Diversity, Molecular Characterization and Expression of T Cell Receptor γ in a Teleost Fish, the Sea Bass (Dicentrarchus labrax, L)

Abstract

Two lineages of T cells, expressing either the αβ T cell receptor (TR) or the γδ TR, exist in Gnathostomes. The latter type of T cells account for 1–10 % of T cells in blood and up to 30 % in the small intestine. They may recognize unconventional antigens (phosphorylated microbial metabolites, lipid antigens) without the need of major histocompatibility class I (MH1) or class II (MH2) presentation. In this work we have described cloning and structural characterization of TR -chain (TRG) from the teleost Dicentrarchus labrax. Further, by means of quantitative PCR analysis, we analyzed TRG expression levels both in poly I:C stimulated leukocytes in vitro, and following infection with betanodavirus in vivo. Two full length cDNAs relative to TRG, with the highest peptide and nucleotide identity with Japanese flounder, were identified. A multiple alignment analysis showed the conservation of peptides fundamental for TRG biological functions, and of the FGXG motif in the FR4 region, typical of most TR and immunoglobulin light chains. A 3D structure consisting of two domains mainly folded as beta strands with a sandwich architecture for each domain was also reported. TRG CDR3 of 8–18 AA in length and diversity in the TRG rearrangements expressed in thymus and intestine for a given V/C combination were evidenced by junction length spectratyping. TRG mRNA expression levels were high in basal conditions both in thymus and intestine, while in kidney and gut leukocytes they were up-regulated after in vitro stimulation by poly I:C. Finally, in juveniles the TRG expression levels were up-regulated in the head kidney and down-regulated in intestine after in vivo infection with betanodavirus. Overall, in this study the involvement of TRG-bearing T cells during viral stimulation was described for the first time, leading to new insights for the identification of T cell subsets in fish.

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

“…The interferon modulator poly I:C was found to induce a potent up-regulation of TCR gamma message in a mixed fraction of leukocytes cultured in vitro. Following a betanodavirus challenge, TCRg transcripts were rapidly downregulated in the intestine and later in the kidney, presumably through changes in gd T cell localization or trafficking patterns 131 ; similar to that described in non-human primate models of simian immunodeficiency virus.…”

Transcriptional Characterization of the T Cell Population within the Salmonid Interbranchial Lymphoid Tissue

“…A rapid redistribution of gd + T cells from mucosal sites to lymphoid sites was observed in macaques (Macaca mulatta) following oral infection of SIV (29). In sea bass (Dicentrarchus labrax), the same observations have been made following viral infection, indicating that gd + T cells have a role in virus-induced immunity also in teleosts (25).…”

“…Their orthologs have been characterized in salmon (23,24). In vertebrates, the ab + T cells reside mainly in secondary lymphoid organs and constitute most mature T cells (25). In mammals, gd + T cells constitute a small population known as intraepithelial lymphocytes, most abundant in the skin, gut, lung, and tongue.…”

Defensive response of European sea bass (Dicentrarchus labrax) against Listonella anguillarum or Photobacterium damselae subsp. piscicida experimental infection

“…This matter is still under investigation for bacterial pathogens such as L. anguillarum (Chaves-Pozo et al, 2004;Caipang et al, 2008;Zhang et al, 2012) and P. damselae subsp. piscicida (Phdp) (dos Santos et al, 2001;Buonocore et al, 2012;Pellizzari et al, 2013).…”

“…In particular, T-lymphocytes are involved in the cellular actions by T-cell receptor (TcR) that has been characterized in sea bass (Scapigliati et al, 2000b;Romano et al, 2011), whereas B lymphocytes are responsible of the humoral secretion of immunoglobulins (IgM) following B-cell receptor activation (BcR) (dos Santos et al, 2001). Specific molecular probes, as well as monoclonal antibodies, have been developed in order to be used as immunological markers and therefore investigated for measuring the specific response to pathogens or vaccines (Scapigliati et al, 2010;Boschi et al, 2011;Buonocore et al, 2012;Galeotti et al, 2013).…”