Avian inflammatory response: mediation by macrophages

The Immuno-Suppressive Effects of Cyclic, Environmental Heat Stress in Broiler Chickens: Local and Systemic Inflammatory Responses to an Intradermal Injection of Lipopolysaccharide

To assess effects of environmental heat stress (HS) on the local and systemic inflammatory responses to lipopolysaccharide (LPS), broilers were reared under thermoneutral (TN) or cyclic HS conditions. Thermoneutral temperatures followed commercial production settings, with HS broilers exposed to 35 °C for 14 h/day from 4 days onward. At 37 days, HS- and TN-broilers were assigned to either LPS (100 μg/mL) or endotoxin-free phosphate-buffered saline (PBS; vehicle) treatments, eight each to HS- and TN-LPS, four each to HS- and TN-PBS. Treatments were administered by intradermal injection of growing feather (GF) pulps; 10 μL/GF; 12 GF/broiler. Blood and GF were collected before and at 6 and 24 h post-injection to assess leukocyte population changes in GF-pulps and blood, reactive oxygen species (ROS) generation and cytokine expression in GF-pulps, and plasma concentrations of alpha-1 acid glycoprotein (AGP-1). HS-LPS broilers had lower (p ≤ 0.05) infiltration of heterophils and macrophages, ROS generation, and inflammatory cytokine expression in GF-pulps, and lacked the increases in heterophil, monocyte, and plasma AGP-1 concentrations observed in TN-LPS broilers. HS-broilers had similar or greater drops in blood lymphocytes 6 h post-LPS or -PBS injection, respectively, and lower baseline levels (p ≤ 0.05) of circulating T- and B-lymphocytes than TN-broilers. Results indicated that cyclic HS reduced the local and systemic acute inflammatory responses to LPS in broilers, likely impairing their innate defense against microbial infection.

A critical assessment of the cellular defences of the avian respiratory system: are birds in general and poultry in particular relatively more susceptible to pulmonary infections/afflictions?

In commercial poultry farming, respiratory diseases cause high morbidities and mortalities, begetting colossal economic losses. Without empirical evidence, early observations led to the supposition that birds in general, and poultry in particular, have weak innate and adaptive pulmonary defences and are therefore highly susceptible to injury by pathogens. Recent findings have, however, shown that birds possess notably efficient pulmonary defences that include: (i) a structurally complex three-tiered airway arrangement with aerodynamically intricate air-flow dynamics that provide efficient filtration of inhaled air; (ii) a specialised airway mucosal lining that comprises air-filtering (ciliated) cells and various resident phagocytic cells such as surface and tissue macrophages, dendritic cells and lymphocytes; (iii) an exceptionally efficient mucociliary escalator system that efficiently removes trapped foreign agents; (iv) phagocytotic atrial and infundibular epithelial cells; (v) phagocytically competent surface macrophages that destroy pathogens and injurious particulates; (vi) pulmonary intravascular macrophages that protect the lung from the vascular side; and (vii) proficiently phagocytic pulmonary extravasated erythrocytes. Additionally, the avian respiratory system rapidly translocates phagocytic cells onto the respiratory surface, ostensibly from the subepithelial space and the circulatory system: the mobilised cells complement the surface macrophages in destroying foreign agents. Further studies are needed to determine whether the posited weak defence of the avian respiratory system is a global avian feature or is exclusive to poultry. This review argues that any inadequacies of pulmonary defences in poultry may have derived from exacting genetic manipulation(s) for traits such as rapid weight gain from efficient conversion of food into meat and eggs and the harsh environmental conditions and severe husbandry operations in modern poultry farming. To reduce pulmonary diseases and their severity, greater effort must be directed at establishment of optimal poultry housing conditions and use of more humane husbandry practices.

Intense Innate Immune Responses and Severe Metabolic Disorders in Chicken Embryonic Visceral Tissues Caused by Infection with Highly Virulent Newcastle Disease Virus Compared to the Avirulent Virus: A Bioinformatics Analysis

The highly virulent Newcastle disease virus (NDV) isolates typically result in severe systemic pathological changes and high mortality in Newcastle disease (ND) illness, whereas avirulent or low-virulence NDV strains can cause subclinical disease with no morbidity and even asymptomatic infections in birds. However, understanding the host’s innate immune responses to infection with either a highly virulent strain or an avirulent strain, and how this response may contribute to severe pathological damages and even mortality upon infection with the highly virulent strain, remain limited. Therefore, the differences in epigenetic and pathogenesis mechanisms between the highly virulent and avirulent strains were explored, by transcriptional profiling of chicken embryonic visceral tissues (CEVT), infected with either the highly virulent NA-1 strain or the avirulent vaccine LaSota strain using RNA-seq. In our current paper, severe systemic pathological changes and high mortality were only observed in chicken embryos infected with the highly virulent NA-1 strains, although the propagation of viruses exhibited no differences between NA-1 and LaSota. Furthermore, virulent NA-1 infection caused intense innate immune responses and severe metabolic disorders in chicken EVT at 36 h post-infection (hpi), instead of 24 hpi, based on the bioinformatics analysis results for the differentially expressed genes (DEGs) between NA-1 and LaSota groups. Notably, an acute hyperinflammatory response, characterized by upregulated inflammatory cytokines, an uncontrolled host immune defense with dysregulated innate immune response-related signaling pathways, as well as severe metabolic disorders with the reorganization of host–cell metabolism were involved in the host defense response to the CEVT infected with the highly virulent NA-1 strain compared to the avirulent vaccine LaSota strain. Taken together, these results indicate that not only the host’s uncontrolled immune response itself, but also the metabolic disorders with viruses hijacking host cell metabolism, may contribute to the pathogenesis of the highly virulent strain in ovo.

Pro-inflammatory cytokine release from chicken peripheral blood mononuclear cells stimulated with lipopolysaccharide

Background and Aim:

The principal cytokines released by the host on infection include pro-inflammatory cytokines such as interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF). These cytokines were regarded as regulators of the host’s response to infection. This study aimed to determine the release of pro-inflammatory cytokines from chicken peripheral blood mononuclear cells (PBMCs) following lipopolysaccharide (LPS) stimulation.

