Figure 2.

The role of B cells in MS pathogenesis. Antigens (viral, processed, novel, or auto) are internalized and presented via antigen presenting cells (APC's, such as dendritic cells, microglia and other mononuclear phagocyte system cells) to antigen-specific naïve T cells and/or B cells. B cells can sometimes act as APC's. Activated B cells undergo clonal expansion and mature into either antigen-specific memory B cells or into plasma cells that secrete antigen-specific antibodies that may have a detrimental (further damage to myelin sheaths of axons) or a beneficial effect (remyelination, clearing the metabolic wastes away, and neurite extension), depending on the microenvironment. The oligoclonal immune response observed in patients with MS thus represents an ambivalent role. It is of priority to determine clinical assays to delineate patients who would respond to B cell depletion therapies, or to remyelination promoting antibody therapy. This approach supports the concept of “individualized medicine”, where deleterious antibodies would be removed from circulation or in other cases endogenous remyelination would be promoted.