Abc complex

The characteristics of all primary antibodies used in this study are summarized in Supplementary Table S1.
Tissue sections (7 μm of thickness) were deparaffined and incubated in H₂O₂ to inhibit endogenous peroxidase. Sections were rinsed in water and then incubated with a blocking solution [10% normal rabbit serum in TBS (Tris 0.01 M, NaCl 0.15 M, pH 7.4)]. After this incubation, sections were incubated overnight with the primary antibody solution and then incubated with anti-mouse or anti-rabbit antibodies conjugated to biotin (Vector) followed by the ABC complex (Vector). Sections were revealed with a peroxidase substrate, a solution of diaminobenzidine as a chromogen (DAKO). Sections immunolabeled with anti-amyloid antibodies were pre-treated with 99% formic acid (Stygelbout et al., 2014 (link)). Tissue sections were stained with hematoxylin, Thioflavin T, Gallyas staining, or DAPI for histological examination as previously described (Ando et al., 2011 (link); Leroy et al., 2012 (link); Poncelet et al., 2019 (link)).
For detection of immunoglobulin extravasation, sections were incubated directly with anti-mouse antibody conjugated to biotin (Vector) followed by the ABC complex (Vector) without primary antibody. Sections were revealed with a peroxidase substrate, a solution of diaminobenzidine as a chromogen.

To quantify bright-field coloration after gold enhancement of QDs, gold enhancement reaction was performed in the microtiter plates and absorbance was measured. 10 μL goat anti-mouse IgG antibody (1:500 / phosphate-buffered saline (PBS)) was immobilized in the wells of microtiter plates (Nunc-Immuno MicroWell 96-well Plates, Thermo Fisher Scientific, MA, USA) overnight at 4 °C. Subsequently, the wells were incubated with 100 μL normal mouse serum (1:500/PBS) for 1 h at room temperature (RT). Some of the wells were further incubated with biotinylated goat anti-mouse IgG (1:1000/PBS) for 1 h, and ABC complex (1:50/PBS, Vector Laboratories, CA, USA) for 1 h at RT, for the subsequent reaction with streptavidin. Wells were washed three times with PBS containing 0.05% Triton X-100 between each step. Subsequently, after washing three times with 0.1 M Tris HCl, QD565-conjugated goat anti-mouse IgG (1: 200/0.1 M Tris HCl, Invitrogen, CA, USA), QD655-conjugated streptavidin (1: 200/0.1 M Tris HCl, Invitrogen, CA, USA), QD705-conjugated goat anti-mouse IgG (1: 200/0.1 M Tris HCl, Invitrogen, CA, USA) were added to each well and allowed to stand for 1 h. After washing three times with 0.1 M Tris HCl, 100 μL GoldEnhance EM plus was added, and reaction was carried out for up to 30 min. Absorbance was measured at 450 nm using Biotrak II (GE healthcare, IL, USA) at 1, 8, 16, and 30 min.