Successful development of methodology for detection of hapten-specific contact hypersensitivity (CHS) memory in swine.

Hapten contact hypersensitivity (CHS) elicits a well-documented inflammation response that can be used to illustrate training of immune cells through hapten-specific CHS memory. The education of hapten-specific memory T cells has been well-established, recent research in mice has expanded the "adaptive" characteristic of a memory response from solely a function of the adaptive immune system, to innate cells as well. To test whether similar responses are seen in a non-rodent model, we used hapten-specific CHS to measure the ear inflammation response of outbred pigs to dinitrofluorobenzene (DNFB), oxazolone (OXA), or vehicle controls. We adapted mouse innate memory literature protocols to the domestic pig model. Animals were challenged up to 32 days post initial sensitization exposure to the hapten, and specific ear swelling responses to this challenge were significant for 7, 21, and 32 days post-sensitization. We established hapten-specific CHS memory exists in a non-rodent model. We also developed a successful protocol for demonstrating these CHS responses in a porcine system.

Effect of prenatal stress on subsequent response to mixing stress and a lipopolysaccharide challenge in pigs.

Sows subjected to prenatal stress have been found to produce offspring that have altered responses to stress. Our objective was to determine if exposing a sow to stress would alter the response of the offspring to lipopolysaccharide (LPS) at 2 mo of age or their response to mixing stress at 4 mo of age. Sow treatments consisted of intravenous injections of ACTH (1 IU/kg of BW), exposure to rough handling for a 10-min duration (rough), or no treatment (control) once per week from d 42 to 77 of gestation. At 2 mo of age, pigs from each treatment, 1 per litter (n = 21, 17, and 15 for the ACTH, rough, and control treatments, respectively), were challenged with 2 µg of LPS/kg of BW or saline, or served as a noninjected control. Their behavioral response to a human approach test and salivary cortisol were measured. At 4 mo of age, 1 pig from each treatment (n = 14, 14, and 15 for the ACTH, rough, and control treatments, respectively) was taken from its home pen and placed in a pen of unfamiliar pigs. At this time, a punch biopsy wound (6 × 6 mm) was created to measure the ability of the pig to heal the wound. At this same time, each pig received a 1-mL intramuscular injection of 20% ovine red blood cells (oRBC), and then a second injection of oRBC at 21 d postmixing. Blood samples were collected 3 times per week for 2 wk and then once a week for 4 more weeks. Blood samples were analyzed for cortisol, porcine corticosteroid-binding globulin, antibody response to oRBC, and nitric oxide production by macrophages. Behavior was recorded during the first 5 d after mixing. All pigs in the LPS challenge responded with characteristic sickness behavior; however, pigs in the rough treatment showed less sickness behavior than those in the other 2 treatments (P < 0.05). Maternal stress treatment did not affect (P < 0.43) salivary cortisol. Pigs from all treatments responded similarly to mixing stress with regard to cortisol, porcine corticosteroid-binding globulin, antibody titers, nitric oxide production, and hematology measures, and all pigs experienced the same amount of aggression in response to mixing. Without altering peripheral measures of stress responsivity, prenatal stress enhanced the ability of pigs to cope with a simulated immune challenge, which could prove to be an adaptation to challenging environments.

Immune response and blood chemistry of pigs fed conjugated linoleic acid.

Immune function (response to concanavalin A, cytokine production, and lymphocyte profiles) and blood chemistry variables were measured in growing-finishing pigs (Yorkshire/Landrace/Duroc dam × Hampshire sire) fed varying percentages of CLA (0, 0.12, 0.25, 0.50, and 1.0%). Blood was collected at 0, 14, 28, 42, and 56 d on feed (DOF). Total white blood cell (WBC) count increased (P < 0.01) linearly to 42 DOF. No differences (P = 0.53) were observed for WBC across CLA treatment. Nitric oxide was greater (P < 0.01) for the 1.0% CLA treatment compared with all other treatments. Flow cytometry using fluorescent labeled monoclonal antibodies to the CD4, CD8, double-positive CD4/CD8, and CD2 surface markers was used to determine lymphocyte subpopulations. Supplementation of CLA had no effect (P = 0.61) on lymphocyte subpopulation cell distribution. Most blood chemistry variables were within the normal metabolic range for pigs. A decrease was observed over DOF for P (P < 0.01) and K (P < 0.05). Additionally, Na and Cl concentrations increased (P < 0.05) from 14 to 28 DOF and decreased over the remainder of the trial. Electrolyte balance was not different (P = 0.38) across CLA treatments and was likely explained by no differences in feed intake among the CLA treatment groups. Blood lipid variables indicated that total cholesterol (P < 0.001), triglycerides (P < 0.001), high-density lipoproteins (P < 0.001), and low-density lipoproteins (P < 0.01) increased as the amount of CLA in the diet increased, but none of the results from these treatments exceeded the normal range of acceptability. These results suggested that CLA was safe when fed to growing-finishing pigs and had little effect on their immune function and blood chemistry variables.

