The role of apoptosis (programmed cell death) in haemopoiesis and the immune system.

Apoptosis, or programmed cell death, is a series of controlled sequential events resulting in the demise of cells without invoking an inflammatory response. It is a naturally occurring process which maintains a cellular balance during both animal development and in the mature adult. Although first described 20 years ago, there is now renewed interest in this phenomenon, particularly in the light of our greater understanding of cellular signalling pathways and their genetic control. This is especially pertinent to haemopoiesis and the overall maintenance of a functional immune system. This review broadly covers the biochemical events of apoptosis and the recognition of apoptotic cells by phagocytes. Reference is made to the selective development of T- and B-cells and to the control of inflammation. Molecular events in apoptosis are also discussed with special reference to aberrant bcl-2 gene expression in follicular B-cell lymphoma and the role of other death genes in the control of apoptosis.