As part of the immune system, dendritic cells are essential for fighting body cells that have degenerated or are infected with a virus. They trigger an immune response by presenting protein fragments, for example of viruses, to T cells. In so doing, they activate the latter so that these recognize the fragments as foreign. Certain membrane proteins, MHC-I molecules, enable this process within dendritic cells. Researchers at Goethe University Frankfurt and its partner institutes have now identified further interaction partners of the protein complex responsible for loading MHC-I molecules in dendritic cells.