Effect of NK cell depletion and complement depletion on cooperation between rituximab and rhApo2L/TRAIL against Ramos RA1 xenografts. CB17 ICR SCID mice bearing subcutaneous Ramos RA1 xenografts were treated (Tx) with rabbit anti–asialo GM1 antibody (aGM1) to deplete NK cells (A; n = 9 mice/group), cobra venom factor (CVF) to deplete complement protein C3 (B; n = 7 mice/group), or aGM1 and CVF (C; n = 10 mice/group) one day prior to the initiation of treatment with vehicle (V), 60 mg/kg rhApo2L/TRAIL (A), 4 mg/kg rituximab (R), or rhApo2L/TRAIL and rituximab (A + R). The data are graphed as a Kaplan-Meier analysis of the time for the tumors to reach 2.5 times their starting size. The aGM1 antibody and CVF were administered 2 times per week for the duration of the experiment. rhApo2L/TRAIL was administered daily for 5 consecutive days followed by a 2-day break and a second round of 5 days of treatment. Rituximab was administered once a week for 2 weeks.