|Budget Amount *help
¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1996 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1995 : ¥1,800,000 (Direct Cost : ¥1,800,000)
Embryonic liver macrophages are derived from intravascular macrophages. Before the initiation of liver hemopoiesis, embryonic peripheral blood contained a few free phagocytes as early as 10 days of gestation. Based on fine structural criteria, lntravascular phagocytes were considered to be specialized scavenger macrophages with the function of clearing the blood, and they are the precursor cells of sinusoidal macrophages at the onset of liver hemopoiesis.
Sinusoidal macrophages move and differentiate into central macrophages of erythroblastic islands. Our ultrahistochemical and ultrastructural studies showed that the central cells in liver erythroblastic islands do not originate from hepatocytes but from sinusoid macrophages and that SBA binding ability is closely concerned with liver macrophage maturation.
Changes of phagocytotic targets of liver macrophage take place in developmental saquence of liver hemopoiesis. Aged primitive erythrocytes, cell fragments of primitive erythrocytes, n
uclei expelled from definitive erythroblasts and dying polymorphonuclear leukocytes were removed from fetal liver by macrophages at the various stages of liver hemopoiesis.
Erythroblastic islands disappear in early neonatal liver and sinusoidal macrophages remain in adult livers. Neonatal liver contained two kinds of macrophages ; sinusoidal scavenger macrophages and central macrophages of erythroblastic islands. After 5 days of age, erythroblasts gradually left the islands, and the macrophages which lost surrounding erythroblasts became starfish-shaped due to many long twisted cytoplasmic projections. Their nuclei became shrinked and condensed, and the cytoplasm was fragmental and removed.