Materials and Methods:

Blood samples were collected from six Betong chickens. To isolate PBMCs, density gradient centrifugation was utilized. PBMC culture in RPMI1640 with 10% fetal bovine serum was stimulated with various concentrations of LPS (0, 0.01, 0.1, and 1.0 μg/mL). The production of TNF-α, IL-1β, and IL-6 was determined using an enzyme-linked immunosorbent assay.

Results:

When the PBMCs were cultured for 24 h with varying doses of LPS, there was no significant variation in cell viability. TNF-α, IL-1β, and IL-6 levels were measured in Betong chicken PBMC. The release of these cytokines increased considerably as LPS concentration (0.01-1 μg/mL) increased (p<0.05).

Conclusion:

In vitro studies of the chicken immune response, notably the release of pro-inflammatory cytokines, can be conducted using PBMCs obtained from chicken blood.

Sickness behaviors across vertebrate taxa: proximate and ultimate mechanisms

There is nothing like a pandemic to get the world thinking about how infectious diseases affect individual behavior. In this respect, sick animals can behave in ways that are dramatically different from healthy animals: altered social interactions and changes to patterns of eating and drinking are all hallmarks of sickness. As a result, behavioral changes associated with inflammatory responses (i.e. sickness behaviors) have important implications for disease spread by affecting contacts with others and with common resources, including water and/or sleeping sites. In this Review, we summarize the behavioral modifications, including changes to thermoregulatory behaviors, known to occur in vertebrates during infection, with an emphasis on non-mammalian taxa, which have historically received less attention. We then outline and discuss our current understanding of the changes in physiology associated with the production of these behaviors and highlight areas where more research is needed, including an exploration of individual and sex differences in the acute phase response and a greater understanding of the ecophysiological implications of sickness behaviors for disease at the population level.

Effects of dietary supplementation of iron as sulphates or glycine chelates on the productive performance and concentrations of acute-phase proteins and iron in the serum and liver tissues of broiler chickens

The aim of the study was to determine the effects of inorganic (ferrous sulfate [FeSO4] and FeSO4 + phytase [FeSO4+F]) and organic forms of iron (ferrous glycine chelate [FeGly], Fe-Gly + phytase [Fe-Gly+F]) on the concentrations of C-reactive protein (CRP), serum amyloid A (SA), alpha- 1-acid glycoprotein (α-AGP), haptoglobin (Hp), transferrin (TRF) and iron in the blood and liver tissue of poultry. Ross 308 roosters were used in this study. The acute-phase protein (AP) levels in the chicken serum and liver tissues were assayed using the double-antibody sandwich ELISA kits for chickens. The iron levels in serum and liver samples were measured using flame atomic absorption spectrophotometry. The results showed that the serum and hepatic iron concentration in the chickens receiving Fe-Gly and Fe-Gly-F were significantly higher than those in the control group and in the chickens receiving iron in the form of sulphates. Further, serum CRP and SA concentrations were lower in the chickens from the supplemented groups than in those from the control. The hepatic CRP concentration was higher in the supplemented groups than in the control group. The serum and hepatic TRF concentration were highest in the chickens receiving FeSO4 and FeSO4-F. The hepatic Hp concentration was higher in the chickens receiving organic forms of iron than in the control chickens, whereas the serum Hp concentrations were similar across the groups. The highest α-1-AGP concentration was found in the livers of the chickens receiving Fe- Gly and Fe-Gly-F. Taken together, these findings suggest that iron had the most beneficial effects for poultry in terms of health, performance and immunity when added to the feed in the form of glycine chelate.

Local and systemic inflammatory responses to lipopolysaccharide in broilers: new insights using a two-window approach

The inflammatory response involves a complex interplay of local tissue activities designed to recruit leukocytes and proteins from the blood to the infected tissue. For egg-type chickens, we established the growing feather (GF) as an accessible tissue test site to monitor tissue responses to injected test-material. For commercial broilers, whose health depends to a large extent on innate immune system functions, the GF test system offers an important novel window to directly assess their natural defenses. This study was conducted to adapt the GF test system for use in broilers, and use it to simultaneously examine local (GF) and systemic (blood) inflammatory responses initiated by GF pulp injection of lipopolysaccharide (LPS). Specifically, GF of 12 male and 12 female, 5-week-old broilers were injected with LPS (16 GF/chicken; 1 μg LPS/GF). Blood and GF were collected at 0 (before), 6, and 24 h after GF injection. GF pulp was used to determine leukocyte-infiltration and gene-expression profiles, reactive-oxygen-species generation, and superoxide dismutase (SOD) activity. Blood was used to determine blood cell profiles and SOD activity. A time effect (P ≤ 0.05) was observed for most aspects examined. In GF, LPS injection resulted in heterophil and monocyte infiltration reaching maximal levels at 6 and 24 h, respectively. Reactive-oxygen-species generation, SOD activity, and mRNA levels of IL-1β, IL-8, IL-6, IL-10, and cathelicidin B1 were elevated, whereas those of TNF-α, LITAF, SOD1, and SOD2 decreased after LPS injection. In blood, levels of heterophils and monocytes were elevated at 6 h, lymphocytes and RBC decreased at 6 h, and thrombocytes and SOD activity increased at 24 h. Assessment of LPS-induced activities at the site of inflammation (GF) provided novel and more relevant insights into temporal, qualitative, and quantitative aspects of inflammatory responses than blood. Knowledge generated from this dual-window approach may find direct application in identification of individuals with robust, balanced innate defenses and provide a platform for studying the effects of exogenous treatments (e.g., nutrients, probiotics, immunomodulators, etc.) on inflammatory responses taking place in a complex tissue.

