Journal: bioRxiv
Article Title: Early Binding of Anti-Amyloid Antibodies to CAA Drives Complement Activation, Inflammation and ARIA in Mice
doi: 10.64898/2026.03.04.709591
Figure Lengend Snippet: a, Schematic of anti-Aβ immunization with 500 µg/wk 3D6 IgG2a mAb and an IgG2a isotype control for 13 weeks from 17 to 20 months in aged male APP/PS1dE9;hAPOE4 AD-like mouse model. For baseline data, baseline control mice were used. For spontaneous hemorrhage detection, 1x PBS-injected aged controls were used. b, T2*-weighted FLASH MRI of 20-month-old male APP/PS1dE9;hApoE4 mice after 13 weeks of passive immunization with 3D6 mAb (500 µg/week), showing cerebral microbleeds as hypointense spots (arrowheads), compared to 1× PBS–treated aged controls. c, Frequency of cerebral microbleeds detected by T2* MRI in 3D6–treated (n = 3) and PBS-treated (n = 4) mice. d, Quantification of Prussian blue–positive (% hemosiderin-stained) area in IgG2a and 3D6–treated mice. Unpaired t-test: **p < 0.005, ***p < 0.0005. Data represent mean ± SEM. e, Representative Prussian blue–stained sections showing hemosiderin deposits (arrowheads, with selected examples in insets) in cortex, hippocampus, thalamus, and cerebellum from 1× PBS (n=4), IgG2a isotype control (n = 5), and 3D6 IgG2a–treated mice (n = 5). Scale bar: 200 µm. f, Immunofluorescence staining in the cerebellum showing 3D6 mAb localization (anti-Ms IgG2a) and C1q deposition at sites of vascular and parenchymal amyloid labeled with Amylo-Glo (AG). g, Detection of activated complement fragments C3b/iC3b/C3c at vascular amyloid sites associated with 3D6 mAb. h, Localization of membrane attack complex (MAC/C5b-9) along vascular amyloid (arrows) and plaques (asterisk) in 3D6–treated mice. Minimal complement staining is observed in IgG2a-treated controls. Scale bars: f–h, 25 µm.
Article Snippet: Following washes in PBS, sections were blocked either in 10% normal goat serum (Gibco, #16210064), or heat inactivated goat serum (Novus Biologicals #S13110H), or normal donkey serum (Sigma, #S30-M) for 1 hour at room temperature followed by overnight 4°C incubation with primary antibodies against C1q (1:500, Abcam #ab182451), C3b/iC3b/C3c (1:300, HycultBiotech #HM1078), C5b-9 (1:300, Bioss #bs-2673R), CD31 (1:500, R&D Systems #AF3628), C3 (1:200, HycultBiotech #HM1045), GFAP (1:1000, Abcam # ab5804), MMR/CD206 (1:300,R&D #AF2535) MMP-9 (1:500, Bioss #bs-0397R), Iba-1 (1:1000; Dako, Wako #019-19741), Iba-1 (1:500, Synaptic Systems, #234308), CD68 (1:500, Bio-Rad #MCA1957), S97 Aβ (pan-Aβ rabbit polyclonal, 1:2000, gift Dr. Dominic Walsh, BWH, USA), CD31 (1:500, R&D #AF3628), Collagen-IV (1:300, Abcam #6586), Alexa Fluor 488 anti-β-Amyloid, aggregated antibody (1: 200, clone A17171C, Biolegend # 856508), Von Willebrand Factor Antibody (1:500, Novus Biologicals #NB600-586).
Techniques: Control, Injection, Staining, Immunofluorescence, Labeling, Membrane