Ligand mobility modulates immunological synapse formation and T cell activation

Area of Science:

• Immunology
• Cell Biology
• Biophysics

Background:

• T cell receptor (TCR) engagement triggers signaling molecule recruitment, forming the immunological synapse (IS) crucial for T cell activation.
• Key signaling molecules like ZAP70 and SLP76 are recruited to the plasma membrane during IS formation.
• The dynamics of molecules within the IS are critical for modulating T cell responses.

Purpose of the Study:

• To investigate how ligand mobility on stimulatory surfaces affects T cell signaling and IS formation.
• To determine the relationship between membrane fluidity and the dynamics of key signaling molecules and cytoskeletal rearrangements.

Main Methods:

• Formation of stimulatory lipid bilayers with varied compositions to control ligand diffusion coefficients.
• Characterization of lipid bilayer properties, including diffusion and fluid connectivity.
• Analysis of T cell activation, IS formation (cSMAC), signaling microcluster (MC) dynamics (ZAP70, SLP76), actin retrograde flow, cell spreading, tyrosine phosphorylation, and intracellular calcium levels.

Main Results:

• Reduced ligand mobility delayed cSMAC formation and decreased CD3ζ accumulation at the IS.
• Increased ligand mobility enhanced ZAP70 microcluster velocity and trajectory length, while SLP76 movement was less affected.
• More fluid membranes promoted greater cell spreading, cytoskeletal contraction, tyrosine phosphorylation, and sustained intracellular calcium elevation.

Conclusions:

• Ligand mobility is a critical factor influencing T cell activation and immunological synapse formation.
• Membrane fluidity directly modulates the dynamics of signaling microclusters and downstream cellular responses.
• Understanding ligand mobility provides insights into optimizing T cell-based therapies and diagnostics.