Prenatal stress effects on pig development and response to weaning.

Exposing a pregnant sow to stress has been shown to affect the resulting offspring. Our objective was to determine if rough handling of pregnant sows altered the physiology of her offspring and if these alterations were different from an experimentally induced model of prenatal stress. Sow treatments consisted of i.v. injections of ACTH (1 IU/kg of BW), exposure to rough handling for 10 min (Rough), or no treatment (Control) once a week during d 42 to 77 of gestation. To determine the plasma cortisol response to treatments, blood (5 mL) was collected from 30 sows after treatment administration. To conduct the prenatal stress study, a separate group of 56 sows was used in 1 of 4 replicates. At birth, production data were collected for each litter, including birth weight, number born, anogenital distance, and pig viability. At weaning, pigs were blocked by BW and sex, and placed in a nursery pen of 6 pigs, with 2 pigs from each treatment group. To assess the effect of treatments on cortisol, corticosteroid-binding globulin (CBG), and hematological cell profiles, blood was collected every other day for 10 d after weaning. Application of treatments caused plasma cortisol concentrations to be greatest in ACTH sows compared with Control sows (P < 0.001), with Rough sows having intermediate values (P = 0.07). Treatments did not affect the number of pigs born, number of stillborn, or pig viability (P > 0.40). The ratio of cortisol to CBG did not differ between treatments (P = 0.09). Hematological variables did not differ between treatments (P > 0.19). Pigs born to ACTH sows had a smaller anogenital distance compared with controls (P < 0.03), with pigs from Rough sows being intermediate. Our data indicate that swine exposed to prenatal stress (ACTH injection) can have alterations in sexual morphology without effects on growth or the immune cell populations measured in this study.

Aerobic exercise, but not flexibility/resistance exercise, reduces serum IL-18, CRP, and IL-6 independent of beta-blockers, BMI, and psychosocial factors in older adults.

Increased serum levels of inflammatory mediators have been associated with numerous disease states including atherosclerosis, Type II diabetes, hypertension, depression, and overall mortality. We hypothesized that a long-term exercise intervention among older adults would reduce serum inflammatory cytokines, and this reduction would be mediated, in part, by improvements in psychosocial factors and/or by beta-adrenergic receptor mechanisms. Adults age 64 were randomly assigned to either an aerobic exercise treatment (CARDIO) or a flexibility/strength exercise treatment (FLEX) 3 days/week, 45 min/day for 10 months. A subgroup of subjects treated with non-selective beta(1)beta(2) adrenergic antagonists were included to evaluate the potential role of beta-adrenergic receptor adaptations as mediators of an exercise-induced change in inflammation. The inflammatory mediators [C-reactive protein (CRP), IL-6, tumor necrosis factor (TNF)-alpha, and IL-18] and the psychosocial factors (depression, perceived stress, optimism, sense of coherence, and social support) were measured pre- and post-intervention. The CARDIO treatment resulted in significant reductions in serum CRP, IL-6, and IL-18 compared to the FLEX treatment (significant treatment x time interaction, p<.05), whereas TNFalpha declined in both groups (main effect of time, p=.001). However, several psychosocial factors (depression, optimism, and sense of coherence) improved in both groups suggesting that the reduction of CRP, IL-6, and IL-18 in the CARDIO group was not mediated by improvements in psychosocial scores. With respect to the potential role of beta-adrenergic receptors, both CARDIO subjects treated with beta-adrenergic antagonists and those who were not treated with those medications demonstrated similar reductions in serum CRP, IL-6, IL-18, and TNFalpha. In summary, we have observed that an aerobic exercise intervention can significantly reduce serum inflammatory mediators, but beta-adrenergic receptors and psychosocial factors do not appear to be involved.

