Spatial requirements for T-cell receptor triggering probed via a DNA origami-based biointerface

Abstract

T-cells detect via their T-cell antigen receptors (TCRs) the presence of single stimulatory antigenic peptide-MHC complexes (pMHCs) which are vastly outnumbered on the surface of antigen-presenting cells (APCs) by structurally similar yet non-stimulatory endogenous pMHCs. While TCR:pMHC binding kinetics, molecular clustering, mechanical forces have been implicated as critical parameters, the precise mechanisms underlying highly sensitized and selective T-cell antigen recognition are not understood. 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 found that single, well-isolated transiently engaging pMHC molecules efficiently stimulate T cells [1]. pMHCs with highly stable TCRinteractions gradually lose this capacity. This points at the dynamics of pMHC:TCR binding as a critical parameter for sensitized antigen detection which we hypothesize to result from serial short-lived engagements of several TCRs in close proximity by single antigenic pMHCs.