T-Cell Receptor Activation Initiates Multiple Modes of Actin Polymerization within the Immune Synapse

The immune synapse is a key point of communication between T cells and antigen presenting cells. The layout of this interface is driven in large part by a complex cytoskeletal structure. This report focuses on modulation of the cytoskeleton by T Cell Receptor (TCR) signaling using micropatterned surfaces presenting OKT3 (an antibody that activates the TCR signaling component CD3) and ICAM-1 to T cells. Previous studies by our group demonstrated that micro-scale features of OKT3 (red, top row) induce lamellipodial polymerization (white arrows) of actin (green) on surrounding regions of ICAM-1. We show here a second type of polymerization, the formation of linear, consolidated F-actin structures from sites of CD3 engagement (blue arrow), resembling actin comets observed in other systems. This mode of actin polymerization occurs concurrent to lamellipodium extension. Furthermore, polymerization is initiated by sharp, external corners of angular patterns of OKT3 (bottom row). This latter result suggests mechanical forces, which are concentrated at such corners under cellular tension, initiate this modality of actin polymerization. The different contributions of these behaviors on immune synapse function remain to be determined.View Large Image | View Hi-Res Image | Download PowerPoint Slide