T Cell/B Cell Collaboration in Multiple Sclerosis: Exploring an Intimate Relationship

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the Central Nervous System (CNS) affecting mostly young adults between 20 and 40 years of age. This disease is the leading cause of non-traumatic disability in young adults.

MS has long been considered a predominantly T-cell mediated disease. However, the remarkable efficacy of anti-CD20 monoclonal antibodies in this disease has demonstrated the major role of B-cell in the pathophysiology of this disease.

The B-cell have many functions: these cells are indeed able to secrete cytokines (pro and anti inflammatory), to present antigens to T lymphocytes, but also to differentiate into plasmocytic cells and thus to secrete immunoglobulins. Several studies have shown that B-cell in patients with MS secrete significantly more pro-inflammatory cytokines (GM-CSF, IL-6, TNFα). In addition, infiltrates and tertiary lymphoid structures have been found in the meninges of patients with MS, particularly in progressive forms of the disease. It seems clear to this day that these cells are strongly involved in the development of MS. Despite the many advances made recently in understanding the role of B-cell in the pathophysiology of MS, the precise involvement of plasma cells and their functions at different stages of the disease remains unclear.

Folluclar helper T cells (TFH) play a crucial role in lymphocyte B differentiation. These cells are located within the germinal centers in the secondary lymphoid organs, and their memory compartment also circulates in the blood. Several circulating TFH subpopulations have recently been defined, with different "helping" capacities.

This study, an ancillary to ABCD-SEP (NCT03744351), will be interested in more precisely characterizing circulating and infiltrating TH cells in Multiple Sclerosis whether at the transcriptomic level or at the functional level.