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

Abstract

In jawed vertebrates, adaptive immune responses are enabled by T cells. Two lineages were characterized based on their T cell receptor (TcR) heterodimers, namely αβ or γδ peptide chains, which display an Ig domain-type sequence that is somatically rearranged. γδ T cells have been less extensively characterized than αβ and teleost fish, in particular, suffer from a severe scarcity of data. In this paper, we worked on the well-known model, the European sea bass Dicentrarchus labrax, to broaden the understanding of teleost γδ-T cells. The T cell receptor chain (TR) γ transcript was expressed at a later developmental stage than TRβ, suggesting a layered appearance of fish immune cells, and the thymus displayed statistically-significant higher mRNA levels than any other organ or lymphoid tissue investigated. The polyclonal antibody developed against the TRγ allowed the localization of TRγ-expressing cells in lymphoid organs along the ontogeny. Cell positivity was investigated through flow cytometry and the highest percentage was found in peripheral blood leukocytes, followed by thymus, gut, gills, spleen and head kidney. Numerous TRγ-expressing cells were localized in the gut mucosa, and the immunogold labelling revealed ultrastructural features that are typical of T cells. At last, microalgae-based diet formulations significantly modulated the abundance of TRγ+ cells in the posterior intestine, hinting at a putative involvement in nutritional immunity. From a comparative immunological perspective, our results contribute to the comprehension of the diversity and functionalities of γδ T cells during the development of a commercially relevant marine teleost model.

Surfing on the waves of the human γδ T cell ontogenic sea

“…Intriguingly, even though γδ‐hi species possess high levels of γδ T cells in the periphery during mid‐late gestation and the first year of life, the proportion of γδ thymocytes remains relatively low than their conventional αβ counterparts 30,49 (Figure 1). Finally, so far, Opossum and European Sea Bass are “the exception that proves the rule,” since in these species γδ T cells do not appear first during the development in the thymus 50,51 (Figure 1).…”

“…[46][47][48] Intriguingly, even though γδ-hi species possess high levels of γδ T cells in the periphery during mid-late gestation and the first year of life, the proportion of γδ thymocytes remains relatively low than their conventional αβ counterparts 30,49 (Figure 1). Finally, so far, Opossum and European Sea Bass are "the exception that proves the rule," since in these species γδ T cells do not appear first during the development in the thymus 50,51 (Figure 1). This apparently conserved early appearance of γδ T cells during ontogeny could be possibly attributed to their unrestricted, thus faster, developing nature, which unlike their conventional counterparts does not require selection mechanisms based on complex antigen-processing machinery with associated presentation on major histocompatibility complex (MHC) class I or MHC class II molecules.…”

First evidence of in vitro cytotoxic effects of marine microlitter on Merluccius merluccius and Mullus barbatus, two Mediterranean commercial fish species

“…Isolation and cultivation of fish primary cells were performed according to published standard procedure (e.g. Miccoli et al, 2021b). Gills (G), head kidney (HK) and spleen (SPL) were dissected from M. merluccius and M. barbatus (n=3) under a sterile laminar flow cabinet previously cleaned with 100% ethanol with sterilized tools (see section 2d), and immediately immersed in cold Hank’s Balanced Salt Solution without calcium and magnesium (HBSS), previously adjusted for appropriate sea water osmolarity (355 mOsm Kg −1 ) with 3M NaCl.…”