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Epidemiology.
Multiple sclerosis (MS) is a chronical neuroinflammatory, demyelinating and degenerative disease of the CNS (central nervous system) including brain, spinal cord and optical nerve. MS affect 2,5 million of people in the world and induce physical disability (motor, sensory, urinary issues, visual, pain, fatigue and cognitive impairment) in young adult at a mean age of 30 years old and especially in women with a sex ratio closed to 3 women for 1 man 1.
During MS, lesions are disseminated in the CNS leading multiple disabilities. The different neurological functions (sensitive, motor, gait, bladder functions, cognition, cranial nerves, etc…) are transmitted in the form of nerve impulses carried by the nerve fibers of the white matter in brain or spinal cord. In the case of MS, the nerve impulse is interrupted in the lesions and is not transmitted to the rest of the body. This leads to the development of variable symptoms such as the temporal-spatial spread of lesions in the brain and bone marrow (Fig. 1) of MS patients.
Two forms of the disease are usually described: primary progressive (PPMS) form (15%) and relapsing-remitting (RRMS) form (85%). Relapsing-remitting form is characterized by relapses, corresponding to the development of new neurological signs followed by partial or total remissions. Inside the group of patients affected by the relapsing-remitting form, 50% will evolve into a secondary progressive (SPMS) form 2.
Risk factor.
MS is a multifactorial disease within some factors were established like genetic predispositions supported by studies in twins 4. In addition, the genetic predisposition associated with certain allele of the HLA-DR 2 locus has been known 5. Moreover, screening of SNP (Single Nucleotide Polymorphisms) databases using Genome-Wide Association Studies data (GWAS) have identified many genetic variants linked to MS susceptibility and some of these variants are linked to the immune system and especially to the T cell response 6. In addition, GWAS supports the hypothesis that MS is initially an immune disease with the human Leukocyte Antigen (HLA) like major susceptibility gene located on the locus of the human Major Histocompatibility Complex (MHC) 6. However, many environmental factors have been highlighted such as smoking 7, Epstein Barr virus exposition 8, obesity 9 and vitamin D deficit.
Diagnostic.
After observation of clinical symptoms, MS is diagnosed according to Mc Donald’s criteria which have evolved from 2001 to 2017 and is characterized by definition of temporal and spatial dissemination of the lesions on MRI 11 (Fig. 2, A-B). Oligoclonal bands (OCB) can also be observed in cerebrospinal fluid (CSF) for 90% of MS patients 12 (Fig. 2, C). The detection of these intrathecal productions contributes to the diagnostic of MS in the last Mc Donald’s 2017 criteria due to the prognosis factor of such findings for MS 13.
Mechanisms implicated in MS.
Pathologically, MS is characterized by inflammation, demyelination, reactive gliosis, and neuroaxonal damage. Indeed, MS is characterized by inflammatory reaction associated with demyelination in the CNS. In parallel with demyelination, a suffering of the axon can lead to axon ruptures and neurodegeneration 15. During remissions, the inflammation is reduced and may disappear from the lesion site. This might allow an initiation of remyelination 16. Remyelination partially restores nerve conduction and reduces clinical symptoms.
The hallmark of MS is the perivenular presence of focal immune cell infiltrates involving macrophages, CD4+ and CD8+ T cells 17, B cells, plasma cells, IgG antibodies and resident activated microglia cells 18. Lesions are classified in active, inactive and shadow plaques 19. Active lesions are characterized by the presence of activate macrophages containing myelin debris. Inactive lesions are characterized by the demyelination of the tissue and the absence of activated macrophages containing myelin debris. Shadow plaques are characterized by focal scar and low density of myelin on the surface of axons.
Table of contents :
List of Abbreviations.
Abstract.
I. Introduction.
A. Multiple sclerosis.
1. Epidemiology.
2. Risk factor.
3. Diagnostic.
4. Mechanisms implicated in MS.
5. Remyelination and/or neurodegeneration.
B. Physio-pathological hypothesis in MS.
C. Immunotherapy.
D. Model of Experimental Autoimmune Encephalomyelitis (EAE).
1. Induced model of EAE.
2. Passive and adoptive model of EAE.
3. Spontaneous model of EAE.
E. B cells.
1. Ontogeny and role of B cells in human.
2. B cells in Multiple sclerosis.
II. Objective
III. Materials and Methods.
A. Mice
B. Scoring.
C. Serum transfer experiment.
D. Samples collection.
E. Cell culture.
F. Anti-MOG and anti-total IgG1 antibodies quantification by ELISA.
G. MOG monomer and tetramer production.
H. RNA extraction.
I. RT and PCRs.
J. Flow cytometric analysis.
K. Sequencing.
L. Analyses of sequences.
M. Statistical analyses.
IV. Results
A. Characterization of TCR1640 mice model in the LIRIC animal facility.
B. Anti-MOG response in the TCR1640 mice model.
C. Localisation of MOG tetramer positive B cells in TCR1640 mice model.
1. MOG monomer staining compare to MOG tetramer staining to track MOG-specific B cells.
2. Efficiency of MOG tetramer staining to track MOG-specific B cells.
3. Search of MOG tetramer positive B cells in different organs.
D. iGB single cell culture and construction of sequences bank.
E. PCR products and bank construction.
F. Transcriptomic analysis.
V. Discussion.
VI. Conclusions and prospects.
Bibliography
