Figure S1.

Binding characterization of IgG:IDS, ETV:IDS, and the polyclonal anti-huIgG reagent used for IHC. (A) Competition binding of ETV:IDS and IgG:IDS as measured by biolayer interferometry. Full-length human TfR-loaded biosensors were used to capture ETV:IDS, IgG:IDS, or an anti-TfR antibody known not to compete with ETV:IDS. The ability to subsequently bind to ETV:IDS was tested, demonstrating that both ETV:IDS and IgG:IDS compete for TfR binding. (B) Binding of ETV:IDS and IgG:IDS to the anti-human IgG H+L polyclonal antibody used in IHC experiments was determined by ELISA; data presented represent the average of three technical replicates, with n = 3 per replicate. a.u., arbitrary unit.