In vivo imaging of rituximab's impact on CD20 and CD45 targeting. Mice with established B-NHL (Granta) xenografts placed in the right flank were pretreated with either 400 μg rituximab or 400 μg 1D8 (control) followed by either 200 μg fluoresceinated tositumomab or fluoresceinated BC8 and imaged after 24 hours. (A) Untreated control. (B) 1D8 plus BC8. (C) Rituximab plus BC8. (D) 1D8 plus tositumomab. (E) Rituximab plus tositumomab.