Hydrolysis of anti–human RBC-IgG by EndoS. (A) Rabbit antiserum against human RBCs was treated with EndoS or PBS and used for sensitization of RBCs. RBC-bound IgG was determined by solubilization of sensitized RBCs followed by Western blot using antiserum rabbit IgG. (B) Glycan hydrolysis of RBC-bound IgG determined by lectin ELISA (OD = 450 nm). (C) RBC-bound antibody was quantified by ELISA (OD = 450 nm) using antiserum against rabbit IgG.