In the excellence clusters, we have previously developed a system in which the interaction of a modified T cell receptor (TCR) with an engineered ligand can be controlled by light. In this system the ligand is a soluble Phytochrome B (PhyB) tetramer. However, the natural ligand is not soluble, but expressed as a membrane protein on another cell. Here, we developed a strategy to generate cells that display PhyB as a membrane-bound protein by expressing the SpyCatcher fused to a transmembrane domain in HEK-293T cells and covalently coupling purified PhyB-SpyTag to these cells. As proof-of-principle, we show that the engineered T cells can be stimulated by the PhyB-coupled HEK-293T cells in a light dependent manner.