4-O-Carboxymethylascochlorin Inhibits Expression Levels of on Inflammation-Related Cytokines and Matrix Metalloproteinase-9 Through NF-κB/MAPK/TLR4 Signaling Pathway in LPS-Activated RAW264.7 Cells

Toll-like receptor 4 (TLR4) and matrix metalloproteinase-9 (MMP-9) are known to play important roles in inflammatory diseases such as arteriosclerosis and plaque instability. The purpose of this study was to perform the effect of 4-O-carboxymethylascochlorin (AS-6) on MMP-9 expression in lipopolysaccharide (LPS)-induced murine macrophages and signaling pathway involved in its anti-inflammatory effect. Effect of AS-6 on MAPK/NF-κB/TLR4 signaling pathway in LPS-activated murine macrophages was examined using ELISA, Western blotting, reverse transcription polymerase chain reaction (RT-PCR) and fluorescence immunoassay. MMP-9 enzyme activity was examined by gelatin zymography. AS-6 significantly suppressed MMP-9 and MAPK/NF-κB expression levels in LPS-stimulated murine macrophages. Expression levels of inducible nitric oxide synthase (iNOS), COX2, MMP-9, JNK, ERK, p38 phosphorylation, and NF-κB stimulated by LPS were also decreased by AS-6. Moreover, AS-6 suppressed TLR4 expression and dysregulated LPS-induced activators of transcription signaling pathway. The results of this study showed that AS-6 can inhibit LPS-stimulated inflammatory response by suppressing TLR4/MAPK/NF-κB signals, suggesting that AS-6 can be used to induce the stability of atherosclerotic plaque and prevent inflammatory diseases in an in vitro model.

Mechanical removal (epidermal scarification) of pododermatitis injuries reduces the presence of both inflammatory tissue and its associated microbiota in broiler feet

Chicken feet have become an important commodity in the international market, representing a significant portion of poultry products exported by countries such as Brazil and the USA. However, the presence of pododermatitis in the footpad is an important barrier to exportation, since importing countries do not accept injured feet or allow the use of automatic equipments to remove the affected tissue. The objective of this research was to evaluate the impact of using an automatic equipment to remove injuries of pododermatitis on histological and microbiological traits of broiler feet processed according to commercial practices. A total of 240 broiler feet obtained from a commercial processing plant was visually classified according to the degree of pododermatitis and distributed in a 4 × 2 factorial arrangement, totalizing eight treatments with 30 replications. Factors were feet classification (1 to 4) and injury removal (yes or no). Feet were sampled for microbiological and histological analysis before and after the mechanical removal of pododermatitis injuries by an automatic machine that promoted footpad epidermal scarification. No significant interaction between feet classification and injury removal was detected for any of the analyzed variables. Also, no significant effect of feet classification was detected on aerobic plate counts, total coliforms and Escherichia coli. Feet inflammation score tended to increase (P = 0.06) according to the downgrading of feet classification, but the mechanical removal of pododermatitis injuries reduced feet inflammation score (P < 0.01), total coliform counts (P = 0.01), and E. coli (P = 0.01) independently of feet classification. Together, these results demonstrate the efficacy of the automatic equipment in removing both the inflammatory tissue and its associated microbiota in broiler feet affected by pododermatitis. Therefore, in addition to the already authorized use of blades, the use of automatic equipments for epidermal scarification in the processing of broiler feet deserves further consideration by the regulatory agencies.

The effects of enzymes and direct fed microbial combination on performance and immune response of broilers under a coccidia challenge

This study evaluated the effect of an enzyme blend (xylanase, amylase and protease; XAP) in combination with a direct fed microbial (DFM) containing three strains of Bacillus spp. on intestinal histology, immune response and performance of broilers. Four dietary treatments were tested in a 2 × 2 factorial trial, including two levels of challenge (without or with coccidial infection), two levels of feed additive (with or without XAP and DFM). Diets were fed ad libitum to male Cobb500 broilers in mash feeds from 1–21 days of age, with eight replicate pens per treatment within brooder-batteries with raised wire floors and built up litter, housing six birds per pen. A mild challenge was introduced by oral gavage at day five to the challenged birds, using a six-fold concentration of coccidial vaccine. A high fibre basal diet formulated with rye and wheat middlings was used to further increase the challenge. Body weight and feed intake were measured and feed conversion ratio (FCR) was calculated during starter (1–12 d), grower (12–21 d) and overall 1–21 days. Intestinal morphology and immune response parameters were measured on day 12 and 21. Compared to the unchallenged groups, the coccidial challenge reduced (P < 0.05) body weight gain (BWG), increased FCR, reduced villus height and increased crypt depth. The challenged birds had increased pro-inflammatory cytokines (IL-6, IL-1β; P < 0.05) in the intestine as well as higher levels of acute phase proteins (APP, haemopexin and α−1-acid glycoprotein) in the plasma and circulating heterophils. XAP + DFM supplementation improved BWG, reduced FCR and increased energy efficiency compared to the non-supplemented groups. The combination of XAP and DFM reduced inflammatory responses such as APP compared to the challenged control group and maintained performance to a comparable level seen in the unchallenged control. The data indicate that XAP enzymes in combination with Bacillus-based DFM may reduce the damage and performance losses induced by coccidial challenge.

Protective roles of free avian respiratory macrophages in captive birds

In the mammalian lung, respiratory macrophages provide front line defense against invading pathogens and particulate matter. In birds, respiratory macrophages are known as free avian respiratory macrophages (FARM) and a dearth of the cells in the avian lung has been purported to foreordain a weak first line of pulmonary defense, a condition associated with high mortality of domestic birds occasioned by respiratory inflictions. Avian pulmonary mechanisms including a three tiered aerodynamic filtration system, tight epithelial junctions and an efficient mucociliary escalator system have been known to supplement FARM protective roles. Current studies, however, report FARM to exhibit an exceptionally efficient phagocytic capacity and are effective in elimination of invading pathogens. In this review, we also report on effects of selective synthetic peroxisome proliferator activated receptor gamma (PPAR γ) agonists on non phlogistic phagocytic properties in the FARM. To develop effective therapeutic interventions targeting FARM in treatment and management of respiratory disease conditions in the poultry, further studies are required to fully understand the role of FARM in innate and adaptive immune responses.

