Multiple sclerosis: autoimmune disease or autoimmune reaction?

Multiple sclerosis (MS) is traditionally considered an autoimmune inflammatory demyelinating disease of the central nervous system (CNS) with much knowledge available to support this view. However, this characterization implies that the primary event is an aberrant immune response directed at CNS antigens, promoting inflammation and later driving progressive axo-glial degeneration. Trials with potent anti-inflammatory agents and detailed neuropathological studies raise questions about this sequence of events. This hypothetical paper argues that MS may be primarily a "cytodegenerative" disease, possibly first involving the oligodendrocyte/myelin unit. Liberation of autoantigens secondarily recruits an immune response, the force of which heavily depends on the host's immune predisposition. Thus, the spectrum of MS from highly aggressive Marburg type, to primary progressive disease with little inflammatory burden, is governed by a "convolution" between the underlying cytodegeneration and the host's immune predilection. Clinical heterogeneity may be a reflection of a variable immune response, whereas in reality, the "real MS" may be a homogeneous degenerative process analogous to well known primary neurodegenerative diseases.