Special Issue "Current Understanding of Fish Immune Systems"

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A special issue of Biology (ISSN 2079-7737).

Deadline for manuscript submissions: closed (15 May 2015)

Special Issue Editor

Guest Editor
Prof. Dr. Brian Dixon

Department of Biology, University of Waterloo, ESC 350, 200 University Ave. W, Waterloo, Ontario, N2L 3G1, Canada
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Special Issue Information

Dear Colleagues,

Fish immunity studies are at a pivotal point. Genomes of zebrafish and fugu have been examined in detail, those of rainbow trout, cod and coelacanths have recently been released, allowing for comparative studies revealing key evolutionary differences, such as lobe-finned fishes more closely resembling tetrapods or the lack of major histocompatibility class II and associated accessory genes in cod. In addition, novel technologies such as RNAseq have permitted large scale views of gene regulation. Functional studies in fish have provided novel regulatory and effector mechanisms that, upon subsequent study, are also present in mammals, such as transferrin activation of macrophages and phagocytic B cells. With this basis, future functional studies will provide even deeper insights into both mechanisms of fish immunity and the evolution of immune systems. For this special issue, we will review the state of the art in key areas of fish immunity as a basis for future studies.

Prof. Dr. Brian Dixon
Guest Editor

Submission

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Keywords

  • teleost
  • immunology
  • comparative immunology
  • innate immunity
  • adaptive immunity

Published Papers (11 papers)

