Binding of wild-type and engineered IgGs to protein A and hFcRn. ELISA screening showing binding of titrated amounts of wild-type IgG1, IgG3, and engineered IgG3 variants to (A) protein A from S aureus, and (B) hFcRn at pH 6.0 and (C) hFcRn at pH 7.4. Wild-type IgG3 and IgG3ΔHinge do not bind to protein A, which confirms that IgG3 and IgG3ΔHinge lack the amino acid residue histidine in position 435. All antibodies bind to hFcRn at pH 6.0, but not at pH 7.4; n = 3. All data are presented as mean ± SD.