Apoptosis is related to many diseases and development. Cell death signals are transduced by death domain (DD), death effector domain (DED), and caspase recruitment domain (CARD) containing molecules. CARD containing proteins include some caspases, Apaf-1, CARD4, IAPs, RICK, ARC, RAIDD, BCL-10, and ASC. A novel CARD-containing protein was recently identified and designated CARD9, which interacts with the CARD activation domain of BCL-10. CARD9 associates with BCL-10 and forms a complex within cells. CARD9 induces apoptosis and activates NF-kappaB. CARD9 is an upstream activator of BCL-10 and NF-kappaB signaling.