How do killer T cells recognise cells in the body that have been infected by viruses? Matter foreign to the body is presented on the surface of these cells as antigens that act as a kind of road sign. A network of accessory proteins – the chaperones – ensure that this sign retains its stability over time. Researchers at Goethe University have now reached a comprehensive understanding of this essential cellular quality control process. Their account of the structural and mechanistic basis of chaperone networks has just appeared in the prestigious science journal Nature Communications. These new findings could be harbingers of progress in areas such as vaccine development.