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Review

Open AccessReview Fish Immunoglobulins
Biology 2016, 5(4), 45; doi:10.3390/biology5040045
Received: 9 October 2016 / Revised: 3 November 2016 / Accepted: 9 November 2016 / Published: 21 November 2016
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Abstract
The B cell receptor and secreted antibody are at the nexus of humoral adaptive immunity. In this review, we summarize what is known of the immunoglobulin genes of jawed cartilaginous and bony fishes. We focus on what has been learned from genomic or
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The B cell receptor and secreted antibody are at the nexus of humoral adaptive immunity. In this review, we summarize what is known of the immunoglobulin genes of jawed cartilaginous and bony fishes. We focus on what has been learned from genomic or cDNA sequence data, but where appropriate draw upon protein, immunization, affinity and structural studies. Work from major aquatic model organisms and less studied comparative species are both included to define what is the rule for an immunoglobulin isotype or taxonomic group and what exemplifies an exception. Full article
(This article belongs to the Special Issue Current Understanding of Fish Immune Systems)
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Open AccessReview The Function of Fish Cytokines
Biology 2016, 5(2), 23; doi:10.3390/biology5020023
Received: 29 February 2016 / Revised: 28 April 2016 / Accepted: 17 May 2016 / Published: 24 May 2016
Cited by 4 | PDF Full-text (780 KB) | HTML Full-text | XML Full-text
Abstract
What is known about the biological activity of fish cytokines is reviewed. Most of the functional studies performed to date have been in teleost fish, and have focused on the induced effects of cytokine recombinant proteins, or have used loss- and gain-of-function experiments
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What is known about the biological activity of fish cytokines is reviewed. Most of the functional studies performed to date have been in teleost fish, and have focused on the induced effects of cytokine recombinant proteins, or have used loss- and gain-of-function experiments in zebrafish. Such studies begin to tell us about the role of these molecules in the regulation of fish immune responses and whether they are similar or divergent to the well-characterised functions of mammalian cytokines. This knowledge will aid our ability to determine and modulate the pathways leading to protective immunity, to improve fish health in aquaculture. Full article
(This article belongs to the Special Issue Current Understanding of Fish Immune Systems)
Open AccessReview Biology of Bony Fish Macrophages
Biology 2015, 4(4), 881-906; doi:10.3390/biology4040881
Received: 26 October 2015 / Revised: 20 November 2015 / Accepted: 24 November 2015 / Published: 30 November 2015
Cited by 2 | PDF Full-text (498 KB) | HTML Full-text | XML Full-text
Abstract
Macrophages are found across all vertebrate species, reside in virtually all animal tissues, and play critical roles in host protection and homeostasis. Various mechanisms determine and regulate the highly plastic functional phenotypes of macrophages, including antimicrobial host defenses (pro-inflammatory, M1-type), and resolution and
[...] Read more.
Macrophages are found across all vertebrate species, reside in virtually all animal tissues, and play critical roles in host protection and homeostasis. Various mechanisms determine and regulate the highly plastic functional phenotypes of macrophages, including antimicrobial host defenses (pro-inflammatory, M1-type), and resolution and repair functions (anti-inflammatory/regulatory, M2-type). The study of inflammatory macrophages in immune defense of teleosts has garnered much attention, and antimicrobial mechanisms of these cells have been extensively studied in various fish models. Intriguingly, both similarities and differences have been documented for the regulation of lower vertebrate macrophage antimicrobial defenses, as compared to what has been described in mammals. Advances in our understanding of the teleost macrophage M2 phenotypes likewise suggest functional conservation through similar and distinct regulatory strategies, compared to their mammalian counterparts. In this review, we discuss the current understanding of the molecular mechanisms governing teleost macrophage functional heterogeneity, including monopoetic development, classical macrophage inflammatory and antimicrobial responses as well as alternative macrophage polarization towards tissues repair and resolution of inflammation. Full article
(This article belongs to the Special Issue Current Understanding of Fish Immune Systems)
Open AccessReview Along the Axis between Type 1 and Type 2 Immunity; Principles Conserved in Evolution from Fish to Mammals
Biology 2015, 4(4), 814-859; doi:10.3390/biology4040814
Received: 8 September 2015 / Revised: 10 October 2015 / Accepted: 19 October 2015 / Published: 17 November 2015
Cited by 3 | PDF Full-text (1842 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A phenomenon already discovered more than 25 years ago is the possibility of naïve helper T cells to polarize into TH1 or TH2 populations. In a simplified model, these polarizations occur at opposite ends of an “immune 1-2 axis”
