Biological Activity of Cytokines: An Evolutionary Perspective

Immune and endocrine alterations at the early stage of inflammatory assemblage in toads after stimulation with heat-killed bacteria (Aeromonas hydrophila)

The red-leg syndrome in amphibians is a condition commonly associated with the bacteria Aeromonas hydrophila and has led to population declines. However, there is little information concerning the inflammatory assemblage in infected anurans. We evaluated immune and endocrine alterations induced by stimulation with heat-killed A. hydrophila injected in Rhinella diptycha toads. Control animals were not manipulated, while the others were separated into groups that received intraperitoneal injection of 300 μl of saline or heat-killed bacteria: groups A1 (3 × 107 cells), A2 (3 × 108 cells), and A3 (3 × 109 cells). Animals were bled and euthanized six hours post-injection. We evaluated neutrophil: lymphocyte ratio (NLR), plasma bacterial killing ability (BKA), testosterone (T), melatonin (MEL), and corticosterone (CORT) plasma levels. Heat-killed A. hydrophila increased CORT and NLR, and decreased MEL, especially at higher concentrations. There was no effect of treatment on T and BKA. We then selected the saline and A3 groups to conduct mRNA expression of several genes including glucocorticoid receptor (GR), toll-like receptor-4 (TLR-4), interferon-γ (IFN-γ), interleukin (IL)-1β, IL-6, and IL-10. We found higher expression of IL-6, IL-1β, IL-10, and IFN-γ in group A3 compared to the saline group. These results indicate the beginning of an inflammatory assemblage, notably at the two highest concentrations of bacteria, and give a better understanding of how anurans respond to an infection within an integrated perspective, evaluating different physiological aspects. Future studies should investigate later phases of the immune response to elucidate more about the inflammation in amphibians challenged with A. hydrophila.

First in vitro and in vivo evaluation of recombinant IL-1β protein as a potential immunomodulator against viral infection in fish

IL-1β is an important proinflammatory cytokine with multifaceted modulatory roles in immune responses. In fish, recombinant IL-1β has been employed in the control of bacterial diseases, while the antiviral mechanisms of IL-1β remain largely unknown, and the efficacy of recombinant IL-1β as an immunomodulator to prevent viral diseases is still not determined. This study evaluated the immunomodulatory effects of recombinant grass carp IL-1β against grass carp reovirus (GCRV) in vitro and in vivo. Firstly, the mature form (Ser111-Lys270) of grass carp IL-1β was identified, and its recombinant protein (designated as rgcIL-1β) was prepared through prokaryotic expression. Then, an in vitro evaluation model for rgcIL-1β activity was established in the CIK cells, with the appropriate concentration (600 ng/mL) and effect time (1 h). In vitro, rgcIL-1β could not only induce the production of proinflammatory cytokines such as IL-1β, IL-6, IL-8, and TNF-α but also a series of antiviral factors including IFN-1, IFN-2, IFN-γ, and ISG15. Mechanistically, transcriptome analysis and western blotting confirmed that rgcIL-1β activated multiple transcriptional factors, including NF-κB, IRF1, IRF3, and IRF8, and the signal pathways associated with inflammatory cytokines and antiviral factors expression. Expectedly, rgcIL-1β treatment significantly inhibited GCRV replication in vitro. In vivo administration of rgcIL-1β via intraperitoneal pre-injection significantly aroused an antiviral response to restrict GCRV replication and intense tissue inflammation in grass carp, demonstrating the immunomodulatory effects of rgcIL-1β. More importantly, rgcIL-1β administrated with 10 ng/g and 1 ng/g could improve the survival rate of grass carp during GCRV infection. This study represents the first time to comprehensively reveal the immunomodulatory and antiviral mechanisms of IL-1β in fish and may also pave the way for further developing recombinant IL-1β as an immunotherapy for the prevention and control of fish viral diseases.

Functional Activity of the Blood System in Two Migratory Bat Species of the Urals

Functional activity of the blood system was studied in two migratory Ural species, Vespertilio murinus Linnaeus, 1758 and Pipistrellus nathusii Keyserling et Blasius, 1839. A multivariate nonparametric ANOVA of red blood parameters showed significant interspecific differences (p < 0.05) between the migrating bats and the resident species pond bat. A certain genetically determined multidirectionality in the mobilization of emergency regulation mechanisms of the lymphoid blood system was observed in bats.