The exercise-induced enhancement of influenza immunity is mediated in part by improvements in psychosocial factors in older adults.

The primary goal of this study was to determine whether exercise-associated improvements of the immune response to influenza vaccination were mediated by improvements in psychosocial factors in older adults. At baseline, prior to the exercise intervention, older adult participants were immunized with influenza vaccine. Blood samples collected pre-immunization, 1, 4, and 12 weeks post-immunization were analyzed for anti-influenza antibody, whereas influenza-specific cytokine (IFNgamma) was evaluated at 1 week post-immunization. Depression and sense of coherence were measured pre-immunization. Four weeks post-immunization, participants were randomly assigned to either an aerobic exercise group (n=14) or a control group (n=14). After a 10-month exercise intervention, the immunization, blood collections, and psychosocial measures were repeated. At the post-intervention evaluation, exercise participants had improved scores on depression and sense of coherence. Also post-intervention, exercise participants had a greater increase in antibody and IFNgamma production. After controlling for the effect of both psychosocial measures, the exercise treatment remained significant with respect to antibody titer suggesting that the increases in antibody were not mediated by improvement in the psychosocial factors. In contrast, the enhancement of IFNgamma appeared to be mediated at least in part by the psychosocial factors. After controlling for psychosocial factors, exercise treatment was no longer significantly related to the change in IFNgamma. Taken together, our findings may suggest that the mechanism(s) of exercise-induced improvement in immunocompetence involve both physiological and psychological pathways.

Reaction of fumonisin with glucose prevents promotion of hepatocarcinogenesis in female F344/N rats while maintaining normal hepatic sphinganine/sphingosine ratios.

The reaction of the primary amine of fumonisin B(1) (FB(1)) with glucose was hypothesized to detoxify this mycotoxin. Eighty 10-day-old female F344/N rats were injected intraperitoneally with diethylnitrosamine (DEN; 15 mg/kg of body weight). At 4 weeks of age, the weaned rats were randomly assigned to one of four treatment groups with 20 rats each. At 9 weeks of age, four rats from each treatment group were killed. At 12 weeks, another five rats from each group were killed. At 20 weeks of age, the remaining rats were killed. In comparison with the rats fed basal diet or FB(1)-glucose (containing 25 ppm of FB(1)), rats fed 8 ppm (residual amount of free FB(1) in the FB(1)-glucose mixture) or 25 ppm of FB(1) had greater alanine aminotransferase activity at 9 and 20 weeks of age (P < 0.001), greater endogenous hepatic prostaglandin E(2) production at 20 weeks of age (P < 0.05), and significantly lower plasma cholesterol at 20 weeks of age (P < 0.01). Placental glutathione S-transferase (PGST)-positive and gamma-glutamyltransferase (GGT)-positive altered hepatic foci (AHF) occurred only in rats fed 25 ppm of FB(1) at 20 weeks of age. Hepatic natural killer (NK) cell activities were similar among the four groups, but the percentage of total liver-associated mononuclear cells exhibiting the NKR-P1(bright) marker was significantly greater in rats fed FB(1)-glucose, FB(1) (8 ppm) and FB(1) (25 ppm) than in control rats at 9 weeks of age, and FB(1)-glucose-treated rats had significantly lower NKR-P1(bright) cells as a percentage of total liver-associated mononuclear cells than rats fed 25 ppm of FB(1) at 20 weeks of age (P < 0.05). PGST- or GGT-positive AHF were not detected in any treatment group at 9 or 12 weeks of age. At 20 weeks of age, half of the rats fed 25 ppm of FB(1) had PGST- and GGT-positive AHF. The sphinganine (Sa) concentration and the Sa/sphingosine (So) ratio were significantly greater in the rats fed 25 ppm of FB(1) diet as compared with the control groups at, respectively, 12 or 20 weeks of age. Therefore, modifying FB(1) with glucose seems to prevent FB(1)-induced hepatotoxicity and promotion of hepatocarcinogenesis. The Sa/So ratio was not the most sensitive biomarker of FB(1) toxicity.

