|M.Sc Student||Najjar Eiman|
|Subject||Assessment of the Immune-Modulatory Effects of Tecfidera|
(Dimethyl Fumarate; DMF) on B Cell Functions in
Patients with Multiple Sclerosis
|Department||Department of Medicine||Supervisor||PROF. Ariel Miller|
|Full Thesis text|
Multiple Sclerosis (MS) is an inflammatory and neurodegenerative disease, characterized by aberrant activity of immune cells, demyelination and neuronal loss. Emerging data have emphasized the importance of B cells in MS pathology. Dimethyl fumarate (DMF, BG-12) is an oral drug approved for patients with relapsing remitting MS (RRMS). The mode of action of DMF is not yet fully elucidated, however is attributed to both anti-oxidative and anti-inflammatory effects. How DMF therapy affects B cells in MS patients has scarcely been studied. In light of the major role of B cells in MS pathogenesis, we aimed in this study to determine the effects of DMF therapy on B cell phenotype and function in patients with MS. 64 RRMS patients were recruited prior to initiation of DMF therapy. Blood was collected at baseline and after 15 weeks of treatment, and PBMCs, B and T cells purified. A clinical follow up of patients was done for 1 year. The proportions of immune cells and B cells subsets, the levels of markers associated with various B cell functions, and the cytokine profile, were assessed by flow cytometry. The stimulatory effect of B cells on T cells was examined in two assays: the cytokine profile of B and T cell co-culture and the proliferative response of T cells in a co-culture. The levels of plasma antibodies IgG and IgM and of Brain-derived Neurotrophic Factor were assessed by ELISA. Migration capacity of immune cells was assessed using a transwell. Correlations between disability progression and the immuno-modulatory effects of DMF were determined. 15w DMF therapy reduced % CD8 T cells and B cells, and modified the proportions of B cell subsets, increasing transitional cells and reducing memory B cells. DMF therapy increased % IL10-producing B cell subsets and their expression of IL10, suggesting an increase in Bregs. This was supported by an increase in CD25, in TGFβ-producing B cells and in TGFβ level. DMF therapy also reduced the pro-inflammatory cytokines LTα and TNFα, while IL4 and IFNγ were elevated. DMF increased the proportion of activated CD69 B cells and antigen presenting molecules ICAM-1 and HLA, but reduced the co-stimulatory CD86. B cells were found to induce TGFβ, LTα and IL4 T cells in the B and T co-culture, with no difference before and after therapy. However, DMF therapy reduced pro-inflammatory IFNγ and TNFα in T cells cultured alone, and increased TGFβ. DMF did not affect the proliferation of T cells alone or in co-culture with B cells. The CXCL12-migratory capacity of CXCR4 immune cells, CD8 T cells and B cells (trend) was reduced after DMF therapy, although CXCR4 expression was elevated; while CXCR5 expression was reduced. We found a positive correlation between the reduction in % B cells or in % TNFαIFNγ T cells and the reduction in disability score. There were some differences in the immunological responses between 1st and 2nd line therapy patients, which may be caused by “carry-over” effects from previous therapy or by the different disease stages. These results contribute to understanding the mode of action of DMF in patients with RRMS, specifically its immunomodulatory effects on B cell functions, and may have relevance to other autoimmune diseases.