Apoptosis and autoimmune diseases.

Every day billions of cells die in our bodies to eliminate those that are harmful, useless, or senescent. The process can be divided into two steps: cell dying and cell clearance. In the first step, death machinery is activated in the cells and quickly kills them. During the second step, dead cells are engulfed by phagocytes, and their components are degraded in the lysosomes of the phagocytes. The death mechanism and the clearance of dead cells have been extensively studied. Mouse lines that are deficient in the death or clearance process have been established, and human patients carrying a mutation in the death machinery have been identified. Data from these mutant mice and human patients indicate that defects in cell death or dead-cell clearance leads to autoimmunity. This review examines the cell death and clearance processes and briefly discusses the diseases they cause.