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Immunomodulation de la fonction thymique et de la différentiation des lymphocytes T chez le bar européen, Dicentrarchus labrax : une perspective évolutive et écotoxicologique

Abstract : Jawed vertebrates have developed an efficient adaptive immune system partly based on T lymphocytes. They develop in an evolutionarily conserved organ, the thymus. In mammals, endogenous oestrogens are well known to regulate thymus function and plasticity. The question is, therefore, whether this is also the case in lower vertebrates, such as teleosts. To achieve these aims, firstly the distribution of oestrogen receptor subtypes was investigated on the background of a detailed description of the functional anatomy of the thymic microenvironment. Secondly, thymic function- and T cell-related gene expression was analysed in the thymus, the head-kidney and the spleen of sea bass exposed to 17ß-oestradiol. Moreover, the oxidative burst capacity in the two latter organs was evaluated in vivo and in vitro in leucocytes of the head-kidney and spleen following exposure to oestrogen. Eventually, age- and size-dependent variations in thymocyte number were examined in sea bass caught at various time points over three years. The thesis provides new insights into the evolution of the immunomodulatory function of oestrogen with respect to the thymic and peripheral T cell differentiation in vertebrates. As a matter of fact, in addition to a highly conserved morpho-functional organisation, the distribution of oestrogen receptor subtypes as well as the oestrogenic effects appear to be evolutionarily conserved. Our results suggest that in sea bass, similar to mammals, oestrogen (1) stimulates a thymic alternative pathway of T cell maturation with innate-like properties, (2) enhances immune tolerance by promoting Treg differentiation, and (3) actively regulate thymic plasticity.
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  • HAL Id : tel-02025928, version 2

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Matthieu Paiola. Immunomodulation de la fonction thymique et de la différentiation des lymphocytes T chez le bar européen, Dicentrarchus labrax : une perspective évolutive et écotoxicologique. Autre [q-bio.OT]. Normandie Université, 2018. Français. ⟨NNT : 2018NORMLH10⟩. ⟨tel-02025928v2⟩

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