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

Abstract

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. Primer walking on bacterial artificial chromosomes (BACs) confirmed that the TRG locus contained seven TRGJ segments and indicated that the locus consists of (Vγ3-Jγ6-Cγ2)-(Vγ1n-Jγ7-Cγ3)-(Vγ2-Jγ5-Jγ4-Jγ3-Jγ2-Jγ1-Cγ1). In comparison for TCRδ, two V families, four TCRδ D sequences, one TCRδ J sequence, and one TCRδ C sequence were identified by cDNA sequencing. Importantly, the finding that some catfish TCRδ cDNAs contain TCR Vα-D-Jδ rearrangements and some TCRα cDNAs contain Vδ-Jα rearrangements strongly implies that the catfish TRA and TRD loci are linked. Finally, primer walking on BACs and Southern blotting suggest that catfish have four TRDD gene segments and a single TRDJ and TRDC gene. As in most vertebrates, all three reading frames of each of the catfish TRDD segments can be used in functional rearrangements, and more than one TRDD segment can be used in a single rearrangement. As expected, catfish TCRδ CDR3 regions are longer and more diverse than TCRγ CDR3 regions, and as a group they utilize more nucleotide additions and contain more nucleotide deletions than catfish TCRγ rearrangements.

Profiling the T Cell Receptor Alpha/Delta Locus in Salmonids

“…TR locus organization has been analyzed in many mammalian species (4,(9)(10)(11)(12)(13)(14)(15) but the data available for teleost and lower ectothermic vertebrates are much more limited (9,11,16,17). The TRB locus has a common genomic structure in several mammalian species, with different numbers of TRBV genes positioned upstream of tandem-aligned TRBD-J-C clusters, each composed of a single D (TRBD) gene, several J (TRBJ) genes, and one C (TRBC) gene (4,10,13,18,19).…”

“…Defining the locus orientation, by the transcriptional orientation of the TRDC and TRAC genes, the teleost TRA/TDR locus is in reverse orientation (REV) on the chromosome, with the TRDD genes at the 5' end of the locus and the TRA/TRD V genes translocated downstream at the 3' end of the locus in opposite orientation (IMGT index > Genomic orientation, http://www.imgt.org/IMGTindex/genomicOrientation.php). TRA and/or TRD genes have been identified in other teleosts, such as channel catfish (Ictalurus punctatus) (16), mandarin fish (Siniperca chuatsi) (27), sea bass (Dicentrachus labrax) (28), common carp (Cyprinus carpio) (29), and flounder (Parlichthys olivaceus) (30), but the organization of genomic locus has yet to be characterized in these species.…”

Physiology and immunology of mucosal barriers in catfish (Ictalurus spp.)

“…These cells were discussed as NK-like and the possibility of TCR gd expression was not ruled out. 120 More recently, new insights into the diversity of gd T cells in channel catfish were revealed by Moulana et al 134 . By using a combination of BLAST analyses, RACE protocols, and primer walking on bacterial artificial chromosomes (BAC), 3 Vg families and 2 Vd families were identified.…”

Molecular, Cellular and Functional Analysis of TRγ Chain along the European Sea Bass Dicentrarchus labrax Development

“…Whereas the αβTcR complex was elucidated in terms of molecular structure, genetics and antigen-recognition processes in several fish species, the existence of a human γδTcR homologue was reported by in silico prediction for the first time in the Japanese flounder Paralichthys olivaceus [8]. Teleost-wise, TRγ and/or TRδ genes were then described only in the common carp Cyprinus carpio [9], Atlantic salmon Salmo salar [10], European sea bass Dicentrarchus labrax [11], channel catfish Ictalurus punctatus [12], mandarin fish Siniperca chuatsi [13], zebrafish Danio rerio [14] and dojo loach Misgurnus anguillicaudatus [15]. Through the characterization of CDR3 loops, γδTcR appears more similar to Ig than it is to αβTcR [8].…”

“…Thirdly, by summarizing information retrieved from mammals and teleost models, γδ T cells have distinct peculiar features, in fact: they (i) are not MHC-restricted; (ii) have natural killer (NK)-cell reactivities and kill stressed, infected and tumoral cells; (iii) have a CD4 − CD8 + phenotype and show phagocytic activity against soluble and particulate antigens; (iv) recognize unconventional antigens including phosphorylated molecules, metabolic intermediates and lipids; (v) may act as pattern recognition receptors and participate in the humoral adaptive response by initiating CD4 + T cell proliferation, inducing B cell activation and IgM production; and (vi) have a role in the production of the mucosal immunity-related fish-specific IgT/Igz isotype [12,14,[19][20][21]. Based on these findings, mammalian γδ T cells were proposed as a primordial lymphocyte population predating αβ T cells and B cells and accordingly located at the interface between innate and acquired immunities [22].…”