Necrosis versus apoptosis

Cells either die in an unregulated distension and protein denaturation (necrosis) or in a tightly programmed series of events (apoptosis) orchestrated by a series of caspase enzymes. Necrotic cells enlarge in the process of dying whereas in apoptosis the cell shrinks and develops surface blebs (far right picture) which contain apoptotically modified self antigens. The larger blebs contain nucleosomal DNA, Ro, La, and the small nuclear ribonucleoproteins. The cells eventually fragment and are cleared by macrophages. It is hypothesized that modified nucleoprotein complexes, which escape phagocytosis, can be taken up by antigen presenting cells with a resulting autoimmune response.