Stimulation of the T cell receptor (TCR) leads to the activation of T cells. The TCR is a complex macromolecular machinery, composed of at least four protein dimers. Its subunits undergo structural alterations during the biogenesis process and later upon ligand binding. In this project we want to unravel the molecular mechanisms that regulate these alterations and to identify the TCR complexome. Hence, we aim to unravel how the biogenesis and complexome control the TCR activity and thus an immune response.