Apoptosis as programmed cell death (PCD): Cupio dissolvi in cell life

Apoptosis is a distinct form of cell death in multicellular organisms, displays characteristic morphologic features, and represents the only currently recognised form of programmed cell death (PCD). It is a process that requires an actively functioning metabolism with protein synthesis, the stimulation of specific enzymatic pathways, and in most cases, gene transcription. In mammals various genes which include c-myc, bcl-2, spg-2, p53 and ras help regulate apoptosis. The activation or repression of the various genes depends on the stimulus of extracellular signals, most often captated by specific receptors. Apoptosis plays a fundamental role in normal tissue development and renewal, immune system responses, and the progression of pathological conditions such as AIDS and tumours. This article reviews the main morphologic, biochemical and genetic aspects of the phenomenon, together with its impact on the natural history and response to therapy of some diseases.