Ophidiomyces ophidiicola detection and infection: a global review on a potential threat to the world’s snake populations

Ophidiomyces ophidiicola (Oo) is one of the most relevant fungal pathogens for snakes. It is the etiological agent of ophidiomycosis, an emerging disease causing dysecdysis, skin abnormalities, crusting cutaneous lesions, and ulcerations. Despite this major tegumentary “tropism”, Oo infection can be systemic and it is capable of inducing visceral lesions. Moreover, ophidiomycosis may lead to abnormalities of reproductive physiology, hunting behavior, and thermoregulation, thus increasing the risks of sublethal effects and predation on affected snakes. Oo seems horizontally transmitted and can induce postnatal mortality. This article reviews published data on Oo detection and infection in all snake species in countries around the world and categorizes these data using new classification parameters. The presence of this fungus has been recorded in 11 states (considering the USA as a whole); however, in four states, the mycosis has only been reported in snakes held in captivity. Detection and/or infection of Oo has been ascertained in 62 snake species, divided into nine families. The taxa have been categorized with diagnostic criteria in order to report, for each species, the highest rank of categorization resulting from all cases. Therefore, 20 species have been included within the class “Ophidiomycosis and Oo shedder”, 11 within “Ophidiomycosis”, 16 in “Apparent ophidiomycosis”, and 15 within “Ophidiomyces ophidiicola present”. We also discuss the significance and limits of case classifications and Oo’s impact on wild populations, and we suggest methods for preliminary surveillance. Standardized methods, interdisciplinary studies, and cooperation between various research institutions may facilitate further Oo screening studies, elucidate the unclear aspects of the disease, and protect ophidiofauna from this emerging threat at the global level.

Evolution of γ chain cytokines: Mechanisms, methods and applications

The common γ chain family of cytokines and their receptors play fundamental roles in the immune system. Evolutionary studies of γ chain cytokines have elegantly illustrated how the immune system adapts to ever-changing environmental conditions. Indeed, these studies have revealed the uniqueness of cytokine evolution, which exhibits strong positive selection pressure needed to adapt to rapidly evolving threats whilst still conserving their receptor binding capabilities. In this review, we summarise the evolutionary mechanisms that gave rise to the characteristically diverse family of γ chain cytokines. We also speculate on the benefits of studying cytokine evolution, which may provide alternative ways to design novel cytokine therapeutic strategies. Additionally, we discuss current evolutionary models that elucidate the emergence of distinct cytokines (IL-4 and IL-13) and cytokine receptors (IL-2Rα and IL-15Rα). Finally, we address and reflect on the difficulties associated with evolutionary studies of rapidly evolving genes and describe a variety of computational methods that have revealed numerous aspects of cytokine evolution.

Immune and endocrine responses of Cururu toads (Rhinella icterica) in their natural habitat after LPS stimulation

Glucocorticoids and melatonin display immunomodulatory functions, with both immune-stimulatory and suppressor effects, depending on the context. While their immune properties are well-explored in mammals, there are still few studies on this immune-endocrine interaction in an inflammatory context in amphibians, all of them under captivity conditions, which can constitute a stressor for these animals. Evaluating how amphibians react to an immune challenge in the field would reveal relevant information regarding how immune-physiological parameters are modulated in natural conditions. This study aimed to investigate the effects of lipopolysaccharide (LPS) injection in male toads (Rhinella icterica) recently captured in their natural habitat in the Atlantic Forest at two different times of the day. We evaluated: splenic cytokines mRNA (interleukin [IL]-1β, IL-6, IL-10, interferon-γ) and complement system protein (C1s), plasma bacterial killing ability (BKA), plasma corticosterone (CORT), melatonin (MEL), and testosterone (T) levels, and neutrophil to lymphocyte ratio (NLR), two hours post-injections. LPS-injection increased NLR, the gene expression of IL-1β, and less evidently CORT levels independently of the time of the day. These results evidence LPS-induced inflammation, similarly observed in toads in captivity. Saline and LPS-injected toads showed a positive correlation between IL-1β and IL-6, both cytokines with pro-inflammatory effects. Also, CORT was negatively associated with T, suggesting inhibition of the hypothalamus-pituitary-gonadal axis in the LPS-stimulated group. Our results are associated with the first stage of the inflammatory assemblage. Studies evaluating further steps of this process might lead to a better understanding of the immune-endocrine relations in amphibians.

Lipopolysaccharide Regulates Pro- and Anti-Inflammatory Cytokines, Corticosterone, and Melatonin in Toads

Glucocorticoids and melatonin (MEL) show integrated and complex immunomodulatory effects, mostly described for endotherms, yet underexplored in amphibians. In this context, the RT-qPCR of molecules mediating inflammatory processes in amphibians is a valuable tool to explore the relationships among molecular biology, endocrine mediators, and immune response in these animals. In this study, toads (Rhinella diptycha) received an intraperitoneal saline injection or lipopolysaccharide (LPS; 2 mg/kg). Six hours post-injection, we analyzed plasma corticosterone (CORT) and MEL levels and pro- and anti-inflammatory molecules (IL-1β, IL-6, IL-10, IFN-γ, and C1s). We found increased CORT and decreased MEL levels in response to LPS. Also, IL-1β, IL-6, and IL-10 were upregulated in LPS-injected toads compared with saline-injected toads. Overall, our results demonstrate an LPS-induced inflammatory response with endocrine and immune modulation in R. diptycha toads, exhibiting expected patterns for an inflammatory stimulus within this time frame (6 h post-injection). Toads were responsive to LPS by secreting different cytokines, such as proinflammatory cytokines IL-1β and IL-6, related to immune cell attraction to inflammatory sites and the anti-inflammatory cytokine IL-10, which limits the rate of leukocyte infiltration, inflammation, and downregulates the expression of proinflammatory cytokines. Increased circulating CORT levels are probably associated with the activation of the hypothalamus-pituitary-interrenal axis by the LPS and the endocrine actions of IL-6. Furthermore, decreased circulating MEL levels are likely due to inhibited MEL secretion by the pineal gland by inflammatory stimuli, indicating the activation/existence of the immune-pineal axis in amphibians.

