Abstract - Reifenscheid

The Chimeric Antigen Receptors (CARs) are genetically engineered receptors which recognize specific proteins on the surface of tumor cells. In CAR-therapy, patient-derived immune cells like natural killer (NK) cells, are equipped with the CARs and are reinfused into the patient. Binding onto the target tumor cell to induce the cytotoxic immune function, leads to the formation of a non-classical immunological synapse containing microclusterd CARs. By the use of Supported Lipid Bilayers (SLBs), a tunable and biomimetic platform, the formation and killing effect of the immunological synapse can be studied under controlled conditions. The planar structure of the SLB in combination with the use of Total Internal Reflection Fluorescence (TIRF) enables the acquisiton of high-resolution and surface sensitive CAR images. It could be shown that the SLB model system sufficiently mimics the tumor cell characteristics. The formed synapse between the CAR-NK cell and SLB or tumor cell look identical. Furthermore the density of the target protein mainly affects the size of the synapse. To quantify the number of molecules (like CARs, adhesion proteins, etc.) sophisticated techniques like the Molecular Brightness Analysis and the Photoactivated Localization Microscopy (PALM) were used. First attempts using these methods provide promising results to get deeper insights on a molecular level.