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The diseases studied in this thesis, Guillain-Barre Syndrome (GBS), Multiple Sclerosis (MS) and Polyneuropathy associated with monoclonal gammopathy of uncertain significance (PNMGUS), are of autoimmune origin with myelin components as putative auto antigens. T cells are important for the pathogenesis, as well as the cytokine network and autoantibodies. For all of these diseases, the immunopathogenisis is not fully understood and even if there are treatments available, none of them are curative and there are side effects. Thus there is a need for further clues in the immune mechanisms. Contrary to PNMGUS and MS, GBS is generally self-limiting. The mechanisms of the beneficial effect of interferon-beta (IFN-s) treatment in MS are not fully understood, (although alterations in the cytokine levels are subject to many reports). In PNMGUS, the proliferation of a monoclonal B cell clone and its antibody production are of great significance, however additional immune mechanisms are also of interest like the role of T cells and the role of B cells as antigen presenting cells.In studies of cytokines, frozen cells are often used, sometimes for practical reasons, so also in this thesis. Therefore effects of cryopreservation on cellular expression/secretion of cytokines were studied. The expression before compared to after cryopreservation of IFN-γ, IL-4, IL-5, IL-9, IL-10 and IL-13 was analysed with ELISA, ELISPOT and/or real time RT-PCR We found that the process of cryopreservation and thawing does affect the expression of cytokines, both at the protein and the mRNA level. The most consistent fmding was that expression of IL-4 was generally decreased in spontaneous and auto-antigen/allergen induced expression in cryopreserved cells. Thus, this study points out the importance of investigation of the effects of freezing for each cytokine, stimuli and patient group before using frozen cells in studies of in vitro cytokine secretion.The secretion of IL-4, IFN-γ, TGF-s, IL-6, and TNF-α during the course of GBS was analysed with ELISPOT and cell-ELISA. Our findings indicate a down-regulatory role for TGF-s and IL-4 in GBS.The longitudinal effects over one year of IFN-s treatment on secretion of IL-4, IFN-γ and IL-10 was analysed with the ELISPOT technique and IL-13 and IL-17 was analysed in cell supernatants with ELISA. A general finding was that surprisingly few changes occurred, and that most changes occurred early (6 weeks - 3 months). However, we found a shift in the cytokine balance towards more IL-4 and IL-10 secretion and/or less IFN-γ secretion during the treatment as the ratios of IL-4/IFN-γ as well as of IL-10/IFN-γ were increased. The interesting pro-inflammatory cytokine IL-17, associated with T cell mediated autoimmunity, has not been previously investigated during IFN-s treatment in MS and our findings of decreased IL-17 levels after one year of treatment could be a beneficial result of the IFN-s treatment.B cell clones from a patient with PNMGUS were successfully established by isolating B cells with myelin protein zero (P0) coated magnetic beads and subsequently transforming with Epstein-Barr virus (EBV). The clones were characterised and for instance they strongly expressed HLA-DR and CD80, compatible with antigen-presenting properties. The cell lines may provide useful tools in studies of PNMGUS.