APOPTOSIS AND THE MAINTENANCE OF HOMEOSTASIS IN THE IMMUNE-SYSTEM

The regulation of cell proliferation and the selection against autorea ctive cells in the lymphoid system both occur through the induction of apoptosis. Many of the signals that induce apoptosis in lymphocytes a re now well defined. Interactions between Fas and its ligand have emer ged as a major mechanism for the deletion of activated peripheral T ce lls and autoreactive B cells. Although the signal-transduction pathway leading from engagement of Fas to apoptosis is not entirely clear, si gnificant advances have been made recently. There has also been progre ss in the elucidation of the mechanisms that regulate apoptosis in the immune system.