Immune responses to improving welfare

The relationship between animal welfare and the immune status of an animal has a complex nature. Indeed, the intuitive notion that "increased vigilance of the immune system is by definition better" because it is expected to better keep the animal healthy, does not hold up under scrutiny. This is mostly due to the fact that the immune system consists of 2 distinct branches, the innate and the adaptive immune system. While they are intimately intertwined and synergistic in the living organism, they are profoundly different in their costs, both in terms of performance and wellbeing. In contrast to the adaptive immune system, the action of the innate immune system has a high metabolic cost as well as undesirable behavioral consequences. When a pathogen breaches the first line of defense (often a mucosal barrier), that organism's molecular signature is recognized by resident macrophages. The macrophages respond by releasing a cocktail of pro-inflammatory cytokines (including interleukin-1 and -6) that signal the brain via multiple pathways (humoral as well as neural) of the ongoing peripheral innate immune response. The behavioral response to the release of proinflammatory cytokines, known as "sickness behavior," includes nearly all the behavioral aspects that are symptomatic for clinical depression in humans. Hence, undesired innate immune activity, such as chronic inflammation, needs to be avoided by the industry. From an immunological standpoint, one of the most pressing poultry industry needs is the refinement of our current veterinary vaccine arsenal. The response to a vaccine, especially to a live attenuated vaccine, is often a combination of innate and adaptive immune activities, and the desired immunogenicity comes at the price of high reactogenicity. The morbidity, albeit limited and transient, caused by live vaccines against respiratory diseases and coccidiosis are good examples. Thankfully, the advent of various post-genomics technologies, such as DNA vaccines and vectored subunit vaccines, offer reason for optimism that substantial progress can be made towards the vaccine refinement goal in the near future.

Activation of peroxisome proliferator-activated receptor gamma induces anti-inflammatory properties in the chicken free avian respiratory macrophages

Background

Activation of peroxisome proliferator activated receptor gamma (PPAR γ) in the alveolar macrophages (AM) by selective synthetic PPAR γ ligands, improves the ability of the cells to resolve inflammation. In birds, respiratory macrophages are known as free avian respiratory macrophages (FARM) and show distinct functional differences from AM. The effects of treating FARM with PPAR γ ligands are unclear.

Methods

FARM were harvested by lavage of chicken respiratory tract and their morphology assessed at microscopic level. The effects of PPAR γ agonists on the FARM in vitro viability, phagocytic capacity and proinflammatory cytokine (TNF-α) production were assessed.

Results

FARM had eccentric nucleus and plasma membrane ruffled with filopodial extensions. Ultrastructurally, numerous vesicular bodies presumed to be lysosomes were present. FARM treated with troglitazone, a selective PPAR γ agonist, had similar in vitro viability with untreated FARM. However, treated FARM co-cultured with polystyrene particles, internalized more particles with a mean volume density of 41 % compared to that of untreated FARM of 21 %. Further, treated FARM significantly decreased LPS-induced TNF-α production in a dose dependent manner.

Conclusion

Results from this study show that PPAR γ synthetic ligands enhance phagocytic ability of FARM. Further the ligands attenuate production of proinflammatory cytokines in the FARM, suggesting potential therapeutic application of PPAR γ ligands in the management of respiratory inflammatory disorders in the poultry industry.

The haematological profile of female bronze turkeys (Meleagris gallopavo) vaccinated with various commercial strains of Newcastle disease

The effects of vaccination on avian blood parameters are poorly understood. The present study was designed to evaluate whether different strains (Ulster 2C, B1, live LaSota and inactivated LaSota) of Newcastle disease vaccines had an effect on the haematological profile of female turkeys. Seventy-five female turkeys were allocated to treatment groups according to vaccination strain. All the birds, except those in the control group, were vaccinated at 32 weeks of age and revaccinated at 40 and 48 weeks of age. Blood samples were obtained for haematological analyses and serum samples for the haemagglutination inhibition test. Haemoglobin concentration was significantly lower (p &lt; 0.05) in vaccinated female turkeys than in the control birds 28 days after vaccination. Monocytes were significantly higher (p &lt; 0.05) in 44-week-old female turkeys vaccinated with inactivated LaSota strain compared with the other groups. Turkeys vaccinated with the B1 strain showed significantly higher (p &lt; 0.05) total white blood cell counts compared with the other groups vaccinated with various commercial strains of the Newcastle disease virus. In conclusion, female turkeys showed significant differences in haemoglobin concentrations, monocytes and white blood cell counts when vaccinated against Newcastle disease.

Short-term survival and effects of transmitter implantation into western grebes using a modified surgical procedure

Two pilot trials and one study in a closely related grebe species suggest that Western grebes (Aechmophorus occidentalis) will not tolerate intracoelomic transmitter implantation with percutaneous antennae and often die within days of surgery. Wild Western grebes (n = 21) were captured to evaluate a modified surgical technique. Seven birds were surgically implanted with intracoelomic transmitters with percutaneous antennae by using the modified technique (transmitter group), 7 received the same surgery without transmitter implantation (celiotomy group), and 7 served as controls (only undergoing anesthesia). Modifications included laterally offsetting the body wall incision from the skin incision, application of absorbable cyanoacrylate tissue glue to the subcutaneous space between the body wall and skin incisions, application of a waterproof sealant to the skin incision after suture closure, and application of a piece of porcine small intestine submucosa to the antenna egress. Survival did not differ among the 3 groups with 7 of 7 control, 6 of 7 celiotomy, and 6 of 7 transmitter birds surviving the 9-day study. Experimental birds were euthanized at the end of the study, and postmortem findings indicated normal healing. Significant differences in plasma chemistry or immune function were not detected among the 3 groups, and only minor differences were detected in red blood cell indices and plasma proteins. After surgery, the birds in the transmitter group spent more time preening tail feathers than those in the control and celiotomy groups. These results demonstrate that, in a captive situation, celiotomy and intracoelomic transmitter implantation caused minimal detectable homeostatic disturbance in this species and that Western grebes can survive implantation of intracoelomic transmitters with percutaneous antennae. It remains to be determined what potential this modified surgical procedure has to improve postoperative survival of Western grebes that are intracelomically implanted with transmitters with percutaneous antennae and released into the wild.

Dietary l-carnitine supplementation enhances the lipopolysaccharide-induced acute phase protein response in broiler chickens

The objective of the present study was to evaluate the potential effects of dietary L-carnitine supplementation on acute phase protein response upon a lipopolysaccharide (LPS) challenge of male broiler chickens receiving a commercial broiler diet supplemented with 15 or 100 mg L-carnitine/kg or an unsupplemented (control) diet from 14 days of age onwards. At 28 days of age, eight chickens per dietary treatment were weighed and subcutaneously injected with 300 microg LPS from E. coli (100 microg LPS/ml saline) or 3 ml saline (unsupplemented group only). During the next 10 days, blood samples were taken repeatedly and analysed for their hemopexin (HX) and alpha-1 acid glycoprotein (AGP) levels. Extra dietary L-carnitine did not affect broiler performance. At day 1 postinjection, plasma HX and AGP levels were significantly increased in all treatment groups. However, the elevations in circulating HX and AGP levels were more pronounced in the L-carnitine supplemented chickens, especially in the 100mg L-carnitine group. It is concluded that extra L-carnitine in the diet of broiler chickens enhances or advances the acute phase protein response. The exact mode of action needs to be elucidated but seems to be consistent with a glucocorticoid mimicking effect.

