A family of receptors called integrins are required for cells to adhere to the extracellular matrix or to each other. Cell adhesion is important in growth and development of organisms, in the trafficking of white cells from the bloodstream into the tissues, and in enabling cancer cells to spread throughout the body. A protein called CD98, which is nomally expressed on activated T cells, has been identified as a regulator of integrin activity. Notably, this protein also promotes the fusion of cells induced by certain viruses. Working out how CD98 is involved in these processes may help in developing drugs to treat viral infections, inflammation and cancer.