Molecular, Cellular and Functional Analysis of TRγ Chain along the European Sea Bass Dicentrarchus labrax Development
Author(s)
Date Issued
2021
Type
article
Volume
22
Issue
7
Start Page
3376
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.