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A phenomenon already discovered more than 25 years ago is the possibility of naïve helper T cells to polarize into TH1 or TH2 populations. In a simplified model, these polarizations occur at opposite ends of an “immune 1-2 axis” (i1-i2 axis) of possible conditions. Additional polarizations of helper/regulatory T cells were discovered later, such as for example TH17 and Treg phenotypes; although these polarizations are not selected by the axis-end conditions, they are affected by i1-i2 axis factors, and may retain more potential for change than the relatively stable TH1 and TH2 phenotypes. I1-i2 axis conditions are also relevant for polarizations of other types of leukocytes, such as for example macrophages. Tissue milieus with “type 1 immunity” (“i1”) are biased towards cell-mediated cytotoxicity, while the term “type 2 immunity” (“i2”) is used for a variety of conditions which have in common that they inhibit type 1 immunity. The immune milieus of some tissues, like the gills in fish and the uterus in pregnant mammals, probably are skewed towards type 2 immunity. An i2-skewed milieu is also created by many tumors, which allows them to escape eradication by type 1 immunity. In this review we compare a number of i1-i2 axis factors between fish and mammals, and conclude that several principles of the i1-i2 axis system seem to be ancient and shared between all classes of jawed vertebrates. Furthermore, the present study is the first to identify a canonical TH2 cytokine locus in a bony fish, namely spotted gar, in the sense that it includes RAD50 and bona fide genes of both IL-4/13 and IL-3/ IL-5/GM-CSF families. Full article
(This article belongs to the Special Issue Current Understanding of Fish Immune Systems)
Open AccessReview Teleost Chemokines and Their Receptors
Biology 2015, 4(4), 756-784; doi:10.3390/biology4040756
Received: 13 August 2015 / Revised: 20 October 2015 / Accepted: 3 November 2015 / Published: 11 November 2015
Cited by 2 | PDF Full-text (33573 KB) | HTML Full-text | XML Full-text
Abstract
Chemokines are a superfamily of cytokines that appeared about 650 million years ago, at the emergence of vertebrates, and are responsible for regulating cell migration under both inflammatory and physiological conditions. The first teleost chemokine gene was reported in rainbow trout in 1998.
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Chemokines are a superfamily of cytokines that appeared about 650 million years ago, at the emergence of vertebrates, and are responsible for regulating cell migration under both inflammatory and physiological conditions. The first teleost chemokine gene was reported in rainbow trout in 1998. Since then, numerous chemokine genes have been identified in diverse fish species evidencing the great differences that exist among fish and mammalian chemokines, and within the different fish species, as a consequence of extensive intrachromosomal gene duplications and different infectious experiences. Subsequently, it has only been possible to establish clear homologies with mammalian chemokines in the case of some chemokines with well-conserved homeostatic roles, whereas the functionality of other chemokine genes will have to be independently addressed in each species. Despite this, functional studies have only been undertaken for a few of these chemokine genes. In this review, we describe the current state of knowledge of chemokine biology in teleost fish. We have mainly focused on those species for which more research efforts have been made in this subject, specially zebrafish (Danio rerio), rainbow trout (Oncorhynchus mykiss) and catfish (Ictalurus punctatus), outlining which genes have been identified thus far, highlighting the most important aspects of their expression regulation and addressing any known aspects of their biological role in immunity. Finally, we summarise what is known about the chemokine receptors in teleosts and provide some analysis using recently available data to help characterise them more clearly. Full article
(This article belongs to the Special Issue Current Understanding of Fish Immune Systems)
Open AccessReview Neutrophil Development, Migration, and Function in Teleost Fish
Biology 2015, 4(4), 715-734; doi:10.3390/biology4040715
Received: 28 September 2015 / Revised: 30 October 2015 / Accepted: 30 October 2015 / Published: 6 November 2015
Cited by 2 | PDF Full-text (5191 KB) | HTML Full-text | XML Full-text
Abstract
It is now widely recognized that neutrophils are sophisticated cells that are critical to host defense and the maintenance of homeostasis. In addition, concepts such as neutrophil plasticity are helping to define the range of phenotypic profiles available to cells in this group
