Kaplan-Meier cumulative survival plots for athymic mice treated with PRIT following the establishment of palpable Raji Burkitt lymphoma xenografts. Mice were treated as described in the legend of Figure 3 and analyzed for survival as a function of time. Treatment groups included mice receiving either anti-CD20 1F5, (B) anti–HLA-DR Lym-1, (C) anti-CD22 HD39, (A-C) control HB8181 Ab conjugates, or (D) a combination of 1F5-SA and Lym-1-SA conjugates.