Fig. 4: NI301A activates ATTR phagocytosis by human macrophages on human heart tissue.

a In vitro ATTR phagocytosis assay performed with human-derived macrophages, fluorescently labeled TTR-L55P protein, and different concentrations of NI301A or isotype control antibodies, with or without Fc-receptor blocking reagent (FcR block) (mean ± SD of triplicates). b In vitro ATTR phagocytosis with both TTR-L55P and NI301A fluorescent conjugates, and quantification of double-positive macrophages by FACS. b₁ Dot plots; b₂ quantification of double-positive cells; b₃ representative double-positive macrophage imaged by confocal microscopy: blue: Dapi, green: TTR-L55P-atto488, red: NI301A-atto550. c Ex vivo tissue amyloid-removal assay performed with human-derived macrophages and NI301A on patient myocardium sections. Representative pair of adjacent tissue sections treated with NI301A or vehicle containing thioflavin S-positive amyloid deposits (quantified deposits in green). White arrows point to amyloid deposits removed by macrophages in the presence of NI301A. d Quantification of thioflavin S-positive amyloid deposit number and total area per tissue section following treatment with increasing concentrations of NI301A or control. Vehicle n = 24 sections, NI301A n = 6 sections per concentration (mean ± SD). One-way ANOVA and Dunnett’s multiple comparisons test (mean difference and 95% CI). Number of deposits: F(4, 43) = 4.73, P = 0.003; 1.0 nM vs. Vehicle: −85.08 (−164.4 to −5.8), *P = 0.031; 10 nM vs. Vehicle: −117.4 (−196.7 to −38.1), **P = 0.0017. Total deposit area: F(4, 43) = 1.91, P = 0.13; 10 nM vs. Vehicle: −278,662 (−560,983 to 3660), °P = 0.054.