Molecules involved in T-cell costimulation.

Maximal expression of the interleukin-2 gene in T cells depends on biochemical signals in addition to those transduced by the T cell antigen receptor. Recent work indicates that the T-cell specific molecule CD28 transduces a 'costimulatory' signal when it binds its ligand, the B7 molecule, on the surface of an antigen-presenting cell. Results from experiments performed during the past year have raised the exciting possibility that immune responses can be either inhibited or augmented by manipulation of the CD28-B7 interaction.