Abstract

The nanoscale spatial organization of ligands and receptors is emerging as an important theme in regulating cell behavior yet inherently challenging to investigate. Antigen recognition by T-cells illustrates this conundrum: while central to adaptive immunity and with most molecular players already identified, knowledge on its operational principles is still limited. We have devised a DNA origami-based biointerface which allows the experimenter to adjust protein distances with nanometer precision as a means to enhance or disturb signaling while being responsive to large scale reorganization processes during cell activation. Applying this biointerface to study the spatial requirements of T-cell activation we find that the smallest signaling-competent receptor unit consists of two stably ligated T-cell receptors (TCRs) within a distance of 20 nanometers. Spatial organization of the physiological ligand pMHC, however, is not a relevant parameter of antigen-mediated T-cell activation as single, well-isolated pMHC molecules efficiently stimulate T-cells.