APOPTOSIS IN LEUKOCYTES

All cells of the hematopoietic system have finite life spans, shorter by far than that of the host. They end their lives by committing a for m of cellular suicide or programmed cell death. The morphology of this process is considerably different from that of necrosis and is called apoptosis. Apoptotic cells undergo a stereotyped sequence of changes, including shrinkage and nuclear collapse. The cell is quickly recogni zed and eaten by a phagocyte, without the elicitation of an inflammato ry response. Although most cells have specific triggers of apoptosis, the killer T cell seems able to induce apoptosis in any cell it recogn izes, The process of apoptosis is regulated by cytokines, and may be m odulated both in vitro and in vivo.