Literatura científica selecionada sobre o tema "Immuno-suppression"

Abstract We and others have recently demonstrated that suberoylanilide hydroxamic acid (SAHA), a histone deacetylase (HDAC) inhibitor with anti-neoplastic properties, reduces experimental acute graft-versus-host disease (GVHD). We have now investigated the mechanisms of action of two HDAC inhibitors, SAHA and ITF 2357, on allogeneic immune responses. Bone marrow derived dendritic cells (DCs) were preincubated with the HDAC inhibitors at nanomolar concentrations for 16–18 hours and stimulated with lipopolysaccharide (LPS). Pretreatment of DCs caused a significant reduction in the secretion of TNF-α, IL-12p70 and IL-6 compared to the untreated controls (P< 0.005). Similar effects were seen using human peripheral blood mononuclear cell derived DCs. Pre-treatment of both murine and human DCs also significantly reduced their in vitro stimulation of allogeneic T cells as measured by proliferation and IFN-γ production (P<0.01). We determined the in vivo relevance of these observations utilizing a mouse model where the responses of allogeneic donor bm12 T cells depended on the function of injected host B6 DCs would stimulate. Recipient Class-II −/− B6 (H-2b) received 11 Gy on day -1 and were injected with 4–5 x 106 wild type B6 DCs treated with SAHA or with media on days -1 and 0 and then transplanted with 2 x 106 T cells and 5 x 106 TCDBM cells from either syngeneic B6 or allogeneic bm12 donors. SAHA treatment of DCs significantly reduced expansion of allogeneic donor CD4+ T cells on day +7 after BMT compared to controls (P<0.05). SAHA treatment induced a similarly significant reduction in the expansion of CD8+ cells in Class I disparate [bm1→β2M−/−] model. In vitro, SAHA treatment significantly suppressed the expression of CD40 and CD80 but did not alter MHC class II expression. Surprisingly, when mixed with normal DCs at 1:1 ratio, SAHA treated DCs dominantly suppressed allogeneic T cell responses. The regulation of T cell proliferation was not reversible by addition of IL-12, TNF-α, IL-18, anti-IL-10 or anti-TGFβ, either alone or in combination. Suppression of allogeneic responses was contact dependent in trans-well experiments. To address whether the regulation of SAHA treated DCs required contact with T cells, we devised a three cell experiment where SAHA treated DCs lacked the capacity to present antigens to T cells. DCs from B6 MHC Class II deficient (H-2b) were treated with SAHA and co-cultured with wild type B6 (H-2b) DCs along with purified allogeneic BALB/c (H-2d) CD4+ T cells in an MLR. Allogeneic CD4+ T cells proliferated well, demonstrating the regulation to be dependent on contact between SAHA treated DCs and T cells. To address the in vivo relevance of this suppression, we utilized a well characterized [BALB/c →B6] mouse model of acute GVHD. Recipient B6 animals received 11Gy on day -1 and were injected with of 5 million host type SAHA treated or control DCs on days −1, 0, and +2. Mice were transplanted on day 0 with 2 x 106 T cells and 5 x 106 BM from either syngeneic B6 or allogeneic BALB/c donors. Injection of SAHA treated DCs resulted in significantly better survival (60% vs. 10%, P < 0.01) and significantly reduced serum levels of TNF-α, donor T cell expansion and histopathology of GVHD on day +7 after BMT compared to the controls. We conclue that HDAC inhibitors are novel immunomodulators that regulate DC function and might represent a novel strategy to prevent GVHD.

Accelerating anthropogenic climate change threatens to destroy coral reefs worldwide through the processes of bleaching and disease. These major contributors to coral mortality are both closely linked with thermal stress intensified by anthropogenic climate change. Disease outbreaks typically follow bleaching events, but a direct positive linkage between bleaching and disease has been debated. By tracking 152 individual coral ramets through the 2014 mass bleaching in a South Florida coral restoration nursery, we revealed a highly significant negative correlation between bleaching and disease in the Caribbean staghorn coral,Acropora cervicornis. To explain these results, we propose a mechanism for transient immunological protection through coral bleaching: removal ofSymbiodiniumduring bleaching may also temporarily eliminate suppressive symbiont modulation of host immunological function. We contextualize this hypothesis within an ecological perspective in order to generate testable predictions for future investigation.

Heavy sports training schedules and competition is often associated with immuno-suppression, and so there is a theoretical justification for providing athletes with nutrients that display immuno-regulatory properties. Among such immuno-nutrients, considerable attention has been paid in recent years to two amino acids, arginine (ARG) and glutamine (GLN). ARG and GLN availability regulate the function ofT lymphocytes, macro phages and polymorphonuclear cells. ARG acts through nitric oxide and polyamine synthesis. The mechanism of action of GLN in immune cells remains unclear. Experience in clinical nutrition suggests that an ARG-enriched diet may limit infectious morbidity in critically ill patients. Data concerning oral/enteral GLN supplementation are more controversial. There have been few trials of supplementation in sports medicine, but results are promising, justifying further studies in which dosages and administration schedules should be taken into account.

