MUC1-specific Abs elicited in MUC1 Tg mice. (A) MUC1 Tg mice (n = 5) were immunized intravenously with isotype mAb-MUC1 or anti–CD19-MUC1 conjugates (50 μg per mouse) with or without CpG (50 μg), 2 times at a 2-week interval. Unimmunized mice were used as controls. Mice were bled at day 21 and the sera were measured for MUC1-specific Abs with different isotype by enzyme-linked immunosorbent assay (ELISA). (B) MUC1 Tg mice were first injected with anti-CD4 mAb (250 μg, intraperitoneally) or isotype control mAb on day −1. Mice were then immunized with anti–CD19-MUC1 plus CpG. The depletion mAb or isotype control mAb was further injected 1 day before boost immunization. Mice were bled at day 21 and the sera were measured for IgG MUC1-specific Abs by ELISA. Data are representative of at least 3 experiments. Error bars show SEM.