Effect of corticosteroid on porcine leukocytes: age-related effects of corticosteroid inhibition on porcine lymphocyte responses to mitogens

Glucocorticoid receptor number and affinity differ between peripheral blood mononuclear cells and granulocytes in domestic pigs

The aim of the present study was to characterize the number and affinity of glucocorticoid receptors (GR) in peripheral blood mononuclear cells (PBMC) and granulocytes of domestic pigs because glucocorticoid signaling is considered important for animal health and welfare. To investigate GR binding characteristics in intact porcine immune cells, blood samples of 6 castrated male pigs were collected via indwelling vein catheters. Porcine PBMC and granulocytes were isolated using two-layer density gradients, followed by radioligand binding assays to determine the number of GR sites per cell and the dissociation constant K_d as a measure for GR binding affinity. The present study revealed a greater number of GR sites per cell (P = 0.039) in PBMC (mean ± SEM: 1,953 ± 207 sites/cell) compared to granulocytes (1,561 ± 159 sites/cell) in domestic pigs. Furthermore, porcine PBMC had a higher GR binding affinity than porcine granulocytes (P = 0.003) as the dissociation constant K_d of PBMC (1.8 ± 0.2 nM) was lower than that of granulocytes (3.5 ± 0.4 nM). Our results point to differences in underlying mechanisms of glucocorticoid signaling in different porcine leukocyte populations.

Outcome of pigs with short gut syndrome submitted to orthotopic intestinal transplantation

PURPOSE

To evaluate the current model of small bowel resection and intestinal transplantation in pigs.

METHODS

Forty two Large White pigs were distributed in five groups: G1(n=6), G2(n=6) and G3(n=6) were submitted to 80%,100% and 100% plus right colon resection respectively and G4(n=7) and G5(n=5) to 100% SBR plus IT without and with immunosuppression based on Tacrolimus and Mycophenolic acid. Evaluation included weight control, clinical status, biochemical analysis and endoscopies for graft biopsies. Follow-up in G1 and 2 was 84 days, while in G3, four and five was ± three weeks.

RESULTS

G1 increased weight suggesting adaptation while G2 and 3 loused weight and inadequate adaptation. G4 and 5 died of acute cellular rejection (ACR) and sepses respectively. Overall survival in G1, 2, 3, 4 and 5 at 30 days was 100, 100, 0 and 20 %, respectively. Medium survival in G4 and 5 was 14 and 16 days.

CONCLUSIONS

The resection of 80% of small intestine in pigs is not suitable for short bowel syndrome induction. Intestinal transplantation with the proposed immunosuppression protocol was effective in prevent the occurrence of severe acute rejection, but inappropriate to increase recipients survival.

Behavioural, endocrine and immune responses to repeated social stress in pregnant gilts

Pregnant sows are exposed to various stressors in intensive pig husbandry that may have negative consequences on their health, reproductive performances and welfare. Social stress is one of these challenges, because gestating sows have to be housed in groups according to EU guidelines (2001/88/CE). The purpose of this study was to determine the consequences of repeated social stress in pregnant female pigs on their behavioural, endocrine and immunological responses and on pregnancy outcome. Pregnant gilts were submitted to a repeated social stress procedure induced by housing unfamiliar gilts in pairs changed twice a week between days 77 and 105 of gestation (S group, n = 18). Control gilts were housed in stable pairs during the same period (C group, n = 18). Agonistic behaviour was observed during the first 3 h after each grouping. Skin lesions were numbered 2 h after each grouping. Salivary cortisol was measured before and repeatedly during the 4 weeks of grouping. Gilts were immunized against keyhole limpet haemocyanin (KLH) on days 81 and 95 of gestation. Immunoglobulins G against KLH, proliferative responses to concanavalin A, lipopolysaccharide, pokeweed mitogen and KLH and peripheral blood leukocyte numbers were evaluated 1 week before the first grouping and 3 days after the last one. Agonistic interactions and skin lesions were observed in S gilts at each grouping, although there was a decline between the first and the last grouping (P < 0.05). The repeated social stress induced a sustained endocrine response as shown by elevated salivary cortisol levels from 1 to 48 h after grouping in S gilts compared to C gilts. The cellular as well as the humoral immunity and the leukocyte numbers were not influenced by social stress. Gestation length tended to be shorter in S gilts (P = 0.09), but litter size, piglet weight or mortality at birth were not affected. Variability of the response of S gilts to groupings was partly explained by their average success value determined according to the outcome (defeat or win) of all the groupings. In conclusion, our study demonstrates that the application of repeated social stress to pregnant gilts during the last third of their gestation repeatedly activates their hypothalamo-pituitary-adrenal axis but does not impair their immune function and pregnancy outcome.

