Granulocyte clearance by apoptosis in the resolution of inflammation.

It has recently been recognized that extravasated granulocytes undergo apoptosis or programmed cell death. This process controls the functional longevity of these cells and is exquisitely modulated by environmental inflammatory mediators. By contrast with necrosis, an alternative fate for granulocytes in tissues, during apoptosis the granulocyte membrane remains intact and potentially injurious granule contents are retained. The intact apoptotic cell is removed by macrophages utilizing novel surface recognition mechanisms which fail to trigger a pro-inflammatory macrophage response. The balance between granulocyte apoptosis and necrosis in inflamed tissues may be an important determinant of the degree of tissue injury, and further dissection of the mechanisms of granulocyte apoptosis and removal may lead to new therapeutic strategies in inflammatory disease.