Basics of cytology and fluid cytology

Cytology as a diagnostic tool has played a major role in the management of diseases affecting domestic mammals for over 20 years. It has also become a valuable diagnostic tool in the evaluation of nondomestic or the so-called "exotic" animal patients, such as small mammals and the lower vertebrates. Common cytologic specimens used to evaluate the exotic animal patient include aspirates of masses and organs, imprints of biopsy material, tracheal wash samples, aspiration of abdominal or coelomic fluid, and fecal smears. In general, the same cytologic sample collection and preparation techniques used for domestic mammals also apply to exotic animal patients. The interpretation of the cytology specimen is generally the same as that of domestic mammals.

The chick chorioallantoic membrane as a novel in vivo model for the testing of biomaterials

Current in vivo models for testing biomaterials are time and labor intensive as well as expensive. This article describes a new approach for testing biomaterials in vivo using the chorioallantoic membrane (CAM) of the developing chicken embryo, as an alternative to the traditional mammalian models. Fertilized chicken eggs were incubated for 4 days, at which time a small window was cut in the shell of the egg. After 1 week of incubation, the CAM received several test materials, including the endotoxin LPS, a cotton thread and a Silastic tubing. One day and 1 week later, the tissue response to the test materials was assessed using gross, histological, and scanning electron microscope evaluations. The inflammatory response of the chorioallantoic membrane to biomaterials was fully characterized and found to be similar to that of the mammalian response and was also seen to vary according to test materials. We also found that the structure and geometry of the test materials greatly influenced the incorporation of the samples in the CAM. The similarity of the tissue response of the CAM with the mammalian models, plus the low cost, simplicity, and possibility to continuously visualize the test site through the shell window make this animal model particularly attractive for the rapid in vivo screening of biomaterials.

Influence of dietary conjugated linoleic acid isomers on early inflammatory responses in male broiler chickens

1. The influence of dietary conjugated linoleic acid isomer (CLA, 0 and 10 g/kg) on the metabolic and physiological responses to immune stimulation induced by a single injection of Salmonella enteritidis lipopolysaccharide (LPS) or repeated injections of LPS and Sephadex G-50 was determined in male broiler chicks. 2. In experiment 1, 10-d-old chicks were fed on experimental diets for 14 d and half of the birds fed on each diet were injected intraperitoneally with LPS (1.5 mg/kg body weight). In experiment 2,7-d-old chicks were fed on experimental diets for 18 d. Immune stimulation was started at 19 d old and continued for 5 d. Half of the birds fed on each diet were injected intraperitoneally with 0.25 mg/kg body weight of LPS at 19, 21 and 23 d of age, and with 250 mg/kg body weight of Sephadex at 20 and 22 d of age to stimulate the immune system. 3. In experiment 1, giving CLA prevented an increase in blood heterophil to lymphocyte ratio 7 h after a single injection of LPS, and increases in plasma ceruloplasmin and alpha 1 acid glycoprotein (AGP) 24 h after the injection, but not 7 h after the injection. CLA also prevented a decrease in food intake for 24 h after LPS injection. 4. In experiment 2, the CLA diet partially prevented reductions in body weight gain and weight gain to feed intake ratio caused by repeated injections of LPS and Sephadex. Feeding CLA prevented increases in plasma ceruloplasmin and AGP at 24 d of age caused by repeated injections of LPS and Sephadex, but not at 20 d of age. 5. These results suggest that feeding CLA alleviates some undesirable metabolic and physiological changes induced by immunological stimulation in male broiler chicks.

Cytokines of birds: conserved functions--a largely different look

Targeted disruptions of the mouse genes for cytokines, cytokine receptors, or components of cytokine signaling cascades convincingly revealed the important roles of these molecules in immunologic processes. Cytokines are used at present as drugs to fight chronic microbial infections and cancer in humans, and they are being evaluated as immune response modifiers to improve vaccines. Until recently, only a few avian cytokines have been characterized, and potential applications thus have remained limited to mammals. Classic approaches to identify cytokine genes in birds proved difficult because sequence conservation is generally low. As new technology and high throughput sequencing became available, this situation changed quickly. We review here recent work that led to the identification of genes for the avian homologs of interferon-alpha/beta (IFN-alpha/beta) and IFN-gamma, various interleukins (IL), and several chemokines. From the initial data on the biochemical properties of these molecules, a picture is emerging that shows that avian and mammalian cytokines may perform similar tasks, although their primary structures in most cases are remarkably different.

Relationship between the level of dietary vitamin E and the immune response of broiler chickens

The relationship between the dietary level of vitamin E (VE) and the immune response of broilers was studied in three experiments. Immunity was assessed as antibody production to infectious bronchitis virus (IBV), SRBC, and Brucella abortus (BA) antigens, mitogenic response to phytohemagglutinin A (PHA) and concanavalin A (Con A), cutaneous basophil hypersensitivity (CBH) to PHA, and lipopolysaccharide induction of acute-phase proteins (APP) and heterophilia. A range of VE (0, 10, 17.5, 25, 37.5, 50, 100, and 200 IU/kg) levels were supplemented to a basal diet (corn-soy) containing 10.2 IU of VE/kg. We found a dose-dependent increase in antibody production in response to attenuated IBV between 0 and 25 IU/kg of supplemented VE and no further increase at higher levels. Antibody levels to SRBC were higher in birds supplemented with 50 IU of VE/kg compared to those supplemented with 0 or 200 IU/kg of VE. Antibody production in response to BA antigens was not influenced by VE. Mitogenic responses were suppressed by supplemented VE in Experiment 1 for PHA (25 IU/kg diet) and Con A (25 and 50 IU/kg diets). CBH and APP levels were not affected by VE. Heterophilia was lowest at 50 IU/kg 6 h after lipopolysaccharide injection (Experiment 1). Our study showed that moderate (25 to 50 IU/kg) levels of VE supplementation were most immunomodulatory and that high levels were less effective.

