The overall objective of this proposal is to understand of the role of integrin cell adhesion receptors in the regulation of immune responses. By understanding the ways in which integrins, their ligands and downstream effectors can regulate immune cells it may be possible to selectively regulate the immune system to prevent inappropriate immune responses and induce beneficial ones. This proposal addresses a mechanism of T cell regulation called transdominant suppression in which ligation of one integrin can selectively inhibit the ability of other integrins to activate.