Extraordinary diversity of the CD28/CTLA4 family across jawed vertebrates.

Members of the CD28 family are critical for the control of immune cell activation. While CD28 and CTLA4 were previously identified in teleost fish, most members of the CD28 family have been described only in tetrapods. Using a comparative genomics approach, we found (co)orthologs of all members of the CD28 family both in Chondrichthyes and basal Osteichthyes groups, but not in Agnathans.

TLR7 in channel catfish (Ictalurus punctatus) is expressed in the endolysosome and is stimulated by synthetic ssRNA analogs, imiquimod, and resiquimod.

Toll-like receptors (TLRs) are pivotal pattern recognition receptors (PRRs) and key mediators of innate immunity. Despite the significance of channel catfish (Ictalurus punctatus) in comparative immunology and aquaculture, its 20 TLR genes remain largely functionally uncharacterized. In this study, our aim was to determine the catfish TLR7 agonists, signaling potential, and cellular localization.

Costimulatory receptors in the channel catfish: CD28 family members and their ligands.

The CD28-B7 interaction is required to deliver a second signal necessary for T-cell activation. Additional membrane receptors of the CD28 and B7 families are also involved in immune checkpoints that positively or negatively regulate leukocyte activation, in particular T lymphocytes. BTLA is an inhibitory receptor that belongs to a third receptor family.

A subset of leukocyte immune-type receptors (LITRs) regulates phagocytosis in channel catfish (Ictalurus punctatus) leukocytes.

Channel catfish, Ictalurus punctatus, leukocyte immune-type receptors (LITRs) constitute a large family of paired, immunoregulatory receptors unique to teleosts. A role for LITRs in phagocytosis has been proposed based on studies in mammalian cell lines; however, LITR-mediated phagocytosis has not been examined in the catfish model. In this study, we use two anti-LITR monoclonal antibodies, CC41 and 125.

Interferons and interferon receptors in the channel catfish, Ictalurus punctatus.

In this work, we describe the complete repertoire of channel catfish, Ictalurus punctatus, IFNs and IFN receptor genes. Based on multiple genomic and transcriptomic resources we identified 16 type I IFN genes, which represent the six type I IFN subgroups previously defined in salmonids (a-f.) No representatives of subgroup h previously only found in percomorphs were identified.

A Comprehensive Annotation of the Channel Catfish () T Cell Receptor Alpha/Delta, Beta, and Gamma Loci.

The complete germline repertoires of the channel catfish, , T cell receptor (TR) loci, TRAD, TRB, and TRG were obtained by analyzing genomic data from PacBio sequencing. The catfish TRB locus spans 214 kb, and contains 112 TRBV genes, a single TRBD gene, 31 TRBJ genes and two TRBC genes. In contrast, the TRAD locus is very large, at 1,285 kb.

Cloning and characterization of antiviral cytotoxic T lymphocytes in channel catfish, Ictalurus punctatus.

To determine the role of piscine anti-viral cytotoxic cells, we analyzed the response of channel catfish to Ictalurid herpesvirus 1, commonly designated channel catfish virus (CCV). Peripheral blood leukocytes (PBL) from catfish immunized with MHC-matched, CCV-infected G14D cells (G14D-CCV) showed marked lysis of G14D-CCV but little to no lysis of uninfected allogenic (3B11) or syngeneic (G14D) cells. Expansion of effectors by in vitro culture in the presence of irradiated G14D-CCV cells generated cultures with enhanced cytotoxicity and often broader target range.

Catfish lymphocytes expressing CC41-reactive leukocyte immune-type receptors (LITRs) proliferate in response to Edwardsiella ictaluri infection in vitro.

Monoclonal antibodies (mAbs) CC34 and CC41 recognize overlapping subsets of leukocyte immune-type receptors (LITRs). The mAb CC34 was raised against the clonal TS32.15 cytotoxic T cell line and the mAb CC41 was raised against the clonal NK cell line TS10.

Characterization of immunoglobulin light chain utilization and variable family diversity in rainbow trout.

