The interaction between the T-cell receptor (TCR) and the antigen-presenting cell (APC) has a central role in the adaptive immune system. It is of the utmost importance that this process is fast, specific, and highly sensitive. The T-cell is able to effectively screen through a sea of self- and harmless antigens in order to rapidly find those that are harmful. Dynamic signaling processes and membrane reorganization events such as the creation of the immunological synapse support this screening procedure. However, preliminary experiments indicate the involvement of mechanical forces in antigen discrimination. Therefore, we seek to characterize the TCR-imposed forces on the APC by directly introducing a force sensor within the immunological synapse. Well defined and calibrated digital, as well as analog, fluorescent molecular sensors will be attached to the peptide-presenting MHC complex (pMHCs). The distance between two introduced fluorophores can be precisely determined via Forster resonance energy transfer microscopy, and will serve as an exact measure for the involved pulling forces. By characterizing a statistically meaningful amount of the aforementioned events, a force map of the immunological synapse can be created. Downstream signaling will be measured via Calcium imaging, and correlated with the stimulatory potency of the involved pMHCs. The aim of this project is to develop a reliable tool to measure molecular forces between two adjacent cells, and to use the topological information to create force maps.