Soft polydimethylsiloxane-supported lipid-bilayers for studying T-cell interactions.

Much of what we know about the early stages of T-cell activation has been obtained from studies of T cells interacting with glass-supported lipid bilayers that favor imaging but are orders-of-magnitude stiffer than typical cells. We developed a method for attaching lipid bilayers to polydimethylsiloxane polymer supports, producing 'soft bilayers' with physiological levels of mechanical resistance (Young's modulus of 4 kPa). Comparisons of T-cell behavior on soft and glass-supported bilayers revealed that, whereas late stages of T-cell activation are thought to be substrate-stiffness dependent, early calcium signaling was unaffected by substrate rigidity, implying that early steps in T-cell receptor triggering are not mechanosensitive. The exclusion of large receptor-type phosphatases was observed on the soft bilayers, however, even though it is yet to be demonstrated at authentic cell-cell contacts. This work sets the stage for an imaging-based exploration of receptor signaling under conditions closely mimicking physiological cell-cell contact.