A primer on cytokines

Cytokines are pleiotropic polypeptides that control the development of and responses mediated by immune cells. Cytokine classification predominantly relies on [1] the target receptor(s), [2] the primary structural features of the extracellular domains of their receptors, and [3] their receptor composition. Functionally, cytokines are either pro-inflammatory or anti-inflammatory, hematopoietic colony-stimulating factors, developmental and would healing maintaining immune homeostasis. When the balance in C can form complex networks amongst themselves that may affect the homeostasis and diseases. Cytokines can affect resistance and susceptibility for many diseases and their availability in the host cytokine production and interaction is disturbed, immunopathogenesis sets in. Therefore, cytokine-targeting bispecific, and chimeric antibodies form a significant mode of immnuo-therapeutics Although the field has grown deep and wide, many areas of cytokine biology remain unknown. Here, we have reviewed these cytokines along with the organization, signaling, and functions through respective cytokine-receptor-families. Being part of the special issue on the Role of Cytokines in Leishmaniasis, this review is intended to be used as an organized primer on cytokines and not a resource for detailed discussion- for which a two-volume Handbook of cytokines is available- on each of the cytokines. Priming the readers on cytokines, we next brief the role of cytokines in Leishmaniasis. In the brief, we do not provide an account of each of the involved cytokines known to date, instead, we offer a temporal relationship between the cytokines and the progress of the infection towards the alternate outcomes- healing or non-healing- of the infection.

Early viral uptake and host-associated immune response in the tissues of seven-band grouper following a bath challenge with nervous necrosis virus

In the present study, early uptake of nervous necrosis virus (NNV) in the tissues (gill, brain, skin, eye, heart) and immune response associated with the uptake in the gill and brain of seven-band grouper was investigated. The gill was found to act as a primary portal of entry for NNV during the initial phase of the water-borne infection. The presence of viral genome and infectious particles was demonstrated using quantitative (qPCR, viral titer) and qualitative (ISH) approach. Initially, an increased viral uptake was noticed, but the virus got cleared from the gills at the later phase of infection. Localization in the brain was evident at the blood-brain barrier followed by the brain parenchyma in the latter stage of infection. Nectin-4, an established NNV receptor, and GHSC70 showed an up-regulated expression throughout the challenge period initially in the gill and at latter phase in brain; however, it seems that the virus does not use gill as a primary replication site but brain as a permissive tissue. Combined activity as reflected by the up-regulation of cytokine, interferon, antigen-presenting cell, and immunoglobulin genes restricts early NNV replication in gill. Observations from the present study provide a better understanding of early NNV entry and also opens a window for further elucidating the modes of NNV neuro-invasion through systemic circulation.

Evolution and function of interleukin-4 receptor signaling in adaptive immunity and neutrophils

The cytokines interleukin (IL)-4 and IL-13, signaling via the IL-4 receptor (IL-4R), orchestrate type 2 immunity to helminth infections and toxins. Activation of epithelial and myeloid cells, and a transient neutrophils influx initiates type 2 immune responses, which are dominated by basophils, eosinophils, mast cells, B cell immunoglobulin E production, and type 2 T helper and T follicular helper cells. Interestingly, IL-4 and IL-13 can curtail chemotaxis and several effector functions of neutrophils in mice and humans. This inhibitory role of IL-4 and IL-13 probably developed to limit tissue damage by neutrophils during type 2 immunity where a "weep and sweep" response aims at expulsion and decreased fecundity, instead of killing, of macroparasites. Here, we review when IL-4R signaling cytokines appeared during evolution relative to neutrophils and adaptive immunity. Neutrophil-like granular phagocytes were present in invertebrates throughout the bilaterian clade, but we were unable to find data on IL-4, IL-13, or their receptors in invertebrates. Conversely, vertebrates had both adaptive immunity and IL-4, IL-13, and IL-4Rs, suggesting that type 2 cytokines evolved together with adaptive immunity. Further studies are necessary to determine whether IL-4R signaling in neutrophils was established simultaneously with the appearance of adaptive immunity or later.