This study characterizes immunoglobulin light chain (IgL) expression and variable family usage in rainbow trout. IgL transcripts were generated by 5' RACE from both immune and TNP-KLH immunized fish. Phylogenetic analysis revealed that the IgL variable regions clustered into seven different families: three kappa families (two newly described in this study), three sigma families, and a single lambda family.

Insights into the dynamics of memory, effector and apoptotic cytotoxic T lymphocytes in channel catfish, Ictalurus punctatus.

In this study, we used the channel catfish model clonal TS32.15 alloantigen-specific cytotoxic T cell (CTL) line to examine the dynamics of memory CTL expansion and senescence in teleosts. Although TS32.

A Leukocyte Immune-Type Receptor Subset Is a Marker of Antiviral Cytotoxic Cells in Channel Catfish, Ictalurus punctatus.

Channel catfish, Ictalurus punctatus, leukocyte immune type receptors (LITRs) represent a multigene family that encodes Ig superfamily proteins that mediate activating or inhibitory signaling. In this study, we demonstrate the use of mAb CC41 to monitor viral cytotoxic responses in catfish and determine that CC41 binds to a subset of LITRs on the surface of catfish clonal CTLs. Homozygous gynogenetic catfish were immunized with channel catfish virus (CCV)-infected MHC-matched clonal T cells (G14D-CCV), and PBL were collected at various times after immunization for flow cytometric analyses.

Antibody Repertoires in Fish.

As in mammals, cartilaginous and teleost fishes possess adaptive immune systems based on antigen recognition by immunoglobulins (Ig), T cell receptors (TCR), and major histocompatibility complex molecules (MHC) I and MHC II molecules. Also it is well established that fish B cells and mammalian B cells share many similarities, including Ig gene rearrangements, and production of membrane Ig and secreted Ig forms. This chapter provides an overview of the IgH and IgL chains in cartilaginous and bony fish, including their gene organizations, expression, diversity of their isotypes, and development of the primary repertoire.

The Src tyrosine kinase Lck binds to CD2, CD4-1, and CD4-2 T cell co-receptors in channel catfish, Ictalurus punctatus.

The binding of the lymphocyte specific protein tyrosine kinase (Lck) to T cell co-receptors is required for T cell development and activation. In mammals, Lck initiates signal transduction by binding to CD4 and CD8 co-receptors and phosphorylating ITAMs in the cytoplasmic tail of the CD3 molecules and the ζ chains. In addition, Lck can also bind to the adhesion molecule CD2 and trigger T cell activation.

Identification of SHIP-1 and SHIP-2 homologs in channel catfish, Ictalurus punctatus.

Src homology domain 2 (SH2) domain-containing inositol 5'-phosphatases (SHIP) proteins have diverse roles in signal transduction. SHIP-1 and SHIP-2 homologs were identified in channel catfish, Ictalurus punctatus, based on sequence homology to murine and human SHIP sequences. Full-length cDNAs for catfish SHIP-1 and SHIP-2 (IpSHIP-1 and IpSHIP-2) were obtained using 5' and 3' RACE protocols.

Identification and characterization of TCRγ and TCRδ chains in channel catfish, Ictalurus punctatus.

Channel catfish, Ictalurus punctatus, T cell receptors (TCR) γ and δ were identified by mining of expressed sequence tag databases, and full-length sequences were obtained by 5'-RACE and RT-PCR protocols. cDNAs for each of these TCR chains encode typical variable (V), diversity (D), joining (J), and constant (C) regions. Three TCRγ V families, seven TCRγ J sequences, and three TCRγ C sequences were identified from sequencing of cDNA.

Channel catfish (Ictalurus punctatus) leukocytes express estrogen receptor isoforms ERα and ERβ2 and are functionally modulated by estrogens.

Estrogens are recognized as modulators of immune responses in mammals and teleosts. While it is known that the effects of estrogens are mediated via leukocyte-specific estrogen receptors (ERs) in humans and mice, leucocyte-specific estrogen receptor expression and the effects of estrogens on this cell population is less explored and poorly understood in teleosts. Here in, we verify that channel catfish (Ictalurus punctaus) leukocytes express ERα and ERβ2.

