B cell activation is regulated by B cell antigen receptor (BCR) signaling and antigen
internalization in immune synapses. Using large-scale imaging across B cell subsets, we
show that in contrast to naive and memory B cells, which gathered antigen towards the
synapse center before internalization, germinal center (GC) B cells extracted antigen by a
distinct pathway using small peripheral clusters. Both naive and GC B cell synapses required
proximal BCR signaling, but GC cells signaled less through the protein kinase C-β (PKC-β)–
NF-κB pathway and produced stronger tugging forces on the BCR, thereby more stringently
regulating antigen binding. Consequently, GC B cells extracted antigen with better affinity
discrimination than naive B cells, suggesting that specialized biomechanical patterns in B cell
synapses regulate T-cell dependent selection of high-affinity B cells in GCs.