Evaluation of cytokines in peripheral blood mononuclear cell supernatants for the diagnosis of tuberculosis

INTRODUCTION

There is active interest in leveraging host immune responses as biomarkers of tuberculosis (TB) disease activity. We had previously evaluated an immunodiagnostic test called the antibody in lymphocyte supernatant (ALS) assay. Here, we aimed to evaluate a panel of inflammatory mediators and associate the responses with the ALS results to identify a biosignature to distinguish TB cases from controls.

METHODOLOGY

In this case-control study, adults with TB were compared to controls who were hospitalized for non-infectious conditions. Blood was collected at baseline and after 4 weeks of TB treatment (from TB cases only). Peripheral blood mononuclear cells were isolated and cultured without antigenic stimulation for 72 hours. Inflammatory mediators were measured using the Multiplex cytokine kit and compared between TB cases and controls; among TB cases, responses were compared over time. ALS and inflammatory mediator results were evaluated using generalized discriminant analysis to identify the optimal biosignature to predict TB.

RESULTS

When comparing inflammatory mediators between groups, IL-1ra, IL-1β, and granulocyte macrophage-colony stimulating factor (GM-CSF) were lower in TB cases (P<0.002). Fibroblast growth factor-basic significantly increased from baseline to week-4 (P=0.002). Generalized discriminant analysis yielded a model with IL-2, tumor necrosis factor-alpha, vascular endothelial growth factor, and ALS, providing a sensitivity of 82.2% and specificity of 76.2%.

CONCLUSION

Our results suggest that IL-1ra, IL-1β, and GM-CSF might be used as diagnostic biomarkers to distinguish between TB cases and non-TB cases. We could not identify a group of mediators that outperformed the diagnostic accuracy of the ALS alone.

Benefits of immune protection versus immunopathology costs: A synthesis from cytokine KO models

The inflammatory response can produce damage to host tissues and in several infectious diseases the most severe symptoms are due to immunopathology rather than a direct effect of pathogen multiplication. One hypothesis for the persistence of inflammatory damage posits that the benefits of protection towards infection outweigh the costs. We used data on knocked-out (KO) cytokine models [and the corresponding wild-type (WT) controls] to test this hypothesis. We computed differences in pathogen load and host survival between WT and KO and divided them by the WT values. Using this ratio provides an internal control for variation in pathogen species, host strain, pathogen dose, and inoculation route. We predicted that i) if mortality is essentially due to immunopathology, there should be a loose association between pathogen load and host survival; ii) if mortality is essentially due to pathogen proliferation, we expect a tight association between pathogen load and host survival. The results provide strong support to this latter hypothesis. In 85% of WT - KO comparisons (n=126), an increase in pathogen load was associated with an increase in host mortality, and a decrease in pathogen load was associated with a decrease in host mortality. Overall, these findings are in agreement with the idea that immunopathology persists because immune protection confers immediate benefits in terms of infection clearance.

Hepcidin, Cathelicidin-1 and IL-8 as immunological markers of responsiveness in early developmental stages of rainbow trout

During the early developmental stage of salmonids, high mortality occurs largely as a result of pathogens. These cause low immune competence in fry, producing disease, decreasing production and finally leading to economic losses. Therefore, the aim of this study was to characterise the developmental stages in which rainbow trout acquires immune response capability when challenged with LPS from Pseudomona aeruginosa for 8 h, studying the hepcidin, cathelicidin-1 and IL-8. Total RNA was extracted from fry at 34, 42, 56 and 66 days post hatching (dph). Hepcidin and cathelicidin-1 transcripts were detected only at days 34 and 42, whereas the IL-8 transcript was detected from day 34 to day 66. To analyse the protein expression in the fry, polyclonal anti-peptide antibodies were generated in rabbit. These three immune sera demonstrated the ability to recognise the whole molecule in biological samples. Immunofluorescence showed that skin, gills and intestine mainly responded to the LPS challenge, indicating that these portals of pathogen entry are capturing LPS. This study constitutes a valuable approach, since it has the potential to identify molecules with biological activity that can be used to evaluate the status of fry in culture.

Cloning, characterization and mRNA expression of interleukin-6 in blunt snout bream (Megalobrama amblycephala)

