The cells after injury undergo degenerative changes and become dead. The most common pattern of cell death recognized is necrosis, called by progressive degenerative action of the enzymes on the lethally injured cells. Degeneration initiates inflammatory response in the surrounding tissue. This attracts leukocytes and nearby phagocytes at the site and these cells start eating and eliminating the dead cells by phagocytosis. Types of necrosis are coagulative necrosis, liquefactive necrosis, gangrenous necrosis, caseous necrosis, fat necrosis, and fibrinoid necrosis. Cellular changes consist of the nucleus changes and characteristics of this change are determined by the manner in which its DNA breaks down, such as karyolysis, pyknosis, and karyorrhexis.