Detection of endogenous IgG immunofluorescence in various brain structures from MPS III patients. In control tissues for MPS III A (A, C, E) and MPS III D (G, I, K, M), IgG was limited to within the capillary lumen. (B) In MPS III A tissues, IgG was detected on the abluminal side of capillaries in the putamen (green, asterisk). No vascular leakage for IgG was identified in hippocampus (D) or cerebellum (F) of this patient. Possible extravasation of leukocytes through vascular wall as indicated by DAPI nuclear staining was seen in cerebellum (F, arrow). In contrast, numerous capillaries in all analyzed brain structures of MPS III D patient (H, J, L, N) appeared blurry; IgG was dispersed into CNS parenchyma (green, asterisks) indicating cerebral microvascular leakage. Arrowhead – capillary, asterisk – vascular leakage. Scale bar in A-N is 25 μm.