Immunohistochemical staining for lysosomes within capillary endothelium in putamen of MPS III patients. In putamen capillaries of control tissues (A, B), evident by expression of the basement membrane collagen IV (arrowhead, red), only minor lysosomal immunoexpression of LAMP-1 (arrows, green) was seen in vessel endothelium. (C, E) High density of LAMP-1 immunoreactivity (arrows, green) was found within MPS III A capillaries (arrowheads, red), along with swelling of endothelial cells. (D) Elevated, but less severe than in MPS III A, LAMP-1 immunoexpression in capillary endothelium was detected in MPS III D putamen (arrow, green). (D, E) Also, increased LAMP-1 immunoreactivity was identified in neural cells from both MPS III cases. Arrows and arrowheads indicate LAMP-1 (green) and collagen IV (red) immunoexpressions, respectively. Magnification in A-E is 40×. (F) Semi-quantitative analysis of LAMP-1 immunoreactivity showed higher lysosomal marker expression within capillary endothelium in MPS III A putamen vs. III D.