(A–D) Rag2^–/– MAFIA mice were adoptively transferred with dye-labeled B cells and subjected to intravital imaging of the liver. (A) Representative time-lapse images recorded before or immediately after anti-CD20 injection. B cells are indicated by white circles. (B) B cell behavior and contact with KCs before or after anti-CD20 injection. Each line represents an individual B cell, red squares represent the time period during which B cells are present in the imaging field without contacting KCs, and green squares indicate the time period during which B cells are associated with a KC. (C) Impaired B cell arrest in FcRγ^–/– mice treated with anti-CD20. Rag2^–/–FcRγ^–/– mice were transferred with dye-labeled B cells and injected with anti-CD20. (D) Rag2^–/– MAFIA mice were injected with a YFP-expressing B cell tumor line. Representative time-lapse images show that tumor cells were rapidly engulfed by KCs upon anti-CD20 injection. Engulfed B cell tumors are indicated by white circles. (E and F) KCs are effectors of anti-CD20 therapy in a model of spontaneously developing B cell lymphoma. Csfr1^gfp/+Cd19^cre/+Rosa26^RFP/+Eμ-myc^+/– mice were subjected to intravital imaging of the liver following anti-CD20 injection. (E) Representative time-lapse images showing the engulfment and subsequent digestion of RFP-expressing lymphoma cells by KCs. (F) Quantification of B cell engulfment by KCs following anti-CD20 therapy. Scale bar: 10 μm.