Opposing effects of prostaglandin E(2)and F(2 alpha) on rat liver-associated natural killer cell activity in vitro.

Strain differences in cancer incidence are proposed to be due partly to differences in immune function. As potential cancer-associated immunological regulators, the concentrations of hepatic prostaglandins E(2)(PGE(2 alpha)and F(2 alpha)(PGF(2 alpha)) were compared in 9-week-old male and female F344/N and Sprague-Dawley (SD) rats. There were no strain or gender differences in the concentrations of hepatic PGE(2). No strain difference was found in the concentration of hepatic PGF(2 alpha), but the hepatic PGF(2 alpha)concentration in female rats was two-fold that of the male rat (130 vs 60 ng/g). PGE(2)significantly inhibited hepatic natural-killer cell (NK) activity in vitro compared with untreated cells from both genders and strains (P<0.05), 25 ng PGE(2)/ml inhibited NK activity significantly more than did 10 ng PGE(2)/ml (P<0.05). In contrast, 50 ng PGF(2 alpha)/ml and 100 ng PGF(2 alpha)/ml significantly stimulated hepatic NK activity compared with untreated hepatic cells from both F344/N and SD rats. This study suggests that prostaglandins may have a negligible net effect on NK activity associated with rat liver, and may be unlikely to mediate cancer-related immune function.

Few differences found between early- and late-weaned pigs raised in the same environment.

Segregation and medicated early weaning are technologies used to optimize the productivity and health of pigs, but these practices may also cause aberrant behaviors indicative of stress. Thus, differences in early- (=10 d of age) and late- (=30 d of age) weaned pigs were investigated. At weaning, pigs were housed in groups of four in 16 pens (eight pens per treatment) in the same facility, and, thus, they were not segregated. Body weights were recorded at birth, weaning, and at approximately 42, 65, 102, 137, and 165 d of age (at slaughter). One-minute, instantaneous scan samples during a 10-min period (at 0600, 1000, 1400, and 1800) were used to record the frequency of lying, standing, and sitting, total number of drinks, feeder investigations, and time spent playing/fighting on 2, 3, and 4 d after weaning. Five-minute, direct observations of each pig were conducted at approximately 40, 60, 80, and 150 d of age. Direct observations were also made of the entire pen for 10 min at approximately 50, 95, 123, and 160 d of age to record aberrant behaviors. At 62 d of age, a handling and blood collection stress was imposed. At 165 d of age, a second stress test was conducted in response to rough handling and transport. Early-weaned pigs spent more time playing/ fighting (P < .006) than late-weaned pigs during the 4 d after weaning, manipulated conspecifics more often at 40 d of age (P < .002), had greater percentage of hemoglobin (P < .03) during Stress Test 1, had greater ADG at 42 d of age (P < .03), and had greater hypothalamic growth hormone-releasing hormone receptor mRNA at slaughter (P < .06). Late-weaned pigs had greater ADG between 137 and 165 d of age (P < .03) and greater pro-opiomelanocortin at slaughter (P < .04). Overall, most differences found between early-weaned and late-weaned pigs were evident soon after weaning, but they disappeared before slaughter.

Flow cytometric analysis of canine colonic mucosal lymphocytes from endoscopically obtained biopsy specimens.

OBJECTIVE: To validate use of canine colonic biopsy specimens obtained via endoscopy as a source of mucosal lymphocytes (ML) for flow cytometric analysis. SAMPLE POPULATION: Mucosal biopsy specimens from 10 adult dogs. PROCEDURE: Mucosal lymphocyte subsets obtained from excised colon were compared with ML subsets obtained from biopsy specimens obtained by use of an endoscopic forceps (6 dogs). Endoscopic colonic biopsy specimens from 4 other dogs were used to define whether obtained ML were predominantly of intraepithelial or lamina propria origin. Mucosal lymphocytes were isolated and labeled, using commercially available monoclonal antibodies directed against canine cell surface antigens. Lymphocyte subsets (cytotoxic or helper T cells; B cells) were determined by use of flow cytometric analysis. RESULTS: A large number of viable ML was obtained after dissociation of the colonic epithelium from excised colon (45.5 + 21.5 X 10(6)) and endoscopic (7.2+/-3.4 X 10(6)) biopsy specimens. Lymphocyte subsets obtained with both methods were identical for each dog and consisted predominantly of intraepithelial lymphocytes, with some lymphocytes from the lamina propria. Collagenase digestion of excised colon also yielded a large number of viable lymphocytes from the lamina propria (56.7+/-20.4 X 10(6)), but collagenase digestion of endoscopic biopsy specimens was less rewarding. CONCLUSION AND CLINICAL RELEVANCE: A representative sample of viable intraepithelial ML is obtainable from endoscopic biopsy specimens. Flow cytometric analysis, a minimally invasive technique, can be used to study ML of client-owned animals.

