Abstract
To understand adaptive immune system in fish, we identified and characterized three kinds of T-cell antigen receptors (TCR α, β, and δ) and one of cytotoxic T cell co-receptor (CD8α) from Japanese flounder (Paralichthys olivaceus) leukocytes cDNA library. From the study of genomic DNA organization the constant genes for TCR α, β, and δ using BAC genomic DNA clones, it was revealed clearly that the TCR α constant gene and TCR δ constant gene are linked at the same locus; similar with that of human and mouse. The expression patterns of TCR α, β, and δ, and CD8α were tested by Northern blot hybridization or RT-PCR and in situ hybridization (ISH). The results of Northern blotting and RT-PCR showed that the lymphoid organs (kidney, spleen and leukocyte cells) and also gill and intestine which have direct contact with pathogens, highly express mRNA of TCR α, β, and δ, CD8α chains. The ISH with anti-sense RNA probes of these cDNA molecules allowed to confirm their respective expression and distribution patterns in some lymphoid organs (peripheral blood and head kidney).