In the present study, the interleukin-6 gene (IL-6) cDNA in blunt snout bream (Megalobrama amblycephala) was identified and its expression profiles under ammonia stress and bacterial challenge were investigated. The IL-6 sequence consisted of 1045 bp, including a 696 bp ORF which translated into a 232 amino acid (AA) protein. The protein contained a putative signal peptide of 24 AA in length. IL-6 expression analysis showed that the it is differentially expressed in various tissues under normal conditions and the highest IL-6 level was observed in the intestine tissue, followed by the liver, and then in the gills. Under ammonia stress, the IL-6 mRNA level both in spleens and intestine increased significantly (P < 0.05), with the maximum levels attained at 6 h, 12 h (72, 10-fold, respectively). Thereafter, they all significantly decreased (P < 0.01) and returned to the basal value within 48 h. Whereas, in livers it slightly decreased at 3 h firstly (0.5-fold), and then significantly (P < 0.05) increased with the maximum level attained 12 h (3-fold). Further expression analysis showed that the mRNA level of IL-6 in spleens, intestine and livers of blunt snout bream all increased significantly (P < 0.05), with maximum values attained at 6 h, 3 h, 6 h (10, 6, 18-fold, respectively) after Aeromonas hydrophila (A. hydrophila) injection, and then decreased to the basal value within 24 h which suggested that IL-6 was involved in the immune response to A. hydrophila. The cloning and expression analysis of the IL-6 provide theoretical basis to further study the mechanism of anti-adverseness and expression characteristics under stress conditions in blunt snout bream.

Effects of Shewanella putrefaciens on innate immunity and cytokine expression profile upon high stocking density of gilthead seabream specimens

High stocking density increases the number of emerging diseases triggering economic losses worldwide. Probiotics provide an effective and natural solution for preventing some diseases through an improvement of innate immune system among others. In the present work dietary administration of the probiotic Shewanella putrefaciens (known as Pdp11) was evaluated under stress by high stocking density after 2 and 4 weeks of administration to gilthead seabream (Sparus aurata) specimens. Results showed an increase in cellular peroxidase and respiratory burst activity as well as a modulation of cytokine profile when Pdp11 was administered to fish reared at high stocking density. Overall, our results showed how Pdp11 is not only able to improve to some extent the cellular and humoral immunity but also to increase the gene expression profile of pro-inflammatory cytokines such as il1b or il6 in response to high stocking density in gilthead seabream. These findings may support the potential use of this probiotic as functional feed against stress in fish farms.

Acute Exposure to Tris(1,3-dichloro-2-propyl) Phosphate (TDCIPP) Causes Hepatic Inflammation and Leads to Hepatotoxicity in Zebrafish

Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) has been frequently detected in environmental media and has adverse health effect on wildlife and humans. It has been implicated to have hepatotoxicity, but its molecular mechanisms remain unclear. In the present study, adult male zebrafish were exposed to TDCIPP and global hepatic gene expression was examined by RNA-Seq and RT-qPCR in order to understand the molecular mechanisms of TDCIPP-induced hepatotoxicity. Our results indicated that TDCIPP exposure significantly up-regulated the expression of genes involved in endoplasmic reticulum stress and Toll-like receptor (TLR) pathway, implying an inflammatory response, which was supported by up-regulation of inflammation-related biomaker genes. Hepatic inflammation was further confirmed by histological observation of increase of infiltrated neutrophils and direct observation of liver recruitment of neutrophils labeled with Ds-Red fluorescent protein of Tg(lysC:DsRed) zebrafish upon TDCIPP exposure. To further characterize the hepatotoxicity of TDCIPP, the expression of hepatotoxicity biomarker genes, liver histopathology and morphology were examined. The exposure to TDCIPP significantly up-regulated the expression of several biomarker genes for hepatotoxicity (gck, gsr and nqo1) and caused hepatic vacuolization and apoptosis as well as increase of the liver size. Collectively, our results suggest that exposure to TDCIPP induces hepatic inflammation and leads to hepatotoxicity in zebrafish.

Induction of anti-inflammatory cytokine expression by IPNV in persistent infection

Infectious Pancreatic Necrosis Virus (IPNV) is the agent of a well-characterized acute disease that produces a systemic infection and high mortality in farmed fish species but also persistent infection in surviving fish after outbreaks. Because viral persistence of susceptible mammal hosts appears to be associated with the modulation of anti-inflammatory cytokine expression, in this study we examined the expression levels of key pro- and anti-inflammatory cytokines in kidney and spleen of trout, as well as humoral immune response (IgM and IgT) during experimental persistent viral infection and in the acute phase of infection as a comparison. IPNV infection in rainbow trout resulted in a distinct profile of cytokine expression depending on the type of infection, acute or persistent. Levels of early pro-inflammatory cytokines, IL-1β and IL-8, did not increase in the head kidney of the fish with persistent asymptomatic infection but increased in some of the symptomatic infected fish. The antiviral cytokine IFNα was not significantly induced in any of the infected fish groups. The level of expression of the Th1-related cytokine IL-12 was significantly higher in trout with persistent asymptomatic infection than in symptomatic fish. This was also accompanied by an increase in IFNγ. The anti-inflammatory cytokines IL-10 and TGF-β1 had distinct expression profiles. While IL-10 expression increased in all infected fish, TGF-β1 was only up-regulated in fish with persistent infection. All infected fish had significantly lower total IgM levels than the non-infected fish whereas IgT levels did not change. Specific and neutralizing antibodies against IPNV were not observed in acute and persistent infection except in the group of fish with the lowest degree of clinical signs. Interestingly, the lack of humoral immune response could be associated with the high expression of anti-inflammatory cytokines, which might inhibit antibody production. The balance between pro-inflammatory Th1 type cytokines and the regulatory cytokines could explain the high percentage of survival and the resolution of the inflammatory response in the IPNV-infected fish but also the establishment of viral persistence.