Altered immunomodulation by glucocorticoids in neonatal pigs exposed to a psychosocial stressor

Stressful early life experiences can have short- and long-term effects on neuroendocrine and immune mechanisms of adaptation, which are primarily modulated by glucocorticoids. This study aimed to examine how the stress and immune systems interact to cope with psychosocial stress induced by a single social isolation (4 h) in neonatal pigs at 7, 21, or 35 d of age. This social isolation provoked increased plasma ACTH and cortisol concentrations and reduced TNF-α levels but had no significant effect on IL-6 levels. Socially isolated piglets had a higher lipopolysaccharide (LPS)-stimulated proliferative response of peripheral blood mononuclear cells (PBMCs) than controls, whereas concanavalin A (ConA)-induced proliferation was not affected by isolation. A single social isolation also induced a dose-dependent cortisol resistance in ConA- and LPS-stimulated PBMCs compared with controls, which may be an adaptive response in the short term. Moreover, LPS-stimulated cultures from control piglets showed a reduction in cortisol sensitivity with increasing age. Conclusively, these findings provide stress-related measures for the psychophysiological assessment of livestock handling practices but might also have implications for stress and health studies in young animals and humans.

Effects of dexamethasone on the pathogenesis of porcine circovirus type 2 infection in piglets

To investigate the effect of immunosuppression on porcine circovirus type 2 (PCV2) infection, hysterectomy-produced, colostrum-deprived piglets were inoculated with the virus by the intranasal or intraperitoneal route, with or without dexamethasone (DEX) treatment. Eleven piglets aged 8 days were divided into four groups, namely group A (four animals given PCV2), B (three given PCV2 with DEX), C (two given sterile medium with DEX) and D (two given sterile medium). No significant clinical signs were observed. Histopathological and immunohistochemical examination revealed granulomatous inflammation and PCV2 antigen in the lymphoid tissues of group B piglets, but not in the other three groups. Flow cytometric analysis of peripheral blood lymphocytes showed a reduced number of CD4+ T cells in DEX-treated piglets (groups A and C). No differences between groups were observed in respect of the number of B cells, serum IgG concentration, or PCV2 antibody titre. These results indicate that DEX influenced the pathogenic effects of PCV2 infection in lymphoid organs, and that suppression of cell-mediated immunity may play a role in the aetiology of postweaning multisystemic wasting syndrome.

Consequences of repeated early isolation in domestic piglets (Sus scrofa) on their behavioural, neuroendocrine, and immunological responses

Stress in the form of intermittent maternal deprivation and social isolation during early postnatal life in rats and monkeys produces persistent changes in physiology and behaviour. In farm animals physiological consequences of disrupting mother-infant interactions with respect to health and animal welfare are relatively unknown. Therefore, the aim of the present study was to investigate the behavioural, neuroendocrine and immunological consequences of a 2 h daily social isolation from day 3 to day 11 of age in domestic piglets as well as potential long-term effects on the brain-endocrine-immune regulation. Repeated social isolation resulted in significantly decreased open-field activity (locomotion, vocalization) during the isolation period, increased basal cortisol concentrations and decreased lymphocyte proliferation in response to concanavalin A and pokeweed mitogen one day after the isolation. There was also a significant increase of interleukin-1beta (IL-1beta) concentration in hippocampus in isolated piglets compared to controls at this time. Six weeks after isolation significant enhanced basal ACTH concentrations as well as higher IL-1beta content and glucocorticoid receptor (GR) binding in hippocampus were found. These endocrine and immune responses were associated with decreased CRH levels in the hypothalamus and increased CRH content in the amygdala. The present data indicate that early social isolation in pigs may cause changes in behavioural, neuroendocrine, and immune regulation and produce long-term effects not only on the activity of the hypothalamic-pituitary-adrenal (HPA) system, but also on the immune-brain circuitry with possible negative consequences in health and welfare of commercial pigs. Using the pig as a suitable animal model, the finding of this study may also have some implications for the etiology of anxiety and depression in humans.

Does cortisol bias cytokine production in cultured porcine splenocytes to a Th2 phenotype?

Glucocorticoids are reported to bias the production of cytokines from a type 1 to a type 2 phenotype. However, this dogma has been advanced largely from studies utilizing potent glucocorticoid analogs, particularly dexamethasone (DEX). Although studies utilizing DEX certainly have clinical and pharmacological relevance, DEX is probably not the best glucocorticoid for studies designed to evaluate the interaction and regulation of endogenous corticosteroids with immune cells in vivo in the domestic pig. Functional measures of immune suppression suggest that the pig is relatively resistant to DEX. Furthermore, type II corticosteroid receptors exclusively bind DEX with high affinity, whereas type I receptors, the so-called mineralocorticoid receptors, have a higher affinity for cortisol. In addition, DEX is not bound by serum binding proteins as are endogenous corticosteroids. These issues prompted us to revisit glucocorticoid regulation of type 1 and type 2 cytokines in cultured pig splenocytes and to test the broad hypothesis that cortisol biases cytokine production in favor of a Th2 response. We evaluated interferon gamma (IFNgamma) (also interleukin 2 (IL-2) in one experiment) and interleukin 10 (IL-10) as representative Th1 and Th2 cytokines, respectively. Furthermore, we evaluated macrophage migration inhibitory factor (MIF) because it is reported to be an essential factor in T cell activation; it is also upregulated by glucocorticoids and reported to be a product of Th2 lymphocytes. In general, both IFNgamma and IL-10 were sensitive to cortisol inhibition early in culture. However, IFNgamma ultimately escaped cortisol inhibition, whereas IL-10 continued to be substantially suppressed by high physiological concentrations of cortisol. Similarly, MIF mRNA could be suppressed by cortisol, but only when cortisol was added to cultures after ConA (concanavalin A) stimulation of splenocytes. So, taken together, our studies do not support the hypothesis that cortisol favors a Th2 cytokine profile in cultured pig splenocytes.

A comparison of the sensitivity of pig and human peripheral blood mononuclear cells to the antiproliferative effects of traditional and newer immunosuppressive agents

Difficulty in preventing rejection of fetal pig islet-like cell clusters (ICCs) transplanted into pigs using traditional forms of immunotherapy has been reported. An in vitro study of the efficacy of seven different immunosuppressive agents to inhibit proliferation of pig peripheral blood mononuclear cells (PBMC) was performed, and a comparison was made between the human and pig to determine if the efficacy of these agents differed between species. The efficacy of cyclosporine (CsA), azathioprine (Aza), methylprednisolone (MP), FK506, rapamycin (RAP), mycophenolate mofetil (MMF) and deoxymethylspergualin (MeDSG) to inhibit pig and human PBMC proliferation in mitogenic experiments using phytohaemagglutinin (PHA) as a stimulus was performed. Further, allogeneic pig mixed lymphocyte reactions (MLR) were used to determine the activity of these agents in a model more comparable to the allograft rejection process. It was found that pig PBMC stimulated with PHA or in a MLR were inhibited by the agents tested, with the exception of MeDSG that was ineffective in mitogenic experiments. The inhibitory effects of these agents differed between PHA and MLR, the respective (50% inhibitory concentration) IC50 values for pig PBMC being 1.7 and 0.08 microg/ml for CsA, 1.4 and 4.4 microg/ml for Aza, 0.11 and 0.002 microg/ml for MP, 3.0 and 2.8 ng/ml for FK506, 2.1 and 0.3 ng/ml for RAP and 10.8 and 454 ng/ml for MME Pig PBMC were less sensitive than human PBMC to the antiproliferative effects of CsA, Aza, FK506, RAP and MMF, but not MP on PHA stimulation, the ratio of the pig to human IC50 values being 19, 11, 13, 2.3, 1.4, and 0.4, respectively. These data suggest that the doses of most immunosuppressive agents administered to prevent rejection in pigs need to be higher than those used to achieve therapeutic benefit in humans.

Effects of social status after mixing on immune, metabolic, and endocrine responses in pigs

The effects of social rank on immune, metabolic, and endocrine responses were studied in 10 newly mixed groups of German Landrace pigs (9 individuals each) at an age of 12 weeks. Immediately after mixing, the agonistic interactions (AI) of all group members were continuously recorded over 3 days (10 h daily). An individual dominance value (DV) was calculated by the number of wins minus defeats in relation to all decisive fights (DV < or = 0, subordinate; DV > 0, dominant). Blood samples were taken 24 h before and 3 days after mixing. The data showed that the social status had a significant effect on lymphocyte proliferation in responses to different mitogens: socially dominant pigs had higher proliferative response than subordinate pigs. In addition, during the observation period the lymphocyte activation by mitogens increased in the dominant animals and decreased in the subordinate animals with increasing number of agonistic interactions. The rise in total serum IgG concentration 3 days after mixing was higher in dominant pigs compared with subordinates. The dominance status did not significantly affect plasma metabolic levels nor cortisol concentrations. However, mixing appeared to increase glucose and total protein values and to decrease alkaline phosphatase and cortisol levels in both, dominant and subordinate pigs. In conclusion, mitogen induced cell proliferation seems to be a valuable marker for acute social stress in pigs.

In vitro effect of glucocorticoids on phagocytic function of sheep alveolar macrophages

The potentiation of infection is a recognized adverse effect of steroids. This study examined the in vitro effect of glucocorticoids on sheep alveolar macrophage phagocytic function, an essential means of cellular defence in the lungs, by evaluating the phagocytosis of zymosan particles after 30 min of contact between alveolar macrophages and steroids. Hydrocortisone, dexamethasone phosphate and methylprednisolone significantly reduced the phagocytic capability of sheep alveolar macrophages, but the effects of dexamethasone isonicotinate, prednisolone and flumethasone were less marked.

In vitro stimulation of antibody production to Mycoplasma hyopneumoniae by porcine peripheral blood mononuclear cells

A method to stimulate and detect the in vitro production of antibodies to Mycoplasma hyopneumoniae by porcine peripheral blood mononuclear cells (PBMC) was established. PBMC were cultured in microtiter plates coated with a sonicated M. hyopneumoniae whole cell antigen and the amount of antibody bound to the coating antigen was determined by an enzyme linked immunosorbent assay (ELISA). In addition, the amount of non-bound antibody was determined by testing the culture supernatants in the ELISA which detects porcine antibodies to M. hyopneumoniae. The production of antibodies, in terms of total absorbance values, was enhanced by including 2.5 ng pokeweed mitogen (PWM) per ml growth medium without altering the specificity of the assay. In a pilot experiment, the applicability of the method to follow the development of antigen-reactive cells during primary and secondary immunizations with M. hyopneumoniae was evaluated. Antigen-reactive cells, identified by their ability to produce antibodies to M. hyopneumoniae in vitro, were detected seven days after the primary immunization and reached their highest antigen reactivity one week later. In comparison, antigen-reactive cells could be detected three days after the booster immunization and remained in the circulation for 2 weeks.

Suppression of bovine lymphocyte responses to mitogens following in vivo and in vitro treatment with dexamethasone

Gnotobiotic calves given intramuscular injections of dexamethasone (DM, 0.5 mg kg-1 day-1) showed marked changes in haematological parameters including a neutrophilia and a lymphopaenia. Not only was there a reduction in the numbers of circulating mononuclear cells, but there was also a significant (P less than 0.01) decrease in the in vitro responsiveness of the remaining circulating peripheral blood lymphocytes to the mitogens, phytohaemagglutinin (PHA), concanavalin A (ConA) and pokeweed mitogen (PWM). Responses to all three mitogens were suppressed to a similar degree. Analysis of the circulating mononuclear cell sub-populations before and during DM treatment demonstrated a selective depletion of B cells; the T lymphocyte sub-population that expresses the gamma/delta form of T cell receptor, are CD2-, CD5+, CD8-, CD4- and constitute a major population in peripheral blood of calves. In vitro studies in gnotobiotic and conventional calves confirmed that DM was highly inhibitory for PHA responses but, in contrast to the in vivo findings, showed little effect of DM on ConA responses. Expression of surface antigens after 72 h in vitro culture in the presence of DM were little affected with the exception of BoCD8 and MHC II, which showed increased and decreased expression, respectively. These observations would suggest that distinct mechanisms are involved in glucocorticosteroid suppression of the responses to these two mitogens.

The influence of corticosteroids on host defense mechanisms

Glucocorticosteroid hormones affect virtually every tissue type in the body, including tissues of host-defense systems. There is an enormous body of literature concerning specific effects of corticosteroids on host defenses. This literature review examines the affects of corticosteroids on leukocyte kinetics, phagocytic immunity, cell-mediated immunity, and humoral immunity in steroid-resistant species.

Necrotizing tracheobronchitis following high frequency ventilation: effect of hydrocortisone

A piglet model of acute respiratory failure was used to determine whether necrotizing tracheobronchitis (NTB) produced during high-frequency pneumatic flow interrupter (HFFI) ventilation could be attenuated by prior administration of 2 mg/kg hydrocortisone IV. Fourteen piglets (means age 3.6 days, means wt 1.4 kg) were anesthetized and paralyzed before saline lung lavage. The animals were randomly assigned to either placebo (P) or hydrocortisone (H) group. Continuous HFFI (10 Hz) was interrupted five times per minute by a 1-second deflationary pause. All animals were kept on 1.0 FI02 with ventilators adjusted to maintain adequate arterial blood gases. Airway pressures were similar for both groups. After 8 hours of ventilation the animals were sacrificed and their lungs inflated with formalin to 40 cm H2O. Sections were obtained from trachea, carina, main stem, and peripheral bronchi. A total airway injury (TAIS) was calculated by a pathologist unaware of treatment assignment. There was a significant difference (p less than 0.01, Wilcoxon rank sum) in TAIS scores between P (means 21.3) and H (means 7.8). In five out of seven P animals and in one out of seven H animals, NTB was severe and extended to the hilar bronchi. Although NTB is multifactorial in origin, the prior use of hydrocortisone may decrease the severity and extent of lesions by modifying the inflammatory response to this specific airway injury.

Disulfide-linked receptors for mitogenic lectins on piglet lymphocytes

The interaction between leucoagglutinating phytohemagglutinin (L-PHA), concanavalin A (Con A), soybean agglutinin (SBA) and lentil lectin (LcH) with disulfide-linked cell surface receptors on lymphocytes from mesenteric lymph nodes of 3-day piglets (PMLN) was investigated. Surface radioiodinated PMLN lymphocytes were lysed with buffer containing Nonidet-P40. The lysates were adsorbed on lectin-agarose derivatives (or bovine serum albumin-agarose). Eluates from the lectin-agarose derivatives were analyzed by one-dimensional or two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis both under reducing and nonreducing conditions. Among the various-lectin-binding polypeptides, L-PHA recognizes a single 92-kDa disulfide-linked moiety in piglet lymphocyte lysate, comprised of polydisperse 52-kDa subunits. In addition to this apparent homodimer, SBA, Con A and LcH bind a much less prominent 82-kDa heterodimer comprised of 47-kDa and 37-kDa polypeptides; these molecules are not observed in eluates of L-PHA. Binding of the 92- and 82-kDa molecules by LcH is inhibited by methyl-alpha-D-mannoside. These results indicate that there are two lectin-binding disulfide-linked glycoproteins on lymphocytes from 3-day piglets which bind preferentially to potent mitogens. The electrophoretic properties of these molecules, under both reducing and nonreducing conditions, as well as their lectin-binding properties are very similar to those observed for antigen receptor molecules on lymphocytes from other species.

Isolation and characterization of porcine natural killer (NK) cells

The morphologic and biological properties of porcine cells mediating natural killer (NK) activity were determined. In a previous study, we demonstrated that lymphocytes from the peripheral blood of pigs greater than 1 week of age possessed NK activity to K562 tumor cells and that lymphocytes from the blood and spleen of pigs greater than 1 day of age were able to mediate natural cytotoxicity against parainfluenza-3 (PI3) virus-infected Vero cells (Yang and Schultz, 1986a). Discontinuous density gradients were used to enrich NK cells. NK cytotoxicity was mainly present in high-density Percoll fractions (50 to 55% and 55 to 60%); little or no NK activity was present in lower density fractions. The NK cell enriched lymphocytes responded to the mitogens PHA, ConA and PWM. NK cells were sensitive to the suppressive effect of corticosteroid, but Protein A did not affect NK activity. The amount of cytotoxicity directly corresponded to the degree of binding that occurred between the NK enriched lymphocyte population and the target cells. Cytochemical and morphological studies demonstrated that these bond cells which are believed to be responsible for the NK activities, were mainly small to medium lymphocytes lacking azurophilic cytoplasmic granules. These findings were confirmed by ultrastructural studies of effector and "target-binding" cells. The results of the present study suggested that the cells mediating NK activity in pigs have the morphological and density characteristics of small and medium sized lymphocytes; findings that differ from those described for NK cells in human and other animal species.