Plasma membrane topography governs the 3D dynamic localization of IgM B cell antigen receptor clusters

Area of Science:

• Immunology
• Cell Biology
• Biophysics

Background:

• B lymphocytes are crucial for adaptive immunity, recognizing antigens via B cell receptors (BCR).
• Lymphocyte microvilli are cell surface protrusions involved in sensory functions, including antigen screening.
• The B cell antigen receptor (BCR), particularly IgM-BCR, plays a vital role in initiating immune responses.

Purpose of the Study:

• To investigate the dynamic cell-surface topography of B cells.
• To understand the spatiotemporal organization of the IgM-BCR on B cell surfaces.
• To elucidate the relationship between cell surface structures and BCR mobility for antigen screening.

Main Methods:

• Utilized lattice light-sheet microscopy for high-resolution imaging of B cells.
• Employed custom-built 4D image analysis to study dynamic cellular processes.
• Investigated Ramos Burkitt's Lymphoma B cells to analyze surface topography and IgM-BCR organization.

Main Results:

• Ramos B cell surfaces exhibit dynamic networks of ridges connecting microvilli.
• IgM-BCR clusters were predominantly found on these ridges and microvilli.
• The organization of the ridge network and IgM-BCR cluster mobility are interdependent and regulated by Arp2/3 complex activity.

Conclusions:

• Dynamic cell surface topography significantly influences IgM-BCR cluster localization and transport.
• These topographical features are essential for efficient antigen screening by B cells.
• Arp2/3 complex activity is a key regulator of both surface dynamics and BCR organization.