Expression of detoxifying enzymes on blood vessels in MS and control brain tissue. CD39 (red) was expressed on blood vessels in brain tissues of both non-demented controls (A) and MS patients (B), partly together with AP (blue) at the endothelial lining (resulting in a purple/black precipitate indicated by the arrow in the inset in A). CD39 was also expressed in the parenchyma on cells with a ramified morphology, most notably in MS tissue. A CD39 single positive blood vessel is indicated by the open arrow (B). CD73 (red) was also found on blood vessels from non-demented controls (C) and MS patients (D), but not on endothelial cells that expressed AP (bright blue, arrow in inset). Instead CD73 reactivity was observed at the border of the Virchow-Robin space, the glia limitans. Open arrows in C indicate AP single positive blood vessels (bright blue). Magnification 250x. AP, alkaline phosphatase; MS, multiple sclerosis.