PI3Ks can be activated by a number of different receptors, including the TcR (T cell receptor), co-stimulatory receptors (CD28), cytokine receptors and chemokine receptors. However, the specific roles of PI3Ks downstream of these receptors vary. CD28 contains the YMNM consensus PI3K-binding motif, and PI3K recruitment by CD28 contributes to or complements TCR-dependent PI3K signaling. Activation of PI3K promotes PIP3 production at the plasma membrane and several potential target molecules for this phospholipid have been implicated in PI3K pathways downstream of the TcR and CD28. Of these targets, at least Vav and Akt have been implicated in CD28 costimulation of T cell activation. AKT/PKB connects PI3K to signaling pathways that promote cytokine transcription, survival, cell-cycle entry and growth.