In vivo depletion of Eµ-TCL-1 × hCD20 Tg leukemic B cells using type I and II antibodies. (A) Eµ-TCL-1 × hCD20 Tg splenic tumors were administered intraperitoneally to hCD20 Tg mice and treated intravenously (250 μg) with anti-CD20 mAbs when CD5⁺ B220^low tumor B cells were clearly detectable by flow cytometry 35 to 42 days later. The percentage of circulating tumor was then measured for the following 21 days (n = 3). Example dot-plots showing tumor cell populations on day 21 (tumor indicated in the boxed area) above, with mean numbers of tumor cells/mL below. Statistical analyses were carried out using 2-way ANOVA with multiple comparisons and significance was accepted at *P < .05. (B) The concentration of anti-CD20 mAbs in the sera of mice in panel A were determined by enzyme-linked immunosorbent assay. ND, not detectable. The results clearly show that RTX is completely lost from the sera by day 14, whereas OBZ gly remains detectable out to day 21, coincident with more prolonged tumor depletion. n = 3 mice per group. Bars represent mean ± standard deviation.