Meningeal T cells associate with diffuse axonal loss in multiple sclerosis spinal cords.

Objective: A link between diffuse axonal loss and diffuse inflammation has been established in the brain of patients with progressive multiple sclerosis (MS). In the present paper, we sought to determine whether such a link could be similarly demonstrated in the spinal cord of patients with progressive MS.

Methods: A neuropathological quantitative assessment of inflammation and axonal loss was performed in the cervical spinal cord of 18 patients with progressive MS and 5 control subjects.

Results: As previously reported, we found a mean 25% decrease of axonal density in the normal-appearing white matter (NAWM) of MS versus control spinal cords. T-cell perivascular infiltrates were rare, but a robust diffuse inflammation was observed in both the normal-appearing parenchyma and the meninges. The extent of diffuse axonal loss in the NAWM correlated with both the density of major histocompatibility complex (MHC) class II(+) microglia in the NAWM and, surprisingly, the density of CD3(+) T cells in the meninges. Interestingly, close interactions between T cells and MHC class II(+) macrophages were observed in the meninges of spinal cords from MS patients.

Interpretation: Recent studies assigned a major role to meningeal B-cell follicles in the pathophysiology of secondary progressive MS. The present work also emphasizes the link between meningeal inflammation and parenchymal lesions and points to a specific role exerted by both meningeal T cells and activated microglia in diffuse axonal loss in the spinal cord.