Real-time imaging of TCR dynamics in vivo reveals rapid TCR clustering and internalization in response to antigen (33.13)

Abstract

Abstract Real-time in vivo imaging has given insight into the cellular dynamics of T cell activation, but less is known about receptor and signaling dynamics in vivo. Live imaging of subcellular signaling complexes has been challenging in living tissues due to low physiological molecular densities, inherent limitations of fluorophores, and strong autofluorescence of tissues. Our goal was to characterize T cell receptor (TCR) dynamics in naïve T cells in the lymph node during their first encounter with dendritic cells (DCs) bearing cognate antigen. To do so we developed a mouse expressing a GFP tagged OT-I TCR to track surface and intracellular TCR, and used image processing facilitated by co-labeling of the T cells to isolate specific fluorescence. In the absence of antigen, the TCR was mainly confined to the cell surface without consistent polarity; however, a small percentage of T cells transiently clustered their TCR. Within 30 min of antigen recognition, many T cells stopped crawling and clustered their TCR. Surprisingly, detectable antigen-dependent TCR clustering duration was short (7.1±5.1 min) and as TCR clustering declined, TCR internalization increased. Thus, naïve T cells in the lymph node can signal through the TCR in response to their first interaction with DCs bearing antigen and these contacts lead to rapid TCR clustering and internalization. This work was funded by the Larry L. Hillblom Foundation and NIH R21.