Differential expression of detoxifying enzymes in MS lesions. AP, CD39 and CD73 expression is shown in a chronic active MS lesion, positive for oil red O (A), lacking reactivity for myelin oligodendrocyte glycoprotein (B) and containing many HLA-DR+ cells (C). The grey matter (border is indicated by dashed line in panels A-D) contains many AP+ blood vessels. CD39 expression is prominent especially at the lesion border (E) while CD73 (F) is present throughout the lesion. CD39 was expressed on cells with a ramified morphology that co-expressed HLA-DR (resulting in purple staining indicated by arrows; G). Open arrows indicate CD39 single-positive cells. CD73 (red) was present as punctate staining in the lesion inside HLA-DR+ cells (blue; H). Note that D, G and H lack hematoxylin counterstaining. Magnification 100x (A-F) and 250x (G,H). AP, alkaline phosphatase; MS, multiple sclerosis.