mTOR--beyond transplantation.

mTOR kinase plays a central role in the activation of many cell types, and blocking mTOR function with rapamycin results in arrest of the cell cycle at the G1 phase. Recently, several additional molecules have been identified in the mTOR pathway, providing further opportunities to interfere with cell activation and develop novel therapeutic agents. Under certain conditions and in specific cell types, activation can occur independently of mTOR and in the presence of rapamycin. Selective inhibition of cell activation in the appropriate setting might prove to be beneficial for several autoimmune or inflammatory diseases.