Antibody formation against rhGAA during ERT in Pompe mice. GAA 129SVE mice were treated with 3 weekly intravenous doses of rhGAA (20 mg/kg). One week, later, plasma samples were collecte, and rhGAA-specific IgG titers were measured. A. GAA-specific IgG1, IgG2a, and IgG2b titers for 8 individual animals. B. Average titers (± SD) for the 3 subclasses. Statistically significant differences are indicated as * for P<0.05, ** for P<0.01, and *** for P<0.001.