoid organs

The effect of social confrontation stress on the normal distribution of blood T cells into lymphoid organs and some other body tissues was studied. Social stress was induced by placing a male Fischer 344 (F334) rat into the home cage of a resident opponent. 51Cr-labeled blood T cells isolated from syngeneic donor, were intravenously injected into recipients immediately before confrontation. The accumulation of 51Cr-labeled T cells in the spleen, mesenteric and cervical lymph nodes 24 h after injection was about 30% lower in socially stressed than in control males. Substantially higher localization was observed in the bone marrow of socially stressed males.

Moderate exercise is associated with enhanced antigen-specific cytokine, but not IgM antibody production in aged mice

It has been suggested that moderate exercise may modulate the immune response in the elderly. We investigated whether moderate exercise had an effect on the immune response to viral infection in both young (2-4 months) and older (16-18 months) male BALB/cJ mice. Exercised (EX) mice ran on a treadmill for 8 weeks at a gradually increasing speed and duration whereas control (CON) mice were only handled briefly during each exercise session and then returned to their cages. Mice were infected with herpes simplex virus type 1 (HSV-1) 24 h post-exercise. Serum IgM anti-HSV antibody, HSV-1 specific Th1/Th2 cytokine production by spleen cells, and cytokine production by alveolar cells were measured 7 days post-infection. In the aged mice, exercise was associated with an enhanced production of the HSV-1 specific Th1-associated cytokines, interleukin (IL)-2 and interferon (IFN)-gamma, but had no effect on the Th2-associated cytokine IL-10 or IgM antibody. No effect of exercise was observed in young mice. IL-12 production was not altered by exercise, but aging was associated with altered IL-12 production in a tissue-specific manner. In conclusion, moderate exercise was associated with increased antigen-specific IL-2 and IFN-gamma production in response to viral challenge in older mice.

Social stress in laboratory rats: behavior, immune function, and tumor metastasis

This report summarizes data from social confrontations studies in laboratory rats dealing with the effects of psychosocial stress on immune functioning and tumor metastasis. The paper focuses on the physiological alterations observed in subdominant males after 2 days of continuous social confrontation. A significant loss of body mass and elevated plasma concentrations of adrenal hormones in subdominant males indicate a stressful social environment. Subdominant males showed lower numbers of blood CD4 and CD8 T cells as well as reduced activity levels of T cells and natural killer (NK) cells relative to control subjects. In order to evaluate the possible health impact of suppressed NK functioning, we used the MADB 106 tumor model. A 10-fold lower tumor clearance in subdominant males demonstrates suppression of the animals' capacity to prevent metastatic development. The relationship between individual behavior and immunological outcome is briefly discussed. Together, the study of male rats in social confrontations appears to be a good model to investigate stress-induced immune modulation and tumor metastasis under relatively naturalistic social conditions.

Psychosocial stressors and mammary tumor growth: an animal model

Stressful life events and the ability to cope with stress may play a role in the progression of breast cancer; however, the complex relationship between stressors and tumor growth is difficult to investigate in humans. Our studies have utilized the androgen-responsive Shionogi mouse mammary carcinoma (AR SC115) in male mice to investigate the effects of social housing condition on tumor growth rates and responses to chemotherapy. We demonstrate that, depending on social housing condition, mammary tumor growth and response to chemotherapy can both increase and decrease. We have examined the possible role(s) of 1) psychosocial variables, 2) testosterone and corticosterone, hormones altered by stress and known to stimulate SC115 cells in vivo and in vitro, 3) NK cells, one of the body's first lines of defense against tumor cells, 4) stress proteins, in mediating the differential tumor growth rates observed in our model. This review discusses the investigations we have undertaken to elucidate the mechanisms through which a psychosocial stressor, social housing condition, can alter tumor growth rate.

Effect of stress on the Schultz-Dale reaction in guinea pig aorta

The smooth muscle of thoracic aorta from guinea pig sensitized with egg albumin (EA) produced an anaphylactic contraction when it was exposed to EA. Experiments were performed to evaluate stress effects on the anaphylactic contraction in guinea pig aortic rings. Two types of stressors were used as immunosuppressor stimuli: physical restraint and shaking of the animals. Both stressors diminished the amplitude of the Schultz-Dale contraction in aortic rings from sensitized guinea pig. The shake stress stimulus interrupted several times during each session induced higher immunosuppression in animals in which the active sensitization and the stress sessions began the same day. Severe restraint stress, prior to active immunization, also suppressed significantly the anaphylactic response. The Schulz-Dale reaction in guinea pig aorta seems to be a valuable technique to study the stress effects on the anaphylactic response.