Inflammation-induced changes in serum modulate chicken macrophage function

Inflammation-induced changes in serum protein profiles and the effects of such serum on a chicken macrophage cell line HD11 were studied to find whether the changes in serum affect cellular immunity. Four-week-old male broiler chickens were injected subcutaneously with either olive oil or 50% croton oil mixed in olive oil to induce inflammation. The birds were bled at 48h after injection, and serum protein profiles were compared using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and densitometric evaluation. At 48h post-injection the serum from croton oil-injected birds showed distinct changes in protein profiles characterized by a selective increase or decrease in levels of several serum proteins. The protein bands which showed increases had relative molecular weights (Mr) corresponding to 65kilo Daltons (kD), 42kD, and two or more proteins with Mr> or =200kD. The levels of serum albumin (49kD), and a 56kD protein were reduced in croton oil-injected birds. The modulating effects of such serum on HD11 cells were studied using bacterial lipopolysaccharide (LPS) or phorbol myristate acetate (PMA) induced functional activation of these cells. The LPS-induced interleukin-6 (IL-6) production by HD11 cells was not affected by the presence of either olive oil-treated control or croton oil-treated inflammatory serum but nitrite production was enhanced by the inflammatory serum. Similarly, inflammatory serum also enhanced PMA-induced respiratory burst measured using dichlorofluorescein diacetate (DCF-DA) oxidation mediated by reactive oxygen intermediates. These results suggest that inflammatory serum can modulate macrophage function by influencing the production of reactive oxygen and nitrogen species which could affect their phagocytic and bactericidal activities.

Isolation, characterization, and cDNA cloning of chicken turpentine-induced protein, a new member of the scavenger receptor cysteine-rich (SRCR) family of proteins

Acute-phase serum proteins were induced by administrating a chicken with turpentine oil. One of these proteins was a new protein that appeared in front of albumin in polyacrylamide disc gel electrophoresis using a 4.5-16% gel. To purify this protein, turpentine-administrated chicken serum was fractionated by ammonium sulfate precipitation at 50% saturation, and the supernatant fraction was chromatographed on a DEAE-Toyopearl 650S column. The purified protein is a mannose-glycoprotein, and its N-terminal sequence, determined by the Edoman method, is not homologous from that of other reported acute-phase proteins. An analysis of physiological function with two different test systems, chemiluminescence measurement and electron spin resonance spectroscopy, showed that the purified protein has antioxidant activity and inhibits superoxide (O(2)) mediated by activation of the receptor. In support of these results, the complete amino acid sequence of 18-B is homologous to the scavenger receptor cysteine-rich (SRCR) family of proteins that participate in the regulation of leukocyte function. 18-B is composed of four SRCR domains, which is different from the previously characterized SRCR family of proteins such as Spalpha, CD6, and CD163. These findings indicate that turpentine-induced 18-B, a new member of scavenger receptor cysteine-rich family, may be implicated in regulation of cell function in a manner of inhibition of the overproduction of the reactive oxygen species.

Effect of dietary concentration of xylitol on growth in male broiler chicks during immunological stress

Two experiments were conducted to determine the effect of dietary xylitol concentration on growth performance, plasma (alpha1 acid glycoprotein (AGP), nitrite, and Fe concentration in male broiler chicks during immunological stress. Ten-day-old chicks were fed a corn-soybean diet containing 15% glucose and 6% xylitol or 15% xylitol with identical metabolizable energy and crude protein content for 12 d in Experiment 1. In Experiment 2, 12-d-old chicks were fed either the 15% glucose or 6% xylitol diet for 7 d. During the final 6 d of each experiment, half of the birds fed each diet were injected intraperitoneally with Escherichia coli lipopolysaccharide (LPS; 0127:B8) on Days 1, 3, and 5 and with Sephadex-G50 superfine on Days 2 and 4 to stimulate the immune system. The xylitol diets partially prevented reductions in body weight gain, feed intake, and feed efficiency caused by LPS and Sephadex injections, but the glucose diet did not. The injections of LPS and Sephadex increased plasma AGP and nitrite concentrations. Plasma AGP concentration on Days 2 and 6 in chicks fed the xylitol diets did not differ from that of chicks fed the glucose diet in both experiments. Nitric oxide production estimated by plasma nitrite concentration following immunological stress did not differ due to dietary treatments in Experiment 2. The LPS and Sephadex resulted in decreased plasma Fe concentration on Day 6 in Experiment 1 in chicks fed glucose but not xylitol. These results indicate that a beneficial effect of dietary xylitol on growth is obtained with 6% xylitol given to chicks 1 d before stimulating the immune system.

Nonspecific cellular defense of the avian respiratory system: a review

The normal, steady-state, avian respiratory system has very low numbers of residing avian respiratory phagocytes (ARP). Birds must rely heavily on the influx of ARP to defend against infectious agents. The system is refractory to elicitation by inert stimulants, but responds efficiently to replicating bacteria, with very rapid influx of large numbers of activated ARP (polymorphonuclear neutrophils, heterophils, and macrophages) with increased phagocytic proportions and capacities. The numbers subside within a few a days. Activated ARP act in a non agent-specific manner: Pasteurella multocida-activated ARP can defend against a severe Escherichia coli airsacculitis. Parenteral routes of stimulation generally are not, respiratory routes are very, efficient in activating ARP. Heterophils are the most efficient in defensive reactions, such as oxidative burst, production of nitric oxide and killing of bacteria. Respiratory viruses may stimulate, but also may diminish some of the defensive functions of ARP. This is also true for attenuated, modified live virus vaccines. These vaccines must be used carefully in the presence of subclinical bacterial, mycoplasmal infections. Published literature on non-specific cellular defense of the avian respiratory system is very limited, particularly about interactions among multiple infectious agents and the system.

