D-mannose-specific Immunoglobulin M in Grass Puffer (Takifugu niphobles), a Nonhost Fish of a Monogenean Ectoparasite Heterobothrium okamotoi, Can Act as a Trigger for its Parasitism.

Heterobothrium okamotoi, a monogenean gill parasite, exhibits high host specificity for the tiger puffer, Takifugu rubripes, and it has been experimentally verified that the parasite cannot colonize either closely related species such as the grass puffer Takifugu niphobles or distantly related fish such as the red seabream Pagrus major. Previously, we demonstrated in T. rubripes that immunoglobulin M (IgM) with d-mannose affinity induced deciliation of the oncomiracidia, the first step of parasitism, indicating that the parasite utilizes the molecule as a receptor for infection.

Original Ligand for LTβR Is LIGHT: Insight into Evolution of the LT/LTβR System.

The lymphotoxin (LT)/LTβ receptor (LTβR) axis is crucial for the regulation of immune responses and development of lymphoid tissues in mammals. Despite the importance of this pathway, the existence and function of LT and LTβR remain obscure for nonmammalian species. In this study, we report a nonmammalian LTβR and its ligand.

SJL-1, a C-type lectin, acts as a surface defense molecule in Japanese sea cucumber, Apostichopus japonicus.

The surface defense molecules of aquatic invertebrates against infectious microorganisms have remained largely unexplored. In the present study, hemagglutinins were isolated from an extract of body surface layer of Japanese sea cucumber, Apostichopus japonicus, by affinity chromatography with fixed rabbit erythrocyte membranes. The N-terminal sequence of a 15-kDa agglutinin was almost identical with that of SJL-1, a C-type lectin formerly identified in this species.

Teleost Basophils Have IgM-Dependent and Dual Ig-Independent Degranulation Systems.

Recently, mammalian basophils have been highlighted as having roles in allergy and antiparasitic immunity; however, there is little information about the functions and evolutionary origin of basophils, because they are the least abundant leukocyte in most vertebrates. In this study, we characterized the teleost basophils that are abundant in the peripheral blood of fugu (). Fugu basophils have two distinct granules: reddish-purple and dark violet ones.

Light- and circadian-controlled genes respond to a broad light spectrum in Puffer Fish-derived Fugu eye cells.

Some cell lines retain intrinsic phototransduction pathways to control the expression of light-regulated genes such as the circadian clock gene. Here we investigated the photosensitivity of a Fugu eye, a cell line established from the eye of Takifugu rubripes, to examine whether such a photosensitive nature is present. Microarray analysis identified 15 genes that showed blue light-dependent change at the transcript level.

Mucosal IgM Antibody with d-Mannose Affinity in Fugu Is Utilized by a Monogenean Parasite for Host Recognition.

How parasites recognize their definitive hosts is a mystery; however, parasitism is reportedly initiated by recognition of certain molecules on host surfaces. Fish ectoparasites make initial contact with their hosts at body surfaces, such as skin and gills, which are covered with mucosa that are similar to those of mammalian guts. Fish are among the most primitive vertebrates with immune systems that are equivalent to those in mammals, and they produce and secrete IgM into mucus.

Serum GlcNAc-binding IgM of fugu (Takifugu rubripes) suppresses the growth of fish pathogenic bacteria: a novel function of teleost antibody.

N-acetyl-d-glucosamine (GlcNAc) is one of the components of peptidoglycan, a biopolymer in the bacterial cell wall. We purified a novel GlcNAc-binding protein, designated as fGBP-78, from sera of fugu (Takifugu rubripes). The fGBP-78 is a heteromer of 78- and 25-kDa subunits.

A trans-species missense SNP in Amhr2 is associated with sex determination in the tiger pufferfish, Takifugu rubripes (fugu).

Heterogametic sex chromosomes have evolved independently in various lineages of vertebrates. Such sex chromosome pairs often contain nonrecombining regions, with one of the chromosomes harboring a master sex-determining (SD) gene. It is hypothesized that these sex chromosomes evolved from a pair of autosomes that diverged after acquiring the SD gene.

Teleost IL-6 promotes antibody production through STAT3 signaling via IL-6R and gp130.