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It is now widely recognized that neutrophils are sophisticated cells that are critical to host defense and the maintenance of homeostasis. In addition, concepts such as neutrophil plasticity are helping to define the range of phenotypic profiles available to cells in this group and the physiological conditions that contribute to their differentiation. Herein, we discuss key features of the life of a teleost neutrophil including their development, migration to an inflammatory site, and contributions to pathogen killing and the control of acute inflammation. The potent anti-microbial mechanisms elicited by these cells in bony fish are a testament to their long-standing evolutionary contributions in host defense. In addition, recent insights into their active roles in the control of inflammation prior to induction of apoptosis highlight their importance to the maintenance of host integrity in these early vertebrates. Overall, our goal is to summarize recent progress in our understanding of this cell type in teleost fish, and to provide evolutionary context for the contributions of this hematopoietic lineage in host defense and an efficient return to homeostasis following injury or infection. Full article
(This article belongs to the Special Issue Current Understanding of Fish Immune Systems)
Open AccessReview Antimicrobial Peptides as Mediators of Innate Immunity in Teleosts
Biology 2015, 4(4), 607-639; doi:10.3390/biology4040607
Received: 31 August 2015 / Revised: 16 September 2015 / Accepted: 17 September 2015 / Published: 25 September 2015
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Abstract
Antimicrobial peptides (AMPs) have been identified throughout the metazoa suggesting their evolutionarily conserved nature and their presence in teleosts is no exception. AMPs are short (18–46 amino acids), usually cationic, amphipathic peptides. While AMPs are diverse in amino acid sequence, with no two
[...] Read more.
Antimicrobial peptides (AMPs) have been identified throughout the metazoa suggesting their evolutionarily conserved nature and their presence in teleosts is no exception. AMPs are short (18–46 amino acids), usually cationic, amphipathic peptides. While AMPs are diverse in amino acid sequence, with no two AMPs being identical, they collectively appear to have conserved functions in the innate immunity of animals towards the pathogens they encounter in their environment. Fish AMPs are upregulated in response to pathogens and appear to have direct broad-spectrum antimicrobial activity towards both human and fish pathogens. However, an emerging role for AMPs as immunomodulatory molecules has become apparent—the ability of AMPs to activate the innate immune system sheds light onto the multifaceted capacity of these small peptides to combat pathogens through direct and indirect means. Herein, this review focuses on the role of teleost AMPs as modulators of the innate immune system and their regulation in response to pathogens or other exogenous molecules. The capacity to regulate AMP expression by exogenous factors may prove useful in modulating AMP expression in fish to prevent disease, particularly in aquaculture settings where crowded conditions and environmental stress pre-dispose these fish to infection. Full article
(This article belongs to the Special Issue Current Understanding of Fish Immune Systems)
Open AccessReview T Cells in Fish
Biology 2015, 4(4), 640-663; doi:10.3390/biology4040640
Received: 2 August 2015 / Revised: 11 September 2015 / Accepted: 14 September 2015 / Published: 25 September 2015
Cited by 2 | PDF Full-text (812 KB) | HTML Full-text | XML Full-text
Abstract
Cartilaginous and bony fish are the most primitive vertebrates with a thymus, and possess T cells equivalent to those in mammals. There are a number of studies in fish demonstrating that the thymus is the essential organ for development of T lymphocytes from
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Cartilaginous and bony fish are the most primitive vertebrates with a thymus, and possess T cells equivalent to those in mammals. There are a number of studies in fish demonstrating that the thymus is the essential organ for development of T lymphocytes from early thymocyte progenitors to functionally competent T cells. A high number of T cells in the intestine and gills has been reported in several fish species. Involvement of CD4+ and CD8α+ T cells in allograft rejection and graft-versus-host reaction (GVHR) has been demonstrated using monoclonal antibodies. Conservation of CD4+ helper T cell functions among teleost fishes has been suggested in a number studies employing mixed leukocyte culture (MLC) and hapten/carrier effect. Alloantigen- and virus-specific cytotoxicity has also been demonstrated in ginbuna and rainbow trout. Furthermore, the important role of cell-mediated immunity rather than humoral immunity has been reported in the protection against intracellular bacterial infection. Recently, the direct antibacterial activity of CD8α+, CD4+ T-cells and sIgM+ cells in fish has been reported. In this review, we summarize the recent progress in T cell research focusing on the tissue distribution and function of fish T cells. Full article
(This article belongs to the Special Issue Current Understanding of Fish Immune Systems)
Open AccessReview The Mucosal Immune System of Teleost Fish
Biology 2015, 4(3), 525-539; doi:10.3390/biology4030525
Received: 2 June 2015 / Revised: 5 August 2015 / Accepted: 5 August 2015 / Published: 12 August 2015
Cited by 8 | PDF Full-text (181 KB) | HTML Full-text | XML Full-text
Abstract
Teleost fish possess an adaptive immune system associated with each of their mucosal body surfaces. Evidence obtained from mucosal vaccination and mucosal infection studies reveal that adaptive immune responses take place at the different mucosal surfaces of teleost. The main mucosa-associated lymphoid tissues
