Anti-CD137 agonistic mAb enhances antilymphoma activity of rituximab in vivo in a disseminated human lymphoma xenotransplant model. SCID mice were inoculated with 3 × 10⁶ luciferase-labeled Raji lymphoma tumor cells intravenously through the retro-orbital sinus. After tumor inoculation, mice received rat IgG control on day 3 (●), rituximab on day 3 (■), anti-CD137 antibody on day 4 (♦), or rituximab on day 3 and anti-CD137 antibody on day 4 (▴). Treatment was continued weekly for a total of 4 weeks. (A) Luciferase imaging of representative mice 10, 20, and 30 days after treatment are shown. Mice (5 per group) were then monitored for quantified bioluminescence (B; *P = .001) and overall survival (C; *P = .013).