Teleost IL-6 is upregulated after antigen stimulation; therefore, we hypothesized that fish IL-6 contributes to antibody production during immune responses against infections. To verify this hypothesis, we first cloned IL-6R and gp130 in fugu (Takifugu rubripes) in the present study. The membrane and soluble forms of IL-6R were identified by the identification of cDNA clones of IL-6R homologues.

Functional analysis of fish BCL-6 and Blimp-1 in vitro: transcriptional repressors for B-cell terminal differentiation in fugu (Takifugu rubripes).

The transcriptional repressors BCL-6 and Blimp-1 are key regulators of B-cell terminal differentiation in mammals. We have previously identified the BCL-6 gene and Blimp-1 gene in fugu (Takifugu rubripes). In the present report, we conducted a functional analysis of fugu BCL-6 and Blimp-1 by using a one-hybrid reporter assay with Gal4 fusion proteins and Gal4DBD luciferase reporter gene.

The plasmablast-like leukocyte in the kidney of fugu (Takifugu rubripes).

In teleosts, the kidney is the major immune organ. From the kidney of fugu (Takifugu rubripes), we isolated a unique leukocyte population. This population shows properties similar to those of mammalian plasmablasts.

Genetic variation and geographic distribution of megalocytiviruses.

Viruses belonging to the genus Megalocytivirus in the family Iridoviridae have caused mass mortalities in marine and freshwater fish in Asian countries. In this study, partial major capsid protein (MCP) gene of seven Japanese and six Korean megalocytiviruses was sequenced and compared with the known megalocytiviruses to evaluate genetic variation and geographic distribution of the viruses. Comparison of MCP gene nucleotide sequences revealed sequence identity of 92.

Effects of tributyltin on the immune system of Japanese flounder (Paralichthys olivaceus).

Effects of tributyltin (TBT) which has been used for antifouling paint of ship's hulls and fishing nets on the immune system in Japanese flounder (Paralichthys olivaceus) were investigated. After short-term exposure to a high level of TBT, leucocytes in the head kidney from 1-year-old flounder were examined for the proportion of neutrophils in total leucocytes. Also examined were their respiratory burst activities using flow cytometry, the reduction of nitroblue tetrazolium (NBT) and lysozyme activities.

Identification of genes encoding critical factors regulating B-cell terminal differentiation in torafugu (Takifugu rubripes).

Many transcription factors, and associated co-factors, are involved in the regulation of B-cell terminal differentiation in mammals. In the teleost and cartilaginous fish, although evidence has strongly suggested the existence of B-cell like lymphocytes, the mechanism of terminal differentiation of B-cells remains to be elucidated. In the present study, we searched for the nucleotide and amino acid sequences similar to the critical regulatory factors facilitating the terminal differentiation of B-cells using the fugu BLAST server.

Molecular cloning of the BCL-6 gene, a transcriptional repressor for B-cell differentiation, in torafugu (Takifugu rubripes).

B-cell lymphoma-6 (BCL-6) is a transcriptional repressor that prevents the terminal differentiation of mature B-cells to plasma cells, and is essential for germinal center formation in the primary lymphoid organs of mammals. In this study, we identified the BCL-6 gene in torafugu (Takifugu rubripes) using the torafugu genome database, and analyzed the expression of BCL-6 mRNA in various tissues of torafugu, using RT-PCR. The BCL-6 gene consisted of eight exons and seven introns spanning a genome of ca.

B-lymphocyte-induced maturation protein-1 (Blimp-1) gene of torafugu (Takifugu rubripes).

Homologous gene of B-lymphocyte-induced maturation protein-1 (Blimp-1) of torafugu (Takifugu rubripes) was identified by tblast search analysis. RT-PCR and 5'RACE clearly defined the sequence of the UTR and coding region which has been ambiguously determined by tblast analysis. Fugu Blimp-1 was mainly expressed in the lymphoid organs.

Monoclonal antibodies recognising serum immunoglobulins and surface immunoglobulin-positive cells of puffer fish, torafugu (Takifugu rubripes).

Immunoglobulin of the torafugu, Takifugu rubripes, was purified by a combination of precipitation by low ionic strength dialysis and gel filtration. The Ig was used to immunise mice for the production of monoclonal antibody (MAb). Supernatants of hybridoma cultures were screened by enzyme-linked immunosorbent assay using purified-torafugu Ig-coated plates, and two stable hybridomas producing MAbs against torafugu Ig were obtained.