Germinal center B cells recognize antigen through a specialized immune synapse architecture

Area of Science:

• Immunology
• Cell Biology
• Biophysics

Background:

• B cell activation relies on B cell antigen receptor (BCR) signaling and antigen internalization within immune synapses.
• Understanding the distinct mechanisms of antigen processing across different B cell subsets is crucial for elucidating adaptive immunity.

Purpose of the Study:

• To investigate the differences in antigen internalization pathways between naive, memory, and germinal center (GC) B cells.
• To explore the role of BCR signaling and biomechanical forces in regulating antigen binding and selection within GC B cells.

Main Methods:

• Large-scale imaging techniques were employed to analyze B cell subsets during immune synapse formation.
• Quantitative analysis of BCR signaling pathways, including protein kinase C-β-NF-κB, and biomechanical forces (tugging forces) was performed.

Main Results:

• Naive and memory B cells internalize antigen by gathering it toward the synapse center.
• Germinal center (GC) B cells utilize a distinct pathway involving peripheral clusters for antigen extraction.
• GC B cells exhibit reduced protein kinase C-β-NF-κB signaling but generate stronger BCR tugging forces, leading to more stringent antigen binding discrimination.

Conclusions:

• Specialized biomechanical patterns in GC B cell synapses facilitate more precise affinity discrimination of antigens.
• These findings suggest a novel mechanism by which GC B cells are selected based on antigen binding strength, impacting T cell-dependent immune responses.