Regulation of chicken haemopoiesis by cytokines

The continuous production, control and functional activation of blood cells involves a complex series of cellular events in which a small population of stem cells generates large numbers of mature cells. The survival, proliferation and development of these cells is strictly dependent on extracellular signals, among these are polypeptide regulators generally known as cytokines. While a large number of mammalian cytokines with proliferative and inhibitory effects have been described in detail, it is surprising that comparatively little is known of the avian system. Given the success of human cytokines as a model, the ability to manipulate the chicken haemopoietic and lymphopoietic systems by precise application of purified cytokines provides a rational approach to defence against disease. As a general caveat, an increased awareness of the existence of regulatory networks and the likelihood that these regulators were designed to function most effectively when acting in combination, will provide an understanding into the regulation of haemopoiesis and hence find application in both clinical and agricultural research.

Effect of dietary xylitol on growth and inflammatory responses in immune stimulated chickens

It has been argued that stimulation of the immune system depresses performance. Accordingly, an experiment was conducted to determine the effect of dietary xylitol (150 g/kg diet) on growth and selected inflammatory responses in male broiler chickens. During the final 6 d of the experimental periods, chicks were injected with antigens: Escherichia coli lipopolysaccharide (LPS) on days 1, 3 and 5 and with Sephadex-G50 superfine on days 2 and 4 to stimulate macrophage functions. The immune stimulation reduced body weight gain and food intake, but enhanced alpha 1 acid glycoprotein (AGP) concentration and interleukin (IL-1) like activity in plasma. Feeding the xylitol diet partially, but significantly, prevented the reductions in body weight gain and food intake, without affecting the early stage of inflammatory responses triggered by LPS and Sephadex injections.

Avian macrophages: regulators of local and systemic immune responses

Macrophages are key regulatory cells of the immune system involved in initiating and directing the innate and specific immune responses, the systemic acute phase response, tissue repair, and tissue remodeling. In the early stages of a challenge from invading microorganisms or from tissue injury, macrophages defend local and systemic homeostasis by initiating a complex series of cellular, biochemical, and behavioral events. These pathophysiological adjustments are mediated by an extensive variety of communication molecules, including: cytokines, cytokine inhibitors, endocrine hormones, eicosanoids, neurotransmitters, and reactive oxygen intermediates. The cytokines produced by macrophages (monokines) are not well characterized relative to their mammalian counterparts, but a variety of chemokine, pro-inflammatory, and colony-stimulating factor activities have been described. Although the sequence homology, and thus species cross-reactivity, between avian and mammalian cytokines is typically low, the functional characteristics appear to be generally similar. The pro-inflammatory cytokines are important initiators and regulators of the local immune response. They are also released in sufficient quantities during some infections to coordinate a systemic acute phase response that impacts the growth, reproduction, and well-being of poultry. An understanding of the mechanisms and molecules used by macrophages to regulate immune and inflammatory responses may permit the development of products, diets, or husbandry techniques to modulate immunity for the enhancement of the productivity of poultry.

Avian heterophils in inflammation and disease resistance

Heterophils are the predominate granulated leukocyte in the acute inflammatory response in gallinaceous birds. Heterophils are highly phagocytic and are capable of a broad spectrum of antimicrobial activity. They accumulate in inflamed tissue, causing tissue damage and forming heterophil granulomas that are morphologically similar to inflammatory lesions in reptiles. The avian heterophil lacks myeloperoxidase and depends primarily on nonoxidative mechanisms for antimicrobial activity. The beta-defensins found in heterophil granules can kill a wide variety of bacterial pathogens and are a major component of the heterophil antimicrobial arsenal. Heterophils form the first line of cellular defense against invading microbial pathogens in the lungs and air sacs where resident macrophages are lacking.

Pathogenicity of Mycoplasma synoviae in broiler chickens

Six isolates of Mycoplasma synoviae, identified as WVU 1853, K1968, K1858, 92D8034, F10-2AS, and FMT, were compared for pathogenicity in broiler chickens. Specific-pathogen-free chickens were inoculated, in two groups of 20, with each isolate by footpad or eyedrop inoculation at 1 day of age and were examined at necropsy 7, 14, 28, and 42 days postinoculation. Specimens were taken for histopathology, culture, polymerase chain reaction assay, and hemagglutination-inhibition serology. Isolates were grouped according to pathogenicity on the basis of differences in lesion development and tissue distribution in the respiratory system, other viscera, and the skeletal system. K1968 (pathogenic) induced lesions in all sites examined in both the footpad and eyedrop inoculation groups. It was detected in all sites following footpad inoculation and in all sites except viscera following eyedrop inoculation. WVU 1853, K1858, and 92D8034 (moderately pathogenic) induced lesions and were detected in all sites following footpad inoculation. With eyedrop inoculation, lesions were identified only in upper and lower respiratory sites, and organisms were detected only in upper respiratory sites. F10-2AS (moderately pathogenic) was similar; however, footpad inoculation failed to induce visceral lesions or permit organism detection in any site. F10-2AS was detected in upper and lower respiratory tissues following eyedrop inoculation. FMT (mildly pathogenic) induced only upper respiratory lesions when either footpad or eyedrop inoculation was used, and detection was restricted to upper respiratory sites following eyedrop inoculation. These results are useful in comparative evaluations of the virulence of other M. synoviae isolates and form a basis for characterization of virulence factors of M. synoviae.

Lead disrupts eicosanoid metabolism, macrophage function, and disease resistance in birds

Lead (Pb) affects elements of humoral and cell-mediated immunity, and diminishes host resistance to infectious disease. Evidence is presented supporting a hypothesis of Pb-induced immunosuppression stemming from altered fatty acid metabolism, and mediated by eicosanoids and macrophages (MO). Chronic Pb exposure increases the proportion of arachidonate (ArA) among fatty acids in lipid from avian tissues, and this change provides precursors for eicosanoids, the oxygenated derivatives of ArA that mediate MO acute inflammatory response. In the current study, we showed that the concentration of ArA in phospholipids of MO elicited from turkey poults fed 100 ppm dietary Pb acetate was twice that of controls. In vitro production of eicosanoids by these MO was substantially increased, and this effect was most pronounced following lipopolysaccharide stimulation: prostaglandin F2 alpha was increased 11-fold, thromboxane B2 increased threefold, and prostaglandin E2 increased by 1.5 times. In vitro phagocytic potential of these MO was suppressed, such that the percentage of MO engulfing sheep red blood cell (RBC) targets was reduced to half that of control MO. In vivo susceptibility of Pb-treated and control birds to Gram-negative bacteria challenge was also evaluated. The morbidity of chicks inoculated with Salmonella gallinarum and fed either control or 200 ppm Pb acetate-supplemented diets was similar, except early in the course of the disease when mortality among Pb-treated birds was marginally greater. In these studies, effects of Pb that could influence immunological homeostasis were demonstrated for MO metabolism of ArA, for production of eicosanoids, and for phagocytosis. There was also the suggestion that these in vitro indices of immune function are related to in vivo disease resistance.