Evolution of TNF-induced apoptosis reveals 550 My of functional conservation

The Precambrian explosion led to the rapid appearance of most major animal phyla alive today. It has been argued that the complexity of life has steadily increased since that event. Here we challenge this hypothesis through the characterization of apoptosis in reef-building corals, representatives of some of the earliest animals. Bioinformatic analysis reveals that all of the major components of the death receptor pathway are present in coral with high-predicted structural conservation with Homo sapiens. The TNF receptor-ligand superfamilies (TNFRSF/TNFSF) are central mediators of the death receptor pathway, and the predicted proteome of Acropora digitifera contains more putative coral TNFRSF members than any organism described thus far, including humans. This high abundance of TNFRSF members, as well as the predicted structural conservation of other death receptor signaling proteins, led us to wonder what would happen if corals were exposed to a member of the human TNFSF (HuTNFα). HuTNFα was found to bind directly to coral cells, increase caspase activity, cause apoptotic blebbing and cell death, and finally induce coral bleaching. Next, immortalized human T cells (Jurkats) expressing a functional death receptor pathway (WT) and a corresponding Fas-associated death domain protein (FADD) KO cell line were exposed to a coral TNFSF member (AdTNF1) identified and purified here. AdTNF1 treatment resulted in significantly higher cell death (P < 0.0001) in WT Jurkats compared with the corresponding FADD KO, demonstrating that coral AdTNF1 activates the H. sapiens death receptor pathway. Taken together, these data show remarkable conservation of the TNF-induced apoptotic response representing 550 My of functional conservation.

Mucosal immunity in the gut: the non-vertebrate perspective

Much is now known about the vertebrate mechanisms involved in mucosal immunity, and the requirement of commensal microbiota at mucosal surfaces for the proper functioning of the immune system. In comparison, very little is known about the mechanisms of immunity at the barrier epithelia of non-vertebrate organisms. The purpose of this review is to summarize key experimental evidence illustrating how non-vertebrate immune mechanisms at barrier epithelia compare to those of higher vertebrates, using the gut as a model organ. Not only effector mechanisms of gut immunity are similar between vertebrates and non-vertebrates, but it also seems that the proper functioning of non-vertebrate gut defense mechanisms requires the presence of a resident microbiota. As more information becomes available, it will be possible to obtain a more accurate picture of how mucosal immunity has evolved, and how it adapts to the organisms' life styles.

Immune modulatory effects of Aloe arborescens extract on the piscine SAF-1 cell line

The pharmacological potential of Aloe arborescens Miller leaf components was investigated, with special attention deserved to immune modulatory effects on the Sparus aurata fibroblast cell line SAF-1. The cells were treated with Aloe extract at different concentrations (1.2-4.8 mg ml(-1)) for various times (24-72 h). The lowest concentration did not provoke any cellular damage observable by SEM and did not affect ATP amounts after 24 and 48 h, while even induced a significant increase over controls after 72 h. We next examined the transcription kinetics of different immune-related genes (IL-1β, TGF-β, TNF-α, COX-2, IFN-I, Mx and MHCI-α) in SAF-1 cells stimulated with LPS or poly I:C. The Aloe extract (1.2 mg ml(-1)) acted as a powerful immune stimulant in LPS- or poly I:C-activated SAF-1 cells, inducing a synergic effect on interconnected genes that are expected to be involved in different aspects of the immune responses. These reports provide a new perspective for the use of A. arborescens to prevent or oppose bacterial and viral fish diseases and to face, as an alternative strategy based on natural plant extracts, the growing unwillingness to rely upon standard solutions involving antibiotics or antimicrobial chemicals.

Environmental associations with gene transcription in Babine Lake rainbow trout: evidence for local adaptation

The molecular genetic mechanisms facilitating local adaptation in salmonids continue to be poorly characterized. Gene transcription is a highly regulated step in the expression of a phenotype and it has been shown to respond to selection and thus may be one mechanism that facilitates the development of local adaptation. Advances in molecular genetic tools and an increased understanding of the functional roles of specific genes allow us to test hypotheses concerning the role of variable environments in shaping transcription at known-function candidate loci. To address these hypotheses, wild rainbow trout were collected in their first summer and subjected to metabolic and immune challenges. We assayed gene transcription at candidate loci that play a role in the molecular genetic response to these stresses, and correlated transcription with temperature data from the streams and the abundance and diversity of bacteria as characterized by massively parallel pyrosequencing. Patterns of transcriptional regulation from resting to induced levels varied among populations for both treatments. Co-inertia analysis demonstrated significant associations between resting levels of metabolic gene transcription and thermal regime (R (2) = 0.19, P = 0.013) as well as in response to challenge (R (2) = 0.39, P = 0.001) and resting state and challenged levels of cytokine gene transcription with relative abundances of bacteria (resting: R (2) = 0.25, P = 0.009, challenged: R (2) = 0.65, P = 0.001). These results show that variable environments, even within a small geographic range (<250 km), can drive divergent selection among populations for transcription of genes related to surviving stress.

