Nanoscale organisation of NK cell receptor-ligand complexes

Natural killer cells (NK cells) are part of the innate immune system and represent lymphocytes - a subgroup of white blood cells. These indispensable guardians of our body flow through the blood in search of cancer cells or cells infected by intracellular microorganisms, such as viruses or bacteria. NK cells must first distinguish these diseased cells from healthy, endogenous cells, which happens with the help of special receptors on their surface. One class of these receptors can bind MHC class I molecules on the surface of target cells. If these MHC class I molecules are absent or their density on the surface of the target cell is reduced due to the infection or tumor, NK cells can recognize and kill them. However, further signals transmitted by activating or inhibitory receptors of NK cells are required for the initiation of cell death. These signals are generated during the interaction of the two cells and the formation of the so-called immunological synapse, and ultimately lead to the activation of the NK cell and destruction of the target cell. While the basic mechanisms for the formation of the synapse and activation of the NK cell are known, detailed knowledge of activating receptor interactions and the generation of signals that lead to NK cell activation is lacking. Shining light on these interactions will allow for the development of tailored immunotherapies, for example to use NK cells to specifically target tumor cells. In this "Joint Project", which is carried out in collaboration with researchers from Charles University in Prague (Czech Republic) and the University of Navo Gorica (Slovenia), we want to investigate the nanoscopic organization of selected NK cell receptors and organizational changes upon interaction with ligands on the membrane of living NK cells. For this purpose, we will create artificial target cell membranes on a coverslip, allow them to interact with NK cells to form the immunological synapse, and then to study the arrangement of NK cell receptors using specially developed single-molecule fluorescence microscopy techniques in combination with tiny molecular sensors ("nanobodies"). Ultimately, these nanobodies tagged with fluorescent dyes will not only be used to visualize the receptors, but also to specifically generate nanostructures of the NK cell receptors in order to gain improved control over NK cell activity. The findings from our studies should therefore pave the way for the development of nanobody-based immunotherapies.