The restraint stress-induced reduction in lymphocyte cell number in lymphoid organs correlates with the suppression of in vivo antibody production

In this study, we examined the effects of restraint stress on some immune parameters such as the in vivo antibody levels, cytokine production, and lymphocyte cell number in the spleen or mesenteric lymph node (MLN). BALB/c mice were thus injected intraperitoneally 2-times with OVA absorbed into alum on days 0 and 21. Before the first injection, the animals were either restrained for 12 h (stress group) or returned to their home cage (control group). Exposure to stress resulted in a reduction in the serum levels of anti-OVA IgE, IgG1, and IgG2a. In addition, stress also caused a decrease in the IL-4 and IFN-gamma levels in the spleen or mesenteric lymph node cell culture supernatants. Furthermore, exposure to stress resulted in a decrease in the splenic and mesenteric lymphocyte cell number when examined immediately after the cessation of stress. This decrease persisted for at least 12 h after the termination of stress and thereafter disappeared 24 h after stress. The stress-induced reductions in antibody and cytokine production occurred only when antigen was given either immediately or 6 h after stress, but not when antigen was given 24 h post stress. These results thus suggest that the restraint stress-induced change in lymphocyte cell number in the spleen or MLN closely correlates with the altered antibody and cytokine levels.

The effect of restraint stress on the kinetics, magnitude, and isotype of the humoral immune response to influenza virus infection

The stress of physical restraint has been shown to modulate the cellular immune response during a viral infection. We have studied the effects of stress on the humoral immune response during infection by influenza virus. Restraint stress altered the kinetics of the antibody response; seroconversion in the IgG and IgA isotypes was delayed in virus-infected C57BL/6 mice subjected to repeated cycles of physical restraint. However, the magnitude and isotype of the mature antibody response were unaffected during the plateau phase; no significant differences were observed between restrained/infected and nonrestrained/infected mice. Thus, the time during infection at which the antibody response was measured was a significant variable in the study of stress-induced alterations of the host's response to a replicating viral antigen. While restraint stress did not significantly affect the magnitude or class of the humoral response, it did alter the kinetics of response.

Stress-induced suppression of experimental allergic encephalomyelitis in the rat

Numerous experiments have demonstrated that physical stress can alter immunological parameters. However, little attention has been paid to the interrelationship between stress and autoimmune processes. The present study was designed to determine the influence of electric shock and sound stress on the development of experimental allergic encephalomyelitis (EAE). Ten-week-old male DA rats highly susceptible to EAE were used. Rats were subjected to the stress procedure during 19 days either before or after immunization with intradermal injection of 0.1 ml of an emulsion containing guinea pig spinal cord (20 mg/rat) in an equal volume of complete Freund's adjuvant (CFA). In addition, rats received subcutaneous injection of Bordetella pertussis in the dorsum of the same foot. Electric stress procedure consisted of 80 inescapable, unpredictable tail shocks (5 s, 1 mA) delivered at the same time each day. Sound stress procedure consisted of exposure of rats to a 90 dB fire alarm bell which rings 60 times for 5 s during one hour, at the same time of the day. Rats were observed daily for clinical signs of EAE and survived animals were sacrificed on day 20 after immunization. The brain and spinal cord sections were examined histologically for mononuclear cell infiltrates characteristics for EAE. The results clearly indicate that inescapable tail shocks suppressed the appearance and development of EAE when rats were subjected to stress procedure during 19 days after immunization, but not when rats were stressed during 19 day before the induction of EAE. On the other hand, in rats exposed to sound stress there was only delay in the onset of the disease.

The effects of stress on the development of immunological memory following low-dose antigen priming in mice

Observable stress effects on immune responses may be a function of the quantitative and qualitative characteristics of the stressor, and the outcome measurement of immunity. Further, the effects of stress on humoral immunity, in particular, may be sensitive to the concentrations of antigen used to elicit a response. We have studied the effects of footshock stress during the time of priming with low concentrations of antigen on the secondary response to another low dose of antigen. The secondary humoral immune response of C3H/HeJ mice to the protein antigen keyhole limpet hemocyanin was examined following footshock, exposure to the apparatus without shock, or exposure to the home cage. Footshock reproducibly depressed the IgG anti-KLH response, and the effect on the IgM response was sporadic. Initially, footshock was administered for 7 days before and 7 days after priming with low amounts of antigen. Subsequent studies demonstrated that a single footshock session delivered 24 h after priming could suppress the IgG anti-KLH response.

Reduced serum antibodies associated with social defeat in rats

Many studies have linked various physical stressors with changes in immune function. The present experiment examined the effect of a social stressor, defeat associated with territorial defense, on serum antibodies to a specific protein, keyhole limpet hemocyanin (KLH). Pairs of male rats formed colonies and experimental rats were intruders. Experimental animals were immunized with KLH prior to exposures to territorially defensive colonies. Control animals were placed into colonies but separated from residents by a Plexiglas barrier. Behavioral measures, including number of bites and total time spent in submissive postures, were taken for colony-intruder interactions. Serum antibody levels were determined from blood samples taken one, two, and three weeks following immunization. Experimental animals had significantly less serum antibodies to KLH than did controls. Within the experimental group, total time spent in submissive postures at week one was significantly correlated with serum antibody levels, such that animals spending the most time in submission had lower antibody levels. Total bites correlated only slightly with antibody levels. The correlation between submission and serum antibody levels increased when the bites factor was partialled out. A stressful social encounter may thus affect immune function in a manner independent of the influence of physical (nociceptive) stressors.