Daidzein and genistein glucuronides in vitro are weakly estrogenic and activate human natural killer cells at nutritionally relevant concentrations.

Daidzein and genistein glucuronides (DG and GG), major isoflavone metabolites, may be partly responsible for biological effects of isoflavones, such as estrogen receptor binding and natural killer cell (NK) activation or inhibition. DG and GG were synthesized using 3-methylcholanthrene-induced rat liver microsomes. The Km and Vmax for daidzein and genistein were 9.0 and 7.7 micromol/L, and 0.7 and 1.6 micromol/(mg protein. min), respectively. The absence of ultraviolet absorbance maxima shifts in the presence of sodium acetate confirmed that the synthesized products were 7-O-glucuronides. DG and GG were further purified by a Sephadex LH-20 column. DG and GG competed with the binding of 17beta-(3H) estradiol to estrogen receptors of B6D2F1 mouse uterine cytosol. The concentrations required for 50% displacement of 17beta-(3H) estradiol (CB50) were: 17beta-estradiol, 1.34 nmol/L; diethylstilbestrol, 1.46 nmol/L; daidzein, 1.6 micromol/L; DG, 14.7 micromol/L; genistein, 0.154 micromol/L; GG, 7.27 micromol/L. In human peripheral blood NK cells, genistein at <0.5 micromol/L and DG and GG at 0.1-10 micromol/L enhanced NK cell-mediated K562 cancer cell killing significantly (P < 0.05). At > 0.5 micromol/L, genistein inhibited NK cytotoxicity significantly (P < 0.05). The glucuronides only inhibited NK cytotoxicity at 50 micromol/L. Isoflavones, and especially the isoflavone glucuronides, enhanced activation of NK cells by interleukin-2 (IL-2), additively. At physiological concentrations, DG and GG were weakly estrogenic, and they activated human NK cells in nutritionally relevant concentrations in vitro, probably at a site different from IL-2 action.

Impact of feeding regimen on behavioral and physiological indicators for feeding motivation and satiety, immune function, and performance of gestating sows.

The effect of daily or interval (every 3 d) feeding on body weight change, blood glucose and cholecystokinin (CCK) concentrations, immune function, and behavioral activity were determined during the gestation period of sows. Sows were fed a corn-soybean meal diet either 2 kg daily or 6 kg once every 3rd d (interval). Body weight changes for the 42-d trial period were not different (P > .05) between regimens. Blood glucose concentrations were similar before feeding (P > .05). Two hours after feeding, glucose concentrations increased in interval-fed sows but not in daily-fed sows (P < .05). Premeal plasma CCK concentrations were greater for daily-fed sows than for interval-fed sows (P < .05). The CCK concentrations in sows of both regimens increased after feeding above premeal levels (P < .05), and interval-fed sows exhibited higher concentrations than daily-fed sows (P < .05). Immune function as evaluated through mitogen-induced proliferation of T cells was greater in daily-fed sows than in interval-fed sows (P < .05). Daily-fed sows were more active overall and on any given day than interval-fed sows (P < .05) and thus seemed to expend more energy. Further, daily-fed sows exhibited higher levels of mouth-based activities (i.e., sham chewing, licking, appetitive and consummatory feeding behavior, and excess drinking) than sows restricted to consumption of one large meal every 3rd d. These indicators suggest that feeding motivation significantly affected overall performance of sows. This study emphasizes the need for evaluating the impact of feeding regimens and meal size on feeding motivation and, ultimately, on the well-being of the gestating sows.

Evidence for the involvement of catecholamines in the 2-DG-induced immunomodulatory effects in spleen.

