Apoptosis is a process of programmed cell death involving a series of biochemical events leading to characteristic cell morphology and death. Apoptosis is mediated by a diverse range of extracellular or intracellular cellular signals. After TNF and Fas activation, a balance is established between pro-apoptotic (BAX, BID, BAK or BAD) and anti-apoptotic (Bcl-X1 and Bcl-2) members of the Bcl-2 family. Using an antibody array kit, researchers can simultaneously detect the relative levels of 43 apoptosis-related proteins in cell lysates.