Depletion of B cells upon single intravenous injection of 5D2.mIgG2a, 5D2.hIgG4 (CHO), or 5D2.hIgG4 (Fut8-KO-CHO) relative to isotype control (anti-ragweed.mIgG2a) in human FcγRIIIa transgenic mice. Two doses were tested (12.5 µg and 125 µg) with the B cells determined by FACS analysis. B cell levels are shown for (A) blood, (B) total spleen, (C) splenic follicular B cells, and (D) splenic marginal zone B cells. B cell levels shown are for 5 d post antibody injection except for blood B cells where levels at 2 d are shown.