The role of catecholamines in immune changes associated with the metabolic stress of 2-deoxy-D-glucose (2-DG) was examined in this study. Male Lewis rats were pretreated with the nonselective beta-adrenergic receptor antagonist nadolol (0-0.5 mg/kg) and then received either a saline or 2-DG (500 mg/kg) injection. Nadolol attenuated the 2-DG-induced suppression of splenic T-cell mitogenic response and interferon-gamma production and increased nitric oxide production by macrophages in a dose-dependent manner. Conversely, nadolol did not attenuate the 2-DG-induced changes in immune parameters in peripheral blood leukocytes. These results suggest that the peripheral release of catecholamines is responsible for 2-DG-induced splenic immune alterations, whereas the peripheral release of catecholamine is not responsible for 2-DG-induced blood immune alterations. Furthermore, the neuroendocrine mechanisms responsible for splenic immune changes induced by the metabolic stress of 2-DG administration were the same as those involved in immune changes induced by physical and psychological stress. Thus, this study suggests that common neuroendocrine pathways exist for several types of stress-induced immunomodulations.

Microglial release of nitric oxide by the synergistic action of beta-amyloid and IFN-gamma.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized histopathologically by a loss of neurons and an accumulation of beta-amyloid plaques, neurofibrillary tangles, dystrophic neurites, and reactive glial cells. While most previous studies on the neurodegeneration of AD have focused on neuronal cells and direct beta-amyloid-mediated neurotoxicity, few have focused on the role of reactive glial cells in beta-amyloid-mediated neurotoxicity. In the present study nitric oxide release from cultured rat microglia was examined by exposing the cells to synthetic beta-amyloid peptides (beta 25-35 and beta 1-40) alone and in combination with the cytokines IFN-alpha/beta (100 U/ml), IL-1 beta (100 U/ml), TNF-alpha (100 U/ml), TNF-beta (100 U/ml), or IFN-gamma (10, 100, 500, or 1000 U/ml). Assessment of microglial release of nitric oxide was based on the colorimetric assay for nitrite in the culture medium and histochemistry for nitric oxide synthase. Of the cytokines tested, only IFN-gamma (1000 U/ml) induced nitric oxide release from microglia. beta 25-35 did not stimulate nitric oxide release by itself, but it did induce nitric oxide release when co-exposed with IFN-gamma (100, 500, and 1000 U/ml). In contrast, beta 1-40 did induce microglial release of nitric oxide by itself, and this effect was enhanced significantly by co-exposure with IFN-gamma (100 U/ml). These findings warrant a further investigation into the role of microglia in the neurodegeneration of Alzheimer's disease via nitric oxide toxicity induced by the synergistic action of beta-amyloid and a costimulatory factor.

Intracerebroventricular injection of corticotropin-releasing hormone in the pig: acute effects on behavior, adrenocorticotropin secretion, and immune suppression.

Corticotropin-releasing hormone (CRH) has been implicated as an important mediator of behavior, immune, and neuroendocrine systems in animals experiencing stress, but its effects on these systems have not been evaluated in an integrated whole animal model. In this experiment we injected porcine and rat CRH (pCRH and rCRH) intracerebroventricularly (icv) and simultaneously and chronologically monitored acute changes in behavior, endocrine, and immune function in the pig. PBS or CRH (15, 50, and 150 micrograms pCRH and 15 and 150 micrograms rCRH) was injected icv, and serial blood samples were collected via an indwelling jugular catheter so that behavior could be monitored simultaneously. The central administration of pCRH and rCRH induced immediate dose-dependent behavioral and physiological responses. Pigs receiving 15 micrograms of either pCRH or rCRH had increased plasma ACTH and were hyperactive and vocal. However, when higher doses (i.e. 50 or 150 micrograms) were administered icv, the endocrine and behavioral responses were accompanied by a profound suppression of Concanavalin-A-induced lymphocyte proliferation. For example, pigs receiving 150 micrograms pCRH had increased plasma ACTH and motor activity at 10 min (P < 0.01) and suppressed lymphocyte proliferation at 30 min (P < 0.001). Whereas ACTH secretion declined after 40 min, the lymphocyte suppression and increased motor activity were sustained, suggesting different control mechanisms. It is suggested that although ACTH and cortisol may have negative feedback effects on ACTH secretion, they did not have these effects on the behavioral action of CRH. Furthermore, although the lowest dose of CRH (15 micrograms) induced motor activity and ACTH secretion, higher doses (50 or 150 micrograms) were necessary for suppression of mitogen-induced lymphocyte proliferation. These findings demonstrate that CRH in the pig brain is active for inducing simultaneous changes in behavioral and physiological systems and are, therefore, consistent with the hypothesis that brain CRH is important in mediating the interaction among behavior, endocrine, and immune systems in animals experiencing stress.

