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. 2023 Jan 15;210(2):204–215. doi: 10.4049/jimmunol.2200157

FIGURE 1.

FIGURE 1.

AL008 is a pan-SIRPα binding Ab that does not bind SIRPβ1 or SIRPγ. (A) Titration curves of AL008 binding to human SIRP proteins by ELISA are shown. (B) AL008 binding to human SIRP Ags overexpressed on cell lines is shown. AL008 was detected with a fluorescent anti-human IgG Fc secondary Ab. The data series for SIRPγ+ cells (green lines) and SIRPβ v1+ cells (gray lines) are superimposable. (C) Surface plasmon resonance was performed with a Biacore T200 system at 25°C to determine the affinity of AL008 for human SIRPα v1. Anti-human IgG was amine-coupled to a Biacore CM5 sensor chip to capture AL008, and soluble His-tagged SIRPα v1 diluted in HBS-EP+ with 1 mg/ml BSA was injected in a concentration series ranging from 0.3215 to 40 nM. The data were analyzed using a 1:1 binding model, and the reported on- and off-rates are representative of three independent experiments. (D) Alanine scanning mutagenesis defined three residues (red spheres) in the IgC2 domain of human SIRPα critical for Ag binding by AL008.