Nowadays, social media help us to keep abreast of current events. As we are unable to process the entire flood of information at once, neural networks extract only the information we need to know. The cells in our body act in a similar manner: In the fight against parasites, viruses and even cancer, a molecular machine called the MHC-I peptide-loading complex selects protein fragments important for the immune system. Researchers at the Max Planck Institute of Biophysics, Goethe University in Frankfurt and Martin Luther University in Halle-Wittenberg have now shed light on how this protein complex is structured and how it works.