The mechanism of anti-CD20–mediated B cell depletion revealed by intravital imaging
Fabricio Montalvao, Zacarias Garcia, Susanna Celli, Béatrice Breart, Jacques Deguine, Nico Van Rooijen, Philippe Bousso
Fabricio Montalvao, Zacarias Garcia, Susanna Celli, Béatrice Breart, Jacques Deguine, Nico Van Rooijen, Philippe Bousso
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Brief Report Immunology

The mechanism of anti-CD20–mediated B cell depletion revealed by intravital imaging

Abstract

Anti-CD20 Ab therapy has proven successful for treating B cell malignancies and a number of autoimmune diseases. However, how anti-CD20 Abs operate in vivo to mediate B cell depletion is not fully understood. In particular, the anatomical location, the type of effector cells, and the mechanism underlying anti-CD20 therapy remain uncertain. Here, we found that the liver is a major site for B cell depletion and that recirculation accounts for the decrease in B cell numbers observed in secondary lymphoid organs. Using intravital imaging, we established that, upon anti-CD20 treatment, Kupffer cells (KCs) mediate the abrupt arrest and subsequent engulfment of B cells circulating in the liver sinusoids. KCs were also effective in depleting malignant B cells in a model of spontaneous lymphoma. Our results identify Ab-dependent cellular phagocytosis by KCs as a primary mechanism of anti-CD20 therapy and provide an experimental framework for optimizing the efficacy of therapeutic Abs.

Authors

Fabricio Montalvao, Zacarias Garcia, Susanna Celli, Béatrice Breart, Jacques Deguine, Nico Van Rooijen, Philippe Bousso

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Figure 1

The liver is a major site for anti-CD20–mediated B cell depletion.

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The liver is a major site for anti-CD20–mediated B cell depletion. (A) C...
(A) C57BL/6 mice were treated with a single injection of anti-CD20. The percentage of remaining B cells (compared with that in untreated mice) was measured over time in the indicated organs. (B) Mice were subjected to partial hepatectomy, splenectomy, or left untreated. The efficacy of B cell depletion was calculated as the fraction of B cells remaining in the blood 16 hours after anti-CD20 injection relative to the same values in mice subjected to surgery but not injected with anti-CD20. *P < 0.05. (C) Recipient Rag2–/– mice were transferred with a 1:1 mixture of untreated and PTX-treated splenocytes and injected with anti-CD20. For each subset, the percentage of B cells at 6 hours after anti-CD20 injection (compared with that in recipients that did not receive anti-CD20) is shown for the indicated organs. (D and E) B cells circulating in the liver arrest immediately following anti-CD20 administration. B cells are indicated by white circles. Mice with RFP-expressing B cells were subjected to intravital imaging of the liver. (D) Representative time-lapse images and (E) quantification before or immediately after injection of anti-CD20 Ab. Each horizontal line represents an individual B cell, and red squares represent the time period during which the B cell is visible in the imaging field. Scale bar: 10 μm.