Transcriptional regulation of cytokines in the intestine of Atlantic cod fed yeast derived mannan oligosaccharide or β-glucan and challenged with Vibrio anguillarum

Immunomodulatory feed additives are expected to exert their primary influence at the intestinal level through the expression of cytokines, which in turn affect the immune responses in fish. In two separate experiments a yeast-derived mannan oligosaccharide product (YM) or a purified β-glucan (BG) product were fed to Atlantic cod (Gadus morhua L.) for 5 weeks, after which they were bath-challenged with a bacterial pathogen--Vibrio anguillarum. The transcription of selected cytokines (proinflammatory--il1b, il8, ifng; anti-inflammatory--il10) in different intestinal segments was analysed using qPCR. In the case of YM study, the effect of the compound was observed in both the posterior intestine and rectum of Atlantic cod, upon challenge with the pathogen. iIl1b expression in the posterior intestine and rectum of post-challenge fish was significantly higher than that of pre-challenge fish. In the case of il8 the difference was confined to rectum. The expression of ifng was altered only in the anterior intestine upon YM feeding. In the BG trial, the additive had a differential effect on the expression of the cytokine genes. In anterior intestine and rectum, the purified β-glucan additive significantly elevated the expression of il1b when challenged with V. anguillarum. An effect of BG on the anti-inflammatory cytokine il10 was visible in the rectum after the pathogen challenge. The differential responses of cytokines in the intestine of fish upon exposure to V. anguillarum suggest that both mannan oligosaccharides and β-glucans impact the ability of Atlantic cod to respond to the pathogen.

Neuroendocrine-immune interaction in fish: differential regulation of phagocyte activity by neuroendocrine factors

Coping with physical, chemical and biological disturbances depends on an extensive repertoire of physiological, endocrinological and immunological responses. Fish provide intriguing models to study bi-directional interaction between the neuroendocrine and the immune systems. Macrophages and granulocytes are the main actors in the first and rapid innate immune response. They are resident in different organs and are moreover rapidly recruited and activated upon infection. They act in response to recognition of pathogen-associated molecular patterns (PAMPs) via a repertoire of surface and intracellular receptors by inducing a plethora of defense reactions aiming to eradicate the pathogen. Subsequent production of inflammatory mediators stimulates other leukocytes required to develop an adaptive and specific antibody response. The type of phagocyte reaction will therefore depend on their differentiation state, specific receptor repertoire and their specific location. Apart from these pathogen induced responses, immune reactivity may be modulated by neuroendocrine factors. Over the last years we extensively studied changes in carp stress axis activity and the effect of its end-products on the immune system in an acute stress paradigm. We focus on specific neuroendocrine receptors on leukocytes and their effect on crucial phagocyte activities. We performed identification and functional analyses of different glucocorticoid, opioid and adrenergic receptors on carp phagocytes. Results show that their ligands of neuroendocrine origin may have substantial impact on specific phagocyte functions in a differential way. Inflammatory and microbicidal responses fight pathogens but may be detrimental to the host tissue. Neuroendocrine modulation may regulate inflammation to reach an optimum defense while preventing excessive host cell damage.

Evolutionary divergence and functions of the human interleukin (IL) gene family

Cytokines play a very important role in nearly all aspects of inflammation and immunity. The term 'interleukin' (IL) has been used to describe a group of cytokines with complex immunomodulatory functions -- including cell proliferation, maturation, migration and adhesion. These cytokines also play an important role in immune cell differentiation and activation. Determining the exact function of a particular cytokine is complicated by the influence of the producing cell type, the responding cell type and the phase of the immune response. ILs can also have pro- and anti-inflammatory effects, further complicating their characterisation. These molecules are under constant pressure to evolve due to continual competition between the host's immune system and infecting organisms; as such, ILs have undergone significant evolution. This has resulted in little amino acid conservation between orthologous proteins, which further complicates the gene family organisation. Within the literature there are a number of overlapping nomenclature and classification systems derived from biological function, receptor-binding properties and originating cell type. Determining evolutionary relationships between ILs therefore can be confusing. More recently, crystallographic data and the identification of common structural motifs have led to a more accurate classification system. To date, the known ILs can be divided into four major groups based on distinguishing structural features. These groups include the genes encoding the IL1-like cytokines, the class I helical cytokines (IL4-like, γ-chain and IL6/12-like), the class II helical cytokines (IL10-like and IL28-like) and the IL17-like cytokines. In addition, there are a number of ILs that do not fit into any of the above groups, due either to their unique structural features or lack of structural information. This suggests that the gene family organisation may be subject to further change in the near future.

