The caspases are a family of cysteine proteases that induce apoptosis in response to a variety of intra- and extracellular stimuli. These enzymes are synthesized as inactive precursors which become cleaved at aspartate-specific sites upon induction of apoptosis. Caspase-2 is an initiator caspase that is prevalent in both the cytosol and nucleus in many cell types. During embryonic development it is expressed at relatively high levels in the central nervous system, liver, kidney, and lungs and is prevalent in numerous tissues in adults. Studies have shown that caspase-2 becomes activated in response to several lethal stimuli including DNA damage, ER stress, and death receptor stimulation and further evidence has suggested a role in reactive oxygen species-induced cell death. The SB123a monoclonal antibody detects bands at ~40 and ~48 kDa corresponding to cleaved and uncleaved forms of caspase-2, respectively.