title: Molecular characterization and increased expression of the Nile tilapia, Oreochromis niloticus (L.), T-cell receptor beta chain in response to Streptococcus agalactiae infection.
abstract: The complete cDNA sequence of the Nile tilapia T-cell receptor (TCR) β chain was cloned using 5' RACE. The full-length, 1263-bp cDNA contained a 942-bp open reading frame (ORF) encoding a 314-amino-acid protein. Sequence analyses revealed that the Nile tilapia TCR β chain contains four conserved cysteine residues involved in the formation of disulphide bridges and a conserved amino acid motif believed to be important for assembly and signalling of the TCR αβ/CD3 complex, both of which are normally found in the TCR β chain of other vertebrates. As detected using semi-quantitative and quantitative RT-PCR, the highest expression level of TCR β was detected in the thymus. Interestingly, Streptococcus agalactiae significantly induced the up-regulation of the TCR β chain, and the strongest up-regulation was detected in the brain and peripheral blood leucocytes (PBLs). In in vitro experiments, concanavalin A and Aeromonas hydrophila were found to significantly increase the expression of the TCR β chain in PBLs after 48 h (P < 0.01) and 72 h (P < 0.05), respectively. Furthermore, real-time PCR analysis showed that intraperitoneal injection (IP) of 10(7) cfu mL(-1) of S. agalactiae could induce TCR β expression that was greater than the expression observed following administration of 10(9) cfu mL(-1). The presence of the TCR β chain in fish detected in this study suggests the presence of T-cell populations that have been found in higher vertebrates, which may play a crucial functional role in the response to fish pathogens.
authors.affiliation: Aquaculture and Aquatic Resources Management Field of Study, School of Environment, Resource and Development, Asian Institute of Technology, Pathumthani, Thailand.
authors.forename: N
authors.initials: N
authors.lastname: Nithikulworawong
authors.forename: A
authors.initials: A
authors.lastname: Yakupitiyage
authors.forename: Sk
authors.initials: S
authors.lastname: Rakshit
authors.forename: P
authors.initials: P
authors.lastname: Srisapoome
mesh_terms: D056704:Adaptive Immunity; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D023681:Cichlids / Q000145:classification / Q000235:genetics* / Q000276:immunology*; D005393:Fish Diseases / Q000276:immunology*; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D007962:Leukocytes / Q000276:immunology / Q000382:microbiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013290:Streptococcal Infections / Q000276:immunology / Q000662:veterinary*; D013292:Streptococcus agalactiae
chemical_list: D016693:Receptors, Antigen, T-Cell, alpha-beta