Comprehensive survey and genomic characterization of Toll-like receptors (TLRs) in channel catfish, Ictalurus punctatus: identification of novel fish TLRs.

A comprehensive survey of channel catfish Toll-like receptors (TLRs) was undertaken following a genomic PCR approach based on degenerate primers. Twenty different TLRs were identified in channel catfish. Channel catfish TLR sequences were characterized by phylogenetic analysis based on their conserved Toll/interleukin-1 receptor domain and by in-depth analysis of leucine-rich repeat (LRR) motifs of the ligand binding extracellular domain (ECD).

CD4+ T-helper cells stimulated in response to placental ischemia mediate hypertension during pregnancy.

We have shown that hypertension in response to chronic placental ischemia is associated with elevated inflammatory cytokines and CD4(+) T cells. However, it is unknown whether these cells play an important role in mediating hypertension in response to placental ischemia. Therefore, we hypothesize that reduced uterine perfusion pressure (RUPP)-induced CD4(+) T cells increase blood pressure during pregnancy.

Insights into the function of IgD.

IgD, previously thought to be a recent addition to the immunoglobulin classes, has long been considered an enigmatic molecule. For example, it was debated if IgD had a specific function other than as an antigen receptor co-expressed with IgM on naive B cells and if it had an important role in mammalian immunity. However, during the past decade extensive sequencing of vertebrate genomes has shown that IgD homologs are present in all vertebrate taxa, except for birds.

Channel catfish CD8α and CD8β co-receptors: characterization, expression and polymorphism.

In this study we report the identification and characterization of channel catfish, Ictalurus punctatus CD8α and CD8β genes. Both genes encode predicted proteins containing a leader, a immunoglobulin superfamily V domain, a stalk/hinge region, a transmembrane region and a positively charged cytoplasmic tail (CYT) containing the conserved teleost C-X-H motif. Catfish CD8α and CD8β are encoded as single copy genes and as in other vertebrates exhibit a conserved head to tail synteny; the CD8β gene is found 14.

Immunoglobulin light (IgL) chains in ectothermic vertebrates.

Four major ancesteral IgL isotypes have been identified κ, λ, σ and σ-cart. However, depending on the vertebrate class the genomic representation of these isotypes differs in regards to what is encoded in the germline and how these genes are organized. Also, the relative contribution of each isotype in immune responses varies.

Conserved natural IgM antibodies mediate innate and adaptive immunity against the opportunistic fungus Pneumocystis murina.

Host defense against opportunistic fungi requires coordination between innate and adaptive immunity for resolution of infection. Antibodies generated in mice vaccinated with the fungus Pneumocystis prevent growth of Pneumocystis organisms within the lungs, but the mechanisms whereby antibodies enhance antifungal host defense are poorly defined. Nearly all species of fungi contain the conserved carbohydrates β-glucan and chitin within their cell walls, which may be targets of innate and adaptive immunity.

Identification of two IgD+ B cell populations in channel catfish, Ictalurus punctatus.

Channel catfish Ictalurus punctatus express two Ig isotypes: IgM and IgD. Although catfish IgM has been extensively studied at the functional and structural levels, much less is known about IgD. In this study, IgM(+)/IgD(+) and IgM(-)/IgD(+) catfish B cell populations were identified through the use of anti-IgM and anti-IgD mAbs.

Expression of alternatively spliced CD45 isoforms by channel catfish clonal T and B cells is dependent on activation state of the cell and regulated by protein synthesis and degradation.

In mammals, expression of the three alternatively spliced exons of the tyrosine phosphatase CD45 is regulated by the developmental and activation state of the cell. In comparison, the channel catfish, Ictalurus punctatus, CD45 homolog contains 18 functional alternatively spliced exons. Since very little is known about CD45 regulation in ectothermic vertebrates, this study examines the regulation of catfish CD45 mRNA isoform expression in clonal T and B cells in response to stimulation.