Macrophage Surface Expression of Annexins I and II in the Phagocytosis of Apoptotic Lymphocytes

Speaker: 江承堯                                                        Time: 11/17/04, 14:00~15:00

Commentator: 林秋烽 博士                                        Place: Room 601

Abstract:

     Phagocytosis of apoptotic cell by macrophage is an important mechanism in homeostasis. When cell undergoes apoptosis, inner membrane phosphatidylserine is exposed on outer membrane surface and induces a “eat me” signal to macrophage (1). Apoptotic cells are recognized and ingested by phagocytes that suppresses autoimmune and inflammatory reactions (2). In this study, the expression of annexin I and annexin II on the surface of macroghage was shown. Furthermore, apoptotic Jurkat T lymphocytes and peripheral T lymphocytes, but not apoptotic thymocytes, were stained with anti-annexin I but not II. Phagocytosis of apoptotic cell by macrophage was inhibited by monoclonal antibodies (mAbs) against annexin I and annexin II, or by pretreatment of macrophages with the same mAbs, but not by anti-annexin V. However phagocytosis of opsonized erythrocytes by macrophage was annexin-independent. Similarly, pre-treatment of apoptotic target cells with anti-annexin mAbs had no effect on macrophage phagocytosis. EGTA pre-treatment of apoptotic cells but not macrophage inhibited the ability of phagocytosis by macrophage. Therefore, annexins may act as the bridge between macrophages and apoptotic targets during phagocytosis, and they play a role as ligand and receptor in this process. 

References:

1.Callahan, M. K., et al. 2003. Phosphatidylserine expression and phagocytosis of       apoptotic thymocytes during differentiation of monocytic cells. J. Leukoc. Biol. 74, 846–856.

2.Fadok, V. A., et al. 1998. Macrophages that have ingested apoptotic cells in vitro inhibit proinflammatory cytokine production through autocrine/paracrine mechanisms involving TGF-beta, PGE2, and PAF. J. Clin. Invest. 101, 890-898.

3.Fan, X., et al. 2004. Macrophage surface expression of annexins I and II in the phagocytosis of apoptotic lymphocytes. Mol. Biol. Cell 15, 2863–2872.