Macrophage phagocytosis of wound neutrophils

Resolution of acute inflammation is thought to require the recognition and phagocytosis of apoptotic neutrophils (PMN) through receptor-ligand interac tions with macrophages (M phi). This hypothesis was tested in rat wounds by quantifying apoptosis in freshly harvested and aged-in-culture PMN taken f rom wounds 1-3 days after injury and by using these wound PMN as phagocytic targets for wound, immune-activated peritoneal, and resident peritoneal M phi. Less than 6% of freshly harvested PMN exhibited characteristics of apo ptosis, On aging in culture, day 1 PMN did not undergo apoptosis, whereas 4 1 +/- 1 and 29 +/- 1% of day 2 and 3 PMN, respectively, developed apoptosis , which corresponded to increased ingestion by M phi. All three M phi popul ations engaged different receptor-ligand pairs for the recognition and phag ocytosis of PMN. Results indicate the resistance of early wound PMN to age- induced apoptosis, demonstrate wound-M phi phagocytosis of wound PMN, and i dentify distinct receptor utilization by wound and other M phi to ingest wo und PMN.