Browsing by Subject "multippeliskleroosi"

Multiple Sclerosis (MS) is an incurable autoimmune demyelinating disease affecting the central nervous system (CNS). Although the detailed pathogenesis remains unclear, recent research has highlighted the involvement of B cells. For decades, however, MS research was based on T cell-focused animal models of autoimmune encephalomyelitis (EAE), which do not reflect the involvement of B cells in the pathogenesis. Therefore, B cell-dependent EAE models are hypothesized to allow a better understanding of MS immunohistopathology and may therefore lead to the development of efficient treatments. In our spontaneous relapsing-remitting (RR) EAE model, B cells are recruited from the endogenous repertoire by transgenic myelin oligodendrocyte glycoprotein (MOG) -reactive T cells, causing the development of EAE in 3–4-month-old mice. Interestingly, MOG-specific antibodies are present long before actual onset of clinical disease and can be detected already in 5-week-old RR mice and disease development in RR mice is dependent both on the presence of (presumably MOG-specific) B cells as well as on stimuli provided by intestinal microbiota. Firstly, we evaluated the broader usability of induced germinal center cell (iGB) culture as a model for B cell repertoire studies. Then, by using iGB culture, we studied whether MOG-specific B cells are present in secondary lymphoid organs of younger than 4-week-old and germ-free RR mice. Finally, this study aimed to investigate whether the repertoire of MOG-specific B cells undergoes significant qualitative changes from young healthy mice to older acutely sick RR mice, and whether at the time of disease onset the recruited MOG-specific B cells expand and mature in the cervical nodes (cLN) or in the CNS. To do so, following the hosting-lab’s previous single-cell RNA sequencing (scRNA-seq) of B cells derived from cLN of 5-week-old RR mice, we performed the scRNA-seq of B cells from CNS, spleen, and cLN of acutely sick RR EAE mice. We demonstrated that iGB culture is an unsuitable tool to expand pre-activated B cells, and hence, in our hands it was inappropriate for repertoire studies. However, iGB culture proved to be useful for screening different organs for MOG-specific B lymphocytes, and we found that anti-MOG antibodies were firstly detected in 3-4-week-old RR mice, and MOG-specific B cells were present also in germ-free RR mice. Our scRNA-seq results revealed many highly expanded MOG-specific B cell clonotypes in acutely sick RR mice. Moreover, the B cell repertoire of sick RR mice was more diverse, including IgG1, IgM, IgG2b, IgG2c, and IgG3 isotypes, compared to healthy 5-week-old RR mice that had only IgG1 or IgM isotypes. Two-thirds of the expanded clonotypes were primarily detected in the CNS in sick RR mice, indicating that clonotypes develop further and continue isotype switching within the CNS. We also detected more somatic mutation in the variable region of expanded clones of sick RR mice compared to 5-week-old RR mice. The results of this study clearly show an antigen-driven evolution of the MOG-specific B cell repertoire from healthy young to acutely sick RR mice, which seems to occur mainly in CNS itself. In contrast, cLN are the major initial priming site of MOG-specific B cells in healthy RR mice, even under germ-free conditions. This suggests that commensal microbiota is not required for initial recruitment of MOG-specific B cells, but for the development of EAE. To further validate our encouraging scRNA-Seq results, it is necessary, in future experiments, to confirm the MOG-specificity of expanded clonotypes.