Stress-induced changes in immune function are associated with increased production of an interleukin-1-like factor in young domestic fowl.

Investigation of the effects of stress on the immune system in young developing animals is hampered by many variables such as maternal interactions and physical size of immune organs. Young, precocial domestic fowl were used to overcome these difficulties. Domestic fowl, 14 days posthatch, served as an animal model to investigate the effects of stress (acute social isolation) on a rapidly developing immune system. Group-housed animals were isolated for 30, 60, or 90 min and assayed for numerative and functional changes in immune parameters in spleen and blood. The socially isolated birds showed an increase in body temperature, indicative of stress. The number of leukocytes/ml of blood increased in a time-dependent fashion, but the number of leukocytes in the spleen did not. The stress of isolation resulted in a significant increase in B-lymphocyte mitogen proliferation at 30 min, which decreased with time. Social stress also induced a time-dependent decrease in T-lymphocyte mitogen proliferation, which was significant by 90 min. Associated with changes in mitogen responsiveness was a significant increase in the production of an IL-1-like factor by splenic adherent cells from animals isolated for 30 min, which decreased in a time-dependent manner to return to baseline by 90 min. Thus, young domestic fowl represent a practical model for the examination of the effects of stress on immune function in a developing animal.

Stress-induced alterations in interferon production and class II histocompatibility antigen expression.

Mild electric foot-shock has been shown to be a stressor that can alter immune responses. Male Lewis rats were exposed to one session of 16 5.0-s 1.6-mA foot-shocks. Production of interferon-gamma by splenocytes in response to concanavalin-A was decreased in spleens from the shocked rats compared to control spleens. Spleen cells from rats treated with nadolol, a peripherally acting beta-adrenergic receptor antagonist, and then shocked, showed dose-dependent attenuation of the suppression of interferon-gamma production. This suggests that catecholamines mediate shock-induced suppression of interferon-gamma production. The percentage of splenic mononuclear cells expressing class II histocompatibility (Ia) antigens on their surfaces from spleens of shocked rats was determined by flow cytometry. Significantly decreased class II positive mononuclear cells were present in the spleens of shocked rats in comparison to the spleens of control rats. This may reflect an alteration of cell trafficking or decreased production of class II antigens.

Alterations in specific antibody production due to rank and social instability.

Separate studies examined the influence of the social environment of male cynomolgus macaques on primary and secondary antibody responses to immunization with tetanus toxoid. All animals showed evidence of both primary and secondary anti-tetanus antibody response. In the first study, subordinate animals had a greater primary antibody response to tetanus toxoid, while a single social reorganization (acute stressor) did not influence the response. In the second study, social rank was not associated with the secondary antibody response but repeated social reorganizations (chronic stressor) resulted in a greater level of specific antibody production in comparison to nonreorganized controls. These effects could not be accounted for on the basis of nonspecific differences in total serum IgG or serum albumin.

Stressor-induced changes in mitogenic activity are not associated with decreased interleukin 2 production or changes in lymphocyte subsets.

Splenic lymphocytes from Lewis rats that received presentations of physically aversive electric shock demonstrated a marked reduction in responsiveness to T-cell mitogens such as concanavalin A. This study examined cellular mechanisms which may be responsible for this functional alteration. There was no difference in distribution of T-cell subsets from shocked and nonshocked rats. There was no difference in the production of interleukin 2 (IL-2) nor was there a difference in the percentage of IL-2 receptor positive T cells or T-cell subsets after culture for 24 hr. However, there was a marked lack of mitogenic stimulation in splenocytes from shocked rats when stimulated with the calcium ionophore A23187. This indicates a defect in the biochemical pathways necessary to activate T-cell mitogenesis.