Intestinal T cells of Dicentrarchus labrax (L.): Gene expression and functional studies

Abstract

Cellular and molecular data have evidenced a gut-associated lymphoid tissue in a variety of teleost species, abundantly containing T cells, whose origin, selection and functions are still unclear. This study reports CD4, CD8-α, MHCI-α, MHCII-β, rag-1 and TCR-β gene transcription along the intestine (anterior, middle and posterior segments) and in the thymus of one year-old Dicentrarchus labrax (L.). Real-time PCR findings depicted a main role of the thymus in T-cell development, but also rag-1 and CD8-α transcripts are detected in the intestine, having significant expression in the posterior segment. In the whole intestine TCR-β and CD8-α exceeded CD4 transcripts. RNA ISH confirmed these data and detailed that mucosal CD8-α+ cells were especially numerous in the epithelium and in aggregates in the lamina propria. Regional differences in T-cell-specific gene expressions are first described in the intestine of a bony fish. High non-specific cytotoxic activity against xenogeneic and allogeneic cells was found in lymphocytes purified from the intestinal mucosa, providing further insight into their local defence roles.

A Review of Immune System Components, Cytokines, and Immunostimulants in Cultured Finfish Species

“…Additionally, T cells have been found to be present in the midgut, harbored in the lamina propria. These T cells can be further divided into regulator and effector populations in order to examine the adaptive response [55]. Atlantic cod (Gadus morhua), in comparison to the foregut and stomach regions [57].…”

Adaptive immune responses at mucosal surfaces of teleost fish

“…However, only recently the presence of CD3εþ T cells in interbranchial lymphoid tissue of salmon gills was reported [85,86] and the authors are convinced that this type of tissue will be discovered in other teleost species too. The beststudied mucosal T cells in fish are IELs, but there is not much information on their functional relevance [83,84,86,87]. In carp, a specific T cell mAb (WCL38; [88]) has been found to react with around 50% of the mucosal T cells, but seldom with peripheral and thymic T cells.…”

Immune Defences of Teleost Fish

“…In situ hybridization studies confirmed the wide distribution of T cells throughout the gut of European sea bass (Picchietti et al 2011) which exhibited cytotoxic function. In fact, lymphocytes purified from intestinal mucosa exhibited significant cytotoxic activity against xenogeneic and allogeneic cell targets (Picchietti et al 2011). The results corroborated previous data showing intraepithelial lymphocytes (IEL) isolated from rainbow trout intestine to be spontaneously cytotoxic against a mouse tumour cell line (McMillan and Secombes 1997).…”

“…In addition an anti-human CD3ε antibody demonstrated an abundance of T cells in the epithelium and lamina propria of common carp (Urán et al 2008) and Atlantic salmon (Bakke-McKellep et al 2007). In situ hybridization studies confirmed the wide distribution of T cells throughout the gut of European sea bass (Picchietti et al 2011) which exhibited cytotoxic function. In fact, lymphocytes purified from intestinal mucosa exhibited significant cytotoxic activity against xenogeneic and allogeneic cell targets (Picchietti et al 2011).…”

“…In contrast, CD4 and MHC IIβ were expressed at higher levels in the anterior and middle regions of the gut. MHC Iα gene transcripts were generally constantly expressed along the length of the gut, independent of CD8α expression (Picchietti et al 2011). Thus, it is clear that the intestinal mucosa can be segregated according to T cell populations and hence functionality.…”