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Molecular characterization and increased expression of the Nile tilapia, Oreochromis niloticus (L.), T‐cell receptor beta chain in response to Streptococcus agalactiae infection
Author(s) -
Nithikulworawong N,
Yakupitiyage A,
Rakshit SK,
Srisapoome P
Publication year - 2012
Publication title -
journal of fish diseases
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.819
H-Index - 85
eISSN - 1365-2761
pISSN - 0140-7775
DOI - 10.1111/j.1365-2761.2012.01353.x
Subject(s) - t cell receptor , biology , nile tilapia , oreochromis , microbiology and biotechnology , complementary dna , open reading frame , cd3 , cd8 , peptide sequence , t cell , gene , immunology , biochemistry , antigen , immune system , fish <actinopterygii> , fishery
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.