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Updated: Jul 4, 2025

Determining the Phagocytic Activity of Clinical Antibody Samples
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Published on: November 30, 2011

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Antibody surface mobility amplifies FcγR signaling via Arp2/3 during phagocytosis

Seongwan Jo1, Brady R Fischer1, Nicholas M Cronin1

  • 1Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota; BioSNTRii, South Dakota State University, Brookings, South Dakota.

Biophysical Journal
|February 7, 2024
PubMed

We report herein that the anti-CD20 therapeutic antibody, rituximab, is rearranged into microclusters within the phagocytic synapse by macrophage Fcγ receptors (FcγR) during antibody-dependent cellular phagocytosis. These microclusters were observed to potently recruit Syk and to undergo rearrangements that were limited by the cytoskeleton of the target cell, with depolymerization of target-cell actin filaments leading to modest increases in phagocytic efficiency. Total internal reflection fluorescence analysis revealed that FcγR total phosphorylation, Syk phosphorylation, and Syk recruitment were enhanced when IgG-FcγR microclustering was enabled on fluid bilayers relative to immobile bilayers in a process that required Arp2/3. We conclude that on fluid surfaces, IgG-FcγR microclustering promotes signaling through Syk that is amplified by Arp2/3-driven actin rearrangements. Thus, the surface mobility of antigens bound by IgG shapes the signaling of FcγR with an unrecognized complexity beyond the zipper and trigger models of phagocytosis.

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