Zoologic companion animal rehabilitation and physical medicine

Injury and illness in zoologic companion animals can lead to significant pain and debilitation. Recovery can be slow and sometimes frustrating. By augmenting recovery from trauma or disease with physical medicine and rehabilitation techniques, recovery can be more rapid and complete. Physical medicine techniques, such as massage, can augment recovery from a painful injury or surgery by reducing edema, improving postoperative ileus, and decreasing anxiety. Familiarity with the tools of rehabilitation along with focus on pain management, strengthening, and proprioception improve patient care.

Understanding the vertebrate immune system: insights from the reptilian perspective

Reptiles are ectothermic amniotes, providing the key link between ectothermic anamniotic fishes and amphibians, and endothermic amniotic birds and mammals. A greater understanding of reptilian immunity will provide important insights into the evolutionary history of vertebrate immunity as well as the growing field of eco-immunology. Like mammals, reptile immunity is complex and involves innate, cell-mediated and humoral compartments but, overall, there is considerably less known about immune function in reptiles. We review the current literature on each branch of the reptilian immune system, placing this information in context to other vertebrates. Further, we identify key areas that are prime for research as well as areas that are lagging because of lack of reagents in non-model systems.

Cell markers and determinants in fish immunology

Despite the impressive increase in the cloning and expression of genes encoding fish immunoregulatory molecules, the knowledge on "in vivo" and "in vitro" functional immunology of the corresponding peptide products is still at an initial stage. This is partly due to the lacking of specific markers for immunoregulatory peptides, that represent an indispensible tool to dissect immune reactions and to trace the fate of cellular events downstream of the activation. In this review we summarise the available information on functional immune activities of some teleost species and discuss the obtained data in an evolutionary and applied context.

Characterization and expression of the transcription factor PU.1 during LPS-induced inflammation in the rainbow trout (Oncorhynchus mykiss)

The transcription factor PU.1 plays a key role in hematopoietic lineage development and therefore in determining immune cell fate. A full length cDNA transcript of 1237 nucleotides encoding a highly conserved putative protein of 293 amino acids was identified by EST analysis in lipopolysaccharide (LPS) activated trout macrophages. Phylogenetic analyses highlight the significant level of structural conservation of the PU.1 transcription factor reinforcing the importance of this molecule in animal immunity. In trout, the PU.1 mRNA shows a tissue-specific expression pattern and is induced in vivo by LPS in muscle, liver, intestine and brain. Furthermore PU.1 is highly expressed in trout macrophages in primary culture. In situ expression analysis in the head kidney describes a large number of PU.1+ve cells distributed through the tissue in both LPS-treated and control animals. Cellular proliferation examined by BrdU immunohistochemistry (IHC) shows that LPS regulates hematopoietic processes in adult fish by stimulating cellular proliferation 3 days after treatment. These studies provide initial insights into hematopoietic/cellular processes in the head kidney of rainbow trout after in vivo LPS challenge.

Cell-mediated immune responses in rainbow trout after DNA immunization against the viral hemorrhagic septicemia virus

To identify viral proteins that induce cell-mediated cytotoxicity (CMC) against viral hemorrhagic septicemia virus (VHSV)-infected cells, rainbow trout were immunized with DNA vectors encoding the glycoprotein G or the nucleocapsid protein N of VHSV. The G protein was a more potent trigger of cytotoxic cells than the N protein. Peripheral blood leukocytes (PBL) isolated from trout immunized against the G protein killed both VHSV-infected MHC class I matched (RTG-2) and VHSV-infected xenogeneic (EPC) target cells, suggesting the involvement of both cytotoxic T lymphocytes (CTL) and NK cells, respectively. In contrast, PBL from trout that were immunized against the N protein only killed VHSV-infected RTG-2 cells, indicating that this protein only elicits a CTL response. Further, a significant killing capacity of these PBL was only observed during summer months. PBL from fish that were immunized against the VHSV G protein significantly killed VHSV-infected but not infectious hematopoietic necrosis virus (IHNV)-infected targets indicating antigen specificity. Thus, this is the first report on cytotoxic immune responses after DNA vaccination in fish. Furthermore, cells isolated from the inflamed site of DNA injection were stained and transferred to isogeneic DNA-vaccinated recipients. Most of the stained donor leukocytes accumulated at the recipients' DNA injection site showing, for the first time, leukocyte homing in fish. Transferred donor leukocytes mainly migrated to the homologous vaccine injection site rather than to injection sites of heterologous vaccines, suggesting the antigen specificity of homing. By demonstrating CMC responses to distinct viral proteins and homing in rainbow trout, these results substantially contribute to the understanding of the teleost immune system.