A Closer look at the dynamics of T Cell Receptor Microclusters

Abstract

T cell activation is initiated when the T cell receptor (TCR), recognizes antigens presented by antigen- presenting cells (APCs). TCRs form microclusters (MCs) within seconds of antigen recognition, which are believed to have an important role in early T cell signaling. During activation, these microclusters move centripetally toward the centre of the immunological synapse (IS) formed between the T cell and APC. Despite their critical role, the mechanisms governing the dynamics and integrity of TCR microclusters remain elusive. This project utilizes Total internal reflection fluorescence microscopy (TIRFM) to investigate the spatiotemporal dynamics of TCR microclusters as they transit toward the IS centre. Mean Square Displacement (MSD) analysis of TCR microclusters provides a quantitative measure of their mobility. Our observations reveal that some microclusters merge and split on their way to the IS center, which indicates that TCR microclusters are far more dynamic than previously thought. To further probe the integrity of these structures, Fluorescence Recovery After Photobleaching (FRAP) is employed at the level of individual microclusters, uncovering whether TCR molecules remain within a microcluster or exchange with the surrounding membrane during migration. These investigations offer insights into TCR microcluster dynamics and their contribution to the spatial organization of signalling at the IS. This project is funded by European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska–Curie grant agreement No 101034277. Presenting Author: Neetu Rajendran, rajendran@iap.tuwien.ac.at