Fig. 4

Double- and triple-label immunohistochemistry (IHC) for UEA-l, COLL4, the plasma proteins fibrinogen (FIBR) or immunoglobulin G fraction (IgG) and the endothelial marker alkaline phosphatase protein (ALPL) in 7 μm thick paraffin sections. a-b The healthy capillary in the control white matter (Co) of a NoSVD case does not have vascular bags (a). Vascular bag (short thick arrow) in a SVD case with multiple layers of COLL4-positive membranes around the UEA-l-labeled endothelium (white arrowhead) of a small vessel (< 10 μm diameter) at a lesion (Le) site. Hematoxylin eosin (H&E) counterstaining reveals eosinophilic material (star) in the vascular bag (b). c-d Capillaries with a UEA-l positive endothelium (white arrowhead) and endothelial cell nuclei (short thin arrows) are surrounded by pericytes (pc) and a sharply delineated area filled with plasma proteins IgG or FIBR (star) suggestive of vascular bagging. Plasma proteins also leak to the white matter parenchyma (large thin arrow), but the widened perivascular space (pvS) outside the vascular bag appears empty. e-f Vascular bags with COLL4-positive walls around the UEA-l positive endothelium are filled with IgG protein (star). g-h ALPL expression is found in the endothelium of small arteries (a) and arterioles (black arrowheads), but is lost at the transition from the pre-capillary arteriole to the capillary (large thick arrow). IgG accumulation found around the pre-capillary arteriole and capillary with erythrocytes (ery) extends into the nearby white matter (stars). Images obtained from Case 2 (ovarian cancer, NoSVD) (a), Case 13 (contralateral subacute ischemic stroke in the territory of the medial cerebral artery (MCA) with thalamic infarction, SVD + VBI) (b-e), and Case 6 (non-hodgkin lymphoma, pure SVD) (f-h). The list of (immuno)histochemical markers is provided on the lower left corner of each image (color-coded for the chromogen used). Uppermost marker: brown (Diaminobenzidine, DAB); Middle (or lower in double-label IHC) marker: blue (SK-4700, Vector Laboratories); Lower stain/marker: H&E or red (SK-4800, Vector Laboratories); ery erythrocyte