Évolution du répertoire des lymphocytes B dans un modèle spontané d’encéphalomyélite auto-immune expérimentale

The project aims to clarify the involvement of B cells in the initiation and progression of multiple sclerosis (MS) using a transcriptomic analysis of B cells in cervical lymph nodes (CLNs) and brain of a transgenic mouse model of spontaneous experimental autoimmune encephalomyelitis (EAE). In this model called TCR1640, transgenic TCR (T cell receptor) for MOG92-106 are supposed to recruit MOG-specific B cells from the endogenous repertoire. The objective of the thesis was to evaluate the dynamics of MOG-specific B cells at the initiation of EAE in the secondary lymphoid organs and the brain. In this TCR1640 model in Lille, the EAE incidence was from 85% at 700 days of life. We checked the performance of a MOG tetramer to detect and isolate MOG-specific B cells. This MOG tetramer allowed us to identify rare MOGtet+ B cells primarily in CLNs and brains of diseased TCR1640 mice. Anti-MOG antibodies in serum were quantified by ELISA and detected in disease-free and diseased TCR1640 mice, without correlation with their age, delay of EAE and clinical score. However, serum transfer experiments showed that there was a difference in humoral activity between sera of disease-free and diseased TCR1640 mice, which aggravated incidence and severity of EAE in the 2D2 mouse (another EAE model). These results suggested the dynamics of the repertoire of MOGtet+ or MOGtet- B cells to a pathogenic repertoire for the EAE development. Induced germinal center B cells culture (iGB) and expansion (on fibroblasts called 40LB cells) of MOGtet+ or total B cells sorted from CLNs and brain of disease-free and diseased TCR1640 mice allowed to define only few clonotyps for IgLKappa chains and IgHG chains. Our findings highlight the difficulty of the iGB single cell culture to expand effector cells and suggest to go directly to single cell sequencing of sorted derived-CLNs and derived-CNS (central nervous system) MOGtet+ B cells from TCR1640 mice. Le projet vise à préciser l’implication des lymphocytes B dans l’initiation et la progression de la sclérose en plaque (SEP) au travers d’une analyse transcriptomique des lymphocyes B dans les ganglions cervicaux lymphatiques (CLN) et cerveau d’un modèle murin transgénique d’encéphalomyélite auto-immune expérimentale (EAE) spontanée. Dans ce modèle appelé TCR1640, les TCR (récepteurs membranaire des lymphocytes T) transgéniques pour MOG92-106 sont supposés recruter des lymphocytes B spécifiques de MOG du répertoire endogène. L’objectif de la th