Fig 1: Type 4 specificity titration. Type 1 anti-trastuzumab antibody AbD18018 in IgG1 format or trastuzumab were coated on a microtiter plate at a concentration of 5 µg/mL. After washing and blocking, the trastuzumab/Type 1 complex was formed by adding 5 µg/mL trastuzumab to the wells coated with the Type 1 antibody. Type 1 and trastuzumab negative controls were incubated with buffer only. After washing Type 4 antibody AbD23820 specific for the trastuzumab/Type 1 complex was titrated in PBST and added. Detection was performed using HRP-conjugated anti-Strep-tag antibody in HISPEC assay diluent followed by QuantaBlu fluorogenic peroxidase substrate.