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Teleost fish possess an adaptive immune system associated with each of their mucosal body surfaces. Evidence obtained from mucosal vaccination and mucosal infection studies reveal that adaptive immune responses take place at the different mucosal surfaces of teleost. The main mucosa-associated lymphoid tissues (MALT) of teleosts are the gut-associated lymphoid tissue (GALT), skin-associated lymphoid tissue (SALT), the gill-associated lymphoid tissue (GIALT) and the recently discovered nasopharynx-associated lymphoid tissue (NALT). Teleost MALT includes diffuse B cells and T cells with specific phenotypes different from their systemic counterparts that have co-evolved to defend the microbe-rich mucosal environment. Both B and T cells respond to mucosal infection or vaccination. Specific antibody responses can be measured in the gills, gut and skin mucosal secretions of teleost fish following mucosal infection or vaccination. Rainbow trout studies have shown that IgT antibodies and IgT+ B cells are the predominant B cell subset in all MALT and respond in a compartmentalized manner to mucosal infection. Our current knowledge on adaptive immunity in teleosts is limited compared to the mammalian literature. New research tools and in vivo models are currently being developed in order to help reveal the great intricacy of teleost mucosal adaptive immunity and help improve mucosal vaccination protocols for use in aquaculture. Full article
(This article belongs to the Special Issue Current Understanding of Fish Immune Systems)
Open AccessReview Antibody Affinity Maturation in Fishes—Our Current Understanding
Biology 2015, 4(3), 512-524; doi:10.3390/biology4030512
Received: 22 May 2015 / Revised: 13 July 2015 / Accepted: 23 July 2015 / Published: 31 July 2015
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Abstract
It has long been believed that fish lack antibody affinity maturation, in part because they were thought to lack germinal centers. Recent research done on sharks and bony fishes indicates that these early vertebrates are able to affinity mature their antibodies. This article
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It has long been believed that fish lack antibody affinity maturation, in part because they were thought to lack germinal centers. Recent research done on sharks and bony fishes indicates that these early vertebrates are able to affinity mature their antibodies. This article reviews the functionality of the fish homologue of the immunoglobulin (Ig) mutator enzyme activation-induced cytidine deaminase (AID). We also consider the protein and molecular evidence for Ig somatic hypermutation and antibody affinity maturation. In the context of recent evidence for a putative proto-germinal center in fishes we propose some possible reasons that observed affinity maturation in fishes often seems lacking and propose future work that might shed further light on this process in fishes. Full article
(This article belongs to the Special Issue Current Understanding of Fish Immune Systems)
Open AccessReview Sensors of Infection: Viral Nucleic Acid PRRs in Fish
Biology 2015, 4(3), 460-493; doi:10.3390/biology4030460
Received: 22 May 2015 / Revised: 19 June 2015 / Accepted: 19 June 2015 / Published: 8 July 2015
Cited by 2 | PDF Full-text (603 KB) | HTML Full-text | XML Full-text
Abstract
Viruses produce nucleic acids during their replication, either during genomic replication or transcription. These nucleic acids are present in the cytoplasm or endosome of an infected cell, or in the extracellular space to be sensed by neighboring cells during lytic infections. Cells have
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Viruses produce nucleic acids during their replication, either during genomic replication or transcription. These nucleic acids are present in the cytoplasm or endosome of an infected cell, or in the extracellular space to be sensed by neighboring cells during lytic infections. Cells have mechanisms of sensing virus-generated nucleic acids; these nucleic acids act as flags to the cell, indicating an infection requiring defense mechanisms. The viral nucleic acids are called pathogen-associated molecular patterns (PAMPs) and the sensors that bind them are called pattern recognition receptors (PRRs). This review article focuses on the most recent findings regarding nucleic acids PRRs in fish, including: Toll-like receptors (TLRs), RIG-I-like receptors (RLRs), cytoplasmic DNA sensors (CDSs) and class A scavenger receptors (SR-As). It also discusses what is currently known of the downstream signaling molecules for each PRR family and the resulting antiviral response, either type I interferons (IFNs) or pro-inflammatory cytokine production. The review highlights what is known but also defines what still requires elucidation in this economically important animal. Understanding innate immune systems to virus infections will aid in the development of better antiviral therapies and vaccines for the future. Full article
(This article belongs to the Special Issue Current Understanding of Fish Immune Systems)

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