The migration of macrophages after phagocytosis in chick bone marrow

The migration of macrophages in chick bone marrow was studied by histoplanimetry after an intravenous injection of colloidal carbon or iron-dextran. In the initial stages after the injection, carbon-laden macrophages were found only in the sinus, where erythrocytopoiesis took place. The carbon-laden macrophages then passed through the sinus wall and gradually migrated from the sinus to the extravascular area (i.e., the granulocytopoietic region) peaking at 1 to 3 days after injection. After 7 days, almost all the carbon-laden macrophages accumulated to form "macrophage islets" mainly around the lymphatic nodules in the extravascular area. In the cases injected with iron-dextran, the movement of iron-laden macrophages was similar to that of the carbon-laden ones. The similarity suggests that the direction and time of migration of macrophages are independent of ingested materials.