Great tits Parus major trade health for reproduction

Reproduction and maintenance compete for resources within a single individual. But do individuals invest in reproduction just as much as remains after the requirements of maintenance are covered, or do they sacrifice their health for the sake of still further increase the investment in current reproduction? This question has been found hard to answer because of difficulties of demonstrating that individuals naturally make a reproductive effort of such a magnitude as to inflict health damage. In this paper we present evidence for a trade-off between reproductive effort and health state in great tits, indicated by a positive correlation between total prefledging brood weight and both intensity of Haemoproteus blood parasite infection and heterophile: lymphocyte (H:L) ratio. H:L ratios, which signal stress in birds, were high both among individuals making an intense reproductive effort and among aberrantly behaving individuals, such as females incubating in empty nests and birds which abandoned their broods after blood sampling. Experimental reduction of clutch size resulted in decreased intensity of Haemoproteus parasitemia, providing further evidence that individual great tits accept immunosuppression to increase their reproductive investment.

Alterations in blood leukocyte populations in Smyth line chickens with autoimmune vitiligo

Smyth line (SL) chickens spontaneously develop a posthatch autoimmune loss of pigment cells (vitiligo) in the feather. Concurrent with the development of Smyth line vitiligo (SLV), mononuclear cell infiltration and altered T cell profiles can be observed in the pulp of developing feathers. To determine whether the development of SLV is preceded by or associated with alterations in blood lymphocyte and leukocyte populations, blood leukocyte profiles were established at various times prior to and throughout the spontaneous development of SLV. The proportions among various blood leukocyte populations (percentage of lymphocytes, monocytes, heterophils, eosinophils, and basophils) were determined by immunofluorescence and flow cytometric analyses. Lymphocyte markers included fluorescence-conjugated monoclonal antibodies to identify T cells (CD3), T helper cells (CD4), cytotoxic T cells (CD8), and B cells (IgM). The proportions among blood lymphocyte populations examined did not differ between SL and MCH-matched parental Brown line (BL) control chickens prior to and throughout the development of SLV. Compared to BL controls, SL chickens had, however, increased proportions of inflammatory leukocytes in the blood, particularly at the time when most hatchmates developed SLV. Examination of leukocyte alterations with respect to first observation of SLV revealed that inflammatory leukocyte levels were elevated early in SLV. Although altered leukocyte profiles in the blood were observed during the development of SLV, blood from SL chickens did not reflect alterations in lymphocyte populations known to occur at the site of melanocyte destruction. The role of inflammatory blood leukocytes in the development of SLV needs to be further investigated.

Polyacrylamide gel electrophoretic patterns of chicken serum in acute inflammation induced by intramuscular injection of turpentine

To develop a method to detect hidden inflammation using serum protein in chickens, changes in serum proteins with acute inflammation were analyzed using a turpentine-induced inflammation model. Inflammation in the pectoral muscle of a 14-wk-old White Leghorn became apparent 3 h after the injection of turpentine and became more severe thereafter. Coincident with the development of inflammation, changes in serum proteins were analyzed by electrophoresis on polyacrylamide gradient gels. The electrophoretic patterns were divided into 21 segments. Two of these segments increased remarkably. These were located near the center of the electrophoretic pattern and were identified as transferrin due to iron staining, correlation of movement against a commercial transferrin sample in SDS-PAGE, and immunoblotting. These results suggest that transferrin may serve as a marker for inflammation in chicken.

Avian leukocytic cytokines

Leukocytic cytokines are produced by cells of the immune system and are prominent regulators of the immune response and in some cases various systemic responses. Leukocytic cytokines are released during immune responses and may act in autocrine, paracrine, or endocrine manners. Although over a dozen avian leukocytic cytokines have been described based on functional activities, characterization at the molecular level is not well developed. Two exceptions are 1) myelomonocytic growth factor, a colony-stimulating factor-like cytokine required for the growth and differentiation of hematopoietic precursor cells, particularly myelomonocytic cells; and 2) the avian transforming growth factor-beta (TGF-beta) family of cytokines, which modulate wound healing, bone metabolism, and cellular differentiation. Cytokines with bioactivities similar to mammalian interleukin (IL)-1, IL-2, IL-6, and interferon-gamma have been at least partially purified. Cytokines with bioactivities similar to mammalian IL-8, colony-stimulating factor, and tumor necrosis factor-alpha have been reported but are not well characterized at the molecular level. With a few exceptions, including TGF-beta and thymulin, highly purified leukocytic cytokines of mammalian origin have diminished or no specific activity in avian assay systems. The chicken IL-1 receptor has been cloned and the predicted amino acid sequence shares 60% homology with the human IL-1 receptor. A component of the chicken IL-2 receptor has been partially purified but little is known about other avian leukocytic cytokine receptors. Potential applications of leukocytic cytokines in poultry production originate from their regulation of a variety of functions such as disease resistance, would healing, bone accretion, nutrient partitioning, appetite, growth, and reproduction.

Profiles of chicken macrophage effector functions

In contrast to the mammalian system, avian species lack the so-called "resident" or "harvestable" macrophage population in the abdominal exudate. However, macrophages can be recruited into the chicken's abdominal cavity (presumably from the blood monocyte pool) if an inflammatory agent such as Sephadex is injected. The kinetics of inflammatory cell recruitment in terms of time, cell type, and state of activation to perform a particular effector function is currently an active area of research. This report will provide information on several chicken macrophage effector functions, including in vivo chemotaxis, phagocytosis, bacterial uptake and killing, biosynthesis of nitric oxide and various enzymes, and monokines such as interleukin-1 and granulocyte colony-stimulating factor.