Figure 1.

Shows a representative chronic active lesion from a patient with progressive multiple sclerosis (MS). (A) Shows anti-proteolipid protein-stained sections obtained from a white matter tissue block of a patient with progressive MS. The white arrowheads mark the boundary of the lesion. (B) Shows the same lesion processed for anti-MHC II immunohistochemistry. (C,D) Show the anti-CD3 and anti-CD8 staining of the lesion at higher magnification, respectively. The arrowheads highlight the cytotoxic CD8⁺ lymphocytes in the brain parenchyma. The paraffin-embedded postmortem brain tissue was obtained through a rapid autopsy protocol from donors with mainly progressive MS in collaboration with the Netherlands Brain Brank, Amsterdam, The Netherlands. The study was approved by the institutional ethics review board, and all donors or their relatives provided written consent for the use of brain tissues and clinical information for research purposes.