What is the principal immunopathology of multiple sclerosis?

• A. T cell–mediated autoimmune demyelination of the CNS
• B. B cell–mediated hypergammaglobulinemia
• C. Immune complex deposition in glomeruli
• D. Autoantibody against acetylcholine receptor at NMJ

Answer: (A)

Multiple sclerosis is driven by an autoimmune attack on central nervous system myelin mediated by T cells. Autoreactive T cells cross the blood–brain barrier, recognize myelin antigens, and recruit macrophages and microglia to inflamed areas, leading to demyelination. The loss of myelin slows or blocks nerve conduction and forms sites of gliosis called plaques; over time, axons can be lost, contributing to permanent deficits. B cells also play a supporting role by presenting antigen and producing antibodies, and CSF often shows oligoclonal bands, but the primary immunopathology is T cell–driven demyelination of CNS white matter. The other options describe processes more characteristic of other diseases: B cell–mediated hypergammaglobulinemia is not the main driver in MS, immune complex deposition in glomeruli occurs in immune complex–mediated nephritis, and autoantibody against the acetylcholine receptor at the neuromuscular junction is typical of myasthenia gravis.