This thesis describes a series of three experiments designed to estimate the nutritional cost of the immune response to the gastrointestinal nematodes Trichostrongylus colubriformis and Teladorsagia circumcincta in sheep. For each experiment, animals were allocated hierarchically by liveweight into one of four groups that were either infected (group IF), similarly infected and concurrently immuno-suppressed with weekly intramuscular injections of 1.3mg kg liveweight (LW)-1 of methylprednisolone acetate (group ISIF), immuno-suppressed only (group IS) or remained as controls (group C). Body composition of all animals was estimated using x-ray computer tomography prior to infection and at the conclusion of each study with bodyweight and faecal nematode egg counts (FEC; eggs gram-1 of fresh faeces (epg)) measured along with blood samples taken for the determination of levels of serum proteins, phosphate and antibodies. In the first trial (Chapter 3), the nutritional cost of both the acquisition and maintenance of immunity to gastro-intestinal nematodes was investigated using immunologically naive 5-month-old lambs and immunologically competent 17-month-old ewes during infection with 2,000 and 4,000 L3 infective T. colubriformis larvae d-1, respectively (80 L3 T. colubriformis larvae kgLW-1 d-1). Profiles of FEC and comparative worm burdens at slaughter indicated an effective immune response was maintained in IF ewes and developed in IF lambs while successfully suppressed in both ISIF lambs and ISIF ewes and was confirmed by serum antibody titres. The typical reduction in voluntary feed intake as a consequence of infection was observed in IF lambs (0.30, p<0.001) but not in IF ewes, ISIF lambs or ISIF ewes, and appeared to be associated with L3 IgA. Gross efficiency of use of metabolizable energy (ME) for net energy (NE) deposition was reduced by 0.20 in lambs during acquisition of immunity and by 0.16 in ewes maintaining an established immunity. Infection in immuno-suppressed animals reduced efficiency by 0.05 and 0.15 for lambs and ewes. These findings allowed the hypothesis that the reduction in feed intake and nutrient utilization in young parasitized sheep is caused by physiological signalling associated with the acquisition phase of the host immune response to infection, rather than simply the damage caused by the parasite per se. The second trial (Chapter 4) investigated the influence of metabolizable protein (MP) supply on the metabolic disturbances associated with the acquisition phase of the immune response during infection with 2,000 L3 T. colubriformis d-1. Groups of lambs were offered either a low protein (L; 62g MP kgDM-1) or high protein diet (H; 95g MP kgDM-1). Patterns of total daily egg excretion indicated that an effective immune response was developed in HIF, but not LIF, HISIF nor LISF and was confirmed by comparative worm burdens. The proportionate reduction in feed intake in immunologically normal animals was reduced through the provision of additional protein, being 0.12 in HIF and 0.23 in LIF. Regardless of diet, infection did not cause a reduction in feed intake in immuno-suppressed animals (p>0.05). Infection proportionately reduced the gross efficiency of ME utilization in immunologically normal animals by 0.23 in HIF (p=0.09) and by 0.51 in LIF (p=0.01), but not in immuno-suppressed animals. Immuno-suppression did not suppress serum L3 IgA levels in seven of the eight HISIF and four of the eight LISIF animals. Furthermore, only four out of the eight immunologically normal animals from both the HIF and LIF groups displayed an L3 IgA response. Consequently, regardless of immuno-suppression treatment, animals were termed as IgA responders (HR or LR) or non-responders (HN or LN). Feed intake was proportionately reduced from day 22 by 0.15 in HR (p=0.03) and by 0.32 in LR (p=0.01), but was not significantly reduced in HN or LN. Gross efficiency of ME utilization was significantly reduced for LN animals only, being proportionately 0.59 (p<0.01). These findings allowed the conclusion that additional MP reduced the consequence of immunological signalling that was displayed in reduced feed intake and in nutrient utilization, both of which appeared to be associated with an IgA response. It is hypothesized that the lessening of nutritional disturbance observed in high protein and immuno-suppressed animals could be a consequence of altered physiological signalling during the immunological cascade. The third trial (Chapter 5) utilized lambs infected with the abomasal parasite T. circumcincta to explore the possibility that the reduction in feed intake and nutrient utilization is a universal phenomenon of the acquisition phase of the immune response to nematode parasites inhabiting different organs along the gastrointestinal tract. In addition, immunological changes at the site of parasite infestation in the abomasal mucosa were measured from serial biopsy tissue samples taken from a further twelve animals that were surgically fitted with an abomasal cannula and either infected (CIF) or concurrently infected and immuno-suppressed as described previously (CISIF). The development of immunity in IF animals was accompanied by a 0.17 proportional decrease in feed intake between days 15 to 28 of infection (p<0.05) and a 0.20 proportional reduction in nutrient utilization (p=0.07), none of which were observed in ISIF animals. While FEC and worm burdens indicated successful immuno-suppression in ISIF animals, both serum IgA and total antibody production were not reduced. The development of immunity in CIF was reflected in an increase in both mast cells and globule leukocytes in serial abomasal tissue biopsies, both of which were reduced in CISIF (p<0.01 for both). In serial biopsy tissue, immuno-suppression did prevent a rise in tissue IgA that was apparent in CIF animals (p<0.01) although these changes were not reflected in serum IgA levels. It appears that the alleviation of the reduction in feed intake and nutrient utilization in young lambs through the use of corticosteroid induced immuno-suppression may be a universal phenomenon for both intestinal and abomasal parasites, but the association with and/or role of IgA during infection with T. circumcincta is unclear. In summary, the reduction in feed intake and nutrient utilization in sheep during infection with both the abomasal nematode T. circumcincta and the small intestine nematode T. colubriformis appears to be associated with a component(s) of the acquisition phase of the host immune response, rather than, as conventionally assumed, the direct mechanical damage of the parasite per se. It is hypothesised that the nutritional disturbance as a consequence of infection in young lambs may be the result of pro-inflammatory cytokines involved in immunological signalling that may also be associated with the production of IgA, the effects of which can be reduced through the provision of adequate MP. These studies provide evidence that the immune response to gastrointestinal parasites is nutritionally costly to the animal and have implications for application of manipulations that are intended to promote the development of a strong immune reaction in high producing animals.

This thesis describes a series of three experiments designed to estimate the nutritional cost of the immune response to the gastrointestinal nematodes Trichostrongylus colubriformis and Teladorsagia circumcincta in sheep. For each experiment, animals were allocated hierarchically by liveweight into one of four groups that were either infected (group IF), similarly infected and concurrently immuno-suppressed with weekly intramuscular injections of 1.3mg kg liveweight (LW)⁻¹ of methylprednisolone acetate (group ISIF), immunosuppressed only (group IS) or remained as controls (group C). Body composition of all animals was estimated using x-ray computer tomography prior to infection and at the conclusion of each study with bodyweight and faecal nematode egg counts (FEC; eggs gram⁻¹ of fresh faeces (epg)) measured along with blood samples taken for the determination of levels of serum proteins, phosphate and antibodies. In the first trial (Chapter 3), the nutritional cost of both the acquisition and maintenance of immunity to gastro-intestinal nematodes was investigated using immunologically naive 5-month-old lambs and immunologically competent 17-month-old ewes during infection with 2,000 and 4,000 L3 infective T. colubriformis larvae d⁻¹, respectively (80 L3 T. colubriformis larvae kgLW⁻¹ d⁻¹). Profiles of FEC and comparative worm burdens at slaughter indicated an effective immune response was maintained in IF ewes and developed in IF lambs while successfully suppressed in both ISIF lambs and ISIF ewes and was confirmed by serum antibody titres. The typical reduction in voluntary feed intake as a consequence of infection was observed in IF lambs (0.30, p<0.001) but not in IF ewes, ISIF lambs or ISIF ewes, and appeared to be associated with L3 IgA. Gross efficiency of use of metabolizable energy (ME) for net energy (NE) deposition was reduced by 0.20 in lambs during acquisition of immunity and by 0.16 in ewes maintaining an established immunity. Infection in immuno-suppressed animals reduced efficiency by 0.05 and 0.15 for lambs and ewes. These findings allowed the hypothesis that the reduction in feed intake and nutrient utilization in young parasitized sheep is caused by physiological signalling associated with the acquisition phase of the host immune response to infection, rather than simply the damage caused by the parasite per se. The second trial (Chapter 4) investigated the influence of metabolizable protein (MP) supply on the metabolic disturbances associated with the acquisition phase of the immune response during infection with 2,000 L3 T. colubriformis d⁻¹. Groups of lambs were offered either a low protein (L; 62g MP kgDM⁻¹) or high protein diet (H; 95g MP kgDM⁻¹). Patterns of total daily egg excretion indicated that an effective immune response was developed in HIF, but not LIF, HISIF nor LISF and was confirmed by comparative worm burdens. The proportionate reduction in feed intake in immunologically normal animals was reduced through the provision of additional protein, being 0.12 in HIF and 0.23 in LIF. Regardless of diet, infection did not cause a reduction in feed intake in immuno-suppressed animals (p>0.05). Infection proportionately reduced the gross efficiency of ME utilization in immunologically normal animals by 0.23 in HIF (p=0.09) and by 0.51 in LIF (p=0.01), but not in immuno-suppressed animals. Immuno-suppression did not suppress serum L3 IgA levels in seven of the eight HISIF and four of the eight LISIF animals. Furthermore, only four out of the eight immunologically normal animals from both the HIF and LIF groups displayed an L3 IgA response. Consequently, regardless of immunosuppression treatment, animals were termed as IgA responders (HR or LR) or non-responders (HN or LN). Feed intake was proportionately reduced from day 22 by 0.15 in HR (p=0.03) and by 0.32 in LR (p=0.01), but was not significantly reduced in HN or LN. Gross efficiency of ME utilization was significantly reduced for LN animals only, being proportionately 0.59 (p<0.01). These findings allowed the conclusion that additional MP reduced the consequence of immunological signalling that was displayed in reduced feed intake and in nutrient utilization, both of which appeared to be associated with an IgA response. It is hypothesized that the lessening of nutritional disturbance observed in high protein and immuno-suppressed animals could be a consequence of altered physiological signalling during the immunological cascade. The third trial (Chapter 5) utilized lambs infected with the abomasal parasite T. circumcincta to explore the possibility that the reduction in feed intake and nutrient utilization is a universal phenomenon of the acquisition phase of the immune response to nematode parasites inhabiting different organs along the gastrointestinal tract. In addition, immunological changes at the site of parasite infestation in the abomasal mucosa were measured from serial biopsy tissue samples taken from a further twelve animals that were surgically fitted with an abomasal cannula and either infected (CIF) or concurrently infected and immuno-suppressed as described previously (CISIF). The development of immunity in IF animals was accompanied by a 0.17 proportional decrease in feed intake between days 15 to 28 of infection (p<0.05) and a 0.20 proportional reduction in nutrient utilization (p=0.07), none of which were observed in ISIF animals. While FEC and worm burdens indicated successful immunosuppression in ISIF animals, both serum IgA and total antibody production were not reduced. The development of immunity in CIF was reflected in an increase in both mast cells and globule leukocytes in serial abomasal tissue biopsies, both of which were reduced in CISIF (p<0.01 for both). In serial biopsy tissue, immuno-suppression did prevent a rise in tissue IgA that was apparent in CIF animals (p<0.01) although these changes were not reflected in serum IgA levels. It appears that the alleviation of the reduction in feed intake and nutrient utilization in young lambs through the use of corticosteroid induced immuno-suppression may be a universal phenomenon for both intestinal and abomasal parasites, but the association with and/or role of IgA during infection with T. circumcincta is unclear. In summary, the reduction in feed intake and nutrient utilization in sheep during infection with both the abomasal nematode T. circumcincta and the small intestine nematode T. colubriformis appears to be associated with a component(s) of the acquisition phase of the host immune response, rather than, as conventionally assumed, the direct mechanical damage of the parasite per se. It is hypothesised that the nutritional disturbance as a consequence of infection in young lambs may be the result of pro-inflammatory cytokines involved in immunological signalling that may also be associated with the production of IgA, the effects of which can be reduced through the provision of adequate MP. These studies provide evidence that the immune response to gastrointestinal parasites is nutritionally costly to the animal and have implications for application of manipulations that are intended to promote the development of a strong immune reaction in high producing animals.

Evaluation of immuno-modulating properties of nanomaterials is important to develop new potential therapeutics for inflammatory diseases and cancer. Activation and suppressive effects of nanomaterials on immune responses occur through various interactions with different host proteins. They can also be engineered as carriers and/or adjuvants for different proteins or antigens. Particles, emulsions, and tubes/rods are the major formats of nanomaterials currently used in biomedical applications. Sometimes, nanomaterials induce side effects like undesired immunosuppression and toxicities, which are major concerns at present in designing optimal nanotherapeutics. This chapter summarizes different types of nanomaterials and their effect on immune responses.

Evaluation of immuno-modulating properties of nanomaterials is important to develop new potential therapeutics for inflammatory diseases and cancer. Activation and suppressive effects of nanomaterials on immune responses occur through various interactions with different host proteins. They can also be engineered as carriers and/or adjuvants for different proteins or antigens. Particles, emulsions, and tubes/rods are the major formats of nanomaterials currently used in biomedical applications. Sometimes, nanomaterials induce side effects like undesired immunosuppression and toxicities, which are major concerns at present in designing optimal nanotherapeutics. This chapter summarizes different types of nanomaterials and their effect on immune responses.