Schwann cells and regenerated peripheral myelin in multiple sclerosis: an ultrastructural study.

Tissue of a multiple sclerosis plaque in the brachium conjunctivum of the pons known to contain peripheral myelin by light microscopic studies were removed from the paraffin block and processed for electron microscopic studies. The cells related to the peripheral myelin possessed the ultrastructural characteristics of Schwann cells, with basement membranes and associated collagen fibers. No continuity was seen with the peripheral within the central nervous tissues by selective maturation of multipotential primitive reticular cells, a phenomenon